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/*
 * Copyright 2016 the original author or authors.
 *
 * 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 ratpack.exec.util.internal;

import com.google.common.collect.Lists;
import ratpack.exec.ExecResult;
import ratpack.exec.Operation;
import ratpack.exec.Promise;
import ratpack.exec.util.SerialBatch;
import ratpack.func.BiAction;
import ratpack.func.BiFunction;
import ratpack.stream.Streams;
import ratpack.stream.TransformablePublisher;
import ratpack.util.Types;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class DefaultSerialBatch implements SerialBatch {

  private final Iterable> promises;

  public DefaultSerialBatch(Iterable> promises) {
    this.promises = promises;
  }

  @Override
  public Promise>> yieldAll() {
    List> promises = Lists.newArrayList(this.promises);
    List> results = Types.cast(promises);
    return Promise.async(d ->
      yieldPromise(promises.iterator(), 0,
        results::set,
        (i, r) -> {
          results.set(i, r);
          return true;
        },
        () -> d.success(results)
      )
    );
  }

  @Override
  public Promise> yield() {
    List results = new ArrayList<>();
    return Promise.async(d ->
      forEach((i, r) -> results.add(r))
        .onError(d::error)
        .then(() -> d.success(results))
    );
  }

  @Override
  public Operation forEach(BiAction consumer) {
    return Promise.async(d ->
      yieldPromise(promises.iterator(), 0, (i, r) -> consumer.execute(i, r.getValue()), (i, r) -> {
        d.error(r.getThrowable());
        return false;
      }, () -> d.success(null))
    ).operation();
  }

  @Override
  public TransformablePublisher publisher() {
    Iterator> iterator = promises.iterator();
    return Streams.flatYield(r -> {
      if (iterator.hasNext()) {
        return iterator.next();
      } else {
        return Promise.value(null);
      }
    });
  }

  private static  void yieldPromise(Iterator> promises, int i, BiAction> withItem, BiFunction, Boolean> onError, Runnable onComplete) {
    if (promises.hasNext()) {
      promises.next().result(r -> {
        if (r.isError()) {
          if (!onError.apply(i, r)) {
            return;
          }
        } else {
          withItem.execute(i, r);
        }
        yieldPromise(promises, i + 1, withItem, onError, onComplete);
      });
    } else {
      onComplete.run();
    }
  }

}