const { Client, GatewayIntentBits } = require('discord.js');
const {
    joinVoiceChannel,
    createAudioPlayer,
    createAudioResource,
    AudioPlayerStatus,
    VoiceConnectionStatus,
    entersState,
    StreamType,
} = require('@discordjs/voice');
const { spawn } = require('child_process');
const { PassThrough } = require('stream');
const fs = require('fs');
const path = require('path');
const crypto = require('crypto');

// ─── Config ──────────────────────────────────────────────────────────────────
// SECURITY: never hardcode a bot token. This file previously had one baked in
// as a fallback — that token is now exposed and should be rotated in the
// Discord Developer Portal ASAP. Only read from the environment.
const TOKEN = process.env.DISCORD_TOKEN;
if (!TOKEN) {
    console.error('❌ Missing DISCORD_TOKEN environment variable.');
    process.exit(1);
}
const PREFIX = '!';
const VOLUME = 0.3; // 0.0 - 1.0

// ─── Cache setup ─────────────────────────────────────────────────────────────
const CACHE_DIR = path.join(__dirname, 'cache');
if (!fs.existsSync(CACHE_DIR)) fs.mkdirSync(CACHE_DIR);

// A real encoded opus file is never this small. Anything under this size is
// treated as a corrupt/truncated download rather than a usable cache entry —
// used both when finalizing a fresh download and when reading an existing
// cache file back off disk.
const MIN_VALID_CACHE_BYTES = 4096;

// Startup cleanup pass:
//  - any leftover .tmp files are from downloads that never finished (e.g.
//    the process was killed mid-write) — never valid, always safe to remove.
//  - any .opus file smaller than MIN_VALID_CACHE_BYTES is a corrupt/truncated
//    cache entry that could have been left behind by an older version of
//    this bot (or a crash right at the rename boundary) — remove it so it
//    gets cleanly redownloaded next time it's requested instead of being
//    served as broken audio.
for (const f of fs.readdirSync(CACHE_DIR)) {
    const full = path.join(CACHE_DIR, f);
    if (f.endsWith('.tmp')) {
        try { fs.unlinkSync(full); } catch {}
    } else if (f.endsWith('.opus')) {
        try {
            if (fs.statSync(full).size < MIN_VALID_CACHE_BYTES) {
                fs.unlinkSync(full);
                console.log(`[Cache] Removed corrupt cache file on startup: ${f}`);
            }
        } catch {}
    }
}

// Metadata cache: maps query/url → { title, duration, url }
const META_FILE = path.join(CACHE_DIR, 'metadata.json');
let metaCache = {};
if (fs.existsSync(META_FILE)) {
    try { metaCache = JSON.parse(fs.readFileSync(META_FILE, 'utf8')); }
    catch { metaCache = {}; }
}

function saveMetaCache() {
    // Write via tmp+rename (same pattern as the audio cache) so a process
    // kill mid-write can never leave metadata.json half-written/corrupt
    // JSON that fails to parse on next boot.
    const tmp = META_FILE + '.tmp';
    try {
        fs.writeFileSync(tmp, JSON.stringify(metaCache, null, 2));
        fs.renameSync(tmp, META_FILE);
    } catch (err) {
        console.error('[Meta] Failed to save metadata cache:', err.message);
    }
}

function getAudioCachePath(url) {
    const hash = crypto.createHash('md5').update(url).digest('hex');
    return path.join(CACHE_DIR, `${hash}.opus`);
}

// A cache file only counts as usable if it exists AND is large enough to be
// real audio. Anything smaller gets deleted on sight so a corrupt entry is
// never served twice.
function isCacheFileValid(cachePath) {
    try {
        return fs.statSync(cachePath).size >= MIN_VALID_CACHE_BYTES;
    } catch {
        return false;
    }
}

function evictIfInvalid(cachePath) {
    if (fs.existsSync(cachePath) && !isCacheFileValid(cachePath)) {
        console.warn(`[Cache] Discarding corrupt/empty cache file: ${path.basename(cachePath)}`);
        try { fs.unlinkSync(cachePath); } catch {}
    }
}

// ─── State (per guild) ────────────────────────────────────────────────────────
const guilds = new Map();

function getState(guildId) {
    if (!guilds.has(guildId)) {
        guilds.set(guildId, {
            connection: null,
            player: null,
            queue: [],
            playing: false,
            textChannel: null,
        });
    }
    return guilds.get(guildId);
}

// ─── Download manager ──────────────────────────────────────────────────────
// Downloads are tracked globally (not per-guild), keyed by URL. This means:
//   - If guild A and guild B both request the same song at the same time,
//     only ONE yt-dlp/ffmpeg pair is spawned; both playbacks tap into it.
//   - If a listener disconnects (skip/leave/stop), the download itself is
//     NOT killed — it keeps writing to disk and completes normally, so the
//     cache is populated correctly for next time instead of ending up with
//     a truncated file.
//   - The cache file only ever appears at its final path once fully written
//     AND large enough to be real audio (write to .tmp, size-check, then
//     atomic rename on success).
//
// IMPORTANT — multi-guild fan-out:
// The shared ffmpeg output is forwarded to the cache file and to every
// subscribed guild MANUALLY (not via stream.pipe()), and a subscriber's
// write() return value is ignored. This is deliberate: with .pipe(), Node
// ties the production rate of the single shared stream to whichever
// destination is slowest to drain. One guild with a stalled voice
// connection (or a paused player) would backpressure the shared download
// and stall the cache write *and every other guild listening to the same
// song*. Writing manually means a stuck subscriber can only ever hurt
// itself. Subscribers also swallow their own 'error'/'close' quietly —
// previously a subscriber being destroyed (e.g. on skip) while still
// attached to the shared stream could throw an unhandled 'error', which
// crashes the entire Node process and kills playback in every guild, not
// just the one that skipped.
const activeDownloads = new Map(); // url -> DownloadJob

class DownloadJob {
    constructor(url) {
        this.url = url;
        this.cachePath = getAudioCachePath(url);
        this.tmpPath = this.cachePath + '.tmp';
        this.subscribers = new Set();
        this.failed = false;
        this._start();
    }

    _start() {
        const ytdlp = spawn('yt-dlp', [
            '-f', 'bestaudio',
            '--no-playlist',
            '-o', '-',
            '--', this.url,
        ], { stdio: ['ignore', 'pipe', 'pipe'] });

        const ffmpeg = spawn('ffmpeg', [
            '-hide_banner', '-loglevel', 'error',
            '-i', 'pipe:0',
            '-af', `volume=${VOLUME}`,
            '-c:a', 'libopus',
            '-b:a', '128k',
            '-f', 'opus',
            'pipe:1',
        ], { stdio: ['pipe', 'pipe', 'pipe'] });

        this.ytdlp = ytdlp;
        this.ffmpeg = ffmpeg;

        ytdlp.stderr.on('data', (d) => console.error('[yt-dlp]', d.toString().trim()));
        ffmpeg.stderr.on('data', (d) => console.error('[ffmpeg]', d.toString().trim()));

        // Child-process pipe streams can each emit their own 'error'
        // (e.g. EPIPE when one side of the pipe dies before the other).
        // Without listeners here that's an unhandled exception that
        // crashes the whole bot — this is the fix for downloads breaking
        // whenever multiple guilds/voice channels were involved.
        ytdlp.stdout.on('error', () => {});
        ffmpeg.stdin.on('error', () => {});
        ffmpeg.stdout.on('error', () => {});

        ytdlp.stdout.pipe(ffmpeg.stdin);

        ytdlp.on('error', (err) => this._fail(err));
        ffmpeg.on('error', (err) => this._fail(err));

        ytdlp.on('exit', (code) => {
            if (code !== 0 && code !== null) {
                console.error(`[yt-dlp] exited with code ${code}`);
                try { ffmpeg.stdin.destroy(); } catch {}
            }
        });

        const cacheStream = fs.createWriteStream(this.tmpPath);
        this.cacheStream = cacheStream;
        cacheStream.on('error', (err) => this._fail(err));

        // Manual fan-out — see class-level comment for why this replaces
        // ffmpeg.stdout.pipe(...) to the cache file and every subscriber.
        ffmpeg.stdout.on('data', (chunk) => {
            if (this.failed) return;
            if (!cacheStream.destroyed) cacheStream.write(chunk);
            for (const sub of this.subscribers) {
                if (!sub.destroyed) sub.write(chunk);
            }
        });

        ffmpeg.stdout.on('end', () => {
            if (this.failed) return;
            if (!cacheStream.destroyed) cacheStream.end();
            for (const sub of this.subscribers) {
                if (!sub.destroyed) sub.end();
            }
        });

        ffmpeg.on('close', (code) => {
            if (code !== 0 && code !== null) {
                this._fail(new Error(`ffmpeg exited with code ${code}`));
            }
        });

        cacheStream.on('finish', () => {
            if (this.failed) return;
            this._finalizeCache();
        });
    }

    _finalizeCache() {
        fs.stat(this.tmpPath, (err, stats) => {
            activeDownloads.delete(this.url);
            if (err) {
                console.error('[Cache] Stat failed:', err.message);
                fs.unlink(this.tmpPath, () => {});
                return;
            }
            // Guard against corrupt/empty cache files — e.g. yt-dlp or
            // ffmpeg exited "cleanly" but produced little/no real audio.
            // Never let a file this small become a permanent cache entry.
            if (stats.size < MIN_VALID_CACHE_BYTES) {
                console.error(`[Cache] Discarding suspiciously small file (${stats.size}B): ${this.url}`);
                fs.unlink(this.tmpPath, () => {});
                return;
            }
            fs.rename(this.tmpPath, this.cachePath, (err) => {
                if (err) {
                    console.error('[Cache] Rename failed:', err.message);
                } else {
                    console.log(`[Cache] Saved: ${path.basename(this.cachePath)}`);
                }
            });
        });
    }

    _fail(err) {
        if (this.failed) return;
        this.failed = true;
        console.error(`[Download] Failed for ${this.url}:`, err.message);
        try { this.ytdlp.kill(); } catch {}
        try { this.ffmpeg.kill(); } catch {}
        try { this.cacheStream.destroy(); } catch {}
        fs.unlink(this.tmpPath, () => {}); // never leave a partial file behind
        for (const sub of this.subscribers) {
            if (!sub.destroyed) sub.destroy(err);
        }
        this.subscribers.clear();
        activeDownloads.delete(this.url);
    }

    // Each consumer (a guild's playback) gets its own independent tap on
    // the shared download. Destroying this tap (e.g. because that guild
    // skipped/stopped/left) must ONLY remove that one listener — it must
    // never affect the shared child processes, the cache write, or any
    // other guild's tap.
    subscribe() {
        const sub = new PassThrough();
        this.subscribers.add(sub);
        const cleanup = () => this.subscribers.delete(sub);
        sub.on('close', cleanup);
        sub.on('end', cleanup);
        // Swallow subscriber-side errors so a torn-down voice stream can
        // never surface as an unhandled 'error' and crash the process.
        sub.on('error', cleanup);
        return sub;
    }
}

function getOrStartDownload(url) {
    let job = activeDownloads.get(url);
    if (!job) {
        console.log(`[Download] Starting: ${url}`);
        job = new DownloadJob(url);
        activeDownloads.set(url, job);
    } else {
        console.log(`[Download] Joining in-progress download: ${url}`);
    }
    return job;
}

// ─── Discord client ───────────────────────────────────────────────────────────
const client = new Client({
    intents: [
        GatewayIntentBits.Guilds,
        GatewayIntentBits.GuildVoiceStates,
        GatewayIntentBits.GuildMessages,
        GatewayIntentBits.MessageContent,
    ],
});

client.once('ready', () => {
    console.log(`✅ Logged in as ${client.user.tag}`);
});

client.on('messageCreate', async (message) => {
    if (message.author.bot) return;
    if (!message.content.startsWith(PREFIX)) return;

    const args = message.content.slice(PREFIX.length).trim().split(/ +/);
    const command = args.shift().toLowerCase();

    try {
        if (command === 'play') {
            const query = args.join(' ');
            if (!query) return message.channel.send('❌ Podaj link lub frazę do wyszukania!');
            await cmdPlay(message, query);

        } else if (command === 'fplay') {
            const query = args.join(' ');
            if (!query) return message.channel.send('❌ Podaj link lub frazę do wyszukania!');
            await cmdPlay(message, query, { force: true });

        } else if (command === 'skip') {
            await cmdSkip(message);

        } else if (command === 'queue') {
            await cmdQueue(message);

        } else if (command === 'stop') {
            await cmdStop(message);

        } else if (command === 'leave') {
            await cmdLeave(message);

        } else if (command === 'help') {
            await message.channel.send(
                '🎵 **Komendy:**\n' +
                '`!play <url/szukaj>` – dodaj utwór do kolejki\n' +
                '`!fplay <url/szukaj>` – wymuś świeże pobranie (ignoruje cache)\n' +
                '`!skip` – pomiń aktualny utwór\n' +
                '`!queue` – pokaż kolejkę\n' +
                '`!stop` – zatrzymaj i wyczyść kolejkę\n' +
                '`!leave` – rozłącz bota'
            );
        }
    } catch (err) {
        console.error(`[ERROR] command=${command}`, err);
        message.channel.send(`⚠️ Błąd: ${err.message}`);
    }
});

// ─── Commands ─────────────────────────────────────────────────────────────────

async function cmdPlay(message, query, { force = false } = {}) {
    const voiceChannel = message.member?.voice?.channel;
    if (!voiceChannel) return message.channel.send('❌ Dołącz do kanału głosowego!');

    const state = getState(message.guildId);
    state.textChannel = message.channel;

    if (!state.connection ||
        state.connection.state.status === VoiceConnectionStatus.Destroyed ||
        state.connection.state.status === VoiceConnectionStatus.Disconnected) {

        console.log(`[Voice] Connecting to: ${voiceChannel.name}`);

        state.connection = joinVoiceChannel({
            channelId: voiceChannel.id,
            guildId: message.guildId,
            adapterCreator: message.guild.voiceAdapterCreator,
            selfDeaf: true,
        });

        state.connection.on('stateChange', (o, n) => console.log(`[Voice] ${o.status} → ${n.status}`));
        state.connection.on('error', (err) => console.error('[Voice error]', err.message));

        try {
            await entersState(state.connection, VoiceConnectionStatus.Ready, 30_000);
            console.log('[Voice] Ready!');
        } catch (err) {
            console.error('[Voice] Connect failed:', err.message);
            state.connection.destroy();
            state.connection = null;
            return message.channel.send('❌ Nie udało się połączyć z kanałem głosowym.');
        }
    }

    if (!state.player) {
        state.player = createAudioPlayer();
        state.connection.subscribe(state.player);

        state.player.on(AudioPlayerStatus.Idle, () => {
            state.playing = false;
            playNext(message.guildId);
        });

        state.player.on('error', (err) => {
            console.error('[Player error]', err.message);
            state.playing = false;
            state.textChannel?.send(`⚠️ Błąd odtwarzacza: ${err.message}`);
            playNext(message.guildId);
        });
    }

    const cacheKey = query.toLowerCase().trim();

    // Force play skips the metadata-cache shortcut entirely: always do a
    // fresh yt-dlp lookup, and below, always wipe any existing audio cache
    // for the resolved URL so playback can't come from a stale/corrupt file.
    if (!force && metaCache[cacheKey]) {
        const song = metaCache[cacheKey];
        evictIfInvalid(getAudioCachePath(song.url));
        const audioCached = isCacheFileValid(getAudioCachePath(song.url));
        console.log(`[Meta] HIT: "${query}" → ${song.url} (audio cached: ${audioCached})`);
        state.queue.push(song);
        await message.channel.send(
            `✅ ${audioCached ? '⚡ Błyskawicznie z cache: ' : 'Dodano do kolejki: '}**${song.title}** [${song.duration}]`
        );
        if (!state.playing) playNext(message.guildId);
        return;
    }

    await message.channel.send(force ? `🔁 Wymuszam ponowne pobranie: **${query}**…` : `🔍 Szukam: **${query}**…`);
    const song = await resolveSong(query);

    metaCache[cacheKey] = song;
    metaCache[song.url.toLowerCase()] = song;
    saveMetaCache();
    console.log(`[Meta] Cached: "${query}" → ${song.url}`);

    if (force) {
        const cachePath = getAudioCachePath(song.url);
        if (fs.existsSync(cachePath)) {
            try {
                fs.unlinkSync(cachePath);
                console.log(`[Cache] Force-cleared: ${path.basename(cachePath)}`);
            } catch (err) {
                console.error('[Cache] Force-clear failed:', err.message);
            }
        }
        // If a download for this URL happens to already be in flight
        // (e.g. another guild requested it a moment ago), that download is
        // already fresh, not served from cache — buildAudioResource will
        // simply join it like any other cache miss, so nothing more to do.
    }

    state.queue.push(song);
    await message.channel.send(`✅ Dodano do kolejki: **${song.title}** [${song.duration}]`);

    if (!state.playing) playNext(message.guildId);
}

async function cmdSkip(message) {
    const state = getState(message.guildId);
    if (!state.playing || !state.player) {
        return message.channel.send('❌ Nic nie jest teraz odtwarzane.');
    }
    state.player.stop();
    await message.channel.send('⏭️ Pominięto utwór.');
}

async function cmdQueue(message) {
    const state = getState(message.guildId);
    if (state.queue.length === 0) {
        return message.channel.send('📭 Kolejka jest pusta.');
    }
    const list = state.queue
        .map((s, i) => `${i + 1}. **${s.title}** [${s.duration}]`)
        .join('\n');
    await message.channel.send(`📜 **Kolejka:**\n${list}`);
}

async function cmdStop(message) {
    const state = getState(message.guildId);
    state.queue = [];
    state.player?.stop();
    state.playing = false;
    await message.channel.send('⏹️ Zatrzymano i wyczyszczono kolejkę.');
}

async function cmdLeave(message) {
    const state = getState(message.guildId);
    state.queue = [];
    state.player?.stop();
    state.playing = false;
    state.connection?.destroy();
    state.connection = null;
    state.player = null;
    await message.channel.send('👋 Rozłączono.');
}

// ─── Playback ─────────────────────────────────────────────────────────────────

function playNext(guildId) {
    const state = getState(guildId);
    if (state.queue.length === 0) {
        state.playing = false;
        state.textChannel?.send('📭 Kolejka zakończona.');
        return;
    }

    const song = state.queue.shift();
    state.playing = true;
    state.textChannel?.send(`▶️ Odtwarzam: **${song.title}** [${song.duration}]`);

    try {
        const resource = buildAudioResource(song.url);
        state.player.play(resource);
    } catch (err) {
        console.error('[playNext error]', err);
        state.textChannel?.send(`⚠️ Nie można odtworzyć: ${err.message}`);
        state.playing = false;
        playNext(guildId);
    }
}

// ─── Audio resource with caching ─────────────────────────────────────────────

function buildAudioResource(url) {
    const cachePath = getAudioCachePath(url);

    // Cache HIT — instant play from disk, but only if the file is actually
    // large enough to be real audio. Because writes are atomic (tmp file +
    // size-check + rename), a file should only ever exist here if it's
    // complete and valid — this check is a last-line-of-defense safety net
    // in case an older/corrupt file is still sitting on disk.
    if (fs.existsSync(cachePath)) {
        if (isCacheFileValid(cachePath)) {
            console.log(`[Cache] HIT: ${path.basename(cachePath)}`);
            return createAudioResource(fs.createReadStream(cachePath), {
                inputType: StreamType.OggOpus,
            });
        }
        console.warn(`[Cache] Corrupt/empty cache file, discarding and redownloading: ${path.basename(cachePath)}`);
        try { fs.unlinkSync(cachePath); } catch {}
    }

    // Cache MISS — join (or start) a shared download for this URL.
    // Skipping/stopping playback later will NOT interrupt this download;
    // it keeps running and completes the cache file in the background.
    const job = getOrStartDownload(url);
    const stream = job.subscribe();

    return createAudioResource(stream, {
        inputType: StreamType.OggOpus,
    });
}

// ─── yt-dlp metadata fetch ────────────────────────────────────────────────────

// Dedupe concurrent identical metadata lookups too (e.g. two people paste
// the same fresh link in the same second) so we don't spawn yt-dlp twice.
const pendingMetadata = new Map(); // cacheKey/query -> Promise

function resolveSong(query) {
    if (pendingMetadata.has(query)) {
        return pendingMetadata.get(query);
    }

    const isUrl = query.startsWith('http://') || query.startsWith('https://');
    const ytQuery = isUrl ? query : `ytsearch1:${query}`;

    const promise = new Promise((resolve, reject) => {
        const proc = spawn('yt-dlp', [
            '--no-playlist',
            '--print', '%(title)s|||%(duration_string)s|||%(webpage_url)s',
            '--', ytQuery,
        ]);

        let stdout = '';
        let stderr = '';
        proc.stdout.on('data', (d) => stdout += d.toString());
        proc.stderr.on('data', (d) => stderr += d.toString());

        proc.on('close', (code) => {
            const line = stdout.split('\n').find(l => l.includes('|||')) || '';
            const parts = line.split('|||');
            if (parts.length >= 3) {
                resolve({
                    title:    parts[0].trim(),
                    duration: parts[1].trim(),
                    url:      parts[2].trim(),
                });
            } else if (code !== 0) {
                reject(new Error(stderr.trim() || `yt-dlp exited with code ${code}`));
            } else {
                resolve({ title: query, duration: '?:??', url: query });
            }
        });
    }).finally(() => {
        pendingMetadata.delete(query);
    });

    pendingMetadata.set(query, promise);
    return promise;
}

// ─── Start ────────────────────────────────────────────────────────────────────
client.login(TOKEN);