const DEFAULT_RECONNECT_MS = 1800;

export const DEFAULT_AGENT_URL = "ws://127.0.0.1:8765/ws/gestures";

export function createMotionAgentProvider(options = {}) {
  const {
    url = DEFAULT_AGENT_URL,
    reconnectMs = DEFAULT_RECONNECT_MS,
    WebSocketCtor = typeof WebSocket !== "undefined" ? WebSocket : null,
    onMessage = () => {},
    onState = () => {},
    onStatus = () => {},
  } = options;

  let socket = null;
  let reconnectTimer = null;
  let disposed = false;
  let connected = false;

  function emitState(detail = {}) {
    onState({
      provider: "motion_agent",
      connected,
      url,
      ...detail,
    });
  }

  function clearReconnect() {
    if (!reconnectTimer) return;
    clearTimeout(reconnectTimer);
    reconnectTimer = null;
  }

  function scheduleReconnect() {
    if (disposed || reconnectTimer) return;
    reconnectTimer = setTimeout(() => {
      reconnectTimer = null;
      connect();
    }, reconnectMs);
  }

  function closeSocket() {
    if (!socket) return;
    const current = socket;
    socket = null;
    current.onopen = null;
    current.onmessage = null;
    current.onerror = null;
    current.onclose = null;
    try {
      current.close();
    } catch (_error) {
      // Browser WebSocket close can throw during teardown in older engines.
    }
  }

  function connect() {
    if (disposed || socket) return;
    if (!WebSocketCtor) {
      emitState({ error: "websocket_unavailable", message: "当前浏览器不支持 WebSocket" });
      return;
    }

    try {
      socket = new WebSocketCtor(url);
    } catch (_error) {
      emitState({ error: "socket_create_failed", message: "无法创建 Motion Agent 连接" });
      scheduleReconnect();
      return;
    }

    socket.onopen = () => {
      connected = true;
      emitState({ connected: true });
      onStatus("动捕 Agent 已连接", "info");
    };
    socket.onmessage = (rawMessage) => onMessage(rawMessage?.data ?? rawMessage);
    socket.onerror = () => {
      emitState({ connected: false, error: "socket_error", message: "Motion Agent 连接异常" });
    };
    socket.onclose = () => {
      connected = false;
      socket = null;
      emitState({ connected: false, message: "Motion Agent 未连接" });
      scheduleReconnect();
    };
  }

  return {
    provider: "motion_agent",
    start() {
      if (disposed) return false;
      connect();
      return true;
    },
    stop() {
      disposed = true;
      clearReconnect();
      closeSocket();
      connected = false;
      emitState({ connected: false });
    },
    isConnected() {
      return connected;
    },
  };
}