/**
 * Copyright (C) 2006 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.internal;

import com.google.common.base.Objects;
import com.google.inject.Binding;
import com.google.inject.Key;
import com.google.inject.Provider;
import com.google.inject.spi.BindingScopingVisitor;
import com.google.inject.spi.ElementVisitor;
import com.google.inject.spi.InstanceBinding;

/**
 * @author crazybob@google.com (Bob Lee)
 */
public abstract class BindingImpl<T> implements Binding<T> {

  private final InjectorImpl injector;
  private final Key<T> key;
  private final Object source;
  private final Scoping scoping;
  private final InternalFactory<? extends T> internalFactory;

  public BindingImpl(InjectorImpl injector, Key<T> key, Object source,
      InternalFactory<? extends T> internalFactory, Scoping scoping) {
    this.injector = injector;
    this.key = key;
    this.source = source;
    this.internalFactory = internalFactory;
    this.scoping = scoping;
  }

  protected BindingImpl(Object source, Key<T> key, Scoping scoping) {
    this.internalFactory = null;
    this.injector = null;
    this.source = source;
    this.key = key;
    this.scoping = scoping;
  }

  public Key<T> getKey() {
    return key;
  }

  public Object getSource() {
    return source;
  }

  private volatile Provider<T> provider;

  public Provider<T> getProvider() {
    if (provider == null) {
      if (injector == null) {
        throw new UnsupportedOperationException("getProvider() not supported for module bindings");
      }

      provider = injector.getProvider(key);
    }
    return provider;
  }

  public InternalFactory<? extends T> getInternalFactory() {
    return internalFactory;
  }

  public Scoping getScoping() {
    return scoping;
  }

  /**
   * Is this a constant binding? This returns true for constant bindings as
   * well as toInstance() bindings.
   */
  public boolean isConstant() {
    return this instanceof InstanceBinding;
  }

  public <V> V acceptVisitor(ElementVisitor<V> visitor) {
    return visitor.visit(this);
  }

  public <V> V acceptScopingVisitor(BindingScopingVisitor<V> visitor) {
    return scoping.acceptVisitor(visitor);
  }

  protected BindingImpl<T> withScoping(Scoping scoping) {
    throw new AssertionError();
  }

  protected BindingImpl<T> withKey(Key<T> key) {
    throw new AssertionError();
  }
  
  @Override public String toString() {
    return Objects.toStringHelper(Binding.class)
        .add("key", key)
        .add("scope", scoping)
        .add("source", source)
        .toString();
  }

  public InjectorImpl getInjector() {
    return injector;
  }
}