KefinTweaks/helpers/websocketHelper.js

(function() {
    'use strict';
    
    const LOG = (...args) => console.log('[KefinTweaks WebSocketHelper]', ...args);
    const WARN = (...args) => console.warn('[KefinTweaks WebSocketHelper]', ...args);
    const ERR = (...args) => console.error('[KefinTweaks WebSocketHelper]', ...args);
    
    // Registry of event listeners: MessageType -> array of callbacks
    const listeners = {};
    
    // Track initialization state
    let isInitialized = false;
    let pollingIntervalId = null;
    
    const POLL_INTERVAL_MS = 1500;
    
    /**
     * Returns the ApiClient WebSocket if available (e.g. after user has logged in).
     */
    function getSocket() {
        if (!window.ApiClient) return null;
        return window.ApiClient.webSocket || window.ApiClient._webSocket || null;
    }
    
    /**
     * Initialize WebSocket monitoring by hooking into ApiClient's WebSocket.
     * Attempts once; returns true if hooked, false if socket not yet available.
     */
    function initialize() {
        if (isInitialized) return true;
        
        try {
            const socket = getSocket();
            if (!socket) return false;
            
            // Store original handler if it exists
            const originalHandler = socket.onmessage;
            
            // Hook into onmessage
            socket.onmessage = function(event) {
                try {
                    // Pass it through so Jellyfin still works normally
                    if (originalHandler) {
                        originalHandler.call(this, event);
                    }
                    
                    // Parse the message data
                    const messageData = event.Data || event.data;
                    const data = typeof messageData === 'string' ? JSON.parse(messageData) : messageData;
                    
                    // Get the MessageType
                    const messageType = data.MessageType;
                    
                    if (messageType && listeners[messageType]) {
                        // Fire all callbacks for this message type
                        listeners[messageType].forEach(callback => {
                            try {
                                callback(data);
                            } catch (err) {
                                ERR(`Error in WebSocket listener for ${messageType}:`, err);
                            }
                        });
                    }
                } catch (err) {
                    // Log parse errors but don't break the original handler
                    WARN('WebSocket message parse error:', err);
                }
            };
            
            isInitialized = true;
            LOG('WebSocket monitoring initialized');
            return true;
        } catch (err) {
            ERR('Error initializing WebSocket monitoring:', err);
            return false;
        }
    }
    
    /**
     * Poll until ApiClient WebSocket is available, then initialize once and stop.
     * Safe to call multiple times; only one polling loop runs.
     */
    function startPolling() {
        if (isInitialized) return;
        if (pollingIntervalId != null) return; // already polling
        if (initialize()) return;
        
        pollingIntervalId = setInterval(() => {
            if (isInitialized) {
                clearInterval(pollingIntervalId);
                pollingIntervalId = null;
                return;
            }
            if (initialize()) {
                clearInterval(pollingIntervalId);
                pollingIntervalId = null;
            }
        }, POLL_INTERVAL_MS);
    }
    
    /**
     * Register a callback to listen for a specific WebSocket message type
     * @param {string} messageType - The MessageType to listen for (e.g., 'UserDataChanged', 'PlaybackStopped')
     * @param {Function} callback - Function to call when the message type is received. Receives the parsed message data.
     */
    function listen(messageType, callback) {
        if (typeof messageType !== 'string' || !messageType) {
            ERR('listen() requires a non-empty string messageType');
            return;
        }
        
        if (typeof callback !== 'function') {
            ERR('listen() requires a callback function');
            return;
        }
        
        // Initialize listeners array for this message type if it doesn't exist
        if (!listeners[messageType]) {
            listeners[messageType] = [];
        }

        // Avoid duplicate registrations of the same callback
        if (listeners[messageType].includes(callback)) {
            LOG(`Listener already registered for message type: ${messageType}`);
            if (!isInitialized) {
                startPolling();
            }
            return;
        }
        
        // Add the callback
        listeners[messageType].push(callback);
        LOG(`Registered listener for message type: ${messageType} (${listeners[messageType].length} total listeners)`);
        
        // Ensure we're polling for WebSocket if not yet initialized
        if (!isInitialized) {
            startPolling();
        }
    }
    
    /**
     * Remove a callback registered with listen().
     * @param {string} messageType
     * @param {Function} callback
     */
    function unlisten(messageType, callback) {
        if (!listeners[messageType]) return;
        listeners[messageType] = listeners[messageType].filter((cb) => cb !== callback);
        LOG(`Unregistered listener for message type: ${messageType} (${listeners[messageType].length} remaining)`);
    }
    
    // Expose the API globally
    window.websocketHelper = {
        listen: listen,
        unlisten: unlisten
    };
    
    // Start polling until ApiClient WebSocket is available (e.g. after user logs in)
    startPolling();
})();