const fs = require("fs-extra");
const path = require("path");
const { exec } = require("child_process");
const util = require("util");
const PostModel = require("../models/PostModel");

const execPromise = util.promisify(exec);

async function runFfmpeg(command) {
  try {
    await execPromise(command);
    return true;
  } catch (error) {
    console.error("[postVideoProcessing]", error.message);
    return false;
  }
}

/** faststart بدون re-encode — شروع پخش سریع‌تر */
async function optimizeVideoFaststart(filePath) {
  if (!(await fs.pathExists(filePath))) return;

  const dir = path.dirname(filePath);
  const base = path.basename(filePath);
  const tempPath = path.join(dir, `faststart-${Date.now()}-${base}`);

  const ok = await runFfmpeg(
    `ffmpeg -i "${filePath}" -c copy -movflags +faststart "${tempPath}" -y`
  );

  if (!ok || !(await fs.pathExists(tempPath))) return;

  try {
    await fs.rename(tempPath, filePath);
    console.log(`[postVideoProcessing] faststart applied: ${base}`);
  } catch (error) {
    await fs.remove(tempPath).catch(() => {});
    console.error("[postVideoProcessing] faststart rename failed:", error.message);
  }
}

/** thumbnail برای poster در گرید و ریلز */
async function generateVideoThumbnail(filePath, postId) {
  if (!(await fs.pathExists(filePath))) return null;

  const thumbDir = path.join(path.dirname(filePath), "..", "thumbnails");
  await fs.ensureDir(thumbDir);

  const thumbName = `${postId}.jpg`;
  const thumbPath = path.join(thumbDir, thumbName);

  const ok = await runFfmpeg(
    `ffmpeg -ss 00:00:00.5 -i "${filePath}" -vframes 1 -q:v 3 -y "${thumbPath}"`
  );

  if (!ok || !(await fs.pathExists(thumbPath))) return null;

  // مسیر نسبی قابل سرو از /storage/posts/thumbnails
  return `/posts/thumbnails/${thumbName}`;
}

async function processPostVideoInBackground(filePath, postId) {
  if (!filePath || !postId) return;

  const existing = await PostModel.findById(postId).select('files post_images').lean();
  const hasCustomCover =
    existing?.files?.some((file) => file.type === 'image') ||
    (existing?.post_images?.length ?? 0) > 0;
  if (hasCustomCover) {
    console.log(`[postVideoProcessing] skip thumbnail (custom cover) post=${postId}`);
    await optimizeVideoFaststart(filePath);
    return;
  }

  console.log(`[postVideoProcessing] start post=${postId}`);

  await optimizeVideoFaststart(filePath);

  const relativeThumb = await generateVideoThumbnail(filePath, postId);
  if (!relativeThumb) return;

  try {
    await PostModel.findByIdAndUpdate(postId, {
      $set: {
        post_images: [relativeThumb],
      },
    });
    console.log(`[postVideoProcessing] thumbnail saved post=${postId} path=${relativeThumb}`);
  } catch (error) {
    console.error("[postVideoProcessing] db update failed:", error.message);
  }
}

module.exports = {
  processPostVideoInBackground,
  optimizeVideoFaststart,
  generateVideoThumbnail,
};