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/**
 * Copyright © 2017 Sven Ruppert ([email protected])
 *
 * 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 org.rapidpm.frp.memoizer;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.function.Supplier;

import org.rapidpm.frp.Transformations;
import org.rapidpm.frp.functions.TriFunction;

/**
 * Copyright (C) 2010 RapidPM
 * 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.
 * 
 * Created by RapidPM - Team on 10.12.16.
 *
 * @author svenruppert
 * @version $Id: $Id
 */
public class Memoizer {
  private final Map memoizationCache = new ConcurrentHashMap<>();

  private Supplier doMemoize(final Supplier function) {
    return new Supplier() {
      private T value;

      @Override
      public T get() {
        if (value == null) value = function.get();
        return value;
      }
    };
  }


  private Function doMemoize(final Function function) {
    return input -> memoizationCache.computeIfAbsent(input, function);
  }

  /**
   * 
memoize.
   *
   * @param function a {@link java.util.function.Supplier} object.
   * @param  a T object.
   * @return a {@link java.util.function.Supplier} object.
   */
  public static  Supplier memoize(final Supplier function) {
    return new Memoizer().doMemoize(function);
  }

  /**
   * memoize.
   *
   * @param function a {@link java.util.function.Function} object.
   * @param  a T object.
   * @param  a U object.
   * @return a {@link java.util.function.Function} object.
   */
  public static  Function memoize(final Function function) {
    return new Memoizer().doMemoize(function);
  }


  /**
   * memoize.
   *
   * @param biFunc a {@link java.util.function.BiFunction} object.
   * @param  a T1 object.
   * @param  a T2 object.
   * @param  a R object.
   * @return a {@link java.util.function.BiFunction} object.
   */
  public static  BiFunction memoize(final BiFunction biFunc) {
    final Function> transformed = Memoizer.memoize(x -> Memoizer.memoize(y -> biFunc.apply(x, y)));
    return Transformations
        .unCurryBiFunction()
        .apply(transformed);
  }

//  public static  BiFunction memoize(final BiFunction biFunc) {
//    final Function> transformed = Memoizer.memoize(x -> Memoizer.memoize(y -> biFunc.apply(x, y)));
//    return (x, y) -> transformed.apply(x).apply(y);
//  }

  /**
   * memoize.
   *
   * @param threeFunc a {@link org.rapidpm.frp.functions.TriFunction} object.
   * @param  a T1 object.
   * @param  a T2 object.
   * @param  a T3 object.
   * @param  a R object.
   * @return a {@link org.rapidpm.frp.functions.TriFunction} object.
   */
  public static  TriFunction memoize(final TriFunction threeFunc) {
    final Function>> transformed
        = Memoizer.memoize(x -> Memoizer.memoize(y -> Memoizer.memoize(z -> threeFunc.apply(x, y, z))));
    return Transformations
        .unCurryTriFunction()
        .apply(transformed);
//    return (x, y, z) -> transformed.apply(x).apply(y).apply(z);
  }

}