/**
 * ─────────────────────────────────────────────
 *  SPB Drive — Personal Cloud Drive
 * ─────────────────────────────────────────────
 *  Author  : Simon-Pierre Boucher
 *  Contact : contact@spboucher.ai
 *  File    : src/preview/thumbs.mjs
 *  Purpose : Thumbnail generation — sharp for images, ffmpeg poster for video,
 *            pdftoppm for PDF page 1; cached by (blob sha, size)
 *  License : MIT © Simon-Pierre Boucher
 * ─────────────────────────────────────────────
 */

import { execFile } from 'node:child_process';
import { existsSync } from 'node:fs';
import { rename, rm } from 'node:fs/promises';
import path from 'node:path';
import { promisify } from 'node:util';
import sharp from 'sharp';
import { config } from '../config.mjs';
import { blobPath } from '../storage/blobs.mjs';
import { enqueue } from './queue.mjs';

const execFileP = promisify(execFile);
const SIZES = new Set([256, 512]);
const EXEC_TIMEOUT = 60_000;

const thumbFile = (sha, size) => path.join(config.cacheDir, 'thumbs', `${sha}.${size}.webp`);

/** True if a binary exists on PATH (cached). */
const binCache = new Map();
export async function hasBin(name) {
  if (binCache.has(name)) return binCache.get(name);
  try {
    await execFileP('which', [name]);
    binCache.set(name, true);
  } catch {
    binCache.set(name, false);
  }
  return binCache.get(name);
}

/**
 * Return the cached thumbnail path for a blob, generating it if needed.
 * @param {'image'|'video'|'pdf'} kind
 * @returns {Promise<string|null>} webp path, or null if not generatable
 */
export async function getThumb(sha, kind, size = 256) {
  const sz = SIZES.has(Number(size)) ? Number(size) : 256;
  const out = thumbFile(sha, sz);
  if (existsSync(out)) return out;

  return enqueue(`thumb:${sha}:${sz}`, async () => {
    if (existsSync(out)) return out;
    const src = blobPath(sha);
    const tmp = `${out}.tmp-${process.pid}`;
    try {
      if (kind === 'image') {
        await sharp(src, { failOn: 'none', limitInputPixels: 512 * 1024 * 1024 })
          .rotate()
          .resize(sz, sz, { fit: 'inside', withoutEnlargement: true })
          .webp({ quality: 80 })
          .toFile(tmp);
      } else if (kind === 'video') {
        if (!(await hasBin('ffmpeg'))) return null;
        // Grab a frame ~10% in; fall back to first frame for tiny clips.
        await execFileP(
          'ffmpeg',
          ['-y', '-ss', '00:00:01', '-i', src, '-frames:v', '1',
            '-vf', `scale='min(${sz},iw)':-2`, '-f', 'webp', tmp],
          { timeout: EXEC_TIMEOUT },
        ).catch(() =>
          execFileP('ffmpeg', ['-y', '-i', src, '-frames:v', '1',
            '-vf', `scale='min(${sz},iw)':-2`, '-f', 'webp', tmp], { timeout: EXEC_TIMEOUT }),
        );
      } else if (kind === 'pdf') {
        if (!(await hasBin('pdftoppm'))) return null;
        const base = `${tmp}-pg`;
        await execFileP('pdftoppm', ['-png', '-f', '1', '-l', '1', '-scale-to', String(sz), src, base], {
          timeout: EXEC_TIMEOUT,
        });
        const png = `${base}-1.png`;
        if (!existsSync(png)) return null;
        await sharp(png).webp({ quality: 80 }).toFile(tmp);
        await rm(png, { force: true });
      } else {
        return null;
      }
      if (!existsSync(tmp)) return null;
      await rename(tmp, out);
      return out;
    } catch {
      await rm(tmp, { force: true });
      return null;
    }
  });
}

/** Probe media duration/dimensions with ffprobe (null if unavailable). */
export async function probeMedia(sha) {
  if (!(await hasBin('ffprobe'))) return null;
  try {
    const { stdout } = await execFileP(
      'ffprobe',
      ['-v', 'quiet', '-print_format', 'json', '-show_format', '-show_streams', blobPath(sha)],
      { timeout: 30_000 },
    );
    const info = JSON.parse(stdout);
    const video = info.streams?.find((s) => s.codec_type === 'video');
    const audio = info.streams?.find((s) => s.codec_type === 'audio');
    return {
      duration: Number(info.format?.duration ?? 0),
      width: video?.width ?? null,
      height: video?.height ?? null,
      videoCodec: video?.codec_name ?? null,
      audioCodec: audio?.codec_name ?? null,
      container: info.format?.format_name ?? null,
    };
  } catch {
    return null;
  }
}