/**
 * ws-client.js — Hermes Gateway WebSocket Client
 *
 * Manages the persistent WebSocket connection between the Nexus (browser) and
 * the Hermes agent gateway. Hermes is the sovereign orchestration layer that
 * routes AI provider responses, Gitea PR events, visitor presence, and chat
 * messages into the 3D world.
 *
 * ## Provider Fallback Chain
 *
 * The Hermes gateway itself manages provider selection (Claude → Gemini →
 * Perplexity → fallback). From the Nexus client's perspective, all providers
 * arrive through the single WebSocket endpoint below. The client's
 * responsibility is to stay connected so no events are dropped.
 *
 * Connection lifecycle:
 *
 *   1. connect()          — opens WebSocket to HERMES_WS_URL
 *   2. onopen             — flushes any queued messages; fires 'ws-connected'
 *   3. onmessage          — JSON-parses frames; dispatches typed CustomEvents
 *   4. onclose / onerror  — fires 'ws-disconnected'; triggers _scheduleReconnect()
 *   5. _scheduleReconnect — exponential backoff (1s → 2s → 4s … ≤ 30s) up to
 *                           10 attempts, then fires 'ws-failed' and gives up
 *
 * Message queue: messages sent while disconnected are buffered in
 * `this.messageQueue` and flushed on the next successful connection.
 *
 * ## Dispatched CustomEvents
 *
 * | type              | CustomEvent name   | Payload (event.detail)             |
 * |-------------------|--------------------|------------------------------------|
 * | chat / chat-message | chat-message     | { type, text, sender?, … }        |
 * | status-update     | status-update      | { type, status, agent?, … }        |
 * | pr-notification   | pr-notification    | { type, action, pr, … }            |
 * | player-joined     | player-joined      | { type, id, name?, … }             |
 * | player-left       | player-left        | { type, id, … }                    |
 * | (connection)      | ws-connected       | { url }                            |
 * | (connection)      | ws-disconnected    | { code }                           |
 * | (terminal)        | ws-failed          | —                                  |
 */

/** Primary Hermes gateway endpoint. */
const HERMES_WS_URL = 'ws://143.198.27.163/api/world/ws';
const SESSION_STORAGE_KEY = 'hermes-session';

/**
 * WebSocketClient — resilient WebSocket wrapper with exponential-backoff
 * reconnection and an outbound message queue.
 */
export class WebSocketClient {
  /**
   * @param {string} [url] - WebSocket endpoint (defaults to HERMES_WS_URL)
   */
  constructor(url = HERMES_WS_URL) {
    this.url = url;
    /** Number of reconnect attempts since last successful connection. */
    this.reconnectAttempts = 0;
    /** Hard cap on reconnect attempts before emitting 'ws-failed'. */
    this.maxReconnectAttempts = 10;
    /** Initial backoff delay in ms (doubles each attempt). */
    this.reconnectBaseDelay = 1000;
    /** Maximum backoff delay in ms. */
    this.maxReconnectDelay = 30000;
    /** @type {WebSocket|null} */
    this.socket = null;
    this.connected = false;
    /** @type {ReturnType<typeof setTimeout>|null} */
    this.reconnectTimeout = null;
    /** Messages queued while disconnected; flushed on reconnect. */
    this.messageQueue = [];
    this.session = null;
  }

  /**
   * Persist session data to localStorage so it survives page reloads.
   * @param {Object} data  Arbitrary session payload (token, id, etc.)
   */
  saveSession(data) {
    try {
      localStorage.setItem(SESSION_STORAGE_KEY, JSON.stringify({ ...data, savedAt: Date.now() }));
      this.session = data;
      console.log('[hermes] Session saved');
    } catch (err) {
      console.warn('[hermes] Could not save session:', err);
    }
  }

  /**
   * Restore session data from localStorage.
   * @returns {Object|null}  Previously saved session, or null if none.
   */
  loadSession() {
    try {
      const raw = localStorage.getItem(SESSION_STORAGE_KEY);
      if (!raw) return null;
      const data = JSON.parse(raw);
      this.session = data;
      console.log('[hermes] Session loaded (savedAt:', new Date(data.savedAt).toISOString(), ')');
      return data;
    } catch (err) {
      console.warn('[hermes] Could not load session:', err);
      return null;
    }
  }

  /**
   * Remove any persisted session from localStorage.
   */
  clearSession() {
    try {
      localStorage.removeItem(SESSION_STORAGE_KEY);
      this.session = null;
      console.log('[hermes] Session cleared');
    } catch (err) {
      console.warn('[hermes] Could not clear session:', err);
    }
  }

  /**
   * Open the WebSocket connection. No-ops if already open or connecting.
   */
  connect() {
    if (this.socket && (this.socket.readyState === WebSocket.OPEN || this.socket.readyState === WebSocket.CONNECTING)) {
      return;
    }

    try {
      this.socket = new WebSocket(this.url);
    } catch (err) {
      console.error('[hermes] WebSocket construction failed:', err);
      this._scheduleReconnect();
      return;
    }

    this.socket.onopen = () => {
      console.log('[hermes] Connected to Hermes gateway');
      this.connected = true;
      this.reconnectAttempts = 0;
      // Restore session if available; send it as the first frame so the server
      // can resume the previous session rather than creating a new one.
      const existing = this.loadSession();
      if (existing?.token) {
        this._send({ type: 'session-resume', token: existing.token });
      }
      this.messageQueue.forEach(msg => this._send(msg));
      this.messageQueue = [];
      window.dispatchEvent(new CustomEvent('ws-connected', { detail: { url: this.url } }));
    };

    this.socket.onmessage = (event) => {
      let data;
      try {
        data = JSON.parse(event.data);
      } catch (err) {
        console.warn('[hermes] Unparseable message:', event.data);
        return;
      }
      this._route(data);
    };

    this.socket.onclose = (event) => {
      this.connected = false;
      this.socket = null;
      console.warn(`[hermes] Connection closed (code=${event.code})`);
      window.dispatchEvent(new CustomEvent('ws-disconnected', { detail: { code: event.code } }));
      this._scheduleReconnect();
    };

    this.socket.onerror = () => {
      // onclose fires after onerror; logging here would be redundant noise
      console.warn('[hermes] WebSocket error — waiting for close event');
    };
  }

  /**
   * Route an inbound Hermes message to the appropriate CustomEvent.
   * Unrecognised types are logged at debug level and dropped.
   *
   * @param {{ type: string, [key: string]: unknown }} data
   */
  _route(data) {
    switch (data.type) {
      case 'session-init':
        // Server issued a new session token — persist it for future reconnects.
        if (data.token) {
          this.saveSession({ token: data.token, clientId: data.clientId });
        }
        window.dispatchEvent(new CustomEvent('session-init', { detail: data }));
        break;

      case 'chat':
      case 'chat-message':
        window.dispatchEvent(new CustomEvent('chat-message', { detail: data }));
        break;

      case 'status-update':
        window.dispatchEvent(new CustomEvent('status-update', { detail: data }));
        break;

      case 'pr-notification':
        window.dispatchEvent(new CustomEvent('pr-notification', { detail: data }));
        break;

      case 'player-joined':
        window.dispatchEvent(new CustomEvent('player-joined', { detail: data }));
        break;

      case 'player-left':
        window.dispatchEvent(new CustomEvent('player-left', { detail: data }));
        break;

      default:
        console.debug('[hermes] Unhandled message type:', data.type, data);
    }
  }

  /**
   * Schedule the next reconnect attempt using exponential backoff.
   *
   * Backoff schedule (base 1 s, cap 30 s):
   *   attempt 1 →  1 s
   *   attempt 2 →  2 s
   *   attempt 3 →  4 s
   *   attempt 4 →  8 s
   *   attempt 5 → 16 s
   *   attempt 6+ → 30 s (capped)
   *
   * After maxReconnectAttempts the client emits 'ws-failed' and stops trying.
   */
  _scheduleReconnect() {
    if (this.reconnectAttempts >= this.maxReconnectAttempts) {
      console.warn('[hermes] Max reconnection attempts reached — giving up');
      window.dispatchEvent(new CustomEvent('ws-failed'));
      return;
    }

    const delay = Math.min(
      this.reconnectBaseDelay * Math.pow(2, this.reconnectAttempts),
      this.maxReconnectDelay
    );
    console.log(`[hermes] Reconnecting in ${delay}ms (attempt ${this.reconnectAttempts + 1}/${this.maxReconnectAttempts})`);
    this.reconnectTimeout = setTimeout(() => {
      this.reconnectAttempts++;
      this.connect();
    }, delay);
  }

  /**
   * Low-level send — caller must ensure socket is open.
   * @param {object} message
   */
  _send(message) {
    this.socket.send(JSON.stringify(message));
  }

  /**
   * Send a message to Hermes. If not currently connected the message is
   * buffered and will be delivered on the next successful connection.
   *
   * @param {object} message
   */
  send(message) {
    if (this.connected && this.socket && this.socket.readyState === WebSocket.OPEN) {
      this._send(message);
    } else {
      this.messageQueue.push(message);
    }
  }

  /**
   * Intentionally close the connection and cancel any pending reconnect.
   * After calling disconnect() the client will not attempt to reconnect.
   */
  disconnect() {
    if (this.reconnectTimeout) {
      clearTimeout(this.reconnectTimeout);
      this.reconnectTimeout = null;
    }
    this.maxReconnectAttempts = 0; // prevent auto-reconnect after intentional disconnect
    if (this.socket) {
      this.socket.close();
      this.socket = null;
    }
  }
}

/** Shared singleton WebSocket client — imported by app.js. */
export const wsClient = new WebSocketClient();