import { DOWNLOAD_PATH } from '$env/static/private';
import { redirect } from '@sveltejs/kit';
import ytdl from 'youtube-dl-exec';

import { json, error } from '@sveltejs/kit';
import type { RequestHandler } from './$types';
import { spawn } from 'child_process';


/**
 * Fetch YouTube metadata (title, uploader/artist)
 */
async function getYouTubeMetadata(link: string) {
    return await ytdl(link, {
        dumpSingleJson: true,
        noCheckCertificates: true,
        noWarnings: true,
        preferFreeFormats: true
    });
}

/**
 * Streams the YouTube video/audio using youtube-dl-exec
 */
function streamYouTube(link: string, format: string): ReadableStream<Uint8Array> {
	return new ReadableStream({
		start(controller) {
			const args = [
				'-o',
				'-',
				format === 'mp3' ? '--embed-metadata' : '',
				'--format',
				format === 'mp3' ? 'bestaudio' : 'best',
				'--audio-format',
				format === 'mp3' ? 'mp3' : '',
				'--no-playlist'
			].filter(Boolean);

			const process = spawn('yt-dlp', [...args, link], { stdio: ['ignore', 'pipe', 'ignore'] });

			process.stdout.on('data', (chunk) => controller.enqueue(chunk));
			process.stdout.on('end', () => controller.close());
			process.stdout.on('error', (err) => {
				console.error('Stream error:', err);
				controller.error(err);
			});
		}
	});
}
/**
 * Sanitize filename by removing unsafe characters
 */
function sanitizeFilename(name: string): string {
    return name.replace(/[\/:*?"<>|]/g, '').trim();
}

export const GET: RequestHandler = async ({ url }) => {
    // Get query params
    const link = url.searchParams.get('link');
    const format = url.searchParams.get('format'); // mp3, mp4
    const source = url.searchParams.get('source'); // youtube or spotify

    // Validate input
    if (!link || !format || !source) {
        throw error(400, 'Missing required query parameters: link, format, or source');
    }
    
    if (source !== 'youtube') {
        throw error(400, 'Currently, only YouTube is supported');
    }

    try {
        // Fetch metadata for filename
        const metadata = await getYouTubeMetadata(link);
        const { title, uploader } = metadata;
        const safeTitle = sanitizeFilename(`${uploader} - ${title}`);
        const filename = `${safeTitle}.${format}`;

		console.log(filename)
        // Stream video/audio
        return new Response(streamYouTube(link, format), {
            headers: {
                'Content-Type': format === 'mp3' ? 'audio/mpeg' : 'video/mp4',
                'Content-Disposition': `attachment; filename="${filename}"`
            }
        });
    } catch (err) {
        console.error('Error fetching metadata:', err);
        throw error(500, 'Failed to fetch video metadata');
    }
};