class ResizeableBuffer {
  constructor(size = 100) {
    this.size = size;
    this.length = 0;
    this.buf = Buffer.allocUnsafe(size);
  }
  prepend(val) {
    if (Buffer.isBuffer(val)) {
      const length = this.length + val.length;
      if (length >= this.size) {
        this.resize();
        if (length >= this.size) {
          throw Error("INVALID_BUFFER_STATE");
        }
      }
      const buf = this.buf;
      this.buf = Buffer.allocUnsafe(this.size);
      val.copy(this.buf, 0);
      buf.copy(this.buf, val.length);
      this.length += val.length;
    } else {
      const length = this.length++;
      if (length === this.size) {
        this.resize();
      }
      const buf = this.clone();
      this.buf[0] = val;
      buf.copy(this.buf, 1, 0, length);
    }
  }
  append(val) {
    const length = this.length++;
    if (length === this.size) {
      this.resize();
    }
    this.buf[length] = val;
  }
  clone() {
    return Buffer.from(this.buf.slice(0, this.length));
  }
  resize() {
    const length = this.length;
    this.size = this.size * 2;
    const buf = Buffer.allocUnsafe(this.size);
    this.buf.copy(buf, 0, 0, length);
    this.buf = buf;
  }
  toString(encoding) {
    if (encoding) {
      return this.buf.slice(0, this.length).toString(encoding);
    } else {
      return Uint8Array.prototype.slice.call(this.buf.slice(0, this.length));
    }
  }
  toJSON() {
    return this.toString("utf8");
  }
  reset() {
    this.length = 0;
  }
}

export default ResizeableBuffer;