import {Dataset, ReadonlyDataset} from "@opennetwork/rdf-dataset"
import {isLiteral, Literal, Quad} from "@opennetwork/rdf-data-model";
import * as ns from "./namespace"

export interface QuestionQuad extends Quad {
  predicate: typeof ns.defaultMain.questionPredicate
  object: typeof ns.defaultMain.answerPredicate
}

export function isQuestionQuad(quad: Quad): quad is QuestionQuad {
  return quad.predicate.equals(ns.defaultMain.questionPredicate) && quad.object.equals(ns.defaultMain.answerPredicate)
}

export interface AnswerQuad extends Quad {
  predicate: typeof ns.defaultMain.answerPredicate
  object: Literal
}

export function isAnswerQuad(quad: Quad): quad is AnswerQuad {
  return quad.predicate.equals(ns.defaultMain.answerPredicate) && isLiteral(quad.object)
}

function question() {
  const questionDataset = new Dataset()
  questionDataset.add(
    new Quad(
      ns.defaultMain.startSubject,
      ns.defaultMain.questionPredicate,
      ns.defaultMain.answerPredicate,
      ns.defaultMain.startSubject
    )
  )
  return questionDataset
}

function assertAnswer(this: ReadonlyDataset<AnswerQuad>) {
  if (this.empty) {
    throw new Error("Expected an answer")
  }
}

async function *defaultMain(this: ReadonlyDataset<Quad>): AsyncIterable<ReadonlyDataset> {

  yield question()

  // console.log(JSON.stringify({ withAnswer: this.toArray() }, undefined, "  "))

  assertAnswer.call(this.filter(isAnswerQuad))

  // Lets do some UI ??
  //
  // const environment = getEnvironment()
  //
  // const config = getEnvironmentConfig()
  //
  // console.log({ config })
  //
  //
  // if (typeof document !== "undefined") {
  //   console.log("we have a DOM")
  // } else if (environment.name === "node") {
  //   console.log("we have a terminal!")
  // } else {
  //
  //   console.log({ environment })
  // }


}

export const DefaultMainSymbol = Symbol("Default Main")
export const main: typeof defaultMain & { [DefaultMainSymbol]?: typeof ns.defaultMain.defaultMain } = defaultMain

main[DefaultMainSymbol] = ns.defaultMain.defaultMain

export function isDefaultMain(fn: typeof defaultMain): fn is typeof defaultMain & { [DefaultMainSymbol]: typeof ns.defaultMain.defaultMain } {
  function isLike(fn: unknown): fn is { [DefaultMainSymbol]: unknown } {
    return !!fn
  }
  return (
    isLike(fn) &&
    ns.defaultMain.defaultMain.equals(fn[DefaultMainSymbol])
  )
}