import path from "node:path";
import { lstat, readdir, stat } from "node:fs/promises";
import type { Dirent } from "node:fs";
import { isTierable } from "yt-dlp-transcript-common/lib/mediaTier";
import { onDrive } from "yt-dlp-transcript-common/lib/storageHealth";
import type { VideoFile } from "../videos/[id]/components/cards/videoFiles";

// ONE VIDEO DIRECTORY'S FILES, for the video page and the videos list's detail
// pane (server only).
//
// RELEASE 17: a tiered file is a RELATIVE SYMLINK in `data/<id>/` into
// `channels/<slug>/media/`, and a dirent `isFile()` filter hides it — on a
// tiered channel the audio would vanish from both pages. So links are listed
// too, and BY FILE KIND:
//
// - a real file is statted directly (the corpus disk);
// - a link is `lstat`ed for its time (the hook gives the link the file's own
//   times, so the corpus disk answers it) and its SIZE is asked of the media
//   drive — every media link of the directory in ONE `onDrive(mediaDir)` call
//   when the channel's media is relocated, so a drive that does not answer
//   costs one budget, not one per file, and a stalled one none at all. A
//   link whose target is not there (an unmounted or renamed-away drive) or
//   whose drive does not answer is listed with `size: null` — the file exists;
//   its bytes are not reachable now.
//
// The mover's tree walk (relocateDir.ts) keeps its own `isFile()`: over
// `data/` it measures the corpus disk's text, over `media/` the real bytes.
export async function loadVideoDirFiles(
  videoDir: string,
  // `config.mediaDir`, when the channel's media is relocated. Absent: an
  // in-place `media/` is on the corpus disk and needs no watchdog.
  mediaDir: string | undefined,
): Promise<{ files: VideoFile[] }> {
  let entries: Dirent[];
  try {
    entries = await readdir(videoDir, { withFileTypes: true });
  } catch {
    return { files: [] };
  }
  const files: VideoFile[] = [];
  const links: Dirent[] = [];
  for (const e of entries) {
    if (e.name.includes(".tmp-")) continue;
    if (e.isFile()) {
      const s = await stat(path.join(videoDir, e.name)).catch(() => null);
      if (s) files.push({ name: e.name, size: s.size, mtime: s.mtimeMs });
    } else if (e.isSymbolicLink()) {
      links.push(e);
    }
  }
  if (links.length > 0) {
    const sizes = new Map<string, number>();
    const statLinks = async (kind: "media" | "other") => {
      for (const e of links) {
        const isMedia = isTierable(e.name);
        if ((kind === "media") !== isMedia) continue;
        const s = await stat(path.join(videoDir, e.name)).catch(() => null);
        if (s?.isFile()) sizes.set(e.name, s.size);
      }
    };
    // A link that is not a media name is not the tier's (nothing makes one);
    // it is statted directly, like the files.
    await statLinks("other");
    try {
      await (mediaDir ? onDrive(mediaDir, () => statLinks("media")) : statLinks("media"));
    } catch {
      /* the drive did not answer: the sizes stay unknown */
    }
    for (const e of links) {
      const l = await lstat(path.join(videoDir, e.name)).catch(() => null);
      if (!l) continue;
      files.push({
        name: e.name,
        size: sizes.get(e.name) ?? null,
        mtime: l.mtimeMs,
      });
    }
  }
  files.sort((a, b) => a.name.localeCompare(b.name));
  return { files };
}