/**
 * @cc-platform/server/websocket — WebSocket manager for bridge + client connections
 *
 * Extracted from the structurally identical WebSocket setup in both
 * remoteturtle/server/server.js and Inventory-Manager-CC/web/server/server.js.
 *
 * Provides:
 *   - URL-based routing (/ws/bridge vs /ws for clients)
 *   - Bridge connection lifecycle (add/remove/message dispatch)
 *   - Client connection lifecycle (add/remove/initial state/broadcast)
 *   - Ping/pong keepalive with stale connection cleanup
 *   - broadcastToClients() and sendToBridge() helpers
 *   - Optional API key auth on WebSocket upgrade
 *
 * Usage:
 *   const { createWebSocketManager } = require('@cc-platform/server/websocket');
 *   const wsManager = createWebSocketManager(httpServer, {
 *     apiKey: process.env.API_KEY,
 *     onBridgeMessage: (ws, data) => { ... },
 *     onClientConnect: (ws) => { ws.send(JSON.stringify(initialState)); },
 *     onClientMessage: (ws, data) => { ... },
 *   });
 *   wsManager.broadcastToClients({ type: 'update', ... });
 */

'use strict';

const { WebSocketServer } = require('ws');
const url = require('url');

/**
 * @typedef {Object} WebSocketManagerOptions
 * @property {string}   [apiKey]              API key for bridge auth (empty = no auth)
 * @property {string}   [bridgePath]          URL path prefix for bridge connections (default: '/ws/bridge')
 * @property {number}   [keepaliveMs]         Keepalive interval in ms (default: 25000)
 * @property {number}   [staleTimeoutMs]      Max time without pong before termination (default: 60000)
 * @property {Function} [onBridgeConnect]     Called when a bridge connects: (ws) => void
 * @property {Function} [onBridgeMessage]     Called for each bridge message: (ws, data) => void
 * @property {Function} [onBridgeDisconnect]  Called when a bridge disconnects: (ws) => void
 * @property {Function} [onClientConnect]     Called when a web client connects: (ws) => void
 * @property {Function} [onClientMessage]     Called for each client message: (ws, data) => void
 * @property {Function} [onClientDisconnect]  Called when a web client disconnects: (ws) => void
 */

/**
 * Create a WebSocket manager with bridge and client connection handling.
 *
 * @param {http.Server} server - The HTTP server to attach to
 * @param {WebSocketManagerOptions} opts - Configuration and callbacks
 * @returns {Object} Manager with bridgeClients, webClients, broadcast/send helpers
 */
function createWebSocketManager(server, opts = {}) {
  const bridgeClients = new Set();
  const webClients = new Set();
  const apiKey = opts.apiKey || '';
  const bridgePath = opts.bridgePath || '/ws/bridge';
  const keepaliveMs = opts.keepaliveMs || 25000;
  const staleTimeoutMs = opts.staleTimeoutMs || 60000;

  const wss = new WebSocketServer({ noServer: true });

  // --- Upgrade handler with optional auth ---
  server.on('upgrade', (request, socket, head) => {
    const parsed = url.parse(request.url, true);
    const pathname = parsed.pathname;

    // Auth check on bridge connections
    if (apiKey && pathname.startsWith(bridgePath)) {
      const key = parsed.query.key || '';
      if (key !== apiKey) {
        socket.write('HTTP/1.1 401 Unauthorized\r\n\r\n');
        socket.destroy();
        return;
      }
    }

    wss.handleUpgrade(request, socket, head, (ws) => {
      wss.emit('connection', ws, request);
    });
  });

  // --- Connection routing ---
  wss.on('connection', (ws, request) => {
    const pathname = url.parse(request.url).pathname;

    // Track pong timestamps for keepalive
    ws._lastPong = Date.now();
    ws.on('pong', () => { ws._lastPong = Date.now(); });

    if (pathname.startsWith(bridgePath)) {
      handleBridgeConnection(ws);
    } else {
      handleClientConnection(ws);
    }
  });

  // --- Bridge connection lifecycle ---
  function handleBridgeConnection(ws) {
    bridgeClients.add(ws);
    console.log(`[ws] Bridge connected (${bridgeClients.size} total)`);

    if (opts.onBridgeConnect) {
      try { opts.onBridgeConnect(ws); } catch (e) {
        console.error('[ws] onBridgeConnect error:', e.message);
      }
    }

    ws.on('message', (raw) => {
      try {
        const data = JSON.parse(raw);
        // Handle ping/pong at the protocol layer
        if (data.type === 'ping') {
          ws.send(JSON.stringify({ type: 'pong' }));
          return;
        }
        if (opts.onBridgeMessage) {
          opts.onBridgeMessage(ws, data);
        }
      } catch (e) {
        console.error('[ws] Bridge message parse error:', e.message);
      }
    });

    ws.on('close', () => {
      bridgeClients.delete(ws);
      console.log(`[ws] Bridge disconnected (${bridgeClients.size} remaining)`);
      if (opts.onBridgeDisconnect) {
        try { opts.onBridgeDisconnect(ws); } catch (e) {
          console.error('[ws] onBridgeDisconnect error:', e.message);
        }
      }
    });

    ws.on('error', (err) => {
      console.error('[ws] Bridge error:', err.message);
      bridgeClients.delete(ws);
    });
  }

  // --- Client connection lifecycle ---
  function handleClientConnection(ws) {
    webClients.add(ws);
    console.log(`[ws] Client connected (${webClients.size} total)`);

    if (opts.onClientConnect) {
      try { opts.onClientConnect(ws); } catch (e) {
        console.error('[ws] onClientConnect error:', e.message);
      }
    }

    ws.on('message', (raw) => {
      try {
        const data = JSON.parse(raw);
        if (opts.onClientMessage) {
          opts.onClientMessage(ws, data);
        }
      } catch (e) {
        console.error('[ws] Client message parse error:', e.message);
      }
    });

    ws.on('close', () => {
      webClients.delete(ws);
      console.log(`[ws] Client disconnected (${webClients.size} remaining)`);
      if (opts.onClientDisconnect) {
        try { opts.onClientDisconnect(ws); } catch (e) {
          console.error('[ws] onClientDisconnect error:', e.message);
        }
      }
    });

    ws.on('error', (err) => {
      console.error('[ws] Client error:', err.message);
      webClients.delete(ws);
    });
  }

  // --- Broadcast helpers ---

  /**
   * Send a JSON message to all connected web clients.
   * Silently skips clients that are not in OPEN state.
   */
  function broadcastToClients(data) {
    const message = JSON.stringify(data);
    webClients.forEach((client) => {
      try {
        if (client.readyState === 1) { // WebSocket.OPEN
          client.send(message);
        }
      } catch (e) {
        console.error('[ws] Broadcast error:', e.message);
      }
    });
  }

  /**
   * Send a JSON message to all connected bridge clients.
   * Returns true if at least one bridge received the message.
   */
  function sendToBridge(data) {
    const message = JSON.stringify(data);
    let sent = false;
    bridgeClients.forEach((bridge) => {
      try {
        if (bridge.readyState === 1) {
          bridge.send(message);
          sent = true;
        }
      } catch (e) {
        console.error('[ws] Bridge send error:', e.message);
      }
    });
    return sent;
  }

  // --- Keepalive ---
  const keepaliveInterval = setInterval(() => {
    const now = Date.now();
    const allClients = [...bridgeClients, ...webClients];
    for (const ws of allClients) {
      if (ws._lastPong && (now - ws._lastPong) > staleTimeoutMs) {
        console.log('[ws] Terminating stale connection');
        ws.terminate();
        continue;
      }
      try {
        ws.ping();
      } catch (e) {
        // Ignore ping errors on closing connections
      }
    }
  }, keepaliveMs);

  // Cleanup on server close
  wss.on('close', () => clearInterval(keepaliveInterval));

  return {
    wss,
    bridgeClients,
    webClients,
    broadcastToClients,
    sendToBridge,
    close() {
      clearInterval(keepaliveInterval);
      wss.close();
    },
  };
}

module.exports = { createWebSocketManager };