function updateheading()
   while (true) do
      lastheading = currentheading
      currentheading = Spring.GetUnitHeading(unitID)
      deltaheading = lastheading - currentheading      
      Sleep (200)

   local _,turretDir,_ = Spring.UnitScript.GetPieceRotation (turret)--pro tip: do this for tilting axis too
   deltaheading = deltaheading * math.pi / 32768
   Turn (turret, y_axis, (deltaheading+turretDir), math.rad(180))
   end   
end

local chassis = piece "chassis"
local flare1 = piece "flare1"

local SIG_RESTORE=2
local SIG_TURRET=4

local attack_mode=0 --will the unit turn turret along movement or focus on the enemy?

--constant for converting unitheadings to radians
local conversion= 2*3.14159/(2^16)
local attack_heading=conversion*Spring.GetUnitHeading(unitID)


local function restore()
   Signal(SIG_RESTORE)
   SetSignalMask(SIG_RESTORE)
   local unit_dir=0

   Sleep(5000)
   --slowly restore to original settings
   while(true) do
     unit_dir=Spring.GetUnitHeading(unitID)
     if (attack_heading<0.03+conversion*unit_dir and attack_heading>-0.03+conversion*unit_dir) then
       attack_heading=conversion*unit_dir

       attack_mode=0         
     end
     --TODO: take into consideration shortest way, as it is now sometimes the
     --longer turn is taken making the poor driver pretty sick xD
     if attack_heading>=0.03+conversion*unit_dir then attack_heading=attack_heading-0.03 end
     if attack_heading<=-0.03+conversion*unit_dir then attack_heading=attack_heading+0.03 end
     Sleep(60)
   end
end

local function turret()
   Signal(SIG_TURRET)
   SetSignalMask(SIG_TURRET)

   local unit_dir=Spring.GetUnitHeading(unitID)

   local diff_dir=0

   Sleep(180)
   while(true) do
     if (attack_mode==1) then
      unit_dir=Spring.GetUnitHeading(unitID)

      --turn the chassis piece to exactly the needed position
      Turn(chassis, y_axis,attack_heading-conversion*unit_dir)

      Sleep(30)
    end

    --normal behaviour when not in combat situation
    if (attack_mode==0) then Sleep(30) end   
   end
end


function script.Create()
 StartThread(turret)
end

function script.Killed(recentDamage, maxHealth)
   Explode(chassis, SFX.SHATTER)    
end

function script.StartMoving ()
  Move(chassis, y_axis, 20,9)
end

function script.StopMoving ()

end

function script.AimFromWeapon1()
   return flare1
end

function script.QueryWeapon1()
   return flare1
end

function script.AimWeapon1( heading, pitch )
   Signal(SIG_RESTORE)
   Signal(1)
   SetSignalMask(1)   
   attack_mode=1
   --aiming animation


   local unit_dir=Spring.GetUnitHeading(unitID)

   while(true) do
     unit_dir=Spring.GetUnitHeading(unitID)
     if (attack_heading<0.10+conversion*unit_dir+heading and attack_heading>-0.10+conversion*unit_dir+heading) then
       --fire shot !
       StartThread(restore)
       return true
         
     end

     --TODO: take into consideration shortest way, as it is now sometimes the
     --longer turn is taken
    -- Spring.Echo("attack heading",attack_heading)
    -- Spring.Echo("wanted heading",conversion*unit_dir+heading)
     if attack_heading>=0.10+conversion*unit_dir+heading then
        attack_heading=attack_heading-0.10
     end
     if attack_heading<=-0.10+conversion*unit_dir+heading then
             attack_heading=attack_heading+0.10
     end

     Sleep(60)
   end

   --attack_heading=2*3.1415926 --this would be a full circle


   StartThread(restore)
   return true

end

--Define the wheel pieces

local wheel_speed = math.rad(180)
--Define the pieces of the weapon
local chassis = piece "chassis"
local turret = piece "turret"
local guns = piece "guns"
local flare1 = piece "flare1"
local flare2 = piece "flare2"
local active_barrel = 1      --the barrel that the next shot will be fired from
local number_of_barrels = 2      --how many barrel there are in total

local SIG_AIM=1
local SIG_RESTORE=2
local SIG_TURRET=4
--constant for converting unitheadings to radians
local conversion= 2*3.14159/(2^16)
local attack_heading=conversion*Spring.GetUnitHeading(unitID)

local attack_mode=0 --will the unit turn turret along movement or focus on the enemy?


local function restore()
   Signal(SIG_RESTORE)
   SetSignalMask(SIG_RESTORE)
   local unit_dir=0
   local turnspeed=0.06 --the speed at which the turett will turn


   Sleep(5000)
   --slowly restore to original settings
   while(true) do
     unit_dir=Spring.GetUnitHeading(unitID)
     --reduce attack_heading & wanted_heading to a number between 0 and 2*PI
     if (attack_heading<0) then
        attack_heading=attack_heading+2*3.14159
     end    
     if (attack_heading>2*3.14159) then
        attack_heading=attack_heading-2*3.14159
     end    

     local wanted_heading=conversion*unit_dir
     if (wanted_heading<0) then
        wanted_heading=wanted_heading+2*3.14159
     end    
     if (wanted_heading>2*3.14159) then
        wanted_heading=wanted_heading-2*3.14159
     end

     local dist1=0
     local dist2=0

     --check if at original position
     --calculate distance from desired rotation
     dist1=attack_heading-wanted_heading
     if (dist1<0) then dist1=-dist1 end
     dist2=(2*3.14159-attack_heading)+wanted_heading
     if (dist2<0) then dist2=-dist2 end

     if (dist1<1.5*turnspeed or dist2<1.5*turnspeed) then
       attack_heading=wanted_heading
       attack_mode=0 --return to normal mode where turret turns along chassis
     end


     if attack_heading>wanted_heading then
        dist1=attack_heading-wanted_heading
        dist2=(2*3.14159-attack_heading)+wanted_heading
        if (dist1 >= dist2) then
         attack_heading=attack_heading+turnspeed
         wanted_heading=-100 --in order not to trigger the 2nd one aswell
        end
        if (dist1 < dist2) then
         attack_heading=attack_heading-turnspeed
         wanted_heading=-100 --in order not to trigger the 2nd one aswell
        end
     end

     if attack_heading<wanted_heading then
        dist1=wanted_heading-attack_heading
        dist2=(2*3.14159-wanted_heading)+attack_heading
        if (dist1 >= dist2) then
         attack_heading=attack_heading-turnspeed
        end
        if (dist1 < dist2) then
         attack_heading=attack_heading+turnspeed
        end
     end


     Sleep(60)
   end
end

local function manageturret()
   Signal(SIG_TURRET)
   SetSignalMask(SIG_TURRET)

   local unit_dir=Spring.GetUnitHeading(unitID)

   local diff_dir=0


   while(true) do
     if (attack_mode==1) then
      unit_dir=Spring.GetUnitHeading(unitID)

      --turn the turret piece to exactly the needed position
      Turn(turret, y_axis,attack_heading-conversion*unit_dir)

      Sleep(30)
    end

    --normal behaviour when not in combat situation
    if (attack_mode==0) then Sleep(30) end   
   end
end


function script.Create()
 StartThread(manageturret)   
end

----driving animation
function script.StartMoving()
   --Turn(guns, x_axis, 0,0.1)
end

function script.StopMoving()

end

----aimining & fire weapon
function script.AimFromWeapon1()
   return turret
end

function script.QueryWeapon1()
   if (active_barrel == 1) then return flare1 end
   if (active_barrel == 2) then return flare2 end
end

function script.AimWeapon1( heading, pitch )
   Signal(SIG_RESTORE)
   Signal(SIG_AIM)
   SetSignalMask(SIG_AIM)   
   attack_mode=1
   Turn(guns, x_axis, -pitch,0.5)
   --aiming animation
   local turnspeed=0.06 --the speed at which the turett will turn

   local unit_dir=Spring.GetUnitHeading(unitID)

   while(true) do
     unit_dir=Spring.GetUnitHeading(unitID)


     --reduce attack_heading & wanted_heading to a number between 0 and 2*PI
     if (attack_heading<0) then
        attack_heading=attack_heading+2*3.14159
     end    
     if (attack_heading>2*3.14159) then
        attack_heading=attack_heading-2*3.14159
     end    
     --Spring.Echo("attack heading",attack_heading)

     local wanted_heading=conversion*unit_dir+heading
     if (wanted_heading<0) then
        wanted_heading=wanted_heading+2*3.14159
     end    
     if (wanted_heading>2*3.14159) then
        wanted_heading=wanted_heading-2*3.14159
     end
     --Spring.Echo("wanted heading",wanted_heading)


     local dist1=0
     local dist2=0

     --check if shot can be fired
     --calculate distance from desired rotation
     dist1=attack_heading-wanted_heading
     if (dist1<0) then dist1=-dist1 end
     dist2=(2*3.14159-attack_heading)+wanted_heading
     if (dist2<0) then dist2=-dist2 end

     if (dist1<1.5*turnspeed or dist2<1.5*turnspeed) then
       attack_heading=wanted_heading
       --fire shot !
       StartThread(restore)
       return true
     end


     if attack_heading>wanted_heading then
        dist1=attack_heading-wanted_heading
        dist2=(2*3.14159-attack_heading)+wanted_heading
        if (dist1 >= dist2) then
         attack_heading=attack_heading+turnspeed
         wanted_heading=-100 --in order not to trigger the 2nd one aswell
        end
        if (dist1 < dist2) then
         attack_heading=attack_heading-turnspeed
         wanted_heading=-100 --in order not to trigger the 2nd one aswell
        end
     end

     if attack_heading<wanted_heading then
        dist1=wanted_heading-attack_heading
        dist2=(2*3.14159-wanted_heading)+attack_heading
        if (dist1 >= dist2) then
         attack_heading=attack_heading-turnspeed
        end
        if (dist1 < dist2) then
         attack_heading=attack_heading+turnspeed
        end
     end


     Sleep(60)
   end

   --attack_heading=2*3.1415926 --this would be a full circle


   StartThread(restore)
   --return true

end