const TASK = {
  taskType: 'template-slide-thumbnail-refresh'
};

async function fetchPlayerInternalBaseUrl(pool) {
  const [rows] = await pool.query(
    `SELECT internal_base_url
     FROM d_players
     WHERE device_id = '1'
     LIMIT 1`
  );

  return String(rows && rows[0] && rows[0].internal_base_url || '').trim().replace(/\/$/, '') || null;
}

function registerTemplateSlideThumbnailRefreshTask(options) {
  const backgroundTaskQueue = options && options.backgroundTaskQueue;
  const captureSlideThumbnail = options && options.captureSlideThumbnail;
  const pool = options && options.pool;
  const common = options && options.common;
  const mediaDir = String(options && options.mediaDir || '').trim();

  if (!backgroundTaskQueue || typeof captureSlideThumbnail !== 'function' || !pool || !common || !mediaDir) {
    throw new Error('registerTemplateSlideThumbnailRefreshTask requires the template thumbnail dependencies.');
  }

  // Walk every slide in the template and regenerate its thumbnail.
  backgroundTaskQueue.setTaskHandler(TASK.taskType, async function (task) {
    const payload = task && task.payload ? task.payload : {};
    const templateId = Number(payload.templateId || 0);
    if (!Number.isFinite(templateId) || templateId <= 0) {
      throw new Error('Template id is required.');
    }

    const playerInternalBaseUrl = await fetchPlayerInternalBaseUrl(pool);
    if (!playerInternalBaseUrl) {
      throw new Error('Player internal base URL is required.');
    }

    const [slides] = await pool.query(
      'SELECT id, thumbnail_path FROM c_slides WHERE template_id = ? ORDER BY id ASC',
      [templateId]
    );

    for (const slide of slides || []) {
      const slideId = Number(slide && slide.id || 0);
      if (!Number.isFinite(slideId) || slideId <= 0) {
        continue;
      }

      await captureSlideThumbnail({
        pool: pool,
        common: common,
        mediaDir: mediaDir,
        baseUrl: playerInternalBaseUrl,
        slideId: slideId,
        previousThumbnailPath: slide && slide.thumbnail_path ? slide.thumbnail_path : null
      });
    }

    return { templateId: templateId, slideCount: Array.isArray(slides) ? slides.length : 0 };
  });
}

module.exports = { registerTemplateSlideThumbnailRefreshTask };