com.github.dm.jrt.operator.GroupByFunctionInvocationFactory 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.core.util.ConstantConditions;
import com.github.dm.jrt.function.FunctionDecorator;

import org.jetbrains.annotations.NotNull;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

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

/**
 * Factory of grouping by key invocations.
 * 
 * Created by davide-maestroni on 08/30/2016.
 *
 * @param  the data type.
 */
class GroupByFunctionInvocationFactory extends InvocationFactory> {

  private final FunctionDecorator mKeyFunction;

  /**
   * Constructor.
   *
   * @param keyFunction the function returning the group key.
   */
  GroupByFunctionInvocationFactory(@NotNull final FunctionDecorator keyFunction) {
    super(asArgs(ConstantConditions.notNull("function instance", keyFunction)));
    mKeyFunction = keyFunction;
  }

  @NotNull
  @Override
  public Invocation> newInvocation() throws Exception {
    return new GroupByFunctionInvocation(mKeyFunction);
  }

  /**
   * Routine invocation grouping data into collections based on the same key.
   *
   * @param  the data type.
   */
  private static class GroupByFunctionInvocation
      extends TemplateInvocation> {

    private final FunctionDecorator mKeyFunction;

    private HashMap> mGroups;

    /**
     * Constructor.
     *
     * @param keyFunction the function returning the group key.
     */
    private GroupByFunctionInvocation(@NotNull final FunctionDecorator keyFunction) {
      mKeyFunction = keyFunction;
    }

    @Override
    public void onComplete(@NotNull final Channel, ?> result) {
      for (final ArrayList inputs : mGroups.values()) {
        result.pass(inputs);
      }
    }

    @Override
    public void onInput(final DATA input, @NotNull final Channel, ?> result) throws
        Exception {
      final Object key = mKeyFunction.apply(input);
      final HashMap> groups = mGroups;
      ArrayList inputs = groups.get(key);
      if (inputs == null) {
        inputs = new ArrayList();
        groups.put(key, inputs);
      }

      inputs.add(input);
    }

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

    @Override
    public void onRestart() {
      mGroups = new HashMap>();
    }
  }
}