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module CollectiveIdea #:nodoc:
module Acts #:nodoc:
module NestedSet #:nodoc:
class Move
attr_reader :target, :position, :instance
def initialize(target, position, instance)
@target = target
@position = position
@instance = instance
end
def move
prevent_impossible_move
bound, other_bound = get_boundaries
# there would be no change
return if bound == right || bound == left
# we have defined the boundaries of two non-overlapping intervals,
# so sorting puts both the intervals and their boundaries in order
a, b, c, d = [left, right, bound, other_bound].sort
lock_nodes_between! a, d
nested_set_scope_without_default_scope.where(where_statement(a, d)).update_all(
conditions(a, b, c, d)
)
end
private
delegate :left, :right, :left_column_name, :right_column_name,
:quoted_left_column_name, :quoted_right_column_name,
:quoted_parent_column_name, :parent_column_name, :nested_set_scope_without_default_scope,
:primary_column_name, :quoted_primary_column_name, :primary_id,
:to => :instance
delegate :arel_table, :class, :to => :instance, :prefix => true
delegate :base_class, :to => :instance_class, :prefix => :instance
def where_statement(left_bound, right_bound)
instance_arel_table[left_column_name].between(left_bound..right_bound).
or(instance_arel_table[right_column_name].between(left_bound..right_bound))
end
# Before Arel 6, there was 'in' method, which was replaced
# with 'between' in Arel 6 and now gives deprecation warnings
# in verbose mode. This is patch to support rails 4.0 (Arel 4)
# and 4.1 (Arel 5).
module LegacyWhereStatementExt
def where_statement(left_bound, right_bound)
instance_arel_table[left_column_name].in(left_bound..right_bound).
or(instance_arel_table[right_column_name].in(left_bound..right_bound))
end
end
prepend LegacyWhereStatementExt unless Arel::Predications.method_defined?(:between)
def conditions(a, b, c, d)
_conditions = case_condition_for_direction(:quoted_left_column_name) +
case_condition_for_direction(:quoted_right_column_name) +
case_condition_for_parent
# We want the record to be 'touched' if it timestamps.
if @instance.respond_to?(:updated_at)
_conditions << ", updated_at = :timestamp"
end
[
_conditions,
{
:a => a, :b => b, :c => c, :d => d,
:primary_id => instance.primary_id,
:new_parent_id => new_parent_id,
:timestamp => Time.now.utc
}
]
end
def case_condition_for_direction(column_name)
column = send(column_name)
"#{column} = CASE " +
"WHEN #{column} BETWEEN :a AND :b " +
"THEN #{column} + :d - :b " +
"WHEN #{column} BETWEEN :c AND :d " +
"THEN #{column} + :a - :c " +
"ELSE #{column} END, "
end
def case_condition_for_parent
"#{quoted_parent_column_name} = CASE " +
"WHEN #{quoted_primary_column_name} = :primary_id THEN :new_parent_id " +
"ELSE #{quoted_parent_column_name} END"
end
def lock_nodes_between!(left_bound, right_bound)
# select the rows in the model between a and d, and apply a lock
instance_base_class.default_scoped.nested_set_scope.
right_of(left_bound).left_of_right_side(right_bound).
select(primary_column_name).
lock(true)
end
def root
position == :root
end
def new_parent_id
case position
when :child then target.primary_id
when :root then nil
else target[parent_column_name]
end
end
def get_boundaries
if (bound = target_bound) > right
bound -= 1
other_bound = right + 1
else
other_bound = left - 1
end
[bound, other_bound]
end
class ImpossibleMove < ActiveRecord::StatementInvalid
end
def prevent_impossible_move
if !root && !instance.move_possible?(target)
error_msg = "Impossible move, target node (#{target.class.name},ID: #{target.id})
cannot be inside moved tree (#{instance.class.name},ID: #{instance.id})."
raise ImpossibleMove, error_msg
end
end
def target_bound
case position
when :child then right(target)
when :left then left(target)
when :right then right(target) + 1
when :root then nested_set_scope_without_default_scope.pluck(right_column_name).max + 1
else raise ActiveRecord::ActiveRecordError, "Position should be :child, :left, :right or :root ('#{position}' received)."
end
end
end
end
end
end
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