import path from "node:path";
import { readFile } from "node:fs/promises";
import type { Paths } from "../lib/paths";
import type { ChannelConfig } from "../lib/channelConfig";
import { defaultWebpageUrl, detectPlatform } from "../lib/platform";
import { extractVideoId } from "../ytdlp/runYtdlp";

async function readPlaylistUrls(playlistPath: string): Promise<string[]> {
  let raw: string;
  try {
    raw = await readFile(playlistPath, "utf8");
  } catch {
    return [];
  }
  return raw
    .split("\n")
    .map((s) => s.trim())
    .filter(Boolean);
}

export async function findVideoSourceUrl(
  paths: Paths,
  slug: string,
  videoId: string,
  config?: ChannelConfig,
): Promise<string | null> {
  const channelRoot = path.join(paths.channelsDir, slug);
  const metaPath = path.join(channelRoot, "data", videoId, "metadata.info.json");
  try {
    const raw = await readFile(metaPath, "utf8");
    const parsed = JSON.parse(raw);
    if (typeof parsed?.webpage_url === "string" && parsed.webpage_url) {
      return parsed.webpage_url;
    }
  } catch {
    // fall through to playlist scan
  }
  // Post-reconcile a video's dir name is its canonical id, so match the
  // requested videoId against each URL's canonical id directly.
  const urls = await readPlaylistUrls(path.join(channelRoot, "playlist"));
  for (const url of urls) {
    if (extractVideoId(url) === videoId) return url;
  }
  // Last resort: re-create the URL from the canonical id (the dir name) and the
  // channel's platform. Only fires when both metadata.info.json and the
  // playlist came up empty, so the exact original URL always wins when present.
  // Requires a known platform — we don't blindly guess one.
  const platform = config?.platform ?? detectPlatform(config?.url ?? null);
  if (platform) return defaultWebpageUrl(platform, videoId);
  return null;
}