tubearr/src/server/routes/adhoc-download.ts

import { type FastifyInstance } from 'fastify';
import { execYtDlp, parseSingleJson, YtDlpError } from '../../sources/yt-dlp';
import type { Platform, ContentType } from '../../types/index';

// ── Types ──

interface PreviewRequestBody {
  url: string;
}

export interface UrlPreviewResponse {
  title: string;
  thumbnail: string | null;
  duration: number | null;
  platform: string;
  channelName: string | null;
  contentType: ContentType;
  platformContentId: string;
  url: string;
}

// ── Helpers ──

const URL_PATTERN = /^https?:\/\/.+/i;

/**
 * Infer platform from yt-dlp extractor key / webpage_url.
 */
function inferPlatform(extractorKey: string, url: string): Platform {
  const key = (extractorKey || '').toLowerCase();
  if (key.includes('youtube') || url.includes('youtube.com') || url.includes('youtu.be')) {
    return 'youtube';
  }
  if (key.includes('soundcloud') || url.includes('soundcloud.com')) {
    return 'soundcloud';
  }
  return 'generic';
}

/**
 * Infer content type from yt-dlp metadata.
 */
function inferContentType(info: Record<string, unknown>): ContentType {
  const isLive = info.is_live === true || info.was_live === true;
  if (isLive) return 'livestream';

  // SoundCloud and audio-only extractors
  const extractor = String(info.extractor_key || '').toLowerCase();
  if (extractor.includes('soundcloud')) return 'audio';

  // Fallback: if there's no video codec, it's audio
  const vcodec = String(info.vcodec || 'none');
  if (vcodec === 'none') return 'audio';

  return 'video';
}

/**
 * Map raw yt-dlp --dump-json output to a preview response.
 */
function mapToPreview(info: Record<string, unknown>, originalUrl: string): UrlPreviewResponse {
  const extractorKey = String(info.extractor_key || info.extractor || '');
  const webpageUrl = String(info.webpage_url || info.url || originalUrl);

  return {
    title: String(info.title || info.fulltitle || 'Untitled'),
    thumbnail: (info.thumbnail as string) || null,
    duration: typeof info.duration === 'number' ? Math.round(info.duration) : null,
    platform: inferPlatform(extractorKey, webpageUrl),
    channelName: (info.channel as string) || (info.uploader as string) || null,
    contentType: inferContentType(info),
    platformContentId: String(info.id || ''),
    url: webpageUrl,
  };
}

// ── Route Plugin ──

/**
 * Ad-hoc download route plugin.
 *
 * Registers:
 *   POST /api/v1/download/url/preview — resolve metadata for a URL via yt-dlp
 */
export async function adhocDownloadRoutes(fastify: FastifyInstance): Promise<void> {
  // ── POST /api/v1/download/url/preview ──

  fastify.post<{ Body: PreviewRequestBody }>(
    '/api/v1/download/url/preview',
    {
      schema: {
        body: {
          type: 'object',
          required: ['url'],
          properties: {
            url: { type: 'string' },
          },
        },
      },
    },
    async (request, reply) => {
      const { url } = request.body;

      // Validate URL format
      if (!url || !URL_PATTERN.test(url)) {
        return reply.status(400).send({
          statusCode: 400,
          error: 'Bad Request',
          message: 'A valid HTTP or HTTPS URL is required',
        });
      }

      try {
        // Use --dump-json to get metadata without downloading
        const result = await execYtDlp(
          ['--dump-json', '--no-download', '--no-playlist', url],
          { timeout: 30_000 },
        );

        const info = parseSingleJson(result.stdout) as Record<string, unknown>;
        const preview = mapToPreview(info, url);

        return reply.status(200).send(preview);
      } catch (err) {
        if (err instanceof YtDlpError) {
          request.log.warn(
            { url, category: err.category, exitCode: err.exitCode },
            'URL preview failed: %s',
            err.message,
          );

          // Map error categories to HTTP status codes
          if (err.isRateLimit) {
            return reply.status(429).send({
              statusCode: 429,
              error: 'Too Many Requests',
              message: 'Rate limited by platform. Try again later.',
            });
          }

          if (err.category === 'private' || err.category === 'geo_blocked' || err.category === 'copyright') {
            return reply.status(422).send({
              statusCode: 422,
              error: 'Unprocessable Entity',
              message: `Content is not accessible: ${err.category.replace('_', ' ')}`,
            });
          }

          if (err.category === 'network') {
            return reply.status(502).send({
              statusCode: 502,
              error: 'Bad Gateway',
              message: 'Failed to reach the content platform. Check the URL and try again.',
            });
          }

          // Generic yt-dlp failure — likely an unsupported URL or invalid content
          return reply.status(422).send({
            statusCode: 422,
            error: 'Unprocessable Entity',
            message: 'Could not resolve metadata for this URL. Verify it points to a supported video or audio page.',
          });
        }

        // Unexpected errors
        request.log.error({ err, url }, 'Unexpected error during URL preview');
        return reply.status(500).send({
          statusCode: 500,
          error: 'Internal Server Error',
          message: 'An unexpected error occurred while resolving URL metadata',
        });
      }
    },
  );
}