'use strict';

// 通用小工具：响应、请求体、文件名/扩展名处理（无状态，可被任意层引用）

const path = require('path');

const MAX_BODY_BYTES = 32 * 1024 * 1024;

const IMAGE_EXT = new Set(['.jpg', '.jpeg', '.png', '.webp', '.gif']);
const MIME_BY_EXT = {
  '.jpg': 'image/jpeg',
  '.jpeg': 'image/jpeg',
  '.png': 'image/png',
  '.webp': 'image/webp',
  '.gif': 'image/gif',
};

// 采集输出根目录下永远跳过的目录名
const SKIP_DIR_NAMES = new Set(['膳绘']);

function sendJson(res, statusCode, obj) {
  const data = JSON.stringify(obj);
  res.writeHead(statusCode, { 'Content-Type': 'application/json; charset=utf-8' });
  res.end(data);
}

function sleep(ms) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

function sanitizeFileName(name) {
  return String(name).replace(/[\\/:*?"<>|]/g, '_').trim() || 'file';
}

function readBody(req) {
  return new Promise((resolve, reject) => {
    const chunks = [];
    let size = 0;
    req.on('data', (c) => chunks.push(c));
    req.on('data', (c) => {
      size += c.length;
      if (size > MAX_BODY_BYTES) {
        req.destroy(new Error('请求体过大'));
        reject(new Error('请求体过大'));
      }
    });
    req.on('end', () => {
      if (!chunks.length) return resolve({});
      try {
        resolve(JSON.parse(Buffer.concat(chunks).toString('utf8')));
      } catch (e) {
        reject(e);
      }
    });
    req.on('error', reject);
  });
}

function guessExtFromUrl(urlStr) {
  try {
    const u = new URL(urlStr);
    let ext = path.extname(u.pathname).replace('.', '').toLowerCase();
    if (ext === 'jpeg') ext = 'jpg';
    if (['jpg', 'png', 'gif', 'webp'].includes(ext)) return ext;
  } catch {
    // fall through
  }
  return 'jpg';
}

module.exports = {
  MAX_BODY_BYTES,
  IMAGE_EXT,
  MIME_BY_EXT,
  SKIP_DIR_NAMES,
  sendJson,
  sleep,
  sanitizeFileName,
  readBody,
  guessExtFromUrl,
};