/*
 * Copyright (C) 2008 Google Inc.
 *
 * 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.google.inject.spi;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.base.Objects;
import com.google.inject.Binder;
import com.google.inject.ConfigurationException;
import com.google.inject.TypeLiteral;
import java.util.Set;

/**
 * A request to inject the instance fields and methods of an instance. Requests are created
 * explicitly in a module using {@link com.google.inject.Binder#requestInjection(Object)
 * requestInjection()} statements:
 *
 * <pre>
 *     requestInjection(serviceInstance);</pre>
 *
 * @author mikeward@google.com (Mike Ward)
 * @since 2.0
 */
public final class InjectionRequest<T> implements Element {

  private final Object source;
  private final TypeLiteral<T> type;
  private final T instance;

  public InjectionRequest(Object source, TypeLiteral<T> type, T instance) {
    this.source = checkNotNull(source, "source");
    this.type = checkNotNull(type, "type");
    this.instance = instance;
  }

  @Override
  public Object getSource() {
    return source;
  }

  /**
   * Returns the instance that injection is being requested on. This may be null for injection
   * requests returned from an Injector, to allow the injector to reclaim memory.
   */
  public T getInstance() {
    return instance;
  }

  public TypeLiteral<T> getType() {
    return type;
  }

  /**
   * Returns the instance methods and fields of {@code instance} that will be injected to fulfill
   * this request.
   *
   * @return a possibly empty set of injection points. The set has a specified iteration order. All
   *     fields are returned and then all methods. Within the fields, supertype fields are returned
   *     before subtype fields. Similarly, supertype methods are returned before subtype methods.
   * @throws ConfigurationException if there is a malformed injection point on the class of {@code
   *     instance}, such as a field with multiple binding annotations. The exception's {@link
   *     ConfigurationException#getPartialValue() partial value} is a {@code Set<InjectionPoint>} of
   *     the valid injection points.
   */
  public Set<InjectionPoint> getInjectionPoints() throws ConfigurationException {
    return InjectionPoint.forInstanceMethodsAndFields(type);
  }

  @Override
  public <R> R acceptVisitor(ElementVisitor<R> visitor) {
    return visitor.visit(this);
  }

  @Override
  public void applyTo(Binder binder) {
    binder.withSource(getSource()).requestInjection(type, instance);
  }

  @Override
  public boolean equals(Object obj) {
    return obj instanceof InjectionRequest
        && Objects.equal(((InjectionRequest<?>) obj).instance, instance)
        && ((InjectionRequest<?>) obj).type.equals(type)
        && ((InjectionRequest<?>) obj).source.equals(source);
  }

  @Override
  public int hashCode() {
    return Objects.hashCode(type, source);
  }
}
