yt-dlp-webui/server/src/core/Process.ts

import { spawn } from 'child_process';
import { join } from 'path';
import { Readable } from 'stream';
import { ISettings } from '../interfaces/ISettings';
import { availableParams } from '../utils/params';
import Logger from '../utils/BetterLogger';
import { IDownloadFormat, IDownloadMetadata } from '../interfaces/IDownloadMetadata';

const log = Logger.instance;

/**
 * Represents a download process that spawns yt-dlp.
 * @param url - The downlaod url.
 * @param params - The cli arguments passed by the frontend.
 * @param settings - The download settings passed by the frontend.
 */

class Process {
    public readonly url: string;
    public readonly params: Array<string>;
    private settings: ISettings;
    private stdout: Readable;
    private pid: number;
    private metadata?: IDownloadMetadata;
    private exePath = join(__dirname, 'yt-dlp');
    private customFileName?: string;

    private readonly template = `download:
    {
        "eta":%(progress.eta)s, 
        "percentage":"%(progress._percent_str)s",
        "speed":"%(progress._speed_str)s",
        "size":%(info.filesize_approx)s
    }`
        .replace(/\s\s+/g, ' ')
        .replace('\n', '');

    constructor(url: string, params: Array<string>, settings: any, customFileName?: string) {
        this.url = url;
        this.params = params || [];
        this.settings = settings
        this.stdout = undefined;
        this.pid = undefined;
        this.metadata = undefined;
        this.customFileName = customFileName;
    }

    /**
     * function that launch the download process, sets the stdout property and the pid
     * @param callback not yet implemented
     * @returns the process instance
     */
    public async start(callback?: Function): Promise<this> {
        const sanitizedParams = this.params.filter((param: string) => availableParams.includes(param));

        if (this.settings?.download_path) {
            if (this.settings.download_path.charAt(this.settings.download_path.length - 1) !== '/') {
                this.settings.download_path = `${this.settings.download_path}/`
            }
        }

        const ytldp = spawn(this.exePath,
            [
                '-o', `${this.settings?.download_path || 'downloads/'}${this.customFileName || '%(title)s'}.%(ext)s`,
                '--progress-template', this.template,
                '--no-colors',
            ]
                .concat(sanitizedParams)
                .concat((this.settings?.cliArgs ?? []).map(arg => arg.split(' ')).flat())
                .concat([this.url])
        );

        this.pid = ytldp.pid;
        this.stdout = ytldp.stdout;

        log.info('proc', `Spawned a new process, pid: ${this.pid}`)

        if (callback) {
            callback()
        }

        return this;
    }

    /**
     * function used internally by the download process to fetch information, usually thumbnail and title
     * @returns Promise to the lock
     */
    public getMetadata(): Promise<IDownloadMetadata> {
        if (!this.metadata) {
            let stdoutChunks = [];
            const ytdlpInfo = spawn(this.exePath, ['-J', this.url]);

            ytdlpInfo.stdout.on('data', (data) => {
                stdoutChunks.push(data);
            });

            return new Promise((resolve, reject) => {
                ytdlpInfo.on('exit', () => {
                    try {
                        const buffer = Buffer.concat(stdoutChunks);
                        const json = JSON.parse(buffer.toString());
                        const info = {
                            formats: json.formats.map((format: IDownloadFormat) => {
                                return {
                                    format_id: format.format_id ?? '',
                                    format_note: format.format_note ?? '',
                                    fps: format.fps ?? '',
                                    resolution: format.resolution ?? '',
                                    vcodec: format.vcodec ?? '',
                                    acodec: format.acodec ?? '',
                                }
                            }).filter((format: IDownloadFormat) => format.format_note !== 'storyboard'),
                            best: {
                                format_id: json.format_id ?? '',
                                format_note: json.format_note ?? '',
                                fps: json.fps ?? '',
                                resolution: json.resolution ?? '',
                                vcodec: json.vcodec ?? '',
                                acodec: json.acodec ?? '',
                            },
                            thumbnail: json.thumbnail,
                            title: json.title,
                        }
                        resolve(info);
                        this.metadata = info;

                    } catch (e) {
                        reject('failed fetching formats, downloading best available');
                    }
                });
            })
        }
        return new Promise((resolve) => { resolve(this.metadata!) });
    }

    /**
     * function that kills the current process
     */
    async kill() {
        spawn('kill', [String(this.pid)]).on('exit', () => {
            log.info('proc', `Stopped ${this.pid} because SIGKILL`)
        });
    }

    /**
     * pid getter function
     * @returns {number} pid
     */
    getPid(): number {
        if (!this.pid) {
            throw "Process isn't started"
        }
        return this.pid;
    }

    /**
     * stdout getter function
     * @returns {Readable} stdout as stream
     */
    getStdout(): Readable {
        return this.stdout
    }
}

export default Process;