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/*
 * Copyright 2013 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.registry.internal;

import com.google.common.base.Predicate;
import com.google.common.collect.Iterables;
import com.google.common.reflect.TypeToken;
import ratpack.func.Action;
import ratpack.registry.PredicateCacheability;
import ratpack.registry.Registry;
import ratpack.util.Types;

import java.util.Map;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.function.Function;

public class CachingRegistry implements Registry {

  private final Registry delegate;

  private final ConcurrentMap, Optional> cache = new ConcurrentHashMap<>();
  private final ConcurrentMap, Iterable> allCache = new ConcurrentHashMap<>();
  private ConcurrentMap, Iterable> predicateCache = new ConcurrentHashMap<>();

  public static Registry of(Registry registry) {
    if (registry instanceof CachingRegistry) {
      return registry;
    } else {
      return new CachingRegistry(registry);
    }
  }

  private CachingRegistry(Registry delegate) {
    this.delegate = delegate;
  }

  private static  V compute(Map map, K key, Function supplier) {
    V value = map.get(key);
    if (value == null) {
      value = supplier.apply(key);
      map.put(key, value);
    }
    return value;
  }

  @Override
  public  Optional maybeGet(TypeToken type) {
    return Types.cast(compute(cache, type, delegate::maybeGet));
  }

  @Override
  public  Iterable getAll(TypeToken type) {
    return Types.cast(compute(allCache, type, delegate::getAll));
  }

  private  Iterable getFromPredicateCache(TypeToken type, Predicate predicate) {
    return Types.cast(compute(predicateCache, new PredicateCacheability.CacheKey<>(type, predicate), k -> delegate.all(type, predicate)));
  }

  @Override
  public  Optional first(TypeToken type, Predicate predicate) {
    if (PredicateCacheability.isCacheable(predicate)) {
      Iterable objects = getFromPredicateCache(type, predicate);
      return Optional.ofNullable(Iterables.getFirst(objects, null));
    } else {
      return delegate.first(type, predicate);
    }
  }

  @Override
  public  Iterable all(TypeToken type, Predicate predicate) {
    if (PredicateCacheability.isCacheable(predicate)) {
      return getFromPredicateCache(type, predicate);
    } else {
      return delegate.all(type, predicate);
    }
  }

  @Override
  public  boolean each(TypeToken type, Predicate predicate, Action action) throws Exception {
    Iterable all = all(type, predicate);
    boolean any = false;
    for (T item : all) {
      any = true;
      action.execute(item);
    }

    return any;
  }

  @Override
  public String toString() {
    return "CachingRegistry{delegate=" + delegate + '}';
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }

    CachingRegistry that = (CachingRegistry) o;

    return delegate.equals(that.delegate);
  }

  @Override
  public int hashCode() {
    return delegate.hashCode();
  }
}