extends Node

# ============================================================================
# SocketIOClient.gd - Socket.IO 协议封装
# ============================================================================
# 封装 Godot 的 WebSocketPeer，实现简化的 Socket.IO 协议
#
# 核心职责:
# - WebSocket 连接管理
# - Socket.IO 消息协议（简化版 JSON 格式）
# - 事件监听器管理
# - 消息发送/接收
#
# 注意事项:
# - 后端使用简化版 Socket.IO（纯 JSON，无二进制协议）
# - 发送消息使用 "t" 字段标识事件类型
# - 所有消息通过 JSON 序列化
# ============================================================================

class_name SocketIOClient

# ============================================================================
# 信号定义
# ============================================================================

# 连接成功信号
signal connected()

# 连接断开信号
# 参数:
#   clean_close: bool - 是否为正常关闭
signal disconnected(clean_close: bool)

# 事件接收信号
# 参数:
#   event_name: String - 事件名称（从 "t" 字段提取）
#   data: Dictionary - 事件数据
signal event_received(event_name: String, data: Dictionary)

# 错误发生信号
# 参数:
#   error: String - 错误信息
signal error_occurred(error: String)

# ============================================================================
# 常量定义
# ============================================================================

# 连接状态枚举
enum ConnectionState {
	DISCONNECTED,   # 未连接
	CONNECTING,     # 连接中
	CONNECTED       # 已连接
}

# ============================================================================
# 成员变量
# ============================================================================

# WebSocket 客户端
var _websocket_peer: WebSocketPeer = WebSocketPeer.new()

# 连接状态
var _connection_state: ConnectionState = ConnectionState.DISCONNECTED

# 服务器 URL
var _server_url: String = ""

# 事件监听器: {event_name: [Callable, ...]}
var _event_listeners: Dictionary = {}

# ============================================================================
# 生命周期方法
# ============================================================================

# 初始化
func _ready() -> void:
	print("SocketIOClient 初始化完成")

# 处理进程 - 轮询 WebSocket 消息
func _process(_delta: float) -> void:
	# 轮询 WebSocket 状态
	_websocket_peer.poll()

	# 检查连接状态变化
	var new_state: ConnectionState = _get_connection_state()
	if new_state != _connection_state:
		_connection_state = new_state
		_on_state_changed(_connection_state)

	# 处理接收到的消息
	_process_incoming_messages()

# ============================================================================
# 公共 API - 连接管理
# ============================================================================

# 连接到服务器
#
# 参数:
#   url: String - WebSocket 服务器 URL (ws:// 或 wss://)
#
# 使用示例:
#   socket_client.connect_to_server("wss://example.com/game")
func connect_to_server(url: String) -> void:
	if _connection_state == ConnectionState.CONNECTED:
		push_warning("已经连接到服务器，无需重复连接")
		return

	_server_url = url
	print("=== SocketIOClient 开始连接 ===")
	print("服务器 URL: ", _server_url)

	# 创建 WebSocket 客户端
	_websocket_peer = WebSocketPeer.new()

	# 发起连接
	var error := _websocket_peer.connect_to_url(url)
	if error != OK:
		push_error("WebSocket 连接失败: %s" % error)
		error_occurred.emit("WebSocket 连接失败")
		return

	_connection_state = ConnectionState.CONNECTING
	print("WebSocket 连接中...")

# 断开连接
func disconnect_from_server() -> void:
	if _connection_state == ConnectionState.DISCONNECTED:
		return

	print("=== SocketIOClient 断开连接 ===")
	_websocket_peer.close()
	_connection_state = ConnectionState.DISCONNECTED
	disconnected.emit(true)

# 检查是否已连接
#
# 返回值:
#   bool - 是否已连接
func is_connected() -> bool:
	return _connection_state == ConnectionState.CONNECTED

# ============================================================================
# 公共 API - 事件发送
# ============================================================================

# 发送事件（对应 socket.emit）
#
# 参数:
#   event_name: String - 事件名称（如 "login", "chat"）
#   data: Dictionary - 事件数据
#
# 使用示例:
#   socket_client.emit("login", {"type": "login", "token": "abc123"})
#   socket_client.emit("chat", {"t": "chat", "content": "Hello", "scope": "local"})
func emit(event_name: String, data: Dictionary) -> void:
	if not is_connected():
		push_error("无法发送事件: 未连接到服务器")
		error_occurred.emit("未连接到服务器")
		return

	# 序列化为 JSON
	var json_string := JSON.stringify(data)
	if json_string.is_empty():
		push_error("JSON 序列化失败")
		error_occurred.emit("JSON 序列化失败")
		return

	# 发送数据包
	var packet := json_string.to_utf8_buffer()
	var error := _websocket_peer.send(packet)

	if error != OK:
		push_error("发送数据包失败: %s" % error)
		error_occurred.emit("发送数据包失败")
		return

	print("📤 发送事件: ", event_name)
	print("   数据: ", json_string if json_string.length() < 200 else json_string.substr(0, 200) + "...")

# ============================================================================
# 公共 API - 事件监听
# ============================================================================

# 添加事件监听器（对应 socket.on）
#
# 参数:
#   event_name: String - 事件名称
#   callback: Callable - 回调函数，接收 data: Dictionary 参数
#
# 使用示例:
#   socket_client.add_event_listener("chat_render", func(data):
#       print("收到消息: ", data.txt)
#   )
func add_event_listener(event_name: String, callback: Callable) -> void:
	if not _event_listeners.has(event_name):
		_event_listeners[event_name] = []

	_event_listeners[event_name].append(callback)
	print("注册事件监听器: ", event_name, " -> ", callback)

# 移除事件监听器
#
# 参数:
#   event_name: String - 事件名称
#   callback: Callable - 要移除的回调函数
func remove_event_listener(event_name: String, callback: Callable) -> void:
	if not _event_listeners.has(event_name):
		return

	var listeners: Array = _event_listeners[event_name]
	listeners.erase(callback)

	if listeners.is_empty():
		_event_listeners.erase(event_name)

	print("移除事件监听器: ", event_name, " -> ", callback)

# ============================================================================
# 内部方法 - 消息处理
# ============================================================================

# 处理接收到的消息
func _process_incoming_messages() -> void:
	# 检查是否有可用数据包
	while _websocket_peer.get_available_packet_count() > 0:
		# 接收数据包
		var packet: PackedByteArray = _websocket_peer.get_packet()

		# 解析为字符串
		var json_string: String = packet.get_string_from_utf8()

		# 解析 JSON
		var json := JSON.new()
		var parse_result := json.parse(json_string)

		if parse_result != OK:
			push_error("JSON 解析失败: " + json_string)
			error_occurred.emit("JSON 解析失败")
			continue

		var data: Dictionary = json.data

		# 提取事件类型（从 "t" 字段）
		var event_name: String = data.get("t", "")
		if event_name.is_empty():
			# 如果没有 "t" 字段，尝试其他方式识别
			if data.has("type"):
				event_name = data["type"]
			elif data.has("code"):
				event_name = "error"
			else:
				push_warning("收到未知格式消息: " + json_string)
				continue

		print("📨 收到事件: ", event_name)
		print("   数据: ", json_string if json_string.length() < 200 else json_string.substr(0, 200) + "...")

		# 调用事件监听器
		_notify_event_listeners(event_name, data)

		# 发射通用信号
		event_received.emit(event_name, data)

# 通知事件监听器
func _notify_event_listeners(event_name: String, data: Dictionary) -> void:
	if not _event_listeners.has(event_name):
		return

	var listeners: Array = _event_listeners[event_name]
	for callback in listeners:
		if callback.is_valid():
			callback.call(data)

# ============================================================================
# 内部方法 - 状态管理
# ============================================================================

# 获取当前连接状态
func _get_connection_state() -> ConnectionState:
	match _websocket_peer.get_ready_state():
		WebSocketPeer.STATE_CONNECTING:
			return ConnectionState.CONNECTING
		WebSocketPeer.STATE_OPEN:
			return ConnectionState.CONNECTED
		WebSocketPeer.STATE_CLOSING:
			return ConnectionState.CONNECTING
		WebSocketPeer.STATE_CLOSED:
			return ConnectionState.DISCONNECTED
		_:
			return ConnectionState.DISCONNECTED

# 连接状态变化处理
func _on_state_changed(new_state: ConnectionState) -> void:
	match new_state:
		ConnectionState.CONNECTED:
			print("✅ WebSocket 连接成功")
			connected.emit()
		ConnectionState.DISCONNECTED:
			print("🔌 WebSocket 连接断开")
			disconnected.emit(false)
		ConnectionState.CONNECTING:
			print("⏳ WebSocket 连接中...")