// Copyright 2019 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

namespace typed_array {
const kBuiltinNameFilter: constexpr string = '%TypedArray%.prototype.filter';

// https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.filter
transitioning javascript builtin TypedArrayPrototypeFilter(
    js-implicit context: NativeContext, receiver: JSAny)(...arguments): JSAny {
  // arguments[0] = callback
  // arguments[1] = thisArg
  try {
    // 1. Let O be the this value.
    // 2. Perform ? ValidateTypedArray(O).
    const array: JSTypedArray = Cast<JSTypedArray>(receiver)
        otherwise ThrowTypeError(
        MessageTemplate::kNotTypedArray, kBuiltinNameFilter);
    const src = typed_array::EnsureAttached(array) otherwise IsDetached;

    // 3. Let len be O.[[ArrayLength]].
    const len: uintptr = src.length;

    // 4. If IsCallable(callbackfn) is false, throw a TypeError exception.
    const callbackfn = Cast<Callable>(arguments[0])
        otherwise ThrowTypeError(MessageTemplate::kCalledNonCallable, arguments[0]);

    // 5. If thisArg is present, let T be thisArg; else let T be undefined.
    const thisArg: JSAny = arguments[1];

    // 6. Let kept be a new empty List.
    // TODO(v8:4153): Support huge TypedArrays here. (growable fixed arrays
    // can't be longer than kMaxSmiValue).
    let kept = growable_fixed_array::NewGrowableFixedArray();
    let witness = typed_array::NewAttachedJSTypedArrayWitness(src);

    // 7. Let k be 0.
    // 8. Let captured be 0.
    // 9. Repeat, while k < len
    for (let k: uintptr = 0; k < len; k++) {
      witness.Recheck() otherwise IsDetached;

      // a. Let Pk be ! ToString(k).
      // b. Let kValue be ? Get(O, Pk).
      const value: JSAny = witness.Load(k);

      // c. Let selected be ToBoolean(? Call(callbackfn, T, « kValue, k, O
      // »)).
      // TODO(v8:4153): Consider versioning this loop for Smi and non-Smi
      // indices to optimize Convert<Number>(k) for the most common case.
      const selected: JSAny = Call(
          context, callbackfn, thisArg, value, Convert<Number>(k),
          witness.GetStable());

      // d. If selected is true, then
      //    i. Append kValue to the end of kept.
      //   ii. Increase captured by 1.
      if (ToBoolean(selected)) kept.Push(value);

      // e.Increase k by 1.
    }

    // 10. Let A be ? TypedArraySpeciesCreate(O, captured).
    const typedArray: JSTypedArray = TypedArraySpeciesCreateByLength(
        kBuiltinNameFilter, array, Unsigned(kept.length));

    // 11. Let n be 0.
    // 12. For each element e of kept, do
    //   a. Perform ! Set(A, ! ToString(n), e, true).
    //   b. Increment n by 1.
    // TODO(v8:4153): Consider passing growable typed array directly to
    // TypedArrayCopyElements() to avoid JSArray materialization. Or collect
    // indices instead of values the loop above.
    const lengthNumber = Convert<Number>(Unsigned(kept.length));
    TypedArrayCopyElements(context, typedArray, kept.ToJSArray(), lengthNumber);

    // 13. Return A.
    return typedArray;
  } label IsDetached deferred {
    ThrowTypeError(MessageTemplate::kDetachedOperation, kBuiltinNameFilter);
  }
}
}