lucida-queue/backend/queueManager.ts

import {fetchMetadata} from "./services/metadata";
import {DEFAULT_LUCIDA_OPTIONS, DownloadResult, LucidaOptions, ProcessingQueue, Queue, QueueItem} from "./types/queue";
import Lucida from "./services/lucida";
import * as fs from "node:fs";

const TIMEOUT: number = 120000;
const RETRIES: number = 5;

const STATE_FILE: string = '/data/state.json';

class QueueManager {
    private readonly queue: Queue;
    private readonly processing: ProcessingQueue;
    private readonly history: Queue;

    private lucida: Lucida | null;
    private lucidaOptions: LucidaOptions;

    public constructor() {
        this.queue = [];
        this.processing = [];
        this.history = [];

        this.lucida = null;
        this.lucidaOptions = DEFAULT_LUCIDA_OPTIONS;

        this.loadState();
    }

    private saveState(): void {
        const state = {
            queue: this.processing.map(pi => pi.item).concat(this.queue),
            history: this.history
        };
        fs.writeFileSync(STATE_FILE, JSON.stringify(state, null, 4));
    }

    private loadState(): void {
        if (!fs.existsSync(STATE_FILE)) {
            return;
        }

        const state = JSON.parse(fs.readFileSync(STATE_FILE, 'utf8'));

        console.log('QueueManager: Restoring state:', state);

        this.queue.push(...state.queue);

        state.history.forEach((item: QueueItem) => {
            if (!this.queue.some(q => q.id === item.id)) {
                if (item.result?.success) {
                    // Add successful items to the history
                    this.history.push(item);
                } else {
                    // Add failed items to the queue
                    this.queue.push(item);
                }
            }
        });

        this.processQueue();
    }

    public setLucidaOptions(options: LucidaOptions): void {
        console.log('QueueManager: Setting Lucida options:', options);
        this.lucidaOptions = options;
    }

    public getQueue(): Queue {
        return this.queue;
    }

    public getProcessing(): ProcessingQueue {
        return this.processing;
    }

    public getHistory(): Queue {
        return this.history;
    }

    public get(index: number): QueueItem {
        if (index < 0 || index >= this.queue.length) {
            throw new Error('Index out of bounds');
        }

        return this.queue[index];
    }

    public async add(song: string): Promise<QueueItem> {
        // Check if the URL is already in the queue.
        if (this.queue.some(q => q.id === song)) {
            throw new Error('Song already in queue');
        }

        const item: QueueItem = {
            id: song,
            song: await fetchMetadata(song)
        };
        this.queue.push(item);
        this.saveState();
        this.processQueue();

        return item;
    }

    public async insertAt(song: string, index: number): Promise<QueueItem> {
        // Check if the URL is already in the queue.
        if (this.queue.some(q => q.id === song)) {
            throw new Error('Song already in queue');
        }

        const item: QueueItem = {
            id: song,
            song: await fetchMetadata(song)
        };
        this.queue.splice(index, 0, item);
        this.saveState();
        this.processQueue();

        return item;
    }

    public async remove(song: string): Promise<QueueItem> {
        const index: number = this.queue.findIndex(q => q.id === song);
        if (index === -1) {
            throw new Error('Song not found');
        }

        const item: QueueItem = this.queue[index];
        this.queue.splice(index, 1);
        this.saveState();
        return item;
    }

    public clear(): void {
        this.queue.length = 0;
        this.saveState();
    }

    public move(song: string, to: number): QueueItem {
        const index: number = this.queue.findIndex(q => q.id === song);
        if (index === -1) {
            throw new Error('Song not found');
        }

        const item: QueueItem = this.queue.splice(index, 1)[0];
        this.queue.splice(to, 0, item);
        this.saveState();
        return item;
    }

    public retry(song: string): QueueItem {
        const index: number = this.history.findIndex(q => q.id === song);
        if (index === -1) {
            throw new Error('Song not found');
        }

        const item: QueueItem = this.history.splice(index, 1)[0];
        item.retries = 0;
        this.queue.push(item);
        this.saveState();
        this.processQueue();

        return item;
    }

    public async processQueue(): Promise<void> {
        if (this.lucida !== null) {
            return;
        }

        this.lucida = new Lucida(this.lucidaOptions);
        await this.lucida.construct();

        while (0 < this.queue.length) {
            const item: QueueItem | undefined = this.queue.shift();
            if (!item) {
                console.log('QueueManager: Detected undefined item');
                continue;
            }

            const current: {item: QueueItem, status: string} = {
                item: item,
                status: 'Starting'
            }
            this.processing.push(current);

            try {
                const timeout: number = (item.timeout ?? TIMEOUT) * item.song.trackCount;
                const result: DownloadResult = await this.lucida.download(item.song.url, '/tmp', timeout, current);

                if (!result.success && (item.retries ?? 0) + 1 < RETRIES) {
                    item.retries = (item.retries ?? 0) + 1;
                    item.timeout = (item.timeout ?? TIMEOUT) * 2;
                    item.result = result;
                    this.queue.push(item);
                    this.saveState();
                } else {
                    item.result = result;
                    this.history.push(item);
                    this.saveState();
                }
            } catch (err) {
                item.result = {
                    success: false,
                    error: err instanceof Error ? err.message : 'Unknown error'
                };
                this.history.push(item);
                this.saveState();
            }

            this.processing.splice(this.processing.indexOf(current), 1);
        }

        await this.lucida.destruct();
        this.lucida = null;
    }

    public async forceStop(): Promise<void> {
        this.processing.forEach(item => {
            item.item.result = {
                success: false,
                error: 'Forced stop'
            };
            this.history.push(item.item);
        })

        if (this.lucida === null) {
            return;
        }

        await this.lucida.destruct('Forced stop');
        this.lucida = null;
    }
}

export default new QueueManager();