// Copyright 2022 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.devtools.build.skyframe;

import static com.google.common.base.Preconditions.checkNotNull;

import java.util.Iterator;
import javax.annotation.Nullable;

/** Simple implementation of {@link SkyframeIterableResult}. */
final class SimpleSkyframeIterableResult implements SkyframeIterableResult {
  private final Iterator<ValueOrUntypedException> valuesOrExceptions;
  private final Runnable valuesMissingCallback;

  SimpleSkyframeIterableResult(
      Runnable valuesMissingCallback, Iterator<ValueOrUntypedException> valuesOrExceptions) {
    this.valuesMissingCallback = checkNotNull(valuesMissingCallback);
    this.valuesOrExceptions = checkNotNull(valuesOrExceptions);
  }

  @Override
  public boolean hasNext() {
    return valuesOrExceptions.hasNext();
  }

  @Nullable
  @Override
  public <E1 extends Exception, E2 extends Exception, E3 extends Exception, E4 extends Exception>
      SkyValue nextOrThrow(
          @Nullable Class<E1> exceptionClass1,
          @Nullable Class<E2> exceptionClass2,
          @Nullable Class<E3> exceptionClass3,
          @Nullable Class<E4> exceptionClass4)
          throws E1, E2, E3, E4 {
    ValueOrUntypedException voe = valuesOrExceptions.next();
    SkyValue value = voe.getValue();
    if (value != null) {
      return value;
    }
    SkyFunctionException.throwIfInstanceOf(
        voe.getException(), exceptionClass1, exceptionClass2, exceptionClass3, exceptionClass4);
    valuesMissingCallback.run();
    return null;
  }
}