# inventory_expansion_system.gd —— 40250 官方背包槽位解锁凭证与扩展系统 1:1
# 严格对照：
#   metin2/src/server/common/length.h (INVENTORY_MAX_NUM = 90, 45格/页)
#   metin2/src/server/share/conf/item_proto.txt (72319 / 72320 储物锁匙)
#   ClientVS22/source/UserInterface/GameType.h (INVENTORY_PAGE_SIZE = 45, 5x9 grid)
extends RefCounted

const PAGE_SIZE := 45                 # 每页 45 格 (5 列 x 9 行)
const BASE_UNLOCKED_PAGES := 2        # 默认前 2 页解锁 (0..89 共 90 格)
const MAX_PAGES := 4                  # 最大 4 页 (共 180 格)
const TOTAL_SLOTS := 180              # 45 * 4 = 180

const SLOTS_PER_STAGE := 5            # 每个解锁阶段解锁 5 格
const TOTAL_EXPANSION_STAGES := 18    # 后 2 页共 90 格，划分为 18 个阶段 (90 / 5 = 18)

const EXPANSION_KEY_VNUM := 72319     # 储物锁匙

# 18 个阶段的锁匙消耗曲线 (1:1 官方阶梯消耗)
# 阶段 1~6 (90..119 格): 1 匙/段
# 阶段 7~12 (120..149 格): 2 匙/段
# 阶段 13~17 (150..174 格): 3 匙/段
# 阶段 18 (175..179 格): 4 匙/段
const STAGE_KEY_COSTS := [
	1, 1, 1, 1, 1, 1,                 # Stage 1..6
	2, 2, 2, 2, 2, 2,                 # Stage 7..12
	3, 3, 3, 3, 3,                    # Stage 13..17
	4                                 # Stage 18
]

# 当前已解锁的扩展阶段数 (0..18)
var unlocked_stages: int = 0
# 背包槽位存储 (slot 0..179 -> item_data Dictionary or null)
var inventory_slots: Array = []

func _init(initial_unlocked_stages: int = 0) -> void:
	unlocked_stages = clamp(initial_unlocked_stages, 0, TOTAL_EXPANSION_STAGES)
	inventory_slots.clear()
	for i in range(TOTAL_SLOTS):
		inventory_slots.append(null)

# 获取当前已解锁的最大格位数 (基础 90 格 + 解锁阶段数 * 5)
func get_unlocked_slot_count() -> int:
	return (BASE_UNLOCKED_PAGES * PAGE_SIZE) + (unlocked_stages * SLOTS_PER_STAGE)

# 检查特定格位是否已解锁
func is_slot_unlocked(slot_idx: int) -> bool:
	if slot_idx < 0 or slot_idx >= TOTAL_SLOTS:
		return false
	return slot_idx < get_unlocked_slot_count()

# 获取下一阶段所需的储物锁匙数量
func get_next_stage_key_cost() -> int:
	if unlocked_stages >= TOTAL_EXPANSION_STAGES:
		return 0
	return STAGE_KEY_COSTS[unlocked_stages]

# 解锁下一阶段背包槽位 (5 格)
func unlock_next_stage(player_keys: int) -> Dictionary:
	var res := {
		"success": false,
		"stage": unlocked_stages,
		"keys_deducted": 0,
		"remaining_keys": player_keys,
		"unlocked_slots": get_unlocked_slot_count(),
		"is_all_unlocked": false,
		"error_code": "OK",
		"message": ""
	}

	if unlocked_stages >= TOTAL_EXPANSION_STAGES:
		res["is_all_unlocked"] = true
		res["error_code"] = "ALREADY_MAX_EXPANDED"
		res["message"] = "背包所有 4 页 180 格位已全部解锁，达到上限！"
		return res

	var needed_keys := get_next_stage_key_cost()
	if player_keys < needed_keys:
		res["error_code"] = "INSUFFICIENT_KEYS"
		res["message"] = "储物锁匙不足！解锁阶段 %d 需要 %d 枚储物锁匙。" % [unlocked_stages + 1, needed_keys]
		return res

	unlocked_stages += 1
	res["success"] = true
	res["stage"] = unlocked_stages
	res["keys_deducted"] = needed_keys
	res["remaining_keys"] = player_keys - needed_keys
	res["unlocked_slots"] = get_unlocked_slot_count()
	res["is_all_unlocked"] = (unlocked_stages >= TOTAL_EXPANSION_STAGES)
	res["message"] = "解锁成功！阶段 %d 已解除封印，新增 5 个可用格位 (当前可用格数: %d)。" % [
		unlocked_stages, res["unlocked_slots"]
	]
	return res

# 检查物品是否能放置在指定格位 (考虑物品高度 height 与跨页/封印限制)
# 在 Metin2 中，背包每行 5 格，高度占据 slot, slot+5, slot+10
func can_place_item_at(slot_idx: int, item_height: int = 1) -> Dictionary:
	var res := { "can_place": false, "error_code": "OK", "message": "" }

	if slot_idx < 0 or slot_idx >= TOTAL_SLOTS:
		res["error_code"] = "OUT_OF_BOUNDS"
		res["message"] = "超出背包格位边界。"
		return res

	var start_page := slot_idx / PAGE_SIZE
	var page_local_slot := slot_idx % PAGE_SIZE
	var row := page_local_slot / 5

	# 跨页检查 (单物品不能从第 1 页跨到底部溢出到第 2 页)
	if row + item_height > 9:
		res["error_code"] = "PAGE_OVERFLOW"
		res["message"] = "物品长度超出单页底部边界。"
		return res

	# 检查高度占用的每一个单元格
	for h in range(item_height):
		var check_slot := slot_idx + (h * 5)
		if not is_slot_unlocked(check_slot):
			res["error_code"] = "SLOT_LOCKED"
			res["message"] = "目标单元格 [%d] 处于锁链封印状态，需使用储物锁匙解锁。" % check_slot
			return res

		if inventory_slots[check_slot] != null:
			res["error_code"] = "SLOT_OCCUPIED"
			res["message"] = "目标单元格已被占用。"
			return res

	res["can_place"] = true
	return res

# 放置物品到背包格位
func put_item(slot_idx: int, item_data: Dictionary, item_height: int = 1) -> Dictionary:
	var check := can_place_item_at(slot_idx, item_height)
	if not check["can_place"]:
		return check

	var it_copy := item_data.duplicate(true)
	it_copy["size"] = item_height
	it_copy["head_slot"] = slot_idx

	for h in range(item_height):
		var cell := slot_idx + (h * 5)
		inventory_slots[cell] = it_copy

	return { "success": true, "error_code": "OK", "slot": slot_idx }

# 从背包移除物品
func remove_item(slot_idx: int) -> Dictionary:
	var res := { "success": false, "item": null, "error_code": "OK" }
	if slot_idx < 0 or slot_idx >= TOTAL_SLOTS or inventory_slots[slot_idx] == null:
		res["error_code"] = "EMPTY_SLOT"
		return res

	var it: Dictionary = inventory_slots[slot_idx]
	var head_slot: int = it.get("head_slot", slot_idx)
	var size: int = it.get("size", 1)

	for h in range(size):
		var cell := head_slot + (h * 5)
		if cell < TOTAL_SLOTS:
			inventory_slots[cell] = null

	res["success"] = true
	res["item"] = it
	return res