# player_trade_exchange_system.gd —— 40250 官方玩家面对面安全交易双向锁定系统 1:1
# 严格对照：
#   metin2/src/server/game/src/exchange.h
#   metin2/src/server/game/src/exchange.cpp
#   metin2/src/server/game/src/char.cpp (OpenExchange, SetExchange, etc.)
extends RefCounted

const EXCHANGE_ITEM_MAX_NUM := 12     # 官方交易面板 12 格 (4x3 布局)
const EXCHANGE_MAX_DISTANCE := 1000   # 官方交易最大距离 1000

# 玩家交易单边状态
class TradeSide:
	var player_id: int
	var player_name: String
	var is_ready: bool = false
	var offered_gold: int = 0
	# 12 个格位: display_pos (0..11) -> item_data Dictionary or null
	var display_slots: Array = []
	# 关联背包位置: display_pos -> inv_slot
	var inv_positions: Dictionary = {}

	func _init(id: int, name: String) -> void:
		player_id = id
		player_name = name
		is_ready = false
		offered_gold = 0
		display_slots.clear()
		for i in range(EXCHANGE_ITEM_MAX_NUM):
			display_slots.append(null)
		inv_positions.clear()

	func count_items() -> int:
		var c := 0
		for it in display_slots:
			if it != null:
				c += 1
		return c

var side_a: TradeSide = null
var side_b: TradeSide = null
var is_active: bool = false

# 模拟玩家的背包与金币引用（便于原子化结算）
# player_data = { "id": int, "name": int, "gold": int, "inv": Array, "max_inv_slots": int }
var player_a_ref: Dictionary = {}
var player_b_ref: Dictionary = {}

func _init() -> void:
	side_a = null
	side_b = null
	is_active = false

# 开启双向交易会话 (1:1 OpenExchange)
func start_exchange(player_a: Dictionary, player_b: Dictionary, distance: float = 200.0) -> Dictionary:
	var res := { "success": false, "error_code": "OK", "message": "" }

	if distance > EXCHANGE_MAX_DISTANCE:
		res["error_code"] = "TOO_FAR"
		res["message"] = "双方距离太远，无法进行交易。"
		return res

	if player_a.get("id") == player_b.get("id"):
		res["error_code"] = "CANNOT_TRADE_SELF"
		res["message"] = "无法与自己进行交易。"
		return res

	# 检查状态
	if player_a.get("is_dead", false) or player_b.get("is_dead", false):
		res["error_code"] = "PLAYER_DEAD"
		res["message"] = "处于死亡状态的玩家无法交易。"
		return res

	if player_a.get("is_in_safebox", false) or player_b.get("is_in_safebox", false) \
		or player_a.get("is_in_shop", false) or player_b.get("is_in_shop", false):
		res["error_code"] = "BUSY_WINDOW"
		res["message"] = "一方正处于其他交互窗口中，无法交易。"
		return res

	player_a_ref = player_a
	player_b_ref = player_b
	side_a = TradeSide.new(player_a["id"], player_a.get("name", "PlayerA"))
	side_b = TradeSide.new(player_b["id"], player_b.get("name", "PlayerB"))
	is_active = true

	res["success"] = true
	res["message"] = "交易窗口已开启。"
	return res

# 获取玩家所属的交易边
func _get_side(player_id: int) -> TradeSide:
	if side_a != null and side_a.player_id == player_id:
		return side_a
	elif side_b != null and side_b.player_id == player_id:
		return side_b
	return null

# 获取交易对手边
func _get_other_side(player_id: int) -> TradeSide:
	if side_a != null and side_a.player_id == player_id:
		return side_b
	elif side_b != null and side_b.player_id == player_id:
		return side_a
	return null

func _get_player_ref(player_id: int) -> Dictionary:
	if player_a_ref.get("id") == player_id:
		return player_a_ref
	elif player_b_ref.get("id") == player_id:
		return player_b_ref
	return {}

# 放入物品到交易栏 (1:1 CExchange::AddItem)
# 核心防调包规则：一旦修改物品，双方锁定状态立即重置为 false！
func add_item(player_id: int, inv_slot: int, display_pos: int) -> Dictionary:
	var res := { "success": false, "error_code": "OK", "message": "" }
	if not is_active:
		res["error_code"] = "TRADE_NOT_ACTIVE"
		return res

	var side := _get_side(player_id)
	var other := _get_other_side(player_id)
	var player_data := _get_player_ref(player_id)
	if side == null or other == null or player_data.is_empty():
		res["error_code"] = "INVALID_PARTICIPANT"
		return res

	if display_pos < 0 or display_pos >= EXCHANGE_ITEM_MAX_NUM:
		res["error_code"] = "INVALID_DISPLAY_POS"
		return res

	if side.display_slots[display_pos] != null:
		res["error_code"] = "SLOT_ALREADY_OCCUPIED"
		return res

	var inv: Array = player_data.get("inv", [])
	if inv_slot < 0 or inv_slot >= inv.size() or inv[inv_slot] == null:
		res["error_code"] = "ITEM_NOT_FOUND"
		return res

	var it: Dictionary = inv[inv_slot]

	# 1:1 防交易检查: ANTI_GIVE 标记 / 灵魂绑定 / 装备中
	if it.get("anti_give", false) or it.get("is_soulbound", false) or it.get("is_equipped", false):
		res["error_code"] = "ITEM_UNTRADEABLE"
		res["message"] = "该物品受法则限制，不可交易或转移。"
		return res

	# 放入交易槽
	side.display_slots[display_pos] = it.duplicate(true)
	side.inv_positions[display_pos] = inv_slot

	# 40250 官方核心安全机制: 重置双方锁定状态！
	side.is_ready = false
	other.is_ready = false

	res["success"] = true
	res["message"] = "物品已上架交易栏，双方就绪状态已重置。"
	return res

# 从交易栏取回物品 (1:1 CExchange::RemoveItem)
# 同样重置双方锁定状态！
func remove_item(player_id: int, display_pos: int) -> Dictionary:
	var res := { "success": false, "error_code": "OK" }
	if not is_active:
		res["error_code"] = "TRADE_NOT_ACTIVE"
		return res

	var side := _get_side(player_id)
	var other := _get_other_side(player_id)
	if side == null or other == null:
		res["error_code"] = "INVALID_PARTICIPANT"
		return res

	if display_pos < 0 or display_pos >= EXCHANGE_ITEM_MAX_NUM or side.display_slots[display_pos] == null:
		res["error_code"] = "SLOT_EMPTY"
		return res

	side.display_slots[display_pos] = null
	side.inv_positions.erase(display_pos)

	# 40250 官方安全机制: 重置双方锁定状态！
	side.is_ready = false
	other.is_ready = false

	res["success"] = true
	return res

# 设置出价金币 (1:1 CExchange::AddGold)
# 同样重置双方锁定状态！
func set_gold(player_id: int, amount: int) -> Dictionary:
	var res := { "success": false, "error_code": "OK", "message": "" }
	if not is_active:
		res["error_code"] = "TRADE_NOT_ACTIVE"
		return res

	var side := _get_side(player_id)
	var other := _get_other_side(player_id)
	var player_data := _get_player_ref(player_id)
	if side == null or other == null or player_data.is_empty():
		res["error_code"] = "INVALID_PARTICIPANT"
		return res

	if amount < 0:
		res["error_code"] = "INVALID_GOLD"
		return res

	if player_data.get("gold", 0) < amount:
		res["error_code"] = "INSUFFICIENT_GOLD"
		res["message"] = "身上金币不足，无法出价。"
		return res

	side.offered_gold = amount

	# 40250 官方安全机制: 重置双方锁定状态！
	side.is_ready = false
	other.is_ready = false

	res["success"] = true
	res["message"] = "出价金额已更新，双方就绪状态已重置。"
	return res

# 点击锁定/同意 (1:1 CExchange::Accept)
# 双方均锁定后自动触发原子化结算
func set_ready(player_id: int, ready_state: bool) -> Dictionary:
	var res := {
		"success": false,
		"trade_completed": false,
		"error_code": "OK",
		"message": ""
	}
	if not is_active:
		res["error_code"] = "TRADE_NOT_ACTIVE"
		return res

	var side := _get_side(player_id)
	var other := _get_other_side(player_id)
	if side == null or other == null:
		res["error_code"] = "INVALID_PARTICIPANT"
		return res

	side.is_ready = ready_state
	res["success"] = true

	# 若双方均已 Ready 锁定，执行原子化交付完成交易 (CExchange::Done)
	if side_a.is_ready and side_b.is_ready:
		var done_res = _execute_atomic_trade()
		if done_res["success"]:
			res["trade_completed"] = true
			res["message"] = "交易成功！双方物品与金币已安全过户。"
		else:
			res["trade_completed"] = false
			res["error_code"] = done_res["error_code"]
			res["message"] = done_res["message"]
	else:
		res["message"] = "已就绪锁定，等待对方确认。"

	return res

# 背包剩余空位计算
func _get_free_inv_slots(player_data: Dictionary) -> int:
	var inv: Array = player_data.get("inv", [])
	var free_count := 0
	for it in inv:
		if it == null:
			free_count += 1
	return free_count

# 原子化事务交付执行 (1:1 CExchange::Done & CheckSpace)
func _execute_atomic_trade() -> Dictionary:
	var res := { "success": false, "error_code": "OK", "message": "" }

	# 1. 再次校验金币是否充足
	if player_a_ref.get("gold", 0) < side_a.offered_gold:
		res["error_code"] = "PLAYER_A_LESS_GOLD"
		res["message"] = "一方金币不足，交易终止。"
		return res
	if player_b_ref.get("gold", 0) < side_b.offered_gold:
		res["error_code"] = "PLAYER_B_LESS_GOLD"
		res["message"] = "一方金币不足，交易终止。"
		return res

	# 2. 空间校验 (CheckSpace):
	# 玩家 A 需容纳 B 给予的所有物品；玩家 B 需容纳 A 给予的所有物品
	# 考虑双方移出物品后腾出的背包空位
	var a_items_count := side_a.count_items()
	var b_items_count := side_b.count_items()

	var a_free := _get_free_inv_slots(player_a_ref) + a_items_count
	var b_free := _get_free_inv_slots(player_b_ref) + b_items_count

	if a_free < b_items_count:
		res["error_code"] = "PLAYER_A_INSUFFICIENT_SPACE"
		res["message"] = "玩家 A 背包空间不足，无法接收对方物品。"
		return res

	if b_free < a_items_count:
		res["error_code"] = "PLAYER_B_INSUFFICIENT_SPACE"
		res["message"] = "玩家 B 背包空间不足，无法接收对方物品。"
		return res

	# 3. 执行金币转移
	player_a_ref["gold"] = player_a_ref.get("gold", 0) - side_a.offered_gold + side_b.offered_gold
	player_b_ref["gold"] = player_b_ref.get("gold", 0) - side_b.offered_gold + side_a.offered_gold

	# 4. 执行物品转移
	# 从 A 背包移除 A 出售的物品
	var inv_a: Array = player_a_ref.get("inv", [])
	for dpos in side_a.inv_positions:
		var inv_slot: int = side_a.inv_positions[dpos]
		inv_a[inv_slot] = null

	# 从 B 背包移除 B 出售的物品
	var inv_b: Array = player_b_ref.get("inv", [])
	for dpos in side_b.inv_positions:
		var inv_slot: int = side_b.inv_positions[dpos]
		inv_b[inv_slot] = null

	# 将 A 的物品放入 B 的背包空位
	for it in side_a.display_slots:
		if it != null:
			for i in range(inv_b.size()):
				if inv_b[i] == null:
					inv_b[i] = it.duplicate(true)
					break

	# 将 B 的物品放入 A 的背包空位
	for it in side_b.display_slots:
		if it != null:
			for i in range(inv_a.size()):
				if inv_a[i] == null:
					inv_a[i] = it.duplicate(true)
					break

	# 5. 关闭会话
	is_active = false
	res["success"] = true
	return res

# 取消交易 (1:1 CExchange::Cancel)
func cancel_trade() -> void:
	is_active = false
	side_a = null
	side_b = null