#!/usr/bin/env ruby -w
# encoding: UTF-8
#
# = TaskScenario.rb -- The TaskJuggler III Project Management Software
#
# Copyright (c) 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014
#               by Chris Schlaeger <cs@taskjuggler.org>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of version 2 of the GNU General Public License as
# published by the Free Software Foundation.
#

require 'taskjuggler/ScenarioData'
require 'taskjuggler/DataCache'

class TaskJuggler

  class TaskScenario < ScenarioData

    attr_reader :isRunAway, :hasDurationSpec

    # Create a new TaskScenario object.
    def initialize(task, scenarioIdx, attributes)
      super
      # Attributed are only really created when they are accessed the first
      # time. So make sure some needed attributes really exist so we don't
      # have to check for existance each time we access them.
      %w( allocate assignedresources booking charge chargeset complete
          competitors criticalness depends duration
          effort effortdone effortleft end forward gauge length
          maxend maxstart minend minstart milestone pathcriticalness
          precedes priority projectionmode responsible
          scheduled shifts start status ).each do |attr|
        @property[attr, @scenarioIdx]
      end
      unless @property.parent
        # The projectionmode attributes is a scenario specific attribute that
        # can be inherited from the project. The normal inherit-from-project
        # mechanism does not support scenario specific inheritance. We have to
        # deal with this separately here. To make it look like a regularly
        # inherted value, we need to switch the AttributeBase mode and restore
        # it afterwards.
          mode = AttributeBase.mode
          AttributeBase.setMode(1)
          @property['projectionmode', @scenarioIdx] =
            @project.scenario(@scenarioIdx).get('projection')
          AttributeBase.setMode(mode)
      end

      # A list of all allocated leaf resources.
      @candidates = []
      @dCache = DataCache.instance
    end

    def markAsScheduled
      return if @scheduled
      @scheduled = true

      Log.msg do
        if @milestone
          typename = 'Milestone'
        elsif @property.leaf?
          typename = 'Task'
        else
          typename = 'Container'
        end
        "#{typename} #{@property.fullId} has been scheduled."
      end
    end

    # Call this function to reset all scheduling related data prior to
    # scheduling.
    def prepareScheduling
      @property['startpreds', @scenarioIdx] = []
      @property['startsuccs', @scenarioIdx] = []
      @property['endpreds', @scenarioIdx] = []
      @property['endsuccs', @scenarioIdx] = []

      @isRunAway = false

      # And as global scoreboard index
      @currentSlotIdx = nil
      # The 'done' variables count scheduled values in number of time slots.
      @doneDuration = 0
      @doneLength = 0
      # Due to the 'efficiency' factor the effort slots must be a float.
      @doneEffort = 0.0

      @nowIdx = @project.dateToIdx(@project['now'])

      @startIsDetermed = nil
      @endIsDetermed = nil

      # To avoid multiple calls to propagateDate() we use these flags to know
      # when we've done it already.
      @startPropagated = false
      @endPropagated = false

      @durationType =
        if @effort > 0
          @hasDurationSpec = true
          :effortTask
        elsif @length > 0
          @hasDurationSpec = true
          :lengthTask
        elsif @duration > 0
          @hasDurationSpec = true
          :durationTask
        else
          # If the task is set as milestone it has a duration spec.
          @hasDurationSpec = @milestone
          :startEndTask
        end

      markAsMilestone

      # For start-end-tasks without allocation, we don't have to do
      # anything but to set the 'scheduled' flag.
      if @durationType == :startEndTask && @start && @end && @allocate.empty?
        markAsScheduled
      end

      # Collect the limits of this task and all parent tasks into a single
      # Array.
      @allLimits = []
      task = @property
      # Reset the counters of all limits of this task.
      task['limits', @scenarioIdx].reset if task['limits', @scenarioIdx]
      until task.nil?
        if task['limits', @scenarioIdx]
          @allLimits << task['limits', @scenarioIdx]
        end
        task = task.parent
      end

      @contendedResources = Hash.new { |hash, key| hash[key] = Hash.new(0) }

      # Collect the mandatory allocations.
      @mandatories = []
      @allocate.each do |allocation|
        @mandatories << allocation if allocation.mandatory
        allocation.lockedResource = nil
      end

      bookBookings

      if @durationType == :startEndTask
        @startIdx = @project.dateToIdx(@start) if @start
        @endIdx = @project.dateToIdx(@end) if @end
      end
    end

    # The parser only stores the full task IDs for each of the dependencies.
    # This function resolves them to task references and checks them. In
    # addition to the 'depends' and 'precedes' property lists we also keep 4
    # additional lists.
    # startpreds: All precedessors to the start of this task
    # startsuccs: All successors to the start of this task
    # endpreds: All predecessors to the end of this task
    # endsuccs: All successors to the end of this task
    # Each list element consists of a reference/boolean pair. The reference
    # points to the dependent task and the boolean specifies whether the
    # dependency originates from the end of the task or not.
    def Xref
      @depends.each do |dependency|
        depTask = checkDependency(dependency, 'depends')
        @startpreds.push([ depTask, dependency.onEnd ])
        depTask[dependency.onEnd ? 'endsuccs' : 'startsuccs', @scenarioIdx].
          push([ @property, false ])
      end

      @precedes.each do |dependency|
        predTask = checkDependency(dependency, 'precedes')
        @endsuccs.push([ predTask, dependency.onEnd ])
        predTask[dependency.onEnd ? 'endpreds' : 'startpreds', @scenarioIdx].
          push([@property, true ])
      end
    end

    # Return true of this Task has a dependency [ _target_, _onEnd_ ] in the
    # dependency category _depType_.
    def hasDependency?(depType, target, onEnd)
      a(depType).include?([target, onEnd])
    end

    def propagateInitialValues
      unless @startPropagated
        if @start
          propagateDate(@start, false, true)
        elsif @property.parent.nil? &&
              @property.canInheritDate?(@scenarioIdx, false)
          propagateDate(@project['start'], false, true)
        end
      end

      unless @endPropagated
        if @end
          propagateDate(@end, true, true)
        elsif @property.parent.nil? &&
              @property.canInheritDate?(@scenarioIdx, true)
          propagateDate(@project['end'], true, true)
        end
      end
    end

    # Before the actual scheduling work can be started, we need to do a few
    # consistency checks on the task.
    def preScheduleCheck
      # Accounts can have sub accounts added after being used in a chargetset.
      # So we need to re-test here.
      @chargeset.each do |chargeset|
        chargeset.each do |account, share|
          unless account.leaf?
            error('account_no_leaf',
                "Chargesets may not include group account #{account.fullId}.")
          end
        end
      end

      @responsible.map! do |resourceId|
        # 'resource' is still just an ID and needs to be converted into a
        # Resource.
        if (resource = @project.resource(resourceId)).nil?
          error('resource_id_expected', "#{resourceId} is not a defined " +
                'resource.', @sourceFileInfo)
        end
        resource
      end
      @responsible.uniq!

      # Leaf tasks can be turned into containers after bookings have been added.
      # We need to check for this.
      unless @property.leaf? || @booking.empty?
        error('container_booking',
              "Container task #{@property.fullId} may not have bookings.")
      end

      # Milestones may not have bookings.
      if @milestone && !@booking.empty?
        error('milestone_booking',
              "Milestone #{@property.fullId} may not have bookings.")
      end

      # All 'scheduled' tasks must have a fixed start and end date.
      if @scheduled && (@start.nil? || @end.nil?)
        error('not_scheduled',
              "Task #{@property.fullId} is marked as scheduled but does not " +
              'have a fixed start and end date.')
      end

      # If an effort has been specified resources must be allocated as well.
      if @effort > 0 && @allocate.empty?
        error('effort_no_allocations',
              "Task #{@property.fullId} has an effort but no resource " +
              "allocations.")
      end

      durationSpecs = 0
      durationSpecs += 1 if @effort > 0
      durationSpecs += 1 if @length > 0
      durationSpecs += 1 if @duration > 0
      durationSpecs += 1 if @milestone

      # The rest of this function performs a number of plausibility tests with
      # regards to task start and end critiria. To explain the various cases,
      # the following symbols are used:
      #
      # |: fixed start or end date
      # -: no fixed start or end date
      # M: Milestone
      # D: start or end dependency
      # x->: ASAP task with duration criteria
      # <-x: ALAP task with duration criteria
      # -->: ASAP task without duration criteria
      # <--: ALAP task without duration criteria

      if @property.container?
        if durationSpecs > 0
          error('container_duration',
                "Container task #{@property.fullId} may not have a duration " +
                "or be marked as milestones.")
        end
      elsif @milestone
        if durationSpecs > 1
          error('milestone_duration',
                "Milestone task #{@property.fullId} may not have a duration.")
        end
        # Milestones can have the following cases:
        #
        #   |  M -   ok     |D M -   ok     - M -   err1   -D M -   ok
        #   |  M |   err2   |D M |   err2   - M |   ok     -D M |   ok
        #   |  M -D  ok     |D M -D  ok     - M -D  ok     -D M -D  ok
        #   |  M |D  err2   |D M |D  err2   - M |D  ok     -D M |D  ok

        # err1: no start and end
        # already handled by 'start_undetermed' or 'end_undetermed'

        # err2: differnt start and end dates
        if @start && @end && @start != @end
          error('milestone_start_end',
                "Start (#{@start}) and end (#{@end}) dates of " +
                "milestone task #{@property.fullId} must be identical.")
        end
      else
        #   Error table for non-container, non-milestone tasks:
        #   AMP: Automatic milestone promotion for underspecified tasks when
        #        no bookings or allocations are present.
        #   AMPi: Automatic milestone promotion when no bookings or
        #   allocations are present. When no bookings but allocations are
        #   present the task inherits start and end date.
        #   Ref. implicitXref()|
        #   inhS: Inherit start date from parent task or project
        #   inhE: Inherit end date from parent task or project
        #
        #   | x-> -   ok     |D x-> -   ok     - x-> -   inhS   -D x-> -   ok
        #   | x-> |   err1   |D x-> |   err1   - x-> |   inhS   -D x-> |   err1
        #   | x-> -D  ok     |D x-> -D  ok     - x-> -D  inhS   -D x-> -D  ok
        #   | x-> |D  err1   |D x-> |D  err1   - x-> |D  inhS   -D x-> |D  err1
        #   | --> -   AMP    |D --> -   AMP    - --> -   AMPi   -D --> -   AMP
        #   | --> |   ok     |D --> |   ok     - --> |   inhS   -D --> |   ok
        #   | --> -D  ok     |D --> -D  ok     - --> -D  inhS   -D --> -D  ok
        #   | --> |D  ok     |D --> |D  ok     - --> |D  inhS   -D --> |D  ok
        #   | <-x -   inhE   |D <-x -   inhE   - <-x -   inhE   -D <-x -   inhE
        #   | <-x |   err1   |D <-x |   err1   - <-x |   ok     -D <-x |   ok
        #   | <-x -D  err1   |D <-x -D  err1   - <-x -D  ok     -D <-x -D  ok
        #   | <-x |D  err1   |D <-x |D  err1   - <-x |D  ok     -D <-x |D  ok
        #   | <-- -   inhE   |D <-- -   inhE   - <-- -   AMP    -D <-- -   inhE
        #   | <-- |   ok     |D <-- |   ok     - <-- |   AMP    -D <-- |   ok
        #   | <-- -D  ok     |D <-- -D  ok     - <-- -D  AMP    -D <-- -D  ok
        #   | <-- |D  ok     |D <-- |D  ok     - <-- |D  AMP    -D <-- |D  ok

        # These cases are normally autopromoted to milestones or inherit their
        # start or end dates. But this only works for tasks that have no
        # allocations or bookings.
        #   -  --> -
        #   |  --> -
        #   |D --> -
        #   -D --> -
        #   -  <-- -
        #   -  <-- |
        #   -  <-- -D
        #   -  <-- |D
        if durationSpecs == 0 &&
           ((@forward && @end.nil? && !hasDependencies(true)) ||
            (!@forward && @start.nil? && !hasDependencies(false)))
          error('task_underspecified',
                "Task #{@property.fullId} has too few specifations to be " +
                "scheduled.")
        end

        #   err1: Overspecified (12 cases)
        #   |  x-> |
        #   |  <-x |
        #   |  x-> |D
        #   |  <-x |D
        #   |D x-> |
        #   |D <-x |
        #   |D <-x |D
        #   |D x-> |D
        #   -D x-> |
        #   -D x-> |D
        #   |D <-x -D
        #   |  <-x -D
        if durationSpecs > 1
          error('multiple_durations',
                "Tasks may only have either a duration, length or effort or " +
                "be a milestone.")
        end
        startSpeced = @property.provided('start', @scenarioIdx)
        endSpeced = @property.provided('end', @scenarioIdx)
        if ((startSpeced && endSpeced) ||
            (hasDependencies(false) && @forward && endSpeced) ||
            (hasDependencies(true) && !@forward && startSpeced)) &&
           durationSpecs > 0 && !@property.provided('scheduled', @scenarioIdx)
          error('task_overspecified',
                "Task #{@property.fullId} has a start, an end and a " +
                'duration specification.')
        end
      end

      if !@booking.empty? && !@forward && !@scheduled
        error('alap_booking',
              'A task scheduled in ALAP mode may only have bookings if it ' +
              'has been marked as fully scheduled. Keep in mind that ' +
              'certain attributes like \'end\' or \'precedes\' automatically ' +
              'switch the task to ALAP mode.')
      end

      @startsuccs.each do |task, onEnd|
        unless task['forward', @scenarioIdx]
          task.data[@scenarioIdx].error(
            'onstart_wrong_direction',
            'Tasks with on-start dependencies must be ASAP scheduled')
        end
      end
      @endpreds.each do |task, onEnd|
        if task['forward', @scenarioIdx]
          task.data[@scenarioIdx].error(
            'onend_wrong_direction',
            'Tasks with on-end dependencies must be ALAP scheduled')
        end
      end
    end

    # When the actual scheduling process has been completed, this function must
    # be called to do some more housekeeping. It computes some derived data
    # based on the just scheduled values.
    def finishScheduling
      # Recursively descend into all child tasks.
      @property.children.each do |task|
        task.finishScheduling(@scenarioIdx)
      end

      @property.parents.each do |pTask|
        # Add the assigned resources to the parent task's list.
        @assignedresources.each do |resource|
          unless pTask['assignedresources', @scenarioIdx].include?(resource)
            pTask['assignedresources', @scenarioIdx] << resource
          end
        end
      end

      # These lists are no longer needed, so let's save some memory. Set it to
      # nil so we can detect accidental use.
      @candidates = nil
      @mandatories = nil
      @allLimits = nil
    end

    # This function is not essential but does perform a large number of
    # consistency checks. It should be called after the scheduling run has been
    # finished.
    def postScheduleCheck
      @errors = 0
      @property.children.each do |task|
        @errors += 1 unless task.postScheduleCheck(@scenarioIdx)
      end

      # There is no point to check the parent if the child(s) have errors.
      return false if @errors > 0

      # Same for runaway tasks. They have already been reported.
      if @isRunAway
        error('sched_runaway', "Some tasks did not fit into the project time " +
              "frame.")
      end

      # Make sure the task is marked complete
      unless @scheduled
        error('not_scheduled',
              "Task #{@property.fullId} has not been marked as scheduled.")
      end

      # If the task has a follower or predecessor that is a runaway this task
      # is also incomplete.
      (@startsuccs + @endsuccs).each do |task, onEnd|
        return false if task.isRunAway(@scenarioIdx)
      end
      (@startpreds + @endpreds).each do |task, onEnd|
        return false if task.isRunAway(@scenarioIdx)
      end

      # Check if the start time is ok
      if @start.nil?
        error('task_start_undef',
              "Task #{@property.fullId} has undefined start time")
      end
      if @start < @project['start'] || @start > @project['end']
        error('task_start_range',
              "The start time (#{@start}) of task #{@property.fullId} " +
              "is outside the project interval (#{@project['start']} - " +
              "#{@project['end']})")
      end
      if !@minstart.nil? && @start < @minstart
        warning('minstart',
               "The start time (#{@start}) of task #{@property.fullId} " +
               "is too early. Must be after #{@minstart}.")
      end
      if !@maxstart.nil? && @start > @maxstart
        warning('maxstart',
               "The start time (#{@start}) of task #{@property.fullId} " +
               "is too late. Must be before #{@maxstart}.")
      end
      # Check if the end time is ok
      error('task_end_undef',
            "Task #{@property.fullId} has undefined end time") if @end.nil?
      if @end < @project['start'] || @end > @project['end']
        error('task_end_range',
              "The end time (#{@end}) of task #{@property.fullId} " +
              "is outside the project interval (#{@project['start']} - " +
              "#{@project['end']})")
      end
      if !@minend.nil? && @end < @minend
        warning('minend',
                "The end time (#{@end}) of task #{@property.fullId} " +
                "is too early. Must be after #{@minend}.")
      end
      if !@maxend.nil? && @end > @maxend
        warning('maxend',
                "The end time (#{@end}) of task #{@property.fullId} " +
                "is too late. Must be before #{@maxend}.")
      end
      # Make sure the start is before the end
      if @start > @end
        error('start_after_end',
              "The start time (#{@start}) of task #{@property.fullId} " +
              "is after the end time (#{@end}).")
      end


      # Check that tasks fits into parent task.
      unless (parent = @property.parent).nil? ||
              parent['start', @scenarioIdx].nil? ||
              parent['end', @scenarioIdx].nil?
        if @start < parent['start', @scenarioIdx]
          error('task_start_in_parent',
                "The start date (#{@start}) of task #{@property.fullId} " +
                "is before the start date (#{parent['start', @scenarioIdx]}) " +
                "of the enclosing task.")
        end
        if @end > parent['end', @scenarioIdx]
          error('task_end_in_parent',
                "The end date (#{@end}) of task #{@property.fullId} " +
                "is after the end date (#{parent['end', @scenarioIdx]}) " +
                "of the enclosing task.")
        end
      end

      # Check that all preceding tasks start/end before this task.
      @depends.each do |dependency|
        task = dependency.task
        limit = task[dependency.onEnd ? 'end' : 'start', @scenarioIdx]
        next if limit.nil?
        if @start < limit ||
           (dependency.gapDuration > 0 &&
            limit + dependency.gapDuration > @start) ||
           (dependency.gapLength > 0 &&
            calcLength(limit, @start) < dependency.gapLength)
          error('task_pred_before',
                "Task #{@property.fullId} (#{@start}) must start " +
                (dependency.gapDuration > 0 ?
                  "#{dependency.gapDuration / (60 * 60 * 24)} days " :
                  (dependency.gapLength > 0 ?
                    "#{@project.slotsToDays(dependency.gapLength)} " +
                    "working days " : '')) +
                "after " +
                "#{dependency.onEnd ? 'end' : 'start'} (#{limit}) of task " +
                "#{task.fullId}. This condition could not be met.")
        end
      end

      # Check that all following tasks end before this task
      @precedes.each do |dependency|
        task = dependency.task
        limit = task[dependency.onEnd ? 'end' : 'start', @scenarioIdx]
        next if limit.nil?
        if limit < @end ||
           (dependency.gapDuration > 0 &&
            limit - dependency.gapDuration < @end) ||
           (dependency.gapLength > 0 &&
            calcLength(@end, limit) < dependency.gapLength)
          error('task_succ_after',
                "Task #{@property.fullId} (#{@end}) must end " +
                (dependency.gapDuration > 0 ?
                   "#{dependency.gapDuration / (60 * 60 * 24)} days " :
                   (dependency.gapLength > 0 ?
                     "#{@project.slotsToDays(dependency.gapLength)} " +
                     "working days " : '')) +
                "before " +
                "#{dependency.onEnd ? 'end' : 'start'} (#{limit}) of task " +
                "#{task.fullId}. This condition could not be met.")
        end
      end

      if @milestone && @start != @end
        error('milestone_times_equal',
              "Milestone #{@property.fullId} must have identical start and " +
              "end date.")
      end

      if @property.leaf? && @effort == 0 && !@milestone && !@allocate.empty? &&
         @assignedresources.empty?
        # The user used an 'allocate' for the task, but did not specify any
        # 'effort'. Actual allocations will only happen when resources are
        # available by chance. If there are no assigned resources, we generate
        # a warning as this is probably not what the user intended.
        warning('allocate_no_assigned',
                "Task #{@property.id} has resource allocation requested, but " +
                "did not get any resources assigned. Either use 'effort' " +
                "to ensure allocations or use a higher 'priority'.")
      end

      thieves = []
      @competitors.each do |t|
        thieves << t if t['priority', @scenarioIdx] < @priority
      end
      unless thieves.empty?
        warning('priority_inversion',
                "Due to a mix of ALAP and ASAP scheduled tasks or a " +
                "dependency on a lower priority tasks the following " +
                "task#{thieves.length > 1 ? 's' : ''} stole resources from " +
                "#{@property.fullId} despite having a lower priority:")
        thieves.each do |t|
          info('priority_inversion_info', "Task #{t.fullId}", t.sourceFileInfo)
        end
      end

      @errors == 0
    end

    def resetLoopFlags
      @deadEndFlags = Array.new(4, false)
    end

    # To ensure that we can properly schedule the project, we need to make
    # sure that it does not contain any circular dependencies. This method
    # recursively checks for such loops by remembering the _path_. Each entry
    # is marks the start or end of a task. _atEnd_ specifies whether we are
    # currently at the start or end of the task. _fromOutside_ specifies
    # whether we are coming from a inside or outside that tasks. See
    # specification below. _forward_ specifies whether we are checking the
    # dependencies from start to end or in the opposite direction. If we are
    # moving forward, we only move from start to end of ASAP tasks, not ALAP
    # tasks and vice versa. For milestones, we ignore the scheduling
    # direction.
    def checkForLoops(path, atEnd, fromOutside, forward)
      # Check if we have been here before on this path.
      if path.include?([ @property, atEnd ])
        warning('loop_detected',
                "Dependency loop detected at #{atEnd ? 'end' : 'start'} " +
                "of task #{@property.fullId}", false)
        skip = true
        path.each do |t, e|
          if t == @property && e == atEnd
            skip = false
            next
          end
          next if skip
          info("loop_at_#{e ? 'end' : 'start'}",
               "Loop ctnd. at #{e ? 'end' : 'start'} of task #{t.fullId}",
               t.sourceFileInfo)
        end
        error('loop_end', "Aborting")
      end
      # Used for debugging only
      if false
        pathText = ''
        path.each do |t, e|
          pathText += "#{t.fullId}(#{e ? 'end' : 'start'}) -> "
        end
        pathText += "#{@property.fullId}(#{atEnd ? 'end' : 'start'})"
        puts pathText
      end
      return if @deadEndFlags[(atEnd ? 2 : 0) + (fromOutside ? 1 : 0)]
      path << [ @property, atEnd ]

      # To find loops we have to traverse the graph in a certain order. When we
      # enter a task we can either come from outside or inside. The following
      # graph explains these definitions:
      #
      #             |      /          \      |
      #  outside    v    /              \    v   outside
      #          +------------------------------+
      #          |    /        Task        \    |
      #       -->|  o   <---          --->   o  |<--
      #          |/ Start                  End \|
      #         /+------------------------------+\
      #       /     ^                        ^     \
      #             |         inside         |
      #
      # At the top we have the parent task. At the botton the child tasks.
      # The horizontal arrors are start predecessors or end successors.
      # As the graph is doubly-linked, we need to becareful to only find real
      # loops. When coming from outside, we only continue to the inside and vice
      # versa. Horizontal moves are only made when we are in a leaf task.
      unless atEnd
        if fromOutside
          if @property.container?
            #
            #         |
            #         v
            #       +--------
            #    -->| o--+
            #       +----|---
            #            |
            #            V
            #
            @property.children.each do |child|
              child.checkForLoops(@scenarioIdx, path, false, true, forward)
            end
          else
            #         |
            #         v
            #       +--------
            #    -->| o---->
            #       +--------
            #
            if (forward && @forward) || @milestone
              checkForLoops(path, true, false, true)
            end
          end
        else
          if @startpreds.empty?
            #
            #         ^
            #         |
            #       +-|------
            #       | o <--
            #       +--------
            #         ^
            #         |
            #
            if @property.parent
              @property.parent.checkForLoops(@scenarioIdx, path, false, false,
                                             forward)
            end
          else

            #       +--------
            #    <---- o <--
            #       +--------
            #          ^
            #          |
            #
            @startpreds.each do |task, targetEnd|
              task.checkForLoops(@scenarioIdx, path, targetEnd, true, forward)
            end
          end
        end
      else
        if fromOutside
          if @property.container?
            #
            #          |
            #          v
            #    --------+
            #       +--o |<--
            #    ---|----+
            #       |
            #       v
            #
            @property.children.each do |child|
              child.checkForLoops(@scenarioIdx, path, true, true, forward)
            end
          else
            #          |
            #          v
            #    --------+
            #     <----o |<--
            #    --------+
            #
            if (!forward && !@forward) || @milestone
              checkForLoops(path, false, false, false)
            end
          end
        else
          if @endsuccs.empty?
            #
            #          ^
            #          |
            #    ------|-+
            #      --> o |
            #    --------+
            #          ^
            #          |
            #
            if @property.parent
              @property.parent.checkForLoops(@scenarioIdx, path, true, false,
                                             forward)
            end
          else
            #    --------+
            #      --> o---->
            #    --------+
            #          ^
            #          |
            #
            @endsuccs.each do |task, targetEnd|
              task.checkForLoops(@scenarioIdx, path, targetEnd, true, forward)
            end
          end
        end
      end

      path.pop
      @deadEndFlags[(atEnd ? 2 : 0) + (fromOutside ? 1 : 0)] = true
      # puts "Finished with #{@property.fullId} #{atEnd ? 'end' : 'start'} " +
      #      "#{fromOutside ? 'outside' : 'inside'}"
    end

    # This function must be called before prepareScheduling(). It compiles the
    # list of leaf resources that are allocated to this task.
    def candidates
      @candidates = []
      @allocate.each do |allocation|
        allocation.candidates.each do |candidate|
          candidate.allLeaves.each do |resource|
            @candidates << resource unless @candidates.include?(resource)
          end
        end
      end
      @candidates
    end

    # This function does some prep work for other functions like
    # calcCriticalness. It compiles a list of all allocated leaf resources and
    # stores it in @candidates. It also adds the allocated effort to
    # the 'alloctdeffort' counter of each resource.
    def countResourceAllocations
      return if @candidates.empty? || @effort <= 0

      avgEffort = @effort / @candidates.length
      @candidates.each do |resource|
        resource['alloctdeffort', @scenarioIdx] += avgEffort
      end
    end

    # Determine the criticalness of the individual task. This is a measure for
    # the likelyhood that this task will get the resources that it needs to
    # complete the effort. Tasks without effort are not cricital. The only
    # exception are milestones which get an arbitrary value between 0 and 2
    # based on their priority.
    def calcCriticalness
      @criticalness = 0.0
      @pathcriticalness = nil

      # Users feel that milestones are somewhat important. So we use an
      # arbitrary value larger than 0 for them. We make it priority dependent,
      # so the user has some control over it. Priority 0 is 0, 500 is 1.0 and
      # 1000 is 2.0. These values are pretty much randomly picked and probably
      # require some more tuning based on real projects.
      if @milestone
        @criticalness = @priority / 500.0
      end

      # Task without efforts of allocations are not critical.
      return if @effort <= 0 || @candidates.empty?

      # Determine the average criticalness of all allocated resources.
      criticalness = 0.0
      @candidates.each do |resource|
        criticalness += resource['criticalness', @scenarioIdx]
      end
      criticalness /= @candidates.length

      # The task criticalness is the product of effort and average resource
      # criticalness.
      @criticalness = @effort * criticalness
    end

    # The path criticalness is a measure for the overall criticalness of the
    # task taking the dependencies into account. The fact that a task is part
    # of a chain of effort-based task raises all the task in the chain to a
    # higher criticalness level than the individual tasks. In fact, the path
    # criticalness of this chain is equal to the sum of the individual
    # criticalnesses of the tasks.
    def calcPathCriticalness(atEnd = false)
      # If we have computed this already, just return the value. If we are only
      # at the end of the task, we do not include the criticalness of this task
      # as it is not really part of the path.
      if @pathcriticalness
        return @pathcriticalness - (atEnd ? 0 : @criticalness)
      end

      maxCriticalness = 0.0

      if atEnd
        # At the end, we only care about pathes through the successors of this
        # task or its parent tasks.
        if (criticalness = calcPathCriticalnessEndSuccs) > maxCriticalness
          maxCriticalness = criticalness
        end
      else
        # At the start of the task, we have two options.
        if @property.container?
          # For container tasks, we ignore all dependencies and check the pathes
          # through all the children.
          @property.children.each do |task|
            if (criticalness = task.calcPathCriticalness(@scenarioIdx, false)) >
              maxCriticalness
              maxCriticalness = criticalness
            end
          end
        else
          # For leaf tasks, we check all pathes through the start successors and
          # then the pathes through the end successors of this task and all its
          # parent tasks.
          @startsuccs.each do |task, onEnd|
            if (criticalness = task.calcPathCriticalness(@scenarioIdx, onEnd)) >
              maxCriticalness
              maxCriticalness = criticalness
            end
          end

          if (criticalness = calcPathCriticalnessEndSuccs) > maxCriticalness
            maxCriticalness = criticalness
          end

          maxCriticalness += @criticalness
        end
      end

      @pathcriticalness = maxCriticalness
    end

    # Check if the task is ready to be scheduled. For this it needs to have at
    # least one specified end date and a duration criteria or the other end
    # date.
    def readyForScheduling?
      # If the tasks has already been scheduled, we still call it 'ready' so
      # it will be removed from the todo list.
      return true if @scheduled

      return false if @isRunAway

      if @forward
        return true if @start && (@hasDurationSpec || @end)
      else
        return true if @end && (@hasDurationSpec || @start)
      end

      false
    end

    # This function is the entry point for the core scheduling algorithm. It
    # schedules the task to completion.  The function returns true if a start
    # or end date has been determined and other tasks may be ready for
    # scheduling now.
    def schedule
      # Check if the task has already been scheduled e. g. by propagateDate().
      return true if @scheduled

      logTag = "schedule_#{@property.id}"
      Log.enter(logTag, "Scheduling task #{@property.id}")
      # Compute the date of the next slot this task wants to have scheduled.
      # This must either be the first slot ever or it must be directly
      # adjecent to the previous slot. If this task has not yet been scheduled
      # at all, @currentSlotIdx is still nil. Otherwise it contains the index
      # of the last scheduled slot.
      if @forward
        # On first call, the @currentSlotIdx is not set yet. We set it to the
        # start slot index or the 'now' slot if we are in projection mode and
        # the tasks has allocations.
        if @currentSlotIdx.nil?
          @currentSlotIdx = @project.dateToIdx(
            @projectionmode && (@project['now'] > @start) && !@allocate.empty? ?
            @project['now'] : @start)
        end
      else
        # On first call, the @currentSlotIdx is not set yet. We set it to the
        # slot index of the slot before the end slot.
        if @currentSlotIdx.nil?
          @currentSlotIdx = @project.dateToIdx(@end) - 1
        end
      end

      # Schedule all time slots from slot in the scheduling direction until
      # the task is completed or a problem has been found.
      # The task may not excede the project interval.
      lowerLimit = @project.dateToIdx(@project['start'])
      upperLimit = @project.dateToIdx(@project['end'])
      delta = @forward ? 1 : -1
      while scheduleSlot
        @currentSlotIdx += delta
        if @currentSlotIdx < lowerLimit || upperLimit < @currentSlotIdx
          markAsRunaway
          Log.exit(logTag, "Scheduling of task #{@property.id} failed")
          return false
        end
      end

      Log.exit(logTag, "Scheduling of task #{@property.id} completed")
      true
    end

    # Set a new start or end date and propagate the value to all other
    # task ends that have a direct dependency to this end of the task.
    def propagateDate(date, atEnd, ignoreEffort = false)
      logTag = "propagateDate_#{@property.id}_#{atEnd ? 'end' : 'start'}"
      Log.enter(logTag, "Propagating #{atEnd ? 'end' : 'start'} date " +
                        "to task #{@property.id}")
      thisEnd = atEnd ? 'end' : 'start'
      otherEnd = atEnd ? 'start' : 'end'
      #puts "Propagating #{thisEnd} date #{date} to #{@property.fullId} " +
      #     "#{ignoreEffort ? "ignoring effort" : "" }"

      # These flags are just used to avoid duplicate calls of this function
      # during propagateInitialValues().
      if atEnd
        @endPropagated = true
      else
        @startPropagated = true
      end

      # For leaf tasks, propagate start may set the date. Container task dates
      # are only set in scheduleContainer().
      if @property.leaf?
        # If we already have a date, we will only shrink the task period with
        # the new date.
        if (setDate = instance_variable_get('@' + thisEnd)) &&
           atEnd ? date > setDate : date < setDate
          Log.msg { "Preserving #{thisEnd} date of #{typename} " +
                    "#{@property.fullId}: #{setDate}" }
          return
        end

        instance_variable_set(('@' + thisEnd).intern, date)
        typename = 'Task'
        if @durationType == :startEndTask
          instance_variable_set(('@' + thisEnd + 'Idx').intern,
                                @project.dateToIdx(date))
          if @milestone
            typename = 'Milestone'
          end
        end
        Log.msg { "Update #{typename} #{@property.fullId}: #{period_to_s}" }
      end

      if @milestone
        # Start and end date of a milestone are identical.
        markAsScheduled
        if a(otherEnd).nil?
          propagateDate(a(thisEnd), !atEnd)
        end
      elsif !@scheduled && @start && @end &&
            !(@length == 0 && @duration == 0 && @effort == 0 &&
              !@allocate.empty?)
        markAsScheduled
      end

      # Propagate date to all dependent tasks. Don't do this for start
      # successors or end predecessors if this task is effort based. In this
      # case, the date might still change to align with the first/last
      # allocation. In these cases, bookResource() has to propagate the final
      # date.
      if atEnd
        if ignoreEffort || @effort == 0
          @endpreds.each do |task, onEnd|
            propagateDateToDep(task, onEnd)
          end
        end
        @endsuccs.each do |task, onEnd|
          propagateDateToDep(task, onEnd)
        end
      else
        if ignoreEffort || @effort == 0
          @startsuccs.each do |task, onEnd|
            propagateDateToDep(task, onEnd)
          end
        end
        @startpreds.each do |task, onEnd|
          propagateDateToDep(task, onEnd)
        end
      end

      # Propagate date to sub tasks which have only an implicit
      # dependency on the parent task and no other criteria for this end of
      # the task.
      @property.children.each do |task|
        if task.canInheritDate?(@scenarioIdx, atEnd)
          task.propagateDate(@scenarioIdx, date, atEnd)
        end
      end

      # The date propagation might have completed the date set of the enclosing
      # containter task. If so, we can schedule it as well.
      @property.parents.each do |parent|
        parent.scheduleContainer(@scenarioIdx)
      end
      Log.exit(logTag, "Finished propagation of " +
                       "#{atEnd ? 'end' : 'start'} date " +
                       "to task #{@property.id}")
    end

    # This function determines if a task can inherit the start or end date
    # from a parent task or the project time frame. +atEnd+ specifies whether
    # the check should be done for the task end (true) or task start (false).
    def canInheritDate?(atEnd)
      # Inheriting a start or end date from the enclosing task or the project
      # is allowed for the following scenarios:
      #   -  --> -   inhS*1  -  <-- -   inhE*1
      #   -  --> |   inhS    |  <-- -   inhE
      #   -  x-> -   inhS    -  <-x -   inhE
      #   -  x-> |   inhS    |  <-x -   inhE
      #   -  x-> -D  inhS    -D <-x -   inhE
      #   -  x-> |D  inhS    |D <-x -   inhE
      #   -  --> -D  inhS    -D <-- -   inhE
      #   -  --> |D  inhS    |D <-- -   inhE
      #   -  <-- |   inhS    |  --> -   inhE
      #
      #   *1 when no bookings but allocations are present

      thisEnd, thatEnd = atEnd ? [ 'end', 'start' ] : [ 'start', 'end' ]
      # Return false if we already have a date for this end or if we have a
      # strong dependency for this end.
      return false if instance_variable_get('@' + thisEnd) ||
                      hasStrongDeps?(atEnd)

      # Containter task can inherit the date if they have no dependencies at
      # this end.
      return true if @property.container?

      hasThatSpec = !instance_variable_get('@' + thatEnd).nil? ||
                    hasStrongDeps?(!atEnd)

      # Check for tasks that have no start and end spec, no duration spec but
      # allocates. They can inherit the start and end date.
      return true if hasThatSpec && !@hasDurationSpec && !@allocate.empty?

      if @forward ^ atEnd
        # the scheduling direction is pointing away from this end
        return true if @hasDurationSpec || !@booking.empty?

        return hasThatSpec
      else
        # the scheduling direction is pointing towards this end
        return !instance_variable_get('@' + thatEnd).nil? &&
               !@hasDurationSpec && @booking.empty? #&& @allocate.empty?
      end
    end

    # Find the smallest possible interval that encloses all child tasks. Abort
    # the operation if any of the child tasks are not yet scheduled.
    def scheduleContainer
      return if @scheduled || !@property.container?

      nStart = nil
      nEnd = nil

      @property.kids.each do |task|
        # Abort if a child has not yet been scheduled. Since we haven't done
        # the consistency check yet, we can't rely on start and end being set
        # if 'scheduled' is set.
        return if (!task['scheduled', @scenarioIdx] ||
                   task['start', @scenarioIdx].nil? ||
                   task['end', @scenarioIdx].nil?)

        if nStart.nil? || task['start', @scenarioIdx] < nStart
          nStart = task['start', @scenarioIdx]
        end
        if nEnd.nil? || task['end', @scenarioIdx] > nEnd
          nEnd = task['end', @scenarioIdx]
        end
      end

      startSet = endSet = false
      # Propagate the dates to other dependent tasks.
      if @start.nil? || @start > nStart
        @start = nStart
        startSet = true
      end
      if @end.nil? || @end < nEnd
        @end = nEnd
        endSet = true
      end
      unless @start && @end
        raise "Start (#{@start}) and end (#{@end}) must be set"
      end
      Log.msg { "Container task #{@property.fullId} completed: #{period_to_s}" }
      markAsScheduled

      # If we have modified the start or end date, we need to communicate this
      # new date to surrounding tasks.
      propagateDate(nStart, false) if startSet
      propagateDate(nEnd, true) if endSet
    end

    # Find the earliest possible start date for the task. This date must be
    # after the end date of all the task that this task depends on.
    # Dependencies may also require a minimum gap between the tasks.
    def earliestStart
      # This is the date that we will return.
      startDate = nil
      @depends.each do |dependency|
        potentialStartDate =
          dependency.task[dependency.onEnd ? 'end' : 'start', @scenarioIdx]
        return nil if potentialStartDate.nil?

        # Determine the end date of a 'length' gap.
        dateAfterLengthGap = potentialStartDate
        gapLength = dependency.gapLength
        while gapLength > 0 && dateAfterLengthGap < @project['end'] do
          if @project.isWorkingTime(dateAfterLengthGap)
            gapLength -= 1
          end
          dateAfterLengthGap += @project['scheduleGranularity']
        end

        # Determine the end date of a 'duration' gap.
        if dateAfterLengthGap > potentialStartDate + dependency.gapDuration
          potentialStartDate = dateAfterLengthGap
        else
          potentialStartDate += dependency.gapDuration
        end

        startDate = potentialStartDate if startDate.nil? ||
                                          startDate < potentialStartDate
      end

      # If any of the parent tasks has an explicit start date, the task must
      # start at or after this date.
      task = @property
      while (task = task.parent) do
        if task['start', @scenarioIdx] &&
           (startDate.nil? || task['start', @scenarioIdx] > startDate)
          startDate = task['start', @scenarioIdx]
          break
        end
      end

      # When the computed start date is after the already determined end date
      # of the task, the start dependencies were too weak. This happens when
      # task B depends on A and they are specified this way:
      # task A: | --> D-
      # task B: -D <-- |
      if @end && (startDate.nil? || startDate > @end)
        error('impossible_start_dep',
              "Task #{@property.fullId} has start date dependencies " +
              "that conflict with the end date #{@end}.")
      end

      startDate
    end

    # Find the latest possible end date for the task. This date must be
    # before the start date of all the task that this task precedes.
    # Dependencies may also require a minimum gap between the tasks.
    def latestEnd
      # This is the date that we will return.
      endDate = nil
      @precedes.each do |dependency|
        potentialEndDate =
          dependency.task[dependency.onEnd ? 'end' : 'start', @scenarioIdx]
        return nil if potentialEndDate.nil?

        # Determine the end date of a 'length' gap.
        dateBeforeLengthGap = potentialEndDate
        gapLength = dependency.gapLength
        while gapLength > 0 && dateBeforeLengthGap > @project['start'] do
          if @project.isWorkingTime(dateBeforeLengthGap -
                                    @project['scheduleGranularity'])
            gapLength -= 1
          end
          dateBeforeLengthGap -= @project['scheduleGranularity']
        end

        # Determine the end date of a 'duration' gap.
        if dateBeforeLengthGap < potentialEndDate - dependency.gapDuration
          potentialEndDate = dateBeforeLengthGap
        else
          potentialEndDate -= dependency.gapDuration
        end

        endDate = potentialEndDate if endDate.nil? || endDate > potentialEndDate
      end

      # If any of the parent tasks has an explicit end date, the task must end
      # at or before this date.
      task = @property
      while (task = task.parent) do
        if task['end', @scenarioIdx] &&
           (endDate.nil? || task['end', @scenarioIdx] < endDate)
          endDate = task['end', @scenarioIdx]
          break
        end
      end

      # When the computed end date is before the already determined start date
      # of the task, the end dependencies were too weak. This happens when
      # task A precedes B and they are specified this way:
      # task A: | --> D-
      # task B: -D <-- |
      if @start && (endDate.nil? || endDate < @start)
        error('impossible_end_dep',
              "Task #{@property.fullId} has end date dependencies " +
              "that conflict with the start date #{@start}.")
      end

      endDate
    end

    def addBooking(booking)
      # This append operation will not trigger a copy to sub-scenarios.
      # Bookings are only valid for the scenario they are defined in.
      @booking << booking
    end

    def query_activetasks(query)
      count = activeTasks(query)

      query.sortable = query.numerical = count
      # For the string output, we only use integer numbers.
      query.string = "#{count.to_i}"
    end

    def query_closedtasks(query)
      count = closedTasks(query)

      query.sortable = query.numerical = count
      # For the string output, we only use integer numbers.
      query.string = "#{count.to_i}"
    end

    def query_competitorcount(query)
      query.sortable = query.numerical = @competitors.length
      query.string = "#{@competitors.length}"
    end

    def query_complete(query)
      # If we haven't calculated the value yet, calculate it first.
      unless @complete
        calcCompletion
      end

      query.sortable = query.numerical = @complete
      # For the string output, we only use integer numbers.
      query.string = "#{@complete.to_i}%"
    end

    # Compute the cost generated by this Task for a given Account during a given
    # interval.  If a Resource is provided as scopeProperty only the cost
    # directly generated by the resource is taken into account.
    def query_cost(query)
      if query.costAccount
        query.sortable = query.numerical = cost =
          turnover(query.startIdx, query.endIdx, query.costAccount,
                   query.scopeProperty)
        query.string = query.currencyFormat.format(cost)
      else
        query.string = 'No \'balance\' defined!'
      end
    end

    # The duration of the task. After scheduling, it can be determined for
    # all tasks. Also for those who did not have a 'duration' attribute.
    def query_duration(query)
      query.sortable = query.numerical = duration =
        (@end - @start) / (60 * 60 * 24)
      query.string = query.scaleDuration(duration)
    end

    # The completed (as of 'now') effort allocated for the task in the
    # specified interval.  In case a Resource is given as scope property only
    # the effort allocated for this resource is taken into account.
    def query_effortdone(query)
      if @effortdone
        effort = @project.convertToDailyLoad(@effortdone *
                                             @project['scheduleGranularity'])
      else
        # For this query, we always override the query period.
        effort = getEffectiveWork(@project.dateToIdx(@project['start'], false),
                                  @project.dateToIdx(@project['now']),
                                  query.scopeProperty)
      end
      query.sortable = query.numerical = effort
      query.string = query.scaleLoad(effort)
    end

    # The remaining (as of 'now') effort allocated for the task in the
    # specified interval.  In case a Resource is given as scope property only
    # the effort allocated for this resource is taken into account.
    def query_effortleft(query)
      # For this query, we always override the query period.
      query.sortable = query.numerical = effort =
        getEffectiveWork(@project.dateToIdx(@project['now']),
                         @project.dateToIdx(@project['end'], false),
                         query.scopeProperty)
      query.string = query.scaleLoad(effort)
    end

    # The effort allocated for the task in the specified interval. In case a
    # Resource is given as scope property only the effort allocated for this
    # resource is taken into account.
    def query_effort(query)
      query.sortable = query.numerical = work =
        getEffectiveWork(query.startIdx, query.endIdx, query.scopeProperty)
      query.string = query.scaleLoad(work)
    end

    def query_followers(query)
      list = []

      # First gather the task that depend on the start of this task.
      @startsuccs.each do |task, onEnd|
        if onEnd
          date = task['end', query.scenarioIdx].to_s(query.timeFormat)
          dep = "[->]"
        else
          date = task['start', query.scenarioIdx].to_s(query.timeFormat)
          dep = "[->["
        end
        list << generateDepencyListItem(query, task, dep, date)
      end
      # Than add the tasks that depend on the end of this task.
      @endsuccs.each do |task, onEnd|
        if onEnd
          date = task['end', query.scenarioIdx].to_s(query.timeFormat)
          dep = "]->]"
        else
          date = task['start', query.scenarioIdx].to_s(query.timeFormat)
          dep = "]->["
        end
        list << generateDepencyListItem(query, task, dep, date)
      end

      query.assignList(list)
    end

    def query_gauge(query)
      # If we haven't calculated the schedule status yet, calculate it first.
      calcGauge unless @gauge

      query.string = @gauge
    end

    # The number of different resources assigned to the task during the query
    # interval. Each resource is counted based on their mathematically rounded
    # efficiency.
    def query_headcount(query)
      headcount = 0
      assignedResources(Interval.new(query.start, query.end)).each do |res|
        headcount += res['efficiency', @scenarioIdx].round
      end

      query.sortable = query.numerical = headcount
      query.string = query.numberFormat.format(headcount)
    end

    def query_inputs(query)
      inputList = PropertyList.new(@project.tasks, false)
      inputs(inputList, true)
      inputList.delete(@property)
      inputList.setSorting([['start', true, @scenarioIdx],
                            ['seqno', true, -1 ]])
      inputList.sort!

      query.assignList(generateTaskList(inputList, query))
    end

    def query_maxend(query)
      queryDateLimit(query, @maxend)
    end

    def query_maxstart(query)
      queryDateLimit(query, @maxstart)
    end

    def query_minend(query)
      queryDateLimit(query, @minend)
    end

    def query_minstart(query)
      queryDateLimit(query, @minstart)
    end

    def query_opentasks(query)
      count = openTasks(query)

      query.sortable = query.numerical = count
      # For the string output, we only use integer numbers.
      query.string = "#{count.to_i}"
    end

    def query_precursors(query)
      list = []

      # First gather the task that depend on the start of this task.
      @startpreds.each do |task, onEnd|
        if onEnd
          date = task['end', query.scenarioIdx].to_s(query.timeFormat)
          dep = "]->["
        else
          date = task['start', query.scenarioIdx].to_s(query.timeFormat)
          dep = "[->["
        end
        list << generateDepencyListItem(query, task, dep, date)
      end
      # Than add the tasks that depend on the end of this task.
      @endpreds.each do |task, onEnd|
        if onEnd
          date = task['end', query.scenarioIdx].to_s(query.timeFormat)
          dep = "]->]"
        else
          date = task['start', query.scenarioIdx].to_s(query.timeFormat)
          dep = "[->]"
        end
        list << generateDepencyListItem(query, task, dep, date)
      end

      query.assignList(list)
    end

    # A list of the resources that have been allocated to work on the task in
    # the report time frame.
    def query_resources(query)
      list = []
      iv = TimeInterval.new(query.start, query.end)
      assignedResources(iv).each do |resource|
        if resource.allocated?(@scenarioIdx, iv, @property)
          if query.listItem
            rti = RichText.new(query.listItem, RTFHandlers.create(@project)).
              generateIntermediateFormat
            unless rti
              error('bad_resource_ts_query',
                    "Syntax error in query statement for task attribute " +
                    "'resources'.")
            end
            q = query.dup
            q.property = resource
            q.scopeProperty = @property
            rti.setQuery(q)
            list << "<nowiki>#{rti.to_s}</nowiki>"
          else
            list << "<nowiki>#{resource.name} (#{resource.fullId})</nowiki>"
          end
        end
      end
      query.assignList(list)
    end

    # Compute the revenue generated by this Task for a given Account during a
    # given interval.  If a Resource is provided as scopeProperty only the
    # revenue directly generated by the resource is taken into account.
    def query_revenue(query)
      if query.revenueAccount
        query.sortable = query.numerical = revenue =
          turnover(query.startIdx, query.endIdx, query.revenueAccount,
                   query.scopeProperty)
        query.string = query.currencyFormat.format(revenue)
      else
        query.string = 'No \'balance\' defined!'
      end
    end

    def query_scheduling(query)
      query.string = @forward ? 'ASAP' : 'ASAP' if @property.leaf?
    end

    def query_status(query)
      # If we haven't calculated the completion yet, calculate it first.
      calcStatus if @status.empty?

      query.string = @status
    end

    def query_targets(query)
      targetList = PropertyList.new(@project.tasks, false)
      targets(targetList, true)
      targetList.delete(@property)
      targetList.setSorting([['start', true, @scenarioIdx],
                             ['seqno', true, -1 ]])
      targetList.sort!

      query.assignList(generateTaskList(targetList, query))
    end


    # Compute the total time _resource_ or all resources are allocated during
    # interval specified by _startIdx_ and _endIdx_.
    def getAllocatedTime(startIdx, endIdx, resource = nil)
      return 0.0 if @milestone || startIdx >= endIdx ||
                    (resource && !@assignedresources.include?(resource))

      @dCache.cached(self, :TaskScenarioAllocatedTime, startIdx, endIdx, resource) do
        allocatedTime = 0.0
        if @property.container?
          @property.kids.each do |task|
            allocatedTime += task.getAllocatedTime(@scenarioIdx,
                                                   startIdx, endIdx, resource)
          end
        else
          if resource
            allocatedTime += resource.getAllocatedTime(@scenarioIdx,
                                                       startIdx, endIdx,
                                                       @property)
          else
            @assignedresources.each do |r|
              allocatedTime += r.getAllocatedTime(@scenarioIdx, startIdx, endIdx,
                                                  @property)
            end
          end
        end
        allocatedTime
      end
    end

    # Compute the effective work a _resource_ or all resources do during the
    # interval specified by _startIdx_ and _endIdx_. The effective work is the
    # actual work multiplied by the efficiency of the resource.
    def getEffectiveWork(startIdx, endIdx, resource = nil)
      # Make sure we have the real Resource and not a proxy.
      resource = resource.ptn if resource
      return 0.0 if @milestone || startIdx >= endIdx ||
                    (resource && !@assignedresources.include?(resource))

      @dCache.cached(self, :TaskScenarioEffectiveWork, startIdx, endIdx,
                     resource) do
        workLoad = 0.0
        if @property.container?
          @property.kids.each do |task|
            workLoad += task.getEffectiveWork(@scenarioIdx, startIdx, endIdx,
                                              resource)
          end
        else
          if resource
            workLoad += resource.getEffectiveWork(@scenarioIdx, startIdx,
                                                  endIdx, @property)
          else
            @assignedresources.each do |r|
              workLoad += r.getEffectiveWork(@scenarioIdx, startIdx, endIdx,
                                             @property)
            end
          end
        end
        workLoad
      end
    end

    # Return a list of intervals that lay within _iv_ and are at least
    # minDuration long and contain no working time.
    def collectTimeOffIntervals(iv, minDuration)
      # This function is often called recursively for the same parameters. We
      # store the results in the cache to avoid repeated computations of the
      # same results.
      @dCache.cached(self, :TaskScenarioCollectTimeOffIntervals, iv,
                     minDuration) do
        il = IntervalList.new
        il << TimeInterval.new(@project['start'], @project['end'])
        if @property.leaf?
          unless (resources = @assignedresources).empty?
            # The task has assigned resources, so we can use their common time
            # off intervals.
            resources.each do |resource|
              il &= resource.collectTimeOffIntervals(@scenarioIdx, iv,
                                                     minDuration)
            end
          else
            # The task has no assigned resources. We simply use the global time
            # off intervals.
            il &= @project.collectTimeOffIntervals(iv, minDuration)
          end
        else
          @property.kids.each do |task|
            il &= task.collectTimeOffIntervals(@scenarioIdx, iv, minDuration)
          end
        end

        il
      end
    end

    # Check if the Task _task_ depends on this task. _depth_ specifies how
    # many dependent task are traversed at max. A value of 0 means no limit.
    # TODO: Change this to a non-recursive implementation.
    def isDependencyOf(task, depth, list = [])
      return true if task == @property

      # If this task is already in the list of traversed task, we can ignore
      # it.
      return false if list.include?(@property)
      list << @property

      @startsuccs.each do |t, onEnd|
        unless onEnd
          # must be a start->start dependency
          return true if t.isDependencyOf(@scenarioIdx, task, depth, list)
        end
      end

      # For task to depend on this task, the start of task must be after the
      # end of this task.
      if task['start', @scenarioIdx] && @end
        return false if task['start', @scenarioIdx] < @end
      end

      # Check if any of the parent tasks is a dependency of _task_.
      t = @property.parent
      while t
        # If the parent is a dependency, than all childs are as well.
        return true if t.isDependencyOf(@scenarioIdx, task, depth, list)
        t = t.parent
      end

      return false if depth == 1

      @endsuccs.each do |ta, onEnd|
        unless onEnd
          # must be an end->start dependency
          return true if ta.isDependencyOf(@scenarioIdx, task, depth - 1, list)
        end
      end

      false
    end

    # If _task_ or any of its sub-tasks depend on this task or any of its
    # sub-tasks, we call this task a feature of _task_.
    def isFeatureOf(task)
      sources = @property.all
      destinations = task.all

      sources.each do |s|
        destinations.each do |d|
          return true if s.isDependencyOf(@scenarioIdx, d, 0)
        end
      end

      false
    end

    # Returns true of the _resource_ is assigned to this task or any of its
    # children.
    def hasResourceAllocated?(interval, resource)
      return false unless @assignedresources.include?(resource)

      if @property.leaf?
        return resource.allocated?(@scenarioIdx, interval, @property)
      else
        @property.kids.each do |t|
          return true if t.hasResourceAllocated?(@scenarioIdx, interval,
                                                 resource)
        end
      end
      false
    end

    # Gather a list of Resource objects that have been assigned to the task
    # (including sub tasks) for the given Interval _interval_.
    def assignedResources(interval = nil)
      interval = Interval.new(a('start'), a('end')) unless interval
      list = []

      if @property.container?
        @property.kids.each do |task|
          list += task.assignedResources(@scenarioIdx, interval)
        end
        list.uniq!
      else
        @assignedresources.each do |resource|
          if resource.allocated?(@scenarioIdx, interval, @property)
            list << resource
          end
        end
      end

      list
    end

  private

    def scheduleSlot
      # Tasks must always be scheduled in a single contigous fashion.
      # Depending on the scheduling direction the next slot must be scheduled
      # either right before or after this slot. If the current slot is not
      # directly aligned, we'll wait for another call with a proper slot. The
      # function returns false if the task has been completely scheduled.
      case @durationType
      when :effortTask
        bookResources if @doneEffort < @effort
        if @doneEffort >= @effort
          # The specified effort has been reached. The task has been fully
          # scheduled now.
          if @forward
            propagateDate(@project.idxToDate(@currentSlotIdx + 1), true, true)
          else
            propagateDate(@project.idxToDate(@currentSlotIdx), false, true)
          end
          return false
        end
      when :lengthTask
        bookResources
        # The doneLength is only increased for global working time slots.
        @doneLength += 1 if onShift?(@currentSlotIdx)

        # If we have reached the specified duration or lengths, we set the end
        # or start date and propagate the value to neighbouring tasks.
        if @doneLength >= @length
          if @forward
            propagateDate(@project.idxToDate(@currentSlotIdx + 1), true)
          else
            propagateDate(@project.idxToDate(@currentSlotIdx), false)
          end
          return false
        end
      when :durationTask
        # The doneDuration counts the number of scheduled slots. It is increased
        # by one with every scheduled slot.
        bookResources
        @doneDuration += 1

        # If we have reached the specified duration or lengths, we set the end
        # or start date and propagate the value to neighbouring tasks.
        if @doneDuration >= @duration
          if @forward
            propagateDate(@project.idxToDate(@currentSlotIdx + 1), true)
          else
            propagateDate(@project.idxToDate(@currentSlotIdx), false)
          end
          return false
        end
      when :startEndTask
        # Task with start and end date but no duration criteria
        bookResources

        # Depending on the scheduling direction we can mark the task as
        # scheduled once we have reached the other end.
        if (@forward && @currentSlotIdx >= @endIdx) ||
           (!@forward && @currentSlotIdx <= @startIdx)
          markAsScheduled
          @property.parents.each do |parent|
            parent.scheduleContainer(@scenarioIdx)
          end
          return false
        end
      else
        raise "Unknown task duration type #{@durationType}"
      end

      true
    end

    def bookResources
      # First check if there is any resource at all for this slot.
      return if !@project.anyResourceAvailable?(@currentSlotIdx) ||
                (@projectionmode && (@nowIdx > @currentSlotIdx))


      # If the task has resource independent allocation limits we need to make
      # sure that none of them is already exceeded.
      return unless limitsOk?(@currentSlotIdx)

      # If the task has shifts to limit the allocations, we check that we are
      # within a defined shift interval. If yes, we need to be on shift to
      # continue.
      if @shifts && @shifts.assigned?(@currentSlotIdx)
         return if !@shifts.onShift?(@currentSlotIdx)
      end

      # We first have to make sure that if there are mandatory resources
      # that these are all available for the time slot.
      takenMandatories = []
      @mandatories.each do |allocation|
        return unless allocation.onShift?(@currentSlotIdx)

        # For mandatory allocations with alternatives at least one of the
        # alternatives must be available.
        found = false
        allocation.candidates(@scenarioIdx).each do |candidate|
          # When a resource group is marked mandatory, all members of the
          # group must be available.
          allAvailable = true
          candidate.allLeaves.each do |resource|
            if !limitsOk?(@currentSlotIdx, resource) ||
               !resource.available?(@scenarioIdx, @currentSlotIdx) ||
               takenMandatories.include?(resource)
              # We've found a mandatory resource that is not available for
              # the slot.
              allAvailable = false
              break
            else
              takenMandatories << resource
            end
          end
          if allAvailable
            found = true
            break
          end
        end

        # At least one mandatory resource is not available. We cannot continue.
        return unless found
      end

      @allocate.each do |allocation|
        next unless allocation.onShift?(@currentSlotIdx)

        # In case we have a persistent allocation we need to check if there
        # is already a locked resource and use it.
        locked_candidate = allocation.lockedResource
        if locked_candidate
          next if bookResource(locked_candidate)

          if allocation.atomic &&
             locked_candidate.bookedTask(@scenarioIdx, @currentSlotIdx)
            rollbackBookings
            return
          end

          if @forward
            next if @currentSlotIdx < locked_candidate.getMaxSlot(@scenarioIdx)
          else
            next if @currentSlotIdx > locked_candidate.getMinSlot(@scenarioIdx)
          end
          # Persistent candidate is gone for the rest of the project!
          # Warn and assign somebody else, if available!
          warning('broken_persistence',
                  "Persistence broken for Task #{@property.fullId} " +
                  "- resource #{locked_candidate.name} is gone")
          allocation.lockedResource = nil
        end

        # Create a list of candidates in the proper order and
        # assign the first one available.
        allocation.candidates(@scenarioIdx).each do |candidate|
          if bookResource(candidate)
            allocation.lockedResource = candidate if allocation.persistent
            break
          end
        end
      end
    end

    def bookResource(resource)
      booked = false
      resource.allLeaves.each do |r|
        # Prevent overbooking when multiple resources are allocated and
        # available. If the task has allocation limits we need to make sure
        # that none of them is already exceeded.
        break if (@effort > 0 && r['efficiency', @scenarioIdx] > 0.0 &&
                  @doneEffort >= @effort) || !limitsOk?(@currentSlotIdx, r)

        if r.book(@scenarioIdx, @currentSlotIdx, @property)
          # This method is _very_ performance sensitive. Uncomment this log
          # message only if you really need it.
          #Log.msg { "Book #{resource.name} on task #{@property.fullId}" }

          # For effort based task we adjust the the start end (as defined by
          # the scheduling direction) to align with the first booked time
          # slot.
          if @effort > 0 && @doneEffort == 0
            if @forward
              propagateDate(@project.idxToDate(@currentSlotIdx), false, true)
              Log.msg { "Task #{@property.fullId} first assignment: " +
                        "#{period_to_s}" }
            else
              propagateDate(@project.idxToDate(@currentSlotIdx + 1), true, true)
              Log.msg { "Task #{@property.fullId} last assignment: " +
                        "#{period_to_s}" }
            end
          end

          @doneEffort += r['efficiency', @scenarioIdx]

          unless @assignedresources.include?(r)
            @assignedresources << r
          end
          booked = true
        elsif (competitor = r.bookedTask(@scenarioIdx, @currentSlotIdx))
          # Keep a list of all the Tasks that have successfully competed for
          # the same resources and are potentially delaying the progress of
          # this Task.
          @competitors << competitor unless @competitors.include?(competitor)
          @contendedResources[competitor][r] += 1
        end
      end

      booked
    end

    def onShift?(sbIdx)
      if @shifts && @shifts.assigned?(sbIdx)
        return @shifts.onShift?(sbIdx)
      else
        return @project.isWorkingTime(sbIdx)
      end
    end

    # Check if all of the task limits are not exceded at the given _sbIdx_. If
    # a _resource_ is provided, the limit for that particular resource is
    # checked. If no resource is provided, only non-resource-specific limits
    # are checked.
    def limitsOk?(sbIdx, resource = nil)
      @allLimits.each do |limit|
        return false unless limit.ok?(sbIdx, true, resource)
      end
      true
    end

    # Limits do not take efficiency into account. Limits are usage limits, not
    # effort limits.
    def incLimits(sbIdx, resource = nil)
      @allLimits.each do |limit|
        limit.inc(sbIdx, resource)
      end
    end


    # Calculate the number of general working time slots between the TjTime
    # objects _d1_ and _d2_.
    def calcLength(d1, d2)
      slots = 0
      while d1 < d2
        slots += 1 if @project.isWorkingTime(d1)
        d1 += @project['scheduleGranularity']
      end
      slots
    end

    # Register the user provided bookings with the Resource scoreboards. A
    # booking describes the assignment of a Resource to a certain Task for a
    # specified TimeInterval.
    def bookBookings
      firstSlotIdx = nil
      lastSlotIdx = nil
      if @effortdone || @effortleft
        # Force task to be scheduled in ASAP mode.
        @forward = true
        unless @start
          error('effort_done_left_start_missing',
                "Task #{@property.fullId} has 'effortdone' or 'effortleft' " +
                "attribute but no start date specified.")
        end
        unless @effort > 0
          error('effort_missing',
                "Task #{@property.fullId} has 'effortdone' or " +
                "'effortleft' attribute but no 'effort'.")
        end
        if @effortdone
          if @effortdone > @effort
            error('effort_done_larger_effort',
                  "Task #{@property.fullId} has larger 'effortdone' " +
                  "than 'effort'.")
          end
          @doneEffort = @effortdone
          if @effortleft
            error('effort_done_and_left',
                  "A task cannot have the 'effortdone' and 'effortleft' " +
                  "attribute.")
          end
        else
          if @effortleft > @effort
            error('effort_left_larger_effort',
                  "Task #{@property.fullId} has larger 'effortleft' " +
                  "than 'effort'.")
          end
          @doneEffort = @effort - @effortleft
        end
        firstSlotIdx = @project.dateToIdx(@start)
        lastSlotIdx = @project.dateToIdx(@project['now'])
      end
      unless (bookings = findBookings).empty?
        if @effortdone || @effortleft
          error('bookings_and_effort',
                "Bookings cannot be used together with 'effortdone' or " +
                "'effortleft' attributes.")
        end
        bookings.each do |booking|
          unless booking.resource.leaf?
            error('booking_resource_not_leaf',
                  "Booked resources may not be group resources",
                  booking.sourceFileInfo)
          end
          unless @forward || @scheduled
            error('booking_forward_only',
                  "Only forward scheduled tasks may have booking statements.")
          end
          booked = false
          booking.intervals.each do |interval|
            startIdx = @project.dateToIdx(interval.start, false)
            endIdx = @project.dateToIdx(interval.end, false)
            startIdx.upto(endIdx - 1) do |idx|
              if booking.resource.bookBooking(@scenarioIdx, idx, booking)
                # Booking was successful for this time slot.
                @doneEffort += booking.resource['efficiency', @scenarioIdx]
                booked = true

                # Store the indexes of the first slot and the slot after the
                # last slot.
                firstSlotIdx = idx if !firstSlotIdx || firstSlotIdx > idx
                lastSlotIdx = idx if !lastSlotIdx || lastSlotIdx < idx
              end
            end
          end
          if booked && !@assignedresources.include?(booking.resource)
            @assignedresources << booking.resource
          end
        end
      end

      # For effort based tasks, or tasks without a start date, with bookings
      # that have not yet been marked as scheduled we set the start date to
      # the date of the first booked slot.
      if (@start.nil? || (@doneEffort > 0 && @effort > 0)) &&
         !@scheduled && firstSlotIdx
        firstSlotDate = @project.idxToDate(firstSlotIdx)
        if @start.nil? || firstSlotDate > @start
          @start = firstSlotDate
          Log.msg { "Task #{@property.fullId} first booking: #{period_to_s}" }
        end
      end

      # Check if the the duration criteria has already been reached by the
      # supplied bookings and set the task end to the last booked slot.
      # Also the task is marked as scheduled.
      if lastSlotIdx && !@scheduled
        tentativeEnd = @project.idxToDate(lastSlotIdx + 1)
        slotDuration = @project['scheduleGranularity']

        if @effort > 0
          if @doneEffort >= @effort
            @end = tentativeEnd
            markAsScheduled
          end
        elsif @length > 0
          @doneLength = 0
          startIdx = @project.dateToIdx(date = @start)
          endIdx = @project.dateToIdx(@project['now'])
          startIdx.upto(endIdx) do |idx|
            @doneLength += 1 if onShift?(idx)
            date += slotDuration
            # Continue not only until the @length has been reached, but also
            # the tentativeEnd date. This allows us to detect overbookings.
            if @doneLength >= @length && date >= tentativeEnd
              endDate = @project.idxToDate(idx + 1)
              @end = [ endDate, tentativeEnd ].max
              markAsScheduled
              break
            end
          end
        elsif @duration > 0
          @doneDuration = ((tentativeEnd - @start) / slotDuration).to_i
          if @doneDuration >= @duration
            @end = tentativeEnd
            markAsScheduled
          elsif @duration * slotDuration < (@project['now'] - @start)
            # This handles the case where the bookings don't provide enough
            # @doneDuration to reach @duration, but the now date would be
            # after the @start + @duration date.
            @end = @start + @duration * slotDuration
            markAsScheduled
          end
        end
      end

      # If the task has bookings, we assume that the bookings describe all
      # work up to the 'now' date.
      if @doneEffort > 0
        @currentSlotIdx = @project.dateToIdx(@project['now'])
      end

      # Finally, we check if the bookings caused more effort, length or
      # duration than was requested by the user. This is only flagged as a
      # warning.
      if @effort > 0
        effort = @project.slotsToDays(@doneEffort)
        effortHours = effort * @project['dailyworkinghours']
        requestedEffort = @project.slotsToDays(@effort)
        requestedEffortHours = requestedEffort * @project['dailyworkinghours']
        if effort > requestedEffort
          warning('overbooked_effort',
                  "The total effort (#{effort}d or #{effortHours}h) of the " +
                  "provided bookings for task #{@property.fullId} exceeds " +
                  "the specified effort of #{requestedEffort}d or " +
                  "#{requestedEffortHours}h.")
        end
      end
      if @length > 0 && @doneLength > @length
        length = @project.slotsToDays(@doneLength)
        requestedLength = @project.slotsToDays(@length)
        warning('overbooked_length',
                "The total length (#{length}d) of the provided bookings " +
                "for task #{@property.fullId} exceeds the specified length " +
                "of #{requestedLength}d.")
      end
      if @duration > 0 && @doneDuration > @duration
        duration = @doneDuration * @project['scheduleGranularity'] /
                   (60.0 * 60 * 24)
        requestedDuration = @duration * @project['scheduleGranularity'] /
                            (60.0 * 60 * 24)
        warning('overbooked_duration',
                "The total duration (#{duration}d) of the provided bookings " +
                "for task #{@property.fullId} exceeds the specified duration " +
                "of #{requestedDuration}d.")
      end

      # If a task has only bookings but no effort, length or duration and is
      # not a milestone but marked as being scheduled, we set the start and
      # end date according to the first/last booking date unless the date has
      # been set already.
      if @scheduled && @effort == 0 && @length == 0 && @duration == 0 &&
         !@milestone
        unless @start || !firstSlotIdx
          @start = @project.idxToDate(firstSlotIdx)
        end
        unless @end || !lastSlotIdx
          @end = @project.idxToDate(lastSlotIdx + 1)
        end
      end
    end

    def rollbackBookings
      @doneEffort = 0.0

      @allocate.each do |allocation|
        allocation.lockedResource = nil
        allocation.candidates(@scenarioIdx).each do |resource|
          resource.allLeaves.each do |r|
            r.rollbackBookings(@scenarioIdx, @property)
          end
        end
      end
    end

    # This function checks if the task has a dependency on another task or
    # fixed date for a certain end. If +atEnd+ is true, the task end will be
    # checked.  Otherwise the start.
    def hasDependencies(atEnd)
      thisEnd = atEnd ? 'end' : 'start'
      !a(thisEnd + 'succs').empty? || !a(thisEnd + 'preds').empty?
    end

    # Return true if this task or any of its parent tasks has at least one
    # predecessor task.
    def hasPredecessors
      t = @property
      while t
        return true unless t['startpreds', @scenarioIdx].empty?
        t = t.parent
      end

      false
    end

    # Return true if this task or any of its parent tasks has at least one
    # sucessor task.
    def hasSuccessors
      t = @property
      while t
        return true unless t['endsuccs', @scenarioIdx].empty?
        t = t.parent
      end

      false
    end

    # Return true if the task has a 'strong' dependency at the start if
    # _atEnd_ is false or at the end. A 'strong' dependency is an outer
    # dependency. At the start a predecessor is strong, and the end a
    # successor. start successors or end predecessors are considered weak
    # dependencies since this task will always have to get the date first and
    # then pass it on to the inner dependencies.
    def hasStrongDeps?(atEnd)
      if atEnd
        return !@endsuccs.empty?
      else
        return !@startpreds.empty?
      end
    end

    def markAsRunaway
      @isRunAway = true
      remainingEffort =
        @project.convertToDailyLoad(@project['scheduleGranularity'] *
            (@effort - @doneEffort))
      warning('runaway', "#{remainingEffort}d of effort of task " +
                         "#{@property.fullId} " +
                         "does not fit into the project time frame. ")
      unless @competitors.empty?
        multi = @competitors.length > 1
        info('runaway_tasks',
             "The following task#{multi ? 's' : ''} " +
             "compete#{multi ? '' : 's'} for the same resources that " +
             "this task is requesting: ")
        @competitors.each do |t|
          res = @contendedResources[t].to_a
          res.sort! { |i, j| j[1] <=> i[1] }
          resList = res.map { |r| "#{r[0].id}(#{r[1]})" }.join(', ')
          info('runaway_competitor',
               "Task #{t.fullId} has conflicts for the following " +
               "resource#{res.length > 1 ? 's' : ''}: #{resList}",
               t.sourceFileInfo)
        end
      end
    end

    # This function determines if a task is a milestones and marks it
    # accordingly.
    def markAsMilestone
      # Containers may not be milestones
      if @milestone && @property.container?
        error('container_milestone',
              "Container task #{@property.fullId} may not be marked " +
              "as a milestone.")
      end

      return if @property.container? || @hasDurationSpec ||
        !@booking.empty? || !@allocate.empty?

      # The following cases qualify for an automatic milestone promotion.
      #   -  --> -
      #   |  --> -
      #   |D --> -
      #   -D --> -
      #   -  <-- -
      #   -  <-- |
      #   -  <-- -D
      #   -  <-- |D
      hasStartSpec = !@start.nil? || !@depends.empty?
      hasEndSpec = !@end.nil? || !@precedes.empty?

      @milestone = (hasStartSpec && @forward && !hasEndSpec) ||
                   (!hasStartSpec && !@forward && hasEndSpec) ||
                   (!hasStartSpec && !hasEndSpec)

      # Milestones may only have start or end date even when the 'scheduled'
      # attribute is set. For further processing, we need to add the missing
      # date.
      if @milestone
        @hasDurationSpec = true
        @end = @start if @start && !@end
        @start = @end if !@start && @end
        Log.msg { "Mark as milestone #{@property.fullId}" }
      end
    end

    def checkDependency(dependency, depType)
      depList = instance_variable_get(('@' + depType).intern)
      if (depTask = dependency.resolve(@project)).nil?
        # Remove the broken dependency. It could cause trouble later on.
        depList.delete(dependency)
        error('task_depend_unknown',
              "Task #{@property.fullId} has unknown #{depType} " +
              "#{dependency.taskId}")
      end

      if depTask == @property
        # Remove the broken dependency. It could cause trouble later on.
        depList.delete(dependency)
        error('task_depend_self', "Task #{@property.fullId} cannot " +
              "depend on self")
      end

      if depTask.isChildOf?(@property)
        # Remove the broken dependency. It could cause trouble later on.
        depList.delete(dependency)
        error('task_depend_child',
              "Task #{@property.fullId} cannot depend on child " +
              "#{depTask.fullId}")
      end

      if @property.isChildOf?(depTask)
        # Remove the broken dependency. It could cause trouble later on.
        depList.delete(dependency)
        error('task_depend_parent',
              "Task #{@property.fullId} cannot depend on parent " +
              "#{depTask.fullId}")
      end

      depList.each do |dep|
        if dep.task == depTask && !dep.equal?(dependency)
          # Remove the broken dependency. It could cause trouble later on.
          depList.delete(dependency)
          error('task_depend_multi',
                "No need to specify dependency #{depTask.fullId} multiple " +
                "times for task #{@property.fullId}.")
        end
      end

      depTask
    end

    # Set @startIsDetermed or @endIsDetermed (depending on _setStart) to
    # _value_.
    def setDetermination(setStart, value)
      setStart ? @startIsDetermed = value : @endIsDetermed = value
    end

    # This function is called to propagate the start or end date of the
    # current task to a dependend Task +task+. If +atEnd+ is true, the date
    # should be propagated to the end of the +task+, otherwise to the start.
    def propagateDateToDep(task, atEnd)
      #puts "Propagate #{atEnd ? 'end' : 'start'} to dep. #{task.fullId}"
      # Don't propagate if the task is already completely scheduled or is a
      # container.
      return if task['scheduled', @scenarioIdx] || task.container?

      # Don't propagate if the task already has a date for that end.
      return unless task[atEnd ? 'end' : 'start', @scenarioIdx].nil?

      # Don't propagate if the task has a duration or is a milestone and the
      # task end to set is in the scheduling direction.
      return if task.hasDurationSpec(@scenarioIdx) &&
                !(atEnd ^ task['forward', @scenarioIdx])

      # Check if all other dependencies for that task end have been determined
      # already and use the latest or earliest possible date. Don't propagate
      # if we don't have all dates yet.
      return if (nDate = (atEnd ? task.latestEnd(@scenarioIdx) :
                                  task.earliestStart(@scenarioIdx))).nil?

      # Looks like it is ok to propagate the date.
      task.propagateDate(@scenarioIdx, nDate, atEnd)
      #puts "Propagate #{atEnd ? 'end' : 'start'} to dep. #{task.fullId} done"
    end

    # This is a helper function for calcPathCriticalness(). It computes the
    # larges criticalness of the pathes through the end-successors of this task
    # and all its parent tasks.
    def calcPathCriticalnessEndSuccs
      maxCriticalness = 0.0
      # Gather a list of all end-successors of this task and its parent task.
      tList = []
      depStruct = Struct.new(:task, :onEnd)
      p = @property
      while (p)
        p['endsuccs', @scenarioIdx].each do |task, onEnd|
          dep = depStruct.new(task, onEnd)
          tList << dep unless tList.include?(dep)
        end
        p = p.parent
      end

      tList.each do |dep|
        criticalness = dep.task.calcPathCriticalness(@scenarioIdx, dep.onEnd)
        maxCriticalness = criticalness if criticalness > maxCriticalness
      end

      maxCriticalness
    end

    # Calculate the current completion degree for tasks that have no user
    # specified completion value.
    def calcCompletion
      # If we already have a value for @complete, we don't need to calculate
      # anything.
      return @complete if @complete

      # We cannot compute a completion degree without a start or end date.
      if @start.nil? || @end.nil?
        @complete = 0.0
        return nil
      end

      @complete = calcTaskCompletion
    end

    def calcTaskCompletion
      completion = 0.0

      if @property.container?
        # For container task the completion degree is the average of the
        # sub tasks.
        @property.kids.each do |child|
          return nil unless (comp = child.calcCompletion(@scenarioIdx))
          completion += comp
        end
        completion /= @property.kids.length
      else
        # For leaf tasks we first compare the start and end dates against the
        # current date.
        if @end <= @project['now']
          # The task has ended already. It's 100% complete.
          completion = 100.0
        elsif @project['now'] <= @start
          # The task has not started yet. Its' 0% complete.
          completion = 0.0
        elsif @effort > 0
          # Effort based leaf tasks. The completion degree is the percentage
          # of effort that has been done already.
          done = getEffectiveWork(@project.dateToIdx(@start, false),
                                  @project.dateToIdx(@project['now']))
          total = @project.convertToDailyLoad(
            @effort * @project['scheduleGranularity'])
          completion = done / total * 100.0
        else
          # Length/duration leaf tasks.
          completion = ((@project['now'] - @start) / (@end - @start)) * 100.0
        end
      end

      completion
    end

    # Calculate the status of the task based on the 'complete' attribute.
    def calcStatus
      # If the completion degree is not yet available, we need to calculate it
      # first.
      calcCompletion unless @complete

      if @complete
        @status = if @complete == 0.0
                    # Milestones are reached, normal tasks started.
                    @milestone ? 'not reached' : 'not started'
                  elsif @complete >= 100.0
                    'done'
                  else
                    'in progress'
                  end
      else
        # The completion degree could not be calculated due to errors. We set
        # the state to unknown.
        @status = 'unknown'
      end
    end

    # The gauge shows if a task is ahead, behind or on schedule. The measure
    # is based on the provided 'complete' value and the current date.
    def calcGauge
      # If the completion degree is not yet available, we need to calculate it
      # first.
      calcCompletion unless @complete

      return @gauge if @gauge

      if @property.container?
        states = [ 'on schedule', 'ahead of schedule', 'behind schedule',
                   'unknown' ]

        gauge = 0
        @property.kids.each do |child|
          if (idx = states.index(child.calcGauge(@scenarioIdx))) > gauge
            gauge = idx
          end
        end
        @gauge = states[gauge]
      else
        @gauge =
          if (calculatedComplete = calcTaskCompletion).nil?
            # The completion degree could not be calculated due to errors. We
            # set the state to unknown.
            'unknown'
          elsif @complete == calculatedComplete
            'on schedule'
          elsif @complete < calculatedComplete
            'behind schedule'
          else
            'ahead of schedule'
          end
      end
    end

    def activeTasks(query)
      return 0 unless TimeInterval.new(@start, @end).
        overlaps?(TimeInterval.new(query.start, query.end))

      if @property.leaf?
        now = @project['now']
        return @start <= now && now < @end ? 1 : 0
      else
        cnt = 0
        @property.kids.each do |task|
          cnt += task.closedTasks(@scenarioIdx, query)
        end
        return cnt
      end
    end

    def closedTasks(query)
      return 0 unless TimeInterval.new(@start, @end).
        overlaps?(TimeInterval.new(query.start, query.end))

      if @property.leaf?
        return @end <= @project['now'] ? 1 : 0
      else
        cnt = 0
        @property.kids.each do |task|
          cnt += task.closedTasks(@scenarioIdx, query)
        end
        return cnt
      end
    end

    def openTasks(query)
      return 0 unless TimeInterval.new(@start, @end).
        overlaps?(TimeInterval.new(query.start, query.end))

      if @property.leaf?
        return @end > @project['now'] ? 1 : 0
      else
        cnt = 0
        @property.kids.each do |task|
          cnt += task.openTasks(@scenarioIdx, query)
        end
        return cnt
      end
    end

    # Recursively compile a list of Task properties which depend on the
    # current task.
    def inputs(foundInputs, includeChildren, checkedTasks = {})
      # Ignore tasks that we have already included in the checked tasks list.
      taskSignature = [ @property, includeChildren ]
      return if checkedTasks.include?(taskSignature)
      checkedTasks[taskSignature] = true

      # An "input" must be a leaf task that has no direct or indirect (through
      # parent) following tasks. Only milestones are recognized as inputs.
      if @property.leaf? && !hasPredecessors && @milestone
        foundInputs << @property
        return
      end

      # We also include inputs of child tasks if requested. The recursive
      # iteration of child tasks is limited to the tested task only. The
      # predecessors children are not iterated. (see further below)
      if includeChildren
        @property.kids.each do |child|
          child.inputs(@scenarioIdx, foundInputs, true, checkedTasks)
        end
      end

      # Now check the direct predecessors.
      @startpreds.each do |t, onEnd|
        t.inputs(@scenarioIdx, foundInputs, false, checkedTasks)
      end

      # Check for indirect predecessors inherited from the ancestors.
      if @property.parent
        @property.parent.inputs(@scenarioIdx, foundInputs, false, checkedTasks)
      end
    end

    # Recursively compile a list of Task properties which depend on the
    # current task.
    def targets(foundTargets, includeChildren, checkedTasks = {})
      # Ignore tasks that we have already included in the checked tasks list.
      taskSignature = [ @property, includeChildren ]
      return if checkedTasks.include?(taskSignature)
      checkedTasks[taskSignature] = true

      # A target must be a leaf function that has no direct or indirect
      # (through parent) following tasks. Only milestones are recognized as
      # targets.
      if @property.leaf? && !hasSuccessors && @milestone
        foundTargets << @property
        return
      end

      @endsuccs.each do |t, onEnd|
        t.targets(@scenarioIdx, foundTargets, false, checkedTasks)
      end

      # Check for indirect followers.
      if @property.parent
        @property.parent.targets(@scenarioIdx, foundTargets, false, checkedTasks)
      end

      # Also include targets of child tasks. The recursive iteration of child
      # tasks is limited to the tested task only. The followers are not
      # iterated.
      if includeChildren
        @property.kids.each do |child|
          child.targets(@scenarioIdx, foundTargets, true, checkedTasks)
        end
      end
    end

    # Compute the turnover generated by this Task for a given Account _account_
    # during the interval specified by _startIdx_ and _endIdx_. These can either
    # be TjTime values or Scoreboard indexes. If a Resource _resource_ is given,
    # only the turnover directly generated by the resource is taken into
    # account.
    def turnover(startIdx, endIdx, account, resource = nil, includeKids = true)
      amount = 0.0
      if @property.container? && includeKids
        @property.kids.each do |child|
          amount += child.turnover(@scenarioIdx, startIdx, endIdx, account,
                                   resource)
        end
      end

      # If we are evaluating the task in the context of a specific resource,
      # we use the chargeset of that resource, not the chargeset of the task.
      chargeset = resource ? resource['chargeset', @scenarioIdx] : @chargeset

      # If there are no chargeset defined for this task, we don't need to
      # compute the resource related or other cost.
      unless chargeset.empty?
        resourceCost = 0.0
        otherCost = 0.0

        # Container tasks don't have resource cost.
        unless @property.container?
          if resource
            resourceCost = resource.cost(@scenarioIdx, startIdx, endIdx,
                                         @property)
          else
            @assignedresources.each do |r|
              resourceCost += r.cost(@scenarioIdx, startIdx, endIdx, @property)
            end
          end
        end

        unless @charge.empty?
          # Add one-time and periodic charges to the amount.
          startDate = startIdx.is_a?(TjTime) ? startIdx :
            @project.idxToDate(startIdx)
          endDate = endIdx.is_a?(TjTime) ? endIdx :
            @project.idxToDate(endIdx)
          iv = TimeInterval.new(startDate, endDate)
          @charge.each do |charge|
            otherCost += charge.turnover(iv)
          end
        end

        totalCost = resourceCost + otherCost
        # Now weight the total cost by the share of the account
        chargeset.each do |set|
          set.each do |accnt, share|
            if share > 0.0 && (accnt == account || accnt.isChildOf?(account))
              amount += totalCost * share
            end
          end
        end
      end

      amount
    end

    def generateDepencyListItem(query, task, dep, date)
      if query.listItem
        rti = RichText.new(query.listItem, RTFHandlers.create(@project)).
          generateIntermediateFormat
        q = query.dup
        q.property = task
        q.setCustomData('dependency', { :string => dep })
        q.setCustomData('date', { :string => date })
        rti.setQuery(q)
        "<nowiki>#{rti.to_s}</nowiki>"
      else
        "<nowiki>#{task.name} (#{task.fullId}) #{dep} #{date}</nowiki>"
      end
    end

    def generateTaskList(taskList, query)
      list = []
      taskList.each do |task|
        date = task['start', @scenarioIdx].
               to_s(@property.project['timeFormat'])
        if query.listItem
          rti = RichText.new(query.listItem, RTFHandlers.create(@project)).
            generateIntermediateFormat
          q = query.dup
          q.property = task
          q.setCustomData('date', { :string => date })
          rti.setQuery(q)
          list << "<nowiki>#{rti.to_s}</nowiki>"
        else
          list << "<nowiki>#{task.name} (#{task.fullId}) #{date}</nowiki>"
        end
      end
      list
    end

    def findBookings
      # Map the index back to the Scenario object.
      scenario = @property.project.scenario(@scenarioIdx)
      # Check if the current scenario should inherit its bookings from the
      # parent. If so, redirect 'scenario' to the parent. The top-level
      # scenario can never inherit bookings.
      while !scenario.get('ownbookings') do
        scenario = scenario.parent
      end
      # Return the bookings of the found scenario.
      @property['booking', @property.project.scenarioIdx(scenario)]
    end

    # Date limits may be nil and this is not an error. TjTime.to_s() would
    # report it as such if we don't use this wrapper method.
    def queryDateLimit(query, date)
      if date
        query.sortable = query.numerical = date
        query.string = date.to_s(query.timeFormat)
      else
        query.sortable = query.numerical = -1
        query.string = ''
      end
    end

    def period_to_s
      "#{@start ? @start.to_s : '<?>'} -> #{@end ? @end.to_s : '<?>'}"
    end

  end

end