import multer from '@koa/multer';
import fs from 'fs';
import path from 'path';

/**
 * 创建 multer 实例
 * @param {Object} options - multer 配置选项
 * @returns {Object} multer 实例
 */
export const createMulter = (options = {}) => {
    // 默认配置
    const defaultOptions = {
        dest: './public/uploads/',
        limits: {
            fileSize: 2 * 1024 * 1024, // 2MB
        }
    };

    // 合并选项
    const mergedOptions = { ...defaultOptions, ...options };

    // 如果没有指定 storage，使用 diskStorage
    if (!mergedOptions.storage) {
        const uploadDir = mergedOptions.dest;
        
        // 确保上传目录存在
        if (!fs.existsSync(uploadDir)) {
            fs.mkdirSync(uploadDir, { recursive: true });
        }

        mergedOptions.storage = multer.diskStorage({
            destination: function (req, file, cb) {
                cb(null, uploadDir);
            },
            filename: function (req, file, cb) {
                const uniqueSuffix = Date.now() + '-' + Math.round(Math.random() * 1E9);
                cb(null, uniqueSuffix + path.extname(file.originalname));
            }
        });
    }

    return multer(mergedOptions);
};

// 默认 multer 实例
const defaultMulter = createMulter();

/**
 * 单文件上传中间件
 * @param {string} fieldName - 表单字段名
 * @param {Object} options - multer 配置选项
 * @returns {Function} koa 中间件
 */
export const uploadSingle = (fieldName = 'file', options = {}) => {
    if (Object.keys(options).length === 0) {
        return defaultMulter.single(fieldName);
    }
    return createMulter(options).single(fieldName);
};

/**
 * 多文件上传中间件
 * @param {string} fieldName - 表单字段名
 * @param {number} maxCount - 最大文件数
 * @param {Object} options - multer 配置选项
 * @returns {Function} koa 中间件
 */
export const uploadMultiple = (fieldName = 'files', maxCount = 5, options = {}) => {
    if (Object.keys(options).length === 0) {
        return defaultMulter.array(fieldName, maxCount);
    }
    return createMulter(options).array(fieldName, maxCount);
};