com.github.dm.jrt.operator.AccumulateFunctionInvocation Maven / Gradle / Ivy

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/*
 * Copyright 2016 Davide Maestroni
 *
 * 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.github.dm.jrt.operator;

import com.github.dm.jrt.core.channel.Channel;
import com.github.dm.jrt.core.invocation.Invocation;
import com.github.dm.jrt.core.invocation.InvocationFactory;
import com.github.dm.jrt.core.invocation.TemplateInvocation;
import com.github.dm.jrt.function.BiFunction;
import com.github.dm.jrt.function.BiFunctionDecorator;
import com.github.dm.jrt.function.Supplier;
import com.github.dm.jrt.function.SupplierDecorator;

import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import static com.github.dm.jrt.core.util.Reflection.asArgs;
import static com.github.dm.jrt.function.Functions.decorate;

/**
 * Invocation implementation accumulating the result returned by a bi-function instance.
 * 
 * Created by davide-maestroni on 10/18/2015.
 *
 * @param   the input data type.
 * @param  the output data type.
 */
class AccumulateFunctionInvocation extends TemplateInvocation {

  private final BiFunction mAccumulateFunction;

  private final SupplierDecorator mSeedSupplier;

  private OUT mAccumulated;

  private boolean mIsFirst;

  /**
   * Constructor.
   *
   * @param seedSupplier       the supplier of initial accumulation values.
   * @param accumulateFunction the accumulating bi-function instance.
   */
  private AccumulateFunctionInvocation(
      @Nullable final SupplierDecorator seedSupplier,
      @NotNull final BiFunction accumulateFunction) {
    mSeedSupplier = seedSupplier;
    mAccumulateFunction = accumulateFunction;
  }

  /**
   * Builds and returns a new accumulating invocation factory backed by the specified bi-function
   * instance.
   *
   * @param accumulateFunction the accumulating bi-function instance.
   * @param                the input data type.
   * @return the invocation factory.
   */
  @NotNull
  static  InvocationFactory functionFactory(
      @NotNull final BiFunction accumulateFunction) {
    return new AccumulateInvocationFactory(null, decorate(accumulateFunction));
  }

  /**
   * Builds and returns a new accumulating invocation factory backed by the specified bi-function
   * instance.
   *
   * @param seedSupplier       the supplier of initial accumulation values.
   * @param accumulateFunction the accumulating bi-function instance.
   * @param                the input data type.
   * @param               the output data type.
   * @return the invocation factory.
   */
  @NotNull
  static  InvocationFactory functionFactory(
      @NotNull final Supplier seedSupplier,
      @NotNull final BiFunction accumulateFunction) {
    return new AccumulateInvocationFactory(decorate(seedSupplier),
        decorate(accumulateFunction));
  }

  @Override
  public void onComplete(@NotNull final Channel result) {
    if (!mIsFirst) {
      result.pass(mAccumulated);
    }
  }

  @Override
  @SuppressWarnings("unchecked")
  public void onInput(final IN input, @NotNull final Channel result) throws Exception {
    if (mIsFirst) {
      mIsFirst = false;
      final SupplierDecorator supplier = mSeedSupplier;
      if (supplier != null) {
        mAccumulated = mAccumulateFunction.apply(supplier.get(), input);

      } else {
        mAccumulated = (OUT) input;
      }

    } else {
      mAccumulated = mAccumulateFunction.apply(mAccumulated, input);
    }
  }

  @Override
  public void onRecycle(final boolean isReused) {
    mAccumulated = null;
  }

  @Override
  public void onRestart() {
    mIsFirst = true;
  }

  /**
   * Class implementing an accumulating invocation factory.
   *
   * @param   the input data type.
   * @param  the output data type.
   */
  private static class AccumulateInvocationFactory extends InvocationFactory {

    private final BiFunctionDecorator mAccumulateFunction;

    private final SupplierDecorator mSeedSupplier;

    /**
     * Constructor.
     *
     * @param seedSupplier       the supplier of initial accumulation values.
     * @param accumulateFunction the accumulating bi-function instance.
     */
    private AccumulateInvocationFactory(
        @Nullable final SupplierDecorator seedSupplier,
        @NotNull final BiFunctionDecorator
            accumulateFunction) {
      super(asArgs(seedSupplier, accumulateFunction));
      mSeedSupplier = seedSupplier;
      mAccumulateFunction = accumulateFunction;
    }

    @NotNull
    @Override
    public Invocation newInvocation() {
      return new AccumulateFunctionInvocation(mSeedSupplier, mAccumulateFunction);
    }
  }
}