export class Stream {
  private pos: number;

  constructor(private data: string) {
    this.data = data;
    this.pos = 0;
  }

  get eof() {
    return this.pos === this.data.length;
  }

  peek() {
    return this.data.slice(this.pos, this.pos + 1);
  }
  read() {
    const value = this.data[this.pos];
    this.pos++;
    return value;
  }
  panic(message: string) {
    throw new Error(`Stream Error: ${message}, at position: ${this.pos}`);
  }
  readSpaces() {
    return this.readWhile(" ", "\t");
  }
  readWhile(...chars: string[]) {
    let value = "";

    while (!this.eof && chars.includes(this.peek())) {
      value += this.read();
    }

    return value;
  }
  readUntil(...chars: string[]) {
    const nextIndex = chars.reduce((index, chr) => {
      const i = this.data.indexOf(chr, this.pos);
      return i < index && i != -1 ? i : index;
    }, this.data.length - 1);

    const value = this.data.substring(this.pos, nextIndex);
    this.pos = nextIndex;

    return value;
  }
}