import { Path } from './path'

export class MetaStream {
  public static readonly Default = () => new MetaStream(
    Path.Default(),
    [][Symbol.iterator]()
  )
  public static readonly From = (s: Iterable<any>) => new MetaStream(
    Path.Default(),
    s[Symbol.iterator]()
  )

  private _next: MetaStream | undefined = undefined
  private _done: boolean | undefined = undefined

  constructor(
    public readonly path: Path,
    public readonly items: Iterator<any>,
    public readonly index = -1,
    public readonly value: any = undefined,
  ) {
  }

  public get done(): boolean {
    if (this._done === undefined) {
      this.next()
    }
    return this._done!
  }

  public next(): MetaStream {
    if (!this._next) {
      const { value, done } = this.items.next()
      const i = this.index + 1
      this._done = done
      if (done) return this
      this._next = new MetaStream(
        this.path.moveTo(i),
        this.items,
        i,
        value,
      )
    }
    return this._next
  }
}