// Vue Mixin - Base64 工具
// 提供 Base64 字串轉換為 Blob 的功能

var Base64Mixin = {
    methods: {
        /**
         * 將 Base64 字串轉換為 Blob 物件
         * @param {string} base64 - Base64 編碼字串
         * @returns {Blob} Excel 格式的 Blob 物件
         */
        Base64ToBlob: function(base64) {
            try {
                if (!base64 || typeof base64 !== 'string') {
                    throw new Error('Invalid input: Base64 string is required');
                }

                var cleanBase64 = base64.replace(/\s/g, '');

                if (!cleanBase64 || !/^[A-Za-z0-9+/]*={0,2}$/.test(cleanBase64)) {
                    throw new Error('Invalid Base64 string format');
                }

                var binaryString = atob(cleanBase64);
                var bytes = new Uint8Array(binaryString.length);
                for (var i = 0; i < binaryString.length; i++) {
                    bytes[i] = binaryString.charCodeAt(i);
                }
                return new Blob([bytes], { type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' });
            } catch (error) {
                console.error('Base64ToBlob error:', error);
                throw error;
            }
        }
    }
};