export function readTextFile(filename: string, encoding: string, callback: (err: Error | null, res?: string) => void) {
    if (typeof encoding === "function") {
        callback = encoding;
        encoding = "utf-8";
    } else if (typeof encoding !== "string") {
        throw new TypeError("encoding must be a string");
    } else if (!isEncodingSupported(encoding)) {
        throw new TypeError("encoding is not supported: " + encoding);
    }
    // isbinaryfile check first because it checks first 1000 bytes of a file
    // so we don't load whole file if it's binary
    isbinaryfile(filename, function (err: Error, isBinary: boolean) {
        if (err) {
            return callback(err);
        }
        if (isBinary) {
            const err2: NodeJS.ErrnoException = new Error("ECHARSET: file is a binary file: " + filename);
            err2.code = "ECHARSET";
            return callback(err2);
        }
        fs.readFile(filename, encoding, function (err2, content) {
            if (err2) {
                return callback(err2);
            }

            content = stripBom(content);

            // \uFFFD is used to replace an incoming character
            // whose value is unknown or unrepresentable
            if (/\uFFFD/.test(content)) {
                const err3: NodeJS.ErrnoException = new Error("ECHARSET: unsupported encoding in file: " + filename);
                err3.code = "ECHARSET";
                return callback(err3);
            }

            callback(null, content);
        });
    });
}

export function isBinaryFileSync(filename: string): boolean {
    return isbinaryfile(filename);
}

export function isBinaryFile(filename: string, callback: (err?: Error, res?: boolean) => void) {
    isbinaryfile(filename, callback);
}