const KNOWN_SIGNATURES = {
    png: '89504E470D0A1A0A',
    jpg: 'FFD8FF',
    jpeg: 'FFD8FF',
    gif: '47494638',
    webp: '52494646',
    docx: '504B0304',
    xlsx: '504B0304',
    pptx: '504B0304',
    doc: 'D0CF11E0',
    xls: 'D0CF11E0',
    ppt: 'D0CF11E0',
    pdf: '25504446',
    txt: 'TYPE_TEXT',
    csv: 'TYPE_TEXT',
    md: 'TYPE_TEXT',
    json: 'TYPE_TEXT',
};
export class FileValidator {
    version = '1.0.0';
    signs = Object.keys(KNOWN_SIGNATURES);
    constructor(options = {}) {
        this.maxSizeMB = options.maxSizeMB || 10;
        if (options.allowedExtensions && Array.isArray(options.allowedExtensions)) {
            this.allowedConfig = {};
            options.allowedExtensions.forEach((ext) => {
                const key = ext.toLowerCase();
                if (KNOWN_SIGNATURES[key]) {
                    this.allowedConfig[key] = KNOWN_SIGNATURES[key];
                } else {
                    console.warn(`[FileValidator] 未知的文件类型: .${key}，已忽略`);
                }
            });
        } else {
            this.allowedConfig = {
                ...KNOWN_SIGNATURES,
            };
        }
    }
    _isValidUTF8(buffer) {
        try {
            const decoder = new TextDecoder('utf-8', {
                fatal: true,
            });
            decoder.decode(buffer);
            return true;
        } catch (e) {
            return false;
        }
    }
    _bufferToHex(buffer) {
        return Array.prototype.map
            .call(new Uint8Array(buffer), (x) => ('00' + x.toString(16)).slice(-2))
            .join('')
            .toUpperCase();
    }
    _countCSVRows(buffer) {
        const decoder = new TextDecoder('utf-8');
        const text = decoder.decode(buffer);
        let rowCount = 0;
        let inQuote = false;
        let len = text.length;
        for (let i = 0; i < len; i++) {
            const char = text[i];
            if (char === '"') {
                inQuote = !inQuote;
            } else if (char === '\n' && !inQuote) {
                rowCount++;
            }
        }
        if (len > 0 && text[len - 1] !== '\n') {
            rowCount++;
        }
        return rowCount;
    }
    _validateTextContent(buffer, extension) {
        let contentStr = '';
        try {
            const decoder = new TextDecoder('utf-8', {
                fatal: true,
            });
            contentStr = decoder.decode(buffer);
        } catch (e) {
            console.warn('UTF-8 解码失败', e);
            return false;
        }
        if (contentStr.includes('\0')) {
            return false;
        }
        if (extension === 'json') {
            try {
                JSON.parse(contentStr);
            } catch (e) {
                console.warn('无效的 JSON 格式');
                return false;
            }
        }
        return true;
    }
    validate(file) {
        return new Promise((resolve, reject) => {
            if (!file || !file.name) return reject('无效的文件对象');
            if (file.size > this.maxSizeMB * 1024 * 1024) {
                return reject(`文件大小超出限制 (最大 ${this.maxSizeMB}MB)`);
            }
            const fileName = file.name.toLowerCase();
            const extension = fileName.substring(fileName.lastIndexOf('.') + 1);
            const expectedMagic = this.allowedConfig[extension];
            if (!expectedMagic) {
                return reject(`不支持的文件格式: .${extension}`);
            }
            const reader = new FileReader();
            reader.onload = (e) => {
                const buffer = e.target.result;
                let isSafe = false;
                if (expectedMagic === 'TYPE_TEXT') {
                    if (this._validateTextContent(buffer, extension)) {
                        isSafe = true;
                    } else {
                        if (extension === 'json') {
                            return reject(`文件异常：不是有效的 JSON 文件`);
                        }
                        return reject(`文件异常：.${extension} 包含非法二进制内容或编码错误`);
                    }
                    if (extension === 'csv' && this.csvMaxRows > 0) {
                        const rows = this._countCSVRows(buffer);
                        if (rows > this.csvMaxRows) {
                            return reject(`CSV 行数超出限制 (当前 ${rows} 行，最大允许 ${this.csvMaxRows} 行)`);
                        }
                    }
                } else {
                    const fileHeader = this._bufferToHex(buffer.slice(0, 8));
                    if (fileHeader.startsWith(expectedMagic)) {
                        isSafe = true;
                    } else {
                        return reject(`文件可能已被篡改 (真实类型与 .${extension} 不符)`);
                    }
                }
                if (isSafe) resolve(true);
            };
            reader.onerror = () => reject('文件读取失败，无法校验');
            if (expectedMagic === 'TYPE_TEXT' && extension === 'json') {
                reader.readAsArrayBuffer(file);
            } else {
                reader.readAsArrayBuffer(file.slice(0, 2048));
            }
        });
    }
}


// 【demo】
// 如果传入了 allowedExtensions，则只使用传入的；否则使用全部 KNOWN_SIGNATURES
// const imageValidator = new FileValidator({
//     maxSizeMB: 5,
//     allowedExtensions: ['png', 'jpg', 'jpeg'],
// });

// imageValidator
//     .validate(file)
//     .then(() => {
//         statusDiv.textContent = `检测通过: ${file.name}`;
//         statusDiv.style.color = 'green';
//         console.log('图片校验通过，开始上传...');
//         // upload(file)...
//     })
//     .catch((err) => {
//         statusDiv.textContent = `检测失败: ${err}`;
//         statusDiv.style.color = 'red';
//     });