/*
 * Copyright (C) 2009 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 static com.google.common.base.Preconditions.checkState;

import com.google.inject.Binder;
import com.google.inject.MembersInjector;
import com.google.inject.TypeLiteral;

A lookup of the members injector for a type. Lookups are created explicitly in a module using getMembersInjector() statements: 
    MembersInjector<PaymentService> membersInjector
        = getMembersInjector(PaymentService.class);
Author:
crazybob@google.com (Bob Lee)
Since:
2.0/**
 * A lookup of the members injector for a type. Lookups are created explicitly in a module using
 * {@link com.google.inject.Binder#getMembersInjector(Class) getMembersInjector()} statements:
 *
 * <pre>
 *     MembersInjector&lt;PaymentService&gt; membersInjector
 *         = getMembersInjector(PaymentService.class);</pre>
 *
 * @author crazybob@google.com (Bob Lee)
 * @since 2.0
 */
public final class MembersInjectorLookup<T> implements Element {

  private final Object source;
  private final TypeLiteral<T> type;
  private MembersInjector<T> delegate;

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

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

  
Gets the type containing the members to be injected. /** Gets the type containing the members to be injected. */
  public TypeLiteral<T> getType() {
    return type;
  }

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

  
Sets the actual members injector.
Throws:
IllegalStateException – if the delegate is already set/**
   * Sets the actual members injector.
   *
   * @throws IllegalStateException if the delegate is already set
   */
  public void initializeDelegate(MembersInjector<T> delegate) {
    checkState(this.delegate == null, "delegate already initialized");
    this.delegate = checkNotNull(delegate, "delegate");
  }

  @Override
  public void applyTo(Binder binder) {
    initializeDelegate(binder.withSource(getSource()).getMembersInjector(type));
  }

  
Returns the delegate members injector, or null if it has not yet been initialized. The delegate will be initialized when this element is processed, or otherwise used to create an injector. /**
   * Returns the delegate members injector, or {@code null} if it has not yet been initialized. The
   * delegate will be initialized when this element is processed, or otherwise used to create an
   * injector.
   */
  public MembersInjector<T> getDelegate() {
    return delegate;
  }

  
Returns the looked up members injector. The result is not valid until this lookup has been initialized, which usually happens when the injector is created. The members injector will throw an IllegalStateException if you try to use it beforehand. /**
   * Returns the looked up members injector. The result is not valid until this lookup has been
   * initialized, which usually happens when the injector is created. The members injector will
   * throw an {@code IllegalStateException} if you try to use it beforehand.
   */
  public MembersInjector<T> getMembersInjector() {
    return new MembersInjector<T>() {
      @Override
      public void injectMembers(T instance) {
        MembersInjector<T> local = delegate;
        if (local == null) {
          throw new IllegalStateException(
              "This MembersInjector cannot be used until the Injector has been created.");
        }
        local.injectMembers(instance);
      }

      @Override
      public String toString() {
        return "MembersInjector<" + type + ">";
      }
    };
  }
}