/// !doc
/// ## Transform to cut string and binary streams
///
/// `import { cutter } from 'f-streams'`
import { Reader } from '../reader';
import { Writer } from '../writer';
///
/// * `transform = cutter(options)`
///   cuts a string or binary stream in chunks of equal size
export interface Options {
    size?: number;
}

export function transform<T>(options?: Options | number) {
    options = options || {};
    const size = typeof options === 'number' ? options : options.size;
    return (reader: Reader<T>, writer: Writer<T>) => {
        if (!size) return reader.pipe(writer);
        let data: any = reader.read();
        while (data !== undefined) {
            if (data.length < size) {
                const d = reader.read();
                if (d === undefined) {
                    if (data.length > 0) writer.write(data);
                    data = d;
                } else {
                    if (typeof data === 'string') data += d;
                    else if (Buffer.isBuffer(data) && Buffer.isBuffer(d)) data = Buffer.concat([data, d]);
                    else if (Array.isArray(data)) data = data.concat(d);
                    else throw new Error('Cannot cut: bad data type: ' + typeof data);
                }
            } else {
                writer.write(data.slice(0, size));
                data = data.slice(size);
            }
        }
    };
}