package OnUnitEnterLeave
import NoWurst
import Unit
import Trigger
import Group
import Player
import MagicFunctions
import AbilityObjEditing
import RegisterEvents
import ObjectIdGenerator
import MapBounds
import ClosureTimers
import Annotations
import Orders

/* 	Provides event API for units entering and leaving the map.
	The event will also fire for preplaced units on the map.

	NOTE: Any move applied to a unit as response to an enter event
		will fire the enter event again. */

let eventTrigger = CreateTrigger()
let preplacedUnits = CreateGroup()

/* Unit stack for nested usage */
unit array tempUnits
var tempUnitsCount = 0

function pushUnit(unit u)
	tempUnits[tempUnitsCount] = u
	tempUnitsCount++

function popUnit()
	tempUnitsCount--

/* @API */

/** Returns the unit that caused the enter/leave event to happen */
public function getEnterLeaveUnit() returns unit
	return tempUnits[tempUnitsCount - 1]

/** Adds a callback that is run when a unit enters the map */
public function onEnter(code c)
	eventTrigger.addCondition(Filter(c))

/** Adds a callback that is run when a unit leaves the map */
public function onLeave(code c)
	eventTrigger.addAction(c)

/* === Internals === */
constant ABILITY_ID = compiletime(ABIL_ID_GEN.next())

function prepareUnit(unit u)
	u..addAbility(ABILITY_ID)..makeAbilityPermanent(ABILITY_ID, true)
	pushUnit(u)
	eventTrigger.evaluate()
	popUnit()

init
	// Make the ability invisible to the player
	for i = 0 to bj_MAX_PLAYER_SLOTS - 1
		players[i].setAbilityAvailable(ABILITY_ID, false)

	nullTimer() ->
		// Create the enter event
		CreateTrigger()..registerEnterRegion(boundRegion, Filter(() -> prepareUnit(GetFilterUnit())))

		// Create the leave event
		registerPlayerUnitEvent(EVENT_PLAYER_UNIT_ISSUED_ORDER) ->
			let leavingUnit = GetTriggerUnit()
			if leavingUnit.getAbilityLevel(ABILITY_ID) == 0 and GetIssuedOrderId() == Orders.undefend
				pushUnit(leavingUnit)
				eventTrigger.execute()
				popUnit()

		// Process preplaced units
		preplacedUnits.enumUnitsInRect(boundRect)
		ForGroup(preplacedUnits, () -> prepareUnit(GetEnumUnit()))
		preplacedUnits..clear()..destr()

@compiletime function generateAbility()
	new AbilityDefinitionDefend(ABILITY_ID)
		..setName("Leave Detect")
		..setEditorSuffix("(OnUnitEnterLeave)")
		..setArtCaster("")
		..setIconNormal("")
		..setRace(Race.Unknown)