const GRID_SIZE = 3;
const TILE_COUNT = GRID_SIZE * GRID_SIZE;

function normalizeQueryValue(value) {
  return String(value || '').trim();
}

function sanitizeFileNamePart(value) {
  const normalized = normalizeQueryValue(value)
    .replace(/[\\/:*?"<>|]/g, '')
    .replace(/\s+/g, '-')
    .slice(0, 32);
  return normalized || 'taonier';
}

function buildShareGridTileFileName(params, tileIndex) {
  const safeTitle = sanitizeFileNamePart(params.title || params.publicWorkCode);
  const safeCode = sanitizeFileNamePart(params.publicWorkCode || 'share');
  const order = String(tileIndex + 1).padStart(2, '0');
  return `${safeTitle}-${safeCode}-${order}.png`;
}

function normalizeShareGridQuery(query) {
  return {
    imageUrl: normalizeQueryValue(query && query.imageUrl),
    title: normalizeQueryValue(query && query.title) || '我的作品',
    publicWorkCode: normalizeQueryValue(query && query.publicWorkCode),
  };
}

function buildShareGridTilePlan(imageWidth, imageHeight) {
  const tileWidth = Math.floor(imageWidth / GRID_SIZE);
  const tileHeight = Math.floor(imageHeight / GRID_SIZE);
  const plan = [];

  for (let row = 0; row < GRID_SIZE; row += 1) {
    for (let col = 0; col < GRID_SIZE; col += 1) {
      const index = row * GRID_SIZE + col;
      const sourceX = col * tileWidth;
      const sourceY = row * tileHeight;
      plan.push({
        index,
        row,
        col,
        sourceX,
        sourceY,
        sourceWidth: col === GRID_SIZE - 1 ? imageWidth - sourceX : tileWidth,
        sourceHeight: row === GRID_SIZE - 1 ? imageHeight - sourceY : tileHeight,
      });
    }
  }

  return plan;
}

module.exports = {
  GRID_SIZE,
  TILE_COUNT,
  buildShareGridTileFileName,
  buildShareGridTilePlan,
  normalizeShareGridQuery,
};