QueueCube/backend/src/MediaPlayer.ts

import { ChildProcess, spawn } from "child_process";
import { Socket } from "net";
import { WebSocket } from "ws";
import { getLinkPreview } from "link-preview-js";
import { PlaylistItem, LinkMetadata } from './types';
import { FavoritesStore } from "./FavoritesStore";

interface PendingCommand {
    resolve: (value: any) => void;
    reject: (reason: any) => void;
}

enum UserEvent {
    PlaylistUpdate      = "playlist_update",
    NowPlayingUpdate    = "now_playing_update",
    VolumeUpdate        = "volume_update",
    FavoritesUpdate     = "favorites_update",
    MetadataUpdate      = "metadata_update",
    MPDUpdate           = "mpd_update",
}

export class MediaPlayer { 
    private playerProcess: ChildProcess;
    private socket: Socket;
    private eventSubscribers: WebSocket[] = [];
    private favoritesStore: FavoritesStore;

    private pendingCommands: Map<number, PendingCommand> = new Map();
    private requestId: number = 1;
    private dataBuffer: string = '';
    private metadata: Map<string, LinkMetadata> = new Map();

    constructor() {
        const socketFilename = Math.random().toString(36).substring(2, 10);
        const socketPath = `/tmp/mpv-${socketFilename}`;

        console.log("Starting player process");
        this.playerProcess = spawn("mpv", [
            "--no-video", 
            "--no-terminal",
            "--idle=yes",
            "--input-ipc-server=" + socketPath
        ]);

        this.socket = new Socket();

        this.playerProcess.on("spawn", () => {
            console.log(`Player process spawned, opening socket @ ${socketPath}`);
            setTimeout(() => {
                this.connectToSocket(socketPath);
            }, 500);
        });

        this.favoritesStore = new FavoritesStore();
        this.favoritesStore.onFavoritesChanged = (favorites) => {
            this.handleEvent(UserEvent.FavoritesUpdate, { favorites });
        };
    }

    public async getPlaylist(): Promise<PlaylistItem[]> {
        return this.writeCommand("get_property", ["playlist"])
            .then((response) => {
                // Enhance playlist items with metadata
                const playlist = response.data as PlaylistItem[];
                return playlist.map((item: PlaylistItem) => ({
                    ...item,
                    metadata: this.metadata.get(item.filename) || {}
                }));
            });
    }

    public async getNowPlaying(): Promise<PlaylistItem> {
        const playlist = await this.getPlaylist();
        const currentlyPlayingSong = playlist.find((item: PlaylistItem) => item.current);
        const fetchMediaTitle = async (): Promise<string> => { 
            return (await this.writeCommand("get_property", ["media-title"])).data;
        };

        if (currentlyPlayingSong !== undefined) {
            // Use media title if we don't have a title
            if (currentlyPlayingSong.title === undefined && currentlyPlayingSong.metadata?.title === undefined) {
                return {
                    ...currentlyPlayingSong,
                    title: await fetchMediaTitle()
                };
            }

            return currentlyPlayingSong;
        } 

        const mediaTitle = await fetchMediaTitle();
        return {
            id: 0,
            filename: mediaTitle,
            title: mediaTitle
        };
    }

    public async getCurrentFile(): Promise<string> {
        return this.writeCommand("get_property", ["stream-open-filename"])
            .then((response) => {
                return response.data;
            });
    }

    public async getPauseState(): Promise<boolean> {
        return this.writeCommand("get_property", ["pause"])
            .then((response) => {
                return response.data;
            });
    }

    public async getVolume(): Promise<number> {
        return this.writeCommand("get_property", ["volume"])
            .then((response) => {
                return response.data;
            });
    }

    public async getIdle(): Promise<boolean> {
        return this.writeCommand("get_property", ["idle"])
            .then((response) => {
                return response.data;
            });
    }

    public async append(url: string) {
        await this.loadFile(url, "append-play");
    }

    public async replace(url: string) {
        await this.loadFile(url, "replace");
    }

    public async play() {
        return this.modify(UserEvent.NowPlayingUpdate, () => this.writeCommand("set_property", ["pause", false]));
    }

    public async pause() {
        return this.modify(UserEvent.NowPlayingUpdate, () => this.writeCommand("set_property", ["pause", true]));
    }

    public async skip() {
        return this.modify(UserEvent.PlaylistUpdate, () => this.writeCommand("playlist-next", []));
    }

    public async skipTo(index: number) {
        return this.modify(UserEvent.PlaylistUpdate, () => this.writeCommand("playlist-play-index", [index]));
    }

    public async previous() {
        return this.modify(UserEvent.PlaylistUpdate, () => this.writeCommand("playlist-prev", []));
    }

    public async deletePlaylistItem(index: number) {
        return this.modify(UserEvent.PlaylistUpdate, () => this.writeCommand("playlist-remove", [index]));
    }
        
    public async setVolume(volume: number) {
        return this.modify(UserEvent.VolumeUpdate, () => this.writeCommand("set_property", ["volume", volume]));
    }

    public subscribe(ws: WebSocket) {
        this.eventSubscribers.push(ws);
    }

    public unsubscribe(ws: WebSocket) {
        this.eventSubscribers = this.eventSubscribers.filter(subscriber => subscriber !== ws);
    }

    public async getFavorites(): Promise<PlaylistItem[]> {
        return this.favoritesStore.getFavorites();
    }

    public async addFavorite(item: PlaylistItem) {
        return this.favoritesStore.addFavorite(item);
    }

    public async removeFavorite(filename: string) {
        return this.favoritesStore.removeFavorite(filename);
    }

    public async clearFavorites() {
        return this.favoritesStore.clearFavorites();
    }

    private async loadFile(url: string, mode: string) {
        this.modify(UserEvent.PlaylistUpdate, () => this.writeCommand("loadfile", [url, mode]));

        this.fetchMetadataAndNotify(url).catch(error => {
            console.warn(`Failed to fetch metadata for ${url}:`, error);
        });
    }

    private async modify<T>(event: UserEvent, func: () => Promise<T>): Promise<T> {
        return func()
            .then((result) => {
                // Notify all subscribers
                this.handleEvent(event, {});
                return result;
        });
    }
    
    private async writeCommand(command: string, args: any[]): Promise<any> {
        return new Promise((resolve, reject) => {
            const id = this.requestId++;
            
            const commandObject = JSON.stringify({
                command: [command, ...args],
                request_id: id
            });

            this.pendingCommands.set(id, { resolve, reject });
            this.socket.write(commandObject + '\n');

            // Add timeout to prevent hanging promises
            setTimeout(() => {
                if (this.pendingCommands.has(id)) {
                    const pending = this.pendingCommands.get(id);
                    if (pending) {
                        pending.reject(new Error('Command timed out'));
                        this.pendingCommands.delete(id);
                    }
                }
            }, 5000);
        });
    }

    private async fetchMetadataAndNotify(url: string) {
        try {
            console.log("Fetching metadata for " + url);
            const metadata = await getLinkPreview(url);
            this.metadata.set(url, {
                title: (metadata as any)?.title,
                description: (metadata as any)?.description,
                siteName: (metadata as any)?.siteName,
            });

            console.log("Metadata fetched for " + url);
            console.log(this.metadata.get(url));
            
            // Notify clients that metadata has been updated
            this.handleEvent(UserEvent.MetadataUpdate, {
                url,
                metadata: this.metadata.get(url)
            });
        } catch (error) {
            throw error;
        }
    }

    private connectToSocket(path: string) {
        this.socket.connect(path);
        this.socket.on("data", data => this.receiveData(data.toString()));
    }

    private handleEvent(event: string, data: any) {
        console.log("Event [" + event + "]: " + JSON.stringify(data, null, 2));

        // Notify all subscribers
        this.eventSubscribers.forEach(subscriber => {
            subscriber.send(JSON.stringify({ event, data }));
        });
    }

    private receiveData(data: string) {
        this.dataBuffer += data;

        const lines = this.dataBuffer.split('\n');

        // Keep last incomplete line in the buffer
        this.dataBuffer = lines.pop() || '';

        for (const line of lines) {
            if (line.trim().length > 0) {
                try {
                    const response = JSON.parse(line);
                    if (response.request_id) {
                        const pending = this.pendingCommands.get(response.request_id);
                        if (pending) {
                            pending.resolve(response);
                            this.pendingCommands.delete(response.request_id);
                        }
                    } else if (response.event) {
                        this.handleEvent(UserEvent.MPDUpdate, response);
                    } else {
                        console.log(response);
                    }
                } catch (error) {
                    console.error('Error parsing JSON:', error);
                }
            }
        }
    }
}