export class MemoryWritableStream extends WritableStream<Uint8Array> {
  private buf: Array<Uint8Array>;

  constructor() {
    const buf = new Array<Uint8Array>();
    super({
      write(chunk: Uint8Array) {
        buf.push(chunk);
      },
    });
    this.buf = buf;
  }

  toUint8Array() {
    let len = 0;
    for (const u8a of this.buf) {
      len += u8a.length;
    }
    const result = new Uint8Array(len);
    let pos = 0;
    for (const u8a of this.buf) {
      result.set(u8a, pos);
      pos += u8a.length;
    }
    return result;
  }

  toString(encoding = "uft-8") {
    return new TextDecoder(encoding.toLowerCase(), { ignoreBOM: true }).decode(
      this.toUint8Array(),
    );
  }
}