import { NextRequest, NextResponse } from 'next/server';
import { downloadVideo } from '@/lib/youtube';
import { isValidYouTubeUrl } from '@/lib/utils';
import type { DownloadRequest, AudioFormat, VideoFormat, FormatType } from '@/lib/types';
import { createReadStream } from 'fs';
import { stat } from 'fs/promises';
import path from 'path';
import { Readable } from 'stream';

const VIDEO_MIME: Record<VideoFormat, string> = {
  mp4: 'video/mp4',
  webm: 'video/webm',
  mkv: 'video/x-matroska',
  avi: 'video/x-msvideo',
};

const AUDIO_MIME: Record<AudioFormat, string> = {
  mp3: 'audio/mpeg',
  wav: 'audio/wav',
  m4a: 'audio/mp4',
  opus: 'audio/ogg',
};

function getMimeType(formatType: FormatType, format: VideoFormat | AudioFormat): string {
  if (formatType === 'video') {
    return VIDEO_MIME[format as VideoFormat] || 'application/octet-stream';
  }
  return AUDIO_MIME[format as AudioFormat] || 'application/octet-stream';
}

async function resolveDownloadPath(downloadUrl: string) {
  const sanitized = downloadUrl.startsWith('/') ? downloadUrl.slice(1) : downloadUrl;
  const filePath = path.join(process.cwd(), 'public', sanitized);
  const fileInfo = await stat(filePath);
  return { filePath, size: fileInfo.size };
}

export async function POST(request: NextRequest) {
  try {
    const body: DownloadRequest = await request.json();
    const { url, format, formatType } = body;

    if (!url || !format || !formatType) {
      return NextResponse.json(
        { success: false, error: 'Missing required fields' },
        { status: 400 }
      );
    }

    if (!isValidYouTubeUrl(url)) {
      return NextResponse.json(
        { success: false, error: 'Invalid YouTube URL' },
        { status: 400 }
      );
    }

    const result = await downloadVideo(body);

    if (!result.success || !result.downloadUrl || !result.filename) {
      return NextResponse.json(
        { success: false, error: result.error || 'Failed to process download' },
        { status: 500 }
      );
    }

    const { filePath, size } = await resolveDownloadPath(result.downloadUrl);
    const nodeStream = createReadStream(filePath);
    const webStream = Readable.toWeb(nodeStream) as unknown as ReadableStream;

    const headers = new Headers();
    headers.set('Content-Type', getMimeType(formatType, format));
    headers.set('Content-Length', size.toString());
    headers.set('Content-Disposition', `attachment; filename="${result.filename}"`);

    return new NextResponse(webStream, { status: 200, headers });
  } catch (error: any) {
    console.error('Direct download error:', error);
    return NextResponse.json(
      { success: false, error: error.message || 'Internal server error' },
      { status: 500 }
    );
  }
}