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Integration with Google Guice for Ratpack applications - https://code.google.com/p/google-guice/
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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.guice.internal;

import com.google.common.base.Function;
import com.google.common.base.Predicate;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.reflect.TypeToken;
import com.google.common.util.concurrent.UncheckedExecutionException;
import com.google.inject.Injector;
import com.google.inject.Provider;
import ratpack.api.Nullable;
import ratpack.func.Action;
import ratpack.registry.NotInRegistryException;
import ratpack.registry.PredicateCacheability;
import ratpack.registry.Registry;

import java.util.Collections;
import java.util.List;
import java.util.concurrent.ExecutionException;

import static ratpack.util.ExceptionUtils.toException;
import static ratpack.util.ExceptionUtils.uncheck;

public class InjectorBackedRegistry implements Registry {

  final Injector injector;

  public InjectorBackedRegistry(Injector injector) {
    this.injector = injector;
  }

  private final LoadingCache, List>> providerCache = CacheBuilder.newBuilder().build(new CacheLoader, List>>() {
    @Override
    public List> load(@SuppressWarnings("NullableProblems") TypeToken key) throws Exception {
      @SuppressWarnings({"unchecked", "RedundantCast"})
      List> providers = (List>) GuiceUtil.allProvidersOfType(injector, key);
      return providers;
    }
  });

  private final LoadingCache, List>> predicateCache = CacheBuilder.newBuilder().build(new CacheLoader, List>>() {
    @Override
    public List> load(@SuppressWarnings("NullableProblems") PredicateCacheability.CacheKey key) throws Exception {
      return get(key);
    }

    private  List> get(PredicateCacheability.CacheKey key) throws ExecutionException {
      List> providers = getProviders(key.type);
      if (providers.isEmpty()) {
        return Collections.emptyList();
      } else {
        ImmutableList.Builder> builder = ImmutableList.builder();
        Predicate predicate = key.predicate;
        for (Provider provider : providers) {
          @SuppressWarnings("unchecked") Provider castProvider = (Provider) provider;
          if (predicate.apply(castProvider.get())) {
            builder.add(castProvider);
          }
        }

        return builder.build();
      }
    }

  });

  @Override
  public  O get(Class type) throws NotInRegistryException {
    return get(TypeToken.of(type));
  }

  @Override
  public  O get(TypeToken type) throws NotInRegistryException {
    O object = maybeGet(type);
    if (object == null) {
      throw new NotInRegistryException(type);
    } else {
      return object;
    }
  }

  public  T maybeGet(Class type) {
    return maybeGet(TypeToken.of(type));
  }

  public  T maybeGet(TypeToken type) {
    List> providers = getProviders(type);
    if (providers.isEmpty()) {
      return null;
    } else {
      @SuppressWarnings("unchecked") T cast = (T) providers.get(0).get();
      return cast;
    }
  }

  private  List> getProviders(TypeToken type) {
    try {
      return providerCache.get(type);
    } catch (ExecutionException | UncheckedExecutionException e) {
      throw uncheck(toException(e.getCause()));
    }
  }

  @Override
  public  Iterable getAll(Class type) {
    return getAll(TypeToken.of(type));
  }

  @Override
  public  Iterable getAll(TypeToken type) {
    final List> providers = getProviders(type);
    if (providers.isEmpty()) {
      return Collections.emptyList();
    } else {
      return Iterables.transform(providers, new Function, O>() {
        @Override
        public O apply(Provider input) {
          @SuppressWarnings("unchecked") O cast = (O) input.get();
          return cast;
        }
      });
    }
  }

  private  List> getAll(TypeToken type, Predicate predicate) {
    try {
      return predicateCache.get(new PredicateCacheability.CacheKey<>(type, predicate));
    } catch (ExecutionException | UncheckedExecutionException e) {
      throw uncheck(toException(e.getCause()));
    }
  }

  @Nullable
  @Override
  public  T first(TypeToken type, Predicate predicate) {
    if (PredicateCacheability.isCacheable(predicate)) {
      List> all = getAll(type, predicate);
      if (all.isEmpty()) {
        return null;
      } else {
        @SuppressWarnings("unchecked") T cast = (T) all.get(0).get();
        return cast;
      }
    } else {
      T object = maybeGet(type);
      if (object != null && predicate.apply(object)) {
        return object;
      } else {
        return null;
      }
    }
  }

  @Override
  public  Iterable all(TypeToken type, Predicate predicate) {
    if (PredicateCacheability.isCacheable(predicate)) {
      @SuppressWarnings("unchecked") List cast = (List) getAll(type, predicate);
      return cast;
    } else {
      return Iterables.filter(getAll(type), predicate);
    }
  }

  @Override
  public  boolean each(TypeToken type, Predicate predicate, Action action) throws Exception {
    if (PredicateCacheability.isCacheable(predicate)) {
      Iterable all = all(type, predicate);
      boolean any = false;
      for (T t : all) {
        any = true;
        action.execute(t);
      }
      return any;
    } else {
      boolean foundMatch = false;
      List> providers = getProviders(type);
      for (Provider provider : providers) {
        @SuppressWarnings("unchecked") T cast = (T) provider.get();
        if (predicate.apply(cast)) {
          action.execute(cast);
          foundMatch = true;
        }
      }
      return foundMatch;
    }
  }

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

    InjectorBackedRegistry that = (InjectorBackedRegistry) o;

    return injector.equals(that.injector);
  }

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

}