const http = require('http');
const https = require('https');
const fs = require('fs');
const path = require('path');
const url = require('url');
const { spawn } = require('child_process');

const DATA_DIR = process.env.DATA_DIR || './data';
const MUSIC_DIR = process.env.MUSIC_DIR || './music';
const PORT = process.env.PORT || 3001;

// Ensure directories exist
if (!fs.existsSync(DATA_DIR)) {
    fs.mkdirSync(DATA_DIR, { recursive: true });
}
if (!fs.existsSync(MUSIC_DIR)) {
    fs.mkdirSync(MUSIC_DIR, { recursive: true });
}

const server = http.createServer((req, res) => {
    // CORS headers
    res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
    res.setHeader('Access-Control-Allow-Headers', 'Content-Type');

    if (req.method === 'OPTIONS') {
        res.writeHead(204);
        res.end();
        return;
    }

    const parsedUrl = url.parse(req.url, true);
    const pathname = parsedUrl.pathname;
    
    // Path format: /kv/:key?token=...
    const match = pathname.match(/^\/kv\/([a-zA-Z0-9_-]+)$/);
    
    if (!match) {
        res.writeHead(404, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ error: 'Invalid path' }));
        return;
    }

    const key = match[1];
    const token = parsedUrl.query.token;

    if (!token) {
        res.writeHead(401, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ error: 'Token required' }));
        return;
    }

    // Simple file-based storage: data/{token}_{key}.json
    // Using token in filename ensures isolation between users
    const safeToken = token.replace(/[^a-zA-Z0-9]/g, '');
    const filePath = path.join(DATA_DIR, `${safeToken}_${key}.json`);

    if (req.method === 'GET') {
        if (fs.existsSync(filePath)) {
            const data = fs.readFileSync(filePath);
            res.writeHead(200, { 'Content-Type': 'application/json' });
            res.end(data);
        } else {
            res.writeHead(200, { 'Content-Type': 'application/json' });
            res.end(JSON.stringify(null)); // Key not found returns null
        }
    } else if (req.method === 'POST') {
        let body = '';
        req.on('data', chunk => body += chunk.toString());
        req.on('end', () => {
            try {
                // Validate JSON
                const data = JSON.parse(body);
                fs.writeFileSync(filePath, body);

                // Try to handle background download if data looks like a song list
                // Execute in background
                tryDownloadSongs(data).catch(err => console.error('Download Manager Error:', err));

                res.writeHead(200, { 'Content-Type': 'application/json' });
                res.end(JSON.stringify({ success: true }));
            } catch (e) {
                console.error(e);
                res.writeHead(400, { 'Content-Type': 'application/json' });
                res.end(JSON.stringify({ error: 'Invalid JSON' }));
            }
        });
    } else {
        res.writeHead(405);
        res.end();
    }
});

server.listen(PORT, () => {
    console.log(`Sync Server running on port ${PORT}`);
    console.log(`Data directory: ${DATA_DIR}`);
    console.log(`Music directory: ${MUSIC_DIR}`);
});

// --- Download Manager ---

async function tryDownloadSongs(data) {
    // Detect if data is a song list
    // Must be an array, and items must have id, name, and (source or platform)
    if (!Array.isArray(data) || data.length === 0) return;
    
    const isSongList = data.every(item =>
        item &&
        typeof item === 'object' &&
        item.id &&
        item.name &&
        (item.source || item.platform)
    );

    if (!isSongList) return;

    console.log(`[Sync] Detected song list. Starting background processing for ${data.length} songs...`);
    
    for (const song of data) {
        try {
            await processSong(song);
        } catch (e) {
            console.error(`[Sync] Error processing ${song.name}:`, e.message);
        }
    }
}

function processSong(song) {
    return new Promise((resolve) => {
        // Sanitize filename with proper encoding handling
        const sanitizeFilename = (str) => {
            if (!str) return 'unknown';
            // Normalize Unicode (NFC) to ensure consistent encoding
            const normalized = str.normalize('NFC');
            // Replace Windows illegal characters and control characters
            return normalized
                .replace(/[\\/:*?"<>|\x00-\x1f\x7f]/g, '_')
                .trim()
                .substring(0, 200); // Limit length to avoid path too long errors
        };

        const safeName = sanitizeFilename(song.name);
        const safeArtist = sanitizeFilename(song.artist);
        const source = song.platform || song.source;
        // Filename: Artist - Name [source_id]
        const baseName = `${safeArtist} - ${safeName} [${source}_${song.id}]`;
        
        // Check if file exists (fuzzy match for extension)
        try {
            const files = fs.readdirSync(MUSIC_DIR);
            const exists = files.some(f => {
                // 1. Exact Match: Artist - Name [source_id].ext
                if (f.startsWith(baseName)) return true;
                
                // 2. Simple Format: Artist - Name.ext
                if (f.startsWith(`${safeArtist} - ${safeName}.`)) return true;
                
                // 3. Simple Format w/o Artist: Name.ext
                if (f.startsWith(`${safeName}.`)) return true;

                // 4. Match prefix ignoring ID: Artist - Name [
                if (f.startsWith(`${safeArtist} - ${safeName} [`)) return true;

                return false;
            });

            if (exists) {
                // console.log(`[Sync] Skipped (Exists): ${song.name}`);
                resolve();
                return;
            }
        } catch (e) {
            console.error('Error reading music dir:', e);
        }

        // Get URL (prefer FLAC)
        const apiUrl = `https://music-dl.sayqz.com/api/?source=${source}&id=${song.id}&type=url&br=flac`;
        
        https.get(apiUrl, (res) => {
            const handleDownload = (url) => {
                let ext = 'mp3';
                if (url.includes('.flac')) ext = 'flac';
                else if (url.includes('.m4a')) ext = 'm4a';
                else if (url.includes('.ogg')) ext = 'ogg';
                else if (url.includes('.wav')) ext = 'wav';

                const tempFile = path.join(MUSIC_DIR, `temp_${Date.now()}_${song.id}.${ext}`);
                const finalFile = path.join(MUSIC_DIR, `${baseName}.${ext}`);

                downloadFile(url, tempFile)
                    .then(async () => {
                        try {
                            // Try to download cover image
                            let coverPath = null;
                            try {
                                const coverUrl = `https://music-dl.sayqz.com/api/?source=${source}&id=${song.id}&type=pic`;
                                coverPath = path.join(MUSIC_DIR, `temp_cover_${Date.now()}_${song.id}.jpg`);
                                await downloadFile(coverUrl, coverPath);
                            } catch (e) {
                                console.warn(`[Sync] Failed to download cover for ${song.name}:`, e.message);
                            }

                            // Write Metadata (Title, Artist, Album, Cover)
                            await writeMetadata(tempFile, finalFile, {
                                title: song.name,
                                artist: song.artist,
                                album: song.album || song.name, // Fallback to song name if album is missing
                                cover: coverPath
                            });

                            console.log(`[Sync] Downloaded & Tagged: ${baseName}.${ext}`);
                            
                            // Cleanup temp files
                            if (fs.existsSync(tempFile)) fs.unlinkSync(tempFile);
                            if (coverPath && fs.existsSync(coverPath)) fs.unlinkSync(coverPath);
                        } catch (err) {
                            console.error(`[Sync] Metadata Error for ${song.name}:`, err.message);
                            // Fallback: Just rename temp to final
                            if (!fs.existsSync(finalFile)) {
                                fs.renameSync(tempFile, finalFile);
                            }
                        }
                        resolve();
                    })
                    .catch(err => {
                        console.error(`[Sync] Download failed for ${song.name}:`, err.message);
                        if (fs.existsSync(tempFile)) fs.unlinkSync(tempFile);
                        resolve();
                    });
            };

            // Handle 302 Redirect (Standard API behavior)
            if (res.statusCode === 302 && res.headers.location) {
                res.resume();
                handleDownload(res.headers.location);
                return;
            }

            if (res.statusCode !== 200) {
                console.error(`[Sync] API Request Failed for ${song.name}: Status ${res.statusCode}`);
                res.resume(); // Consume response data to free up memory
                resolve();
                return;
            }

            let data = '';
            res.on('data', chunk => data += chunk);
            res.on('end', () => {
                try {
                    const apiRes = JSON.parse(data);
                    const url = apiRes.url;
                    
                    if (!url) {
                        console.log(`[Sync] No URL found for ${song.name}`);
                        resolve();
                        return;
                    }
                    handleDownload(url);
                } catch (e) {
                    console.error('[Sync] API Parse Error:', e);
                    console.error('[Sync] Raw Response:', data);
                    resolve();
                }
            });
        }).on('error', (e) => {
            console.error(`[Sync] API Request Error: ${e.message}`);
            resolve();
        });
    });
}

function downloadFile(url, dest) {
    return new Promise((resolve, reject) => {
        const protocol = url.startsWith('https') ? https : http;
        protocol.get(url, (res) => {
            // Handle Redirects
            if (res.statusCode >= 300 && res.statusCode < 400 && res.headers.location) {
                downloadFile(res.headers.location, dest).then(resolve).catch(reject);
                return;
            }
            if (res.statusCode !== 200) {
                reject(new Error(`Status code ${res.statusCode}`));
                return;
            }
            const file = fs.createWriteStream(dest);
            res.pipe(file);
            file.on('finish', () => {
                file.close(() => resolve());
            });
            file.on('error', (err) => {
                fs.unlink(dest, () => {});
                reject(err);
            });
        }).on('error', (err) => {
            fs.unlink(dest, () => {});
            reject(err);
        });
    });
}

function writeMetadata(inputPath, outputPath, metadata) {
    return new Promise((resolve, reject) => {
        const args = ['-i', inputPath];

        // Add cover input if available
        if (metadata.cover) {
            args.push('-i', metadata.cover);
            args.push('-map', '0:0'); // Map audio from first input
            args.push('-map', '1:0'); // Map image from second input
            args.push('-c:v', 'mjpeg'); // Convert cover to jpeg
            
            // ID3v2 metadata for MP3 (cover art)
            if (outputPath.endsWith('.mp3')) {
                 args.push('-id3v2_version', '3');
                 args.push('-metadata:s:v', 'title="Album cover"');
                 args.push('-metadata:s:v', 'comment="Cover (front)"');
            } else if (outputPath.endsWith('.flac')) {
                args.push('-disposition:v', 'attached_pic');
            }
        } else {
             args.push('-c', 'copy');
        }

        // Add metadata tags
        args.push(
            '-metadata', `title=${metadata.title}`,
            '-metadata', `artist=${metadata.artist}`,
            '-metadata', `album=${metadata.album}`
        );

        // Required for FLAC + Cover to work properly without re-encoding audio
        if (outputPath.endsWith('.flac') && metadata.cover) {
             args.push('-c:a', 'copy');
        } else if (outputPath.endsWith('.mp3') && metadata.cover) {
             args.push('-c:a', 'copy');
        }

        args.push('-y', outputPath);

        const ffmpeg = spawn('ffmpeg', args);
        
        // Capture stderr for debugging
        let stderr = '';
        ffmpeg.stderr.on('data', (data) => {
            stderr += data.toString();
        });

        ffmpeg.on('close', (code) => {
            if (code === 0) resolve();
            else {
                console.error(`FFmpeg Error Output: ${stderr}`);
                reject(new Error(`FFmpeg exited with code ${code}`));
            }
        });

        ffmpeg.on('error', (err) => {
            reject(err);
        });
    });
}