cruiseAltitude = 250
diveDistance = 100
-- Gain from 1 to 10
rollGain = 5
yawGain = 5
pitchGain = 5
minTargetAltitude = -5
blueprintName = "SNUKEB"

-- internal variables (do not touch)
runOnce = true
swarmId = 0


function GetIntercept(I, Pos, Info)

  -- get my vehicle info
  local mySpeed = I:GetForwardsVelocityMagnitude()
  local myAltitude = I:GetConstructCenterOfMass().y

  --I:LogToHud(mySpeed .. " " Pos.Range)

  -- My attempt to make very basic prediction
  local Prediction = Info.AimPointPosition + Info.Velocity * ((Pos.Range / mySpeed) / 4)

  -- Aim straight after we reach "diveDistance"
  local adjustedDistance = math.max(0,Pos.GroundDistance - diveDistance)

  -- if we get above cruiseAltitude, lower the height aimpoint
  local height = Prediction.y + adjustedDistance / math.max(1, (myAltitude / cruiseAltitude) * 4)

  return I:GetTargetPositionInfoForPosition(0, Prediction.x, height, Prediction.z)

end

function NavigateToPoint(I, Pos)

--Roll
  local roll = I:GetConstructRoll()
  if( roll >180 ) then roll = roll-360 end
  if(roll>0) then I:RequestControl(2,3,math.min(1,math.abs(roll)/(180/rollGain))) end -- roll right
  if(roll<0) then I:RequestControl(2,2,math.min(1,math.abs(roll)/(180/rollGain))) end -- roll left


--Yaw
  if(Pos.Azimuth>0) then I:RequestControl(2,0,math.min(1,math.abs(Pos.Azimuth)/(180/yawGain))) end --yaw left
  if(Pos.Azimuth<0) then I:RequestControl(2,1,math.min(1,math.abs(Pos.Azimuth)/(180/yawGain))) end --yaw right

--Pitch
  if(Pos.Elevation>0) then I:RequestControl(2,4,math.min(1,math.abs(Pos.Elevation)/(180/pitchGain))) end --elevate up
  if(Pos.Elevation<0) then I:RequestControl(2,5,math.min(1,math.abs(Pos.Elevation)/(180/pitchGain))) end --elevate down

--I:LogToHud(Pos.Azimuth)

end

function SmartTargeting(I)

  -- swarmId is number of this craft in a swarm of similar crafts

  if(runOnce) then
    -- runOnce to false, so we dont run this again
    runOnce = false

    --Count how many similar units are in a 1km radius
    -- and assign myself a flight number
    local numFriendlies = I:GetFriendlyCount()
    for i = 0, numFriendlies-1, 1 do
      local friendlyInfo = I:GetFriendlyInfo(i)
      if(friendlyInfo.BlueprintName == blueprintName) then
        swarmId = swarmId+1
      end
    end
    I:Log("Set swarmId: " .. swarmId)
  end

--Count number of possilbe targets we could engage
  local numTargets= I:GetNumberOfTargets(0)
  local numValidTargets= 0

  for i = 0, numTargets-1, 1 do
    local TargetInfo = I:GetTargetInfo(0,i)
    if(TargetInfo.Valid and (TargetInfo.Position.y > minTargetAltitude)) then
      numValidTargets= numValidTargets+1
    end
  end


--return a target number
  local myTarget = 0
  if( numValidTargets > 0)then
    myTarget= swarmId%numValidTargets
    if (myTarget == 0 ) then
      myTarget = numValidTargets
    end
    myTarget = myTarget-1
  end
  I:LogToHud(blueprintName .. " swarmId: " .. swarmId .. " targeting: " .. myTarget)
  return myTarget
end


function Update(I)
  local myTarget = SmartTargeting(I)
  local TargetPos = I:GetTargetPositionInfo(0, myTarget )
  local TargetInfo = I:GetTargetInfo(0, myTarget)

  if (I:GetNumberOfMainframes() > 0 and I:GetNumberOfTargets(0) > 0) then
    if TargetPos.Valid then
      local intercept = GetIntercept(I, TargetPos, TargetInfo )
      NavigateToPoint(I, intercept)
      --thrust full speed
      I:RequestThrustControl(0)
    end
    else
      local myPos = I:GetConstructCenterOfMass()
      local intercept =I:GetTargetPositionInfoForPosition(0,
      myPos.x+I:GetConstructRightVector().x*50,
      cruiseAltitude,
      myPos.z+I:GetConstructRightVector().z*50)
      NavigateToPoint(I, intercept)
      --thrust low speed
      I:RequestThrustControl(0,0.25)
  end

  -- self destruct NOTE: does not work as of 1.966 -- commented out
  -- since NUKE is not a weapon-type and I:GetWeaponCount() returns 0
  -- if((I:GetVelocityMagnitude()<25 and TargetPos.Valid and TargetPos.Range<100)) then
  -- local aim = I:GetConstructForwardVector()
  -- I:AimWeaponInDirection(0, aim.x,aim.y,aim.z, 0)
  -- I:FireWeapon(0,0)
  -- end
end