import { surroundingAgent } from '../host-defined/engine.mts';
import { Q, X, type ValueCompletion } from '../completion.mts';
import {
  Value, type Arguments, type FunctionCallContext,
} from '../value.mts';
import type { ValueEvaluator, YieldEvaluator } from '../evaluator.mts';
import { bootstrapPrototype } from './bootstrap.mts';
import type { SetObject } from './Set.mts';
import {
  Assert,
  CreateArrayFromList,
  CreateIteratorFromClosure,
  GeneratorResume,
  Realm,
  RequireInternalSlot,
  Yield,
  type GeneratorObject,
} from '#self';

/** https://tc39.es/ecma262/#sec-createsetiterator */
export function CreateSetIterator(set: Value, kind: 'key+value' | 'value'): ValueCompletion<GeneratorObject> {
  // 1. Assert: kind is key+value or value.
  Assert(kind === 'key+value' || kind === 'value');
  // 2. Perform ? RequireInternalSlot(set, [[SetData]]).
  Q(RequireInternalSlot(set, 'SetData'));
  // 3. Let closure be a new Abstract Closure with no parameters that captures set and kind and performs the following steps when called:
  const closure = function* closure(): YieldEvaluator {
    // a. Let index be 0.
    let index = 0;
    // b. Let entries be the List that is set.[[SetData]].
    const entries = (set as SetObject).SetData;
    // c. Let numEntries be the number of elements of entries.
    let numEntries = entries.length;
    // d. Repeat, while index < numEntries,
    while (index < numEntries) {
      // i. Let e be entries[index].
      const e = entries[index];
      // ii. Set index to index + 1.
      index += 1;
      // iii. If e is not empty, then
      if (e !== undefined) {
        // 1. If kind is key+value, then
        if (kind === 'key+value') {
          // a. Perform ? Yield(! CreateArrayFromList(« e, e »)).
          Q(yield* Yield(X(CreateArrayFromList([e, e]))));
        } else { // 2. Else,
          // a. Assert: kind is value.
          Assert(kind === 'value');
          // b. Perform ? Yield(e).
          Q(yield* Yield(e));
        }
      }
      // iv. Set numEntries to the number of elements of entries.
      numEntries = entries.length;
    }
    // NON-SPEC
    generator.HostCapturedValues = undefined;
    // e. Return undefined.
    return Value.undefined;
  };
  // 4. Return ! CreateIteratorFromClosure(closure, "%SetIteratorPrototype%", %SetIteratorPrototype%).
  const generator = X(CreateIteratorFromClosure(closure, Value('%SetIteratorPrototype%'), surroundingAgent.intrinsic('%SetIteratorPrototype%'), ['HostCapturedValues'], [set]));
  return generator;
}

/** https://tc39.es/ecma262/#sec-%setiteratorprototype%.next */
function* SetIteratorPrototype_next(_args: Arguments, { thisValue }: FunctionCallContext): ValueEvaluator {
  // 1. Return ? GeneratorResume(this value, empty, "%SetIteratorPrototype%").
  return Q(yield* GeneratorResume(thisValue, undefined, Value('%SetIteratorPrototype%')));
}

export function bootstrapSetIteratorPrototype(realmRec: Realm) {
  const proto = bootstrapPrototype(realmRec, [
    ['next', SetIteratorPrototype_next, 0],
  ], realmRec.Intrinsics['%Iterator.prototype%'], 'Set Iterator');

  realmRec.Intrinsics['%SetIteratorPrototype%'] = proto;
}