--[[
-- Basic tasks for a pilot, no need to reinvent the wheel with these.
--
-- Idea is to have it all here and only really work on the "control"
-- functions and such for each AI.
--]]


--[[
-- Faces the target.
--]]
function __face ()
   local target = ai.target()
   ai.face( target )
end
function __face_towards ()
   local target = ai.target()
   local off = ai.face( target )
   if math.abs(off) < 5 then
      ai.poptask()
   end
end


--[[
-- Brakes the ship
--]]
function brake ()
   ai.brake()
   if ai.isstopped() then
      ai.stop()
      ai.poptask()
      return
   end
end


--[[
-- Brakes the ship
--]]
function __subbrake ()
   ai.brake()
   if ai.isstopped() then
      ai.stop()
      ai.popsubtask()
      return
   end
end


--[[
-- Move in zigzag around a direction
--]]
function __zigzag ( dir, angle )
   if mem.pm == nil then
      mem.pm = 1
   end

   if (mem.pm*dir < angle-20) or (mem.pm*dir > angle+25) then
      -- Orientation is totally wrong: reset timer
      ai.settimer(0, 2000)
   end

   if (mem.pm*dir < angle) then
      ai.turn(-mem.pm)
   else
      ai.turn(mem.pm)
      if (mem.pm*dir < angle+5) then -- Right orientation, wait for max vel
         --if ai.ismaxvel() then -- TODO : doesn't work well
         if ai.timeup(0) then
            mem.pm = -mem.pm
         end
      end
   end
   ai.accel()
end


--[[
-- Goes to a target position without braking
--]]
function __goto_nobrake ()
   local target   = ai.target()
   local dir      = ai.face( target, nil, true )
   __goto_generic( target, dir, false )
end


--[[
-- Goes to a target position without braking
--]]
function __goto_nobrake_raw ()
   local target   = ai.target()
   local dir      = ai.face( target )
   __goto_generic( target, dir, false )
end


--[[
-- Goes to a precise position.
--]]
function __goto_precise ()
   local target   = ai.target()
   local dir      = ai.face( target, nil, true )
   local dist     = ai.dist( target )

   -- Handle finished
   if ai.isstopped() and dist < 10 then
      ai.poptask() -- Finished
      return
   end

   local bdist    = ai.minbrakedist()

   -- Need to get closer
   if dir < 10 and dist > bdist then
      ai.accel()

   -- Need to start braking
   elseif dist < bdist then
      ai.pushsubtask("__subbrake")
   end
end




--[[
-- Goes to a target position roughly
--]]
function goto ()
   local target   = ai.target()
   local dir      = ai.face( target, nil, true )
   __goto_generic( target, dir, true )
end


--[[
-- Goto without velocity compensation.
--]]
function goto_raw ()
   local target   = ai.target()
   local dir      = ai.face( target )
   __goto_generic( target, dir, true )
end


--[[
-- Generic GOTO function.
--]]
function __goto_generic( target, dir, brake, subtask )
   local dist     = ai.dist( target )
   local bdist
   if brake then
      bdist    = ai.minbrakedist()
   else
      bdist    = 50
   end

   -- Need to get closer
   if dir < 10 and dist > bdist then
      ai.accel()

   -- Need to start braking
   elseif dist < bdist then
      ai.poptask()
      if brake then
         ai.pushtask("brake")
      end
      return
   end
end


--[[
-- Follows it's target.
--]]
function follow ()
   local target = ai.target()
 
   -- Will just float without a target to escort.
   if not target:exists() then
      ai.poptask()
      return
   end

   local dir   = ai.face(target)
   local dist  = ai.dist(target)
 
   -- Must approach
   if dir < 10 and dist > 300 then
      ai.accel()
 
   end
end
function follow_accurate ()
   local target = ai.target()
   local p = ai.pilot()
 
   -- Will just float without a target to escort.
   if not target:exists() then
      ai.poptask()
      return
   end

   local goal = ai.follow_accurate(target, mem.radius, 
         mem.angle, mem.Kp, mem.Kd)

   local mod = vec2.mod(goal - p:pos())

   --  Always face the goal
   local dir   = ai.face(goal)

   if dir < 10 and mod > 300 then
      ai.accel()
   end

end

-- Default action for non-leader pilot in fleet
function follow_fleet ()
   local leader = ai.pilot():leader()
 
   if leader == nil or not leader:exists() then
      ai.poptask()
      return
   end

   if mem.app == nil then
      mem.app = true
   end

   local goal = leader
   if mem.form_pos ~= nil then
      local angle, radius, method = unpack(mem.form_pos)
      goal = ai.follow_accurate(leader, radius, angle, mem.Kp, mem.Kd, method)
   end

   local dir   = ai.face(goal)
   local dist  = ai.dist(goal)

   if mem.app == true then 
      if dist > 10 then
         if dir < 10 then  -- Must approach
            ai.accel()
         end
      else  -- No need to approach anymore
         mem.app = false
      end
   else
      if dist > 300 then   -- Must approach
         mem.app = true
      else   -- Face forward
         goal = ai.pilot():pos() + leader:vel()
         ai.face(goal)
      end
   end
end

--[[
-- Tries to runaway and jump asap.
--]]
function __runaway ()
   runaway()
end

--[[
-- Runaway without jumping
--]]
function __runaway_nojump ()
   runaway_nojump()
end


--[[
-- Tries to hyperspace asap.
--]]
function __hyperspace ()
   hyperspace()
end
function __hyperspace_shoot ()
   local target = ai.target()
   if target == nil then
      target = ai.rndhyptarget()
      if target == nil then
         return
      end
   end
   local pos = ai.sethyptarget(target)
   ai.pushsubtask( "__hyp_approach_shoot", pos )
end
function __hyp_approach_shoot ()
   -- Shoot and approach
   __move_shoot()
   __hyp_approach()
end


function __land ()
   land()
end

function __land_shoot ()
   __choose_land_target ()
   ai.pushsubtask( "__landgo_shoot" )
end

function __landgo_shoot ()
   __move_shoot()
   __landgo()
end

function __move_shoot ()
   -- Shoot while going somewhere
   -- The difference with run_turret is that we pick a new enemy in this one
   if ai.hasturrets() then
      enemy = ai.getenemy()
      if enemy ~= nil then
         ai.weapset( 3 )
         ai.settarget( enemy )
         ai.shoot( true )
      end
   end
end


--[[
-- Attempts to land on a planet.
--]]
function __choose_land_target ()
   -- Only want to land once, prevents guys from never leaving.
   if mem.landed then
      ai.poptask()
      return
   end

   -- Set target if necessary
   local target = ai.target()
   if target ~= nil then
      mem.land = target
   end

   -- Make sure mem.land is valid target
   if mem.land == nil then
      local landplanet = ai.landplanet()
      if landplanet ~= nil then
         mem.land = landplanet

      -- Bail out if no valid planet could be found.
      else
         warn(string.format(_("Pilot '%s' tried to land with no landable assets!"),
               ai.pilot():name()))
         ai.poptask()
         return
      end
   end
end

function land ()
   __choose_land_target ()
   ai.pushsubtask( "__landgo" )
end
function __landgo ()
   local target   = mem.land
   
   local dist     = ai.dist( target )
   local bdist    = ai.minbrakedist()

   -- 2 methods depending on mem.careful
   local dir
   if not mem.careful or dist < 3*bdist then
      dir = ai.face( target )
   else
      dir = ai.careful_face( target )
   end

   -- Need to get closer
   if dir < 10 and dist > bdist then
      ai.accel()

   -- Need to start braking
   elseif dist < bdist then
      ai.pushsubtask( "__landstop" )
   end

end
function __landstop ()
   ai.brake()
   if ai.isstopped() then
      ai.stop() -- Will stop the pilot if below err vel
      if not ai.land() then
         ai.popsubtask()
      else
         ai.pilot():msg(ai.pilot():followers(), "land")
         ai.poptask() -- Done, pop task
      end
   end
end


--[[
-- Attempts to run away from the target.
--]]
function runaway ()

   -- Target must exist
   local target = ai.target()
   if not target:exists() then
      ai.poptask()
      return
   end

   -- See if there's a target to use when running
   local t = ai.nearhyptarget()
   local p = ai.nearestplanet()

   if p == nil and t == nil then
      ai.pushsubtask( "__run_target" )
   elseif p == nil then
      local pos = ai.sethyptarget(t)
      ai.pushsubtask( "__run_hyp", pos )
   elseif t == nil then
      mem.land = p:pos()
      ai.pushsubtask( "__landgo" )
   else 
      -- find which one is the closest
      local pilpos = ai.pilot():pos()
      local modt = vec2.mod(t:pos()-pilpos) 
      local modp = vec2.mod(p:pos()-pilpos)
      if modt < modp then
         local pos = ai.sethyptarget(t)
         ai.pushsubtask( "__run_hyp", pos )
      else
         mem.land = p:pos()
         ai.pushsubtask( "__run_landgo" )
      end
   end
end
function runaway_nojump ()
   if __run_target() then return end
   __run_turret()
end
function __run_target ()
   local target = ai.target()
   local pilot  = ai.pilot()

   -- Target must exist
   if not target:exists() then
      ai.poptask()
      return true
   end

   -- Good to set the target for distress calls
   ai.settarget( target )

   -- See whether we have a chance to outrun the attacker
   local relspe = pilot:stats().speed_max/target:stats().speed_max
   if pilot:stats().mass <= 400 and relspe <= 1.01 and ai.hasprojectile() and (not ai.hasafterburner()) then
      -- Pilot is agile, but too slow to outrun the enemy: dodge
      local dir = ai.dir(target) + 180      -- Reverse (run away)
      if dir > 180 then dir = dir - 360 end -- Because of periodicity
      __zigzag(dir, 70)
   else
      ai.face(target, true)
      ai.accel()
   end

   -- Afterburner handling.         
   if ai.hasafterburner() and pilot:energy() > 10 then
      ai.weapset( 8, true )
   end

   return false
end
function __run_turret ()
   -- Shoot the target
   local target   = ai.target()
   if target:exists() then
      ai.hostile(target)
      ai.settarget( target )
      local dist    = ai.dist(target)
      -- See if we have some turret to use
      if ai.hasturrets() then
         if dist < ai.getweaprange(true) then
            ai.weapset( 3 )
            ai.shoot( true )
         end
      end
   end
end
function __run_hyp ()
   -- Shoot the target
   __run_turret()

   -- Go towards jump
   local jump     = ai.subtarget()
   local jdir
   local bdist    = ai.minbrakedist()
   local jdist    = ai.dist(jump)
   local pilot    = ai.pilot()

   if jdist > bdist then

      local dozigzag = false
      if ai.target():exists() then
         local relspe = pilot:stats().speed_max/ai.target():stats().speed_max
         if pilot:stats().mass <= 400 and relspe <= 1.01 and ai.hasprojectile() and
            (not ai.hasafterburner()) and jdist > 3*bdist then
            dozigzag = true
         end
      end

      if dozigzag then
         -- Pilot is agile, but too slow to outrun the enemy: dodge
         local dir = ai.dir(jump)
         __zigzag(dir, 70)
      else
         if jdist > 3*bdist and pilot:stats().mass < 600 then
            jdir = ai.careful_face(jump)
         else --Heavy ships should rush to jump point
            jdir = ai.face(jump)
         end
         if jdir < 10 then       
            ai.accel()
         end
      end
   else
      ai.pushsubtask( "__run_hypbrake" )
   end

   --Afterburner: activate while far away from jump
   if ai.hasafterburner() and pilot:energy() > 10 then
      if jdist > 3 * bdist then
         ai.weapset( 8, true )
      else
         ai.weapset( 8, false )
      end
   end
end
function __run_hypbrake ()

   -- The braking
   ai.brake()
   if ai.isstopped() then
      ai.stop()
      ai.popsubtask()
      ai.pushsubtask( "__hyp_jump" )
   end
end

function __run_landgo ()
   -- Shoot the target
   __run_turret()

   local target   = mem.land
   local dist     = ai.dist( target )
   local bdist    = ai.minbrakedist()
   local pilot    = ai.pilot()

   if dist < bdist then -- Need to start braking
      ai.pushsubtask( "__landstop" )
   else

      local dozigzag = false
      if ai.target():exists() then
         local relspe = pilot:stats().speed_max/ai.target():stats().speed_max
         if pilot:stats().mass <= 400 and relspe <= 1.01 and ai.hasprojectile() and
            (not ai.hasafterburner()) and dist > 3*bdist then
            dozigzag = true
         end
      end

      if dozigzag then
         -- Pilot is agile, but too slow to outrun the enemy: dodge
         local dir = ai.dir(target)
         __zigzag(dir, 70)
      else

         -- 2 methods depending on mem.careful
         local dir
         if not mem.careful or dist < 3*bdist then
            dir = ai.face( target )
         else
            dir = ai.careful_face( target )
         end
         if dir < 10 then
            ai.accel()
         end
      end
   end

   --Afterburner
   if ai.hasafterburner() and pilot:energy() > 10 then
      if dist > 3 * bdist then
         ai.weapset( 8, true )
      else
         ai.weapset( 8, false )
      end
   end

end


--[[
-- Starts heading away to try to hyperspace.
--]]
function hyperspace ()
   local target = ai.target()
   if target == nil then
      target = ai.rndhyptarget()
      if target == nil then
         return
      end
   end
   local pos = ai.sethyptarget(target)
   ai.pushsubtask( "__hyp_approach", pos )
end
function __hyp_approach ()
   local target   = ai.subtarget()
   local dir
   local dist     = ai.dist( target )
   local bdist    = ai.minbrakedist()

   -- 2 methods for dir
   if not mem.careful or dist < 3*bdist then
      dir = ai.face( target )
   else
      dir = ai.careful_face( target )
   end

   -- Need to get closer
   if dir < 10 and dist > bdist then
      ai.accel()
   -- Need to start braking
   elseif dist < bdist then
      ai.pushsubtask("__hyp_brake")
   end
end
function __hyp_brake ()
   ai.brake()
   if ai.isstopped() then
      ai.stop()
      ai.popsubtask()
      ai.pushsubtask("__hyp_jump")
   end
end
function __hyp_jump ()
   if ai.hyperspace() == nil then
      ai.pilot():msg(ai.pilot():followers(), "hyperspace", ai.nearhyptarget())
      ai.poptask()
   else
      ai.popsubtask()
   end
end


--[[
-- Boards the target
--]]
function board ()
   local target = ai.target()

   -- Make sure pilot exists
   if not target:exists() then
      ai.poptask()
      return
   end

   -- Must be able to board
   if not ai.canboard(target) then
      ai.poptask()
      return
   end

   -- Get ready to board
   ai.settarget(target)
   local dir   = ai.face(target)
   local dist  = ai.dist(target)
   local bdist = ai.minbrakedist(target)

   -- See if must brake or approach
   if dist < bdist then
      ai.pushsubtask( "__boardstop", target )
   elseif dir < 10 then
      ai.accel()
   end
end


--[[
-- Attempts to brake on the target.
--]]
function __boardstop ()
   target = ai.target()

   -- make sure pilot exists
   if not target:exists() then
      ai.poptask()
      return
   end

   -- Make sure can board
   if not ai.canboard(target) then
      ai.poptask()
      return
   end

   -- Set target
   ai.settarget(target)
   local vel = ai.relvel(target)

   if vel < 10 then
      -- Try to board
      if ai.board(target) then
         ai.poptask()
         return
      end
   end

   -- Just brake
   ai.brake()

   -- If stopped try again
   if ai.isstopped() then
      ai.popsubtask()
   end
end



--[[
-- Boards the target
--]]
function refuel ()

   -- Get the target
   local target = ai.target()

   -- make sure pilot exists
   if not target:exists() then
      ai.poptask()
      return
   end

   -- See if finished refueling
   if not ai.pilot():flags().refueling then
      ai.poptask()
      return
   end

   -- Get ready to board
   ai.settarget(target)
   local dir   = ai.face(target)
   local dist  = ai.dist(target)
   local bdist = ai.minbrakedist(target)

   -- See if must brake or approach
   if dist < bdist then
      ai.pushsubtask( "__refuelstop", target )
   elseif dir < 10 then
      ai.accel()
   end
end

--[[
-- Attempts to brake on the target.
--]]
function __refuelstop ()
   local target = ai.target()

   -- make sure pilot exists
   if not target:exists() then
      ai.poptask()
      return
   end

   -- Set the target
   ai.settarget(target)

   -- See if finished refueling
   if not ai.pilot():flags().refueling then
      ai.pilot():comm(target, _("Finished fuel transfer."))
      ai.poptask()

      -- Untarget
      ai.settarget( ai.pilot() )
      return
   end

   -- Try to board
   if ai.refuel(target) then
      return
   end

   -- Just brake
   ai.brake()

   -- If stopped try again
   if ai.isstopped() then
      ai.popsubtask()
   end
end

--[[
-- Mines an asteroid
--]]
function mine ()
   ai.weapset( 1 )
   local fieldNast = ai.target()
   local field     = fieldNast[1]
   local ast       = fieldNast[2]
   local p         = ai.pilot()
   local wrange    = ai.getweaprange()
   local erange    = 100
   local trange    = math.min( math.max( erange, wrange * 3 / 4 ), wrange )
   local mbd       = ai.minbrakedist()

   -- See if there's a gatherable; if so, pop this task and gather instead
   local gat = ai.getgatherable( wrange )
   if gat ~= nil and ai.gatherablepos( gat ) ~= nil then
      ai.poptask()
      ai.pushtask("gather")
      return
   end

   ai.setasterotarget( field, ast )

   local target, vel = system.asteroidPos( field, ast )

   local dist, angle = vec2.polar( p:pos() - target )

   -- First task : place the ship close to the asteroid
   local goal = ai.face_accurate( target, vel, trange, angle, mem.Kp, mem.Kd )

   local dir  = ai.face(goal)
   local mod  = ai.dist(goal)

   if dir < 10 and mod > mbd then
      ai.accel()
   end
   
   local relpos = vec2.add( p:pos(), vec2.mul(target,-1) ):mod()
   local relvel = vec2.add( p:vel(), vec2.mul(vel,-1) ):mod()

   if relpos < wrange and relvel < 10 then
      ai.pushsubtask("__killasteroid")
   end
end
function __killasteroid ()
   local fieldNast = ai.target()
   local field     = fieldNast[1]
   local ast       = fieldNast[2]
   local wrange    = ai.getweaprange()

   local target = system.asteroidPos( field, ast )
   local dir  = ai.face(target)

    -- See if there's a gatherable; if so, pop this task and gather instead
   local gat = ai.getgatherable( wrange )
   if gat ~= nil and ai.gatherablepos( gat ) ~= nil then
      ai.poptask()
      ai.pushtask("gather")
      return
   end

   -- Have to start over if we're out of range for some reason
   if ai.dist(target) > wrange then
      ai.poptask()
      return
   end

   -- Second task : destroy it
   if dir < 8 then
      ai.weapset( 1 )
      ai.shoot()
      ai.shoot(true)
   end
   if system.asteroidDestroyed( field, ast ) then
      ai.poptask()
      -- Last task : gather
      ai.pushtask("gather")
   end
end

--[[
-- Attempts to seek and gather gatherables
--]]
function gather ()
   if ai.pilot():cargoFree() == 0 then --No more cargo
      ai.poptask()
      return
   end

   local gat = ai.getgatherable( ai.getweaprange() )

   if gat == nil then -- Nothing to gather
      ai.poptask()
      return
   end

   local target, vel = ai.gatherablepos( gat )
   if target == nil then -- gatherable disappeared
      ai.poptask()
      return
   end

   local goal = ai.face_accurate( target, vel, 0, 0, mem.Kp, mem.Kd )

   local dir  = ai.face(goal)
   local mod  = ai.dist(goal)

   if dir < 10 and mod > 100 then
      ai.accel()
   end
end