/*
 * 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.inject.Binding;
import com.google.inject.Injector;
import com.google.inject.Key;
import com.google.inject.MembersInjector;
import com.google.inject.Module;
import com.google.inject.Provider;
import com.google.inject.Scope;
import com.google.inject.Stage;
import com.google.inject.TypeLiteral;
import com.google.inject.internal.util.Stopwatch;
import com.google.inject.spi.Dependency;
import com.google.inject.spi.TypeConverterBinding;
import java.lang.annotation.Annotation;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Set;

Builds a tree of injectors. This is a primary injector, plus child injectors needed for each Binder.newPrivateBinder() private environment. The primary injector is not necessarily a top-level injector. 
Injector construction happens in two phases.

Static building. In this phase, we interpret commands, create bindings, and inspect
    dependencies. During this phase, we hold a lock to ensure consistency with parent injectors.
    No user code is executed in this phase.
Dynamic injection. In this phase, we call user code. We inject members that requested injection. This may require user's objects be created and their providers be called. And we create eager singletons. In this phase, user code may have started other threads. This phase is not executed for injectors created using the tool stage 
Author:
crazybob@google.com (Bob Lee), jessewilson@google.com (Jesse Wilson)/**
 * Builds a tree of injectors. This is a primary injector, plus child injectors needed for each
 * {@code Binder.newPrivateBinder() private environment}. The primary injector is not necessarily a
 * top-level injector.
 *
 * <p>Injector construction happens in two phases.
 *
 * <ol>
 * <li>Static building. In this phase, we interpret commands, create bindings, and inspect
 *     dependencies. During this phase, we hold a lock to ensure consistency with parent injectors.
 *     No user code is executed in this phase.
 * <li>Dynamic injection. In this phase, we call user code. We inject members that requested
 *     injection. This may require user's objects be created and their providers be called. And we
 *     create eager singletons. In this phase, user code may have started other threads. This phase
 *     is not executed for injectors created using {@link Stage#TOOL the tool stage}
 * </ol>
 *
 * @author crazybob@google.com (Bob Lee)
 * @author jessewilson@google.com (Jesse Wilson)
 */
public final class InternalInjectorCreator {

  private final Stopwatch stopwatch = new Stopwatch();
  private final Errors errors = new Errors();

  private final Initializer initializer = new Initializer();
  private final ProcessedBindingData bindingData;
  private final InjectionRequestProcessor injectionRequestProcessor;

  private final InjectorShell.Builder shellBuilder = new InjectorShell.Builder();
  private List<InjectorShell> shells;

  public InternalInjectorCreator() {
    injectionRequestProcessor = new InjectionRequestProcessor(errors, initializer);
    bindingData = new ProcessedBindingData();
  }

  public InternalInjectorCreator stage(Stage stage) {
    shellBuilder.stage(stage);
    return this;
  }

  
Sets the parent of the injector to-be-constructed. As a side effect, this sets this injector's stage to the stage of parent and sets requireExplicitBindings() if the parent injector also required them. /**
   * Sets the parent of the injector to-be-constructed. As a side effect, this sets this injector's
   * stage to the stage of {@code parent} and sets {@link #requireExplicitBindings()} if the parent
   * injector also required them.
   */
  public InternalInjectorCreator parentInjector(InjectorImpl parent) {
    shellBuilder.parent(parent);
    return this;
  }

  public InternalInjectorCreator addModules(Iterable<? extends Module> modules) {
    shellBuilder.addModules(modules);
    return this;
  }

  public Injector build() {
    if (shellBuilder == null) {
      throw new AssertionError("Already built, builders are not reusable.");
    }

    // Synchronize while we're building up the bindings and other injector state. This ensures that
    // the JIT bindings in the parent injector don't change while we're being built
    synchronized (shellBuilder.lock()) {
      shells = shellBuilder.build(initializer, bindingData, stopwatch, errors);
      stopwatch.resetAndLog("Injector construction");

      initializeStatically();
    }

    injectDynamically();

    if (shellBuilder.getStage() == Stage.TOOL) {
      // wrap the primaryInjector in a ToolStageInjector
      // to prevent non-tool-friendy methods from being called.
      return new ToolStageInjector(primaryInjector());
    } else {
      return primaryInjector();
    }
  }

  
Initialize and validate everything. /** Initialize and validate everything. */
  private void initializeStatically() {
    bindingData.initializeBindings();
    stopwatch.resetAndLog("Binding initialization");

    for (InjectorShell shell : shells) {
      shell.getInjector().index();
    }
    stopwatch.resetAndLog("Binding indexing");

    injectionRequestProcessor.process(shells);
    stopwatch.resetAndLog("Collecting injection requests");

    bindingData.runCreationListeners(errors);
    stopwatch.resetAndLog("Binding validation");

    injectionRequestProcessor.validate();
    stopwatch.resetAndLog("Static validation");

    initializer.validateOustandingInjections(errors);
    stopwatch.resetAndLog("Instance member validation");

    new LookupProcessor(errors).process(shells);
    for (InjectorShell shell : shells) {
      ((DeferredLookups) shell.getInjector().lookups).initialize(errors);
    }
    stopwatch.resetAndLog("Provider verification");

    // This needs to come late since some user bindings rely on requireBinding calls to create
    // jit bindings during the LookupProcessor.
    bindingData.initializeDelayedBindings();
    stopwatch.resetAndLog("Delayed Binding initialization");

    for (InjectorShell shell : shells) {
      if (!shell.getElements().isEmpty()) {
        throw new AssertionError("Failed to execute " + shell.getElements());
      }
    }

    errors.throwCreationExceptionIfErrorsExist();
  }

  
Returns the injector being constructed. This is not necessarily the root injector. /** Returns the injector being constructed. This is not necessarily the root injector. */
  private Injector primaryInjector() {
    return shells.get(0).getInjector();
  }

  
Inject everything that can be injected. This method is intentionally not synchronized. If we
locked while injecting members (ie. running user code), things would deadlock should the user
code build a just-in-time binding from another thread.
/**
   * Inject everything that can be injected. This method is intentionally not synchronized. If we
   * locked while injecting members (ie. running user code), things would deadlock should the user
   * code build a just-in-time binding from another thread.
   */
  private void injectDynamically() {
    injectionRequestProcessor.injectMembers();
    stopwatch.resetAndLog("Static member injection");

    initializer.injectAll(errors);
    stopwatch.resetAndLog("Instance injection");
    errors.throwCreationExceptionIfErrorsExist();

    if (shellBuilder.getStage() != Stage.TOOL) {
      for (InjectorShell shell : shells) {
        loadEagerSingletons(shell.getInjector(), shellBuilder.getStage(), errors);
      }
      stopwatch.resetAndLog("Preloading singletons");
    }
    errors.throwCreationExceptionIfErrorsExist();
  }

  
Loads eager singletons, or all singletons if we're in Stage.PRODUCTION. Bindings discovered
while we're binding these singletons are not be eager.
/**
   * Loads eager singletons, or all singletons if we're in Stage.PRODUCTION. Bindings discovered
   * while we're binding these singletons are not be eager.
   */
  void loadEagerSingletons(InjectorImpl injector, Stage stage, final Errors errors) {
    List<BindingImpl<?>> candidateBindings = new ArrayList<>();
    @SuppressWarnings("unchecked") // casting Collection<Binding> to Collection<BindingImpl> is safe
    Collection<BindingImpl<?>> bindingsAtThisLevel =
        (Collection) injector.state.getExplicitBindingsThisLevel().values();
    candidateBindings.addAll(bindingsAtThisLevel);
    synchronized (injector.state.lock()) {
      // jit bindings must be accessed while holding the lock.
      candidateBindings.addAll(injector.jitBindings.values());
    }
    InternalContext context = injector.enterContext();
    try {
      for (BindingImpl<?> binding : candidateBindings) {
        if (isEagerSingleton(injector, binding, stage)) {
          Dependency<?> dependency = Dependency.get(binding.getKey());
          Dependency previous = context.pushDependency(dependency, binding.getSource());

          try {
            binding.getInternalFactory().get(context, dependency, false);
          } catch (InternalProvisionException e) {
            errors.withSource(dependency).merge(e);
          } finally {
              context.popStateAndSetDependency(previous);
            }
        }
      }
    } finally {
      context.close();
    }
  }

  private boolean isEagerSingleton(InjectorImpl injector, BindingImpl<?> binding, Stage stage) {
    if (binding.getScoping().isEagerSingleton(stage)) {
      return true;
    }

    // handle a corner case where a child injector links to a binding in a parent injector, and
    // that binding is singleton. We won't catch this otherwise because we only iterate the child's
    // bindings.
    if (binding instanceof LinkedBindingImpl) {
      Key<?> linkedBinding = ((LinkedBindingImpl<?>) binding).getLinkedKey();
      return isEagerSingleton(injector, injector.getBinding(linkedBinding), stage);
    }

    return false;
  }

  
Injector exposed to users in Stage.TOOL. /** {@link Injector} exposed to users in {@link Stage#TOOL}. */
  static class ToolStageInjector implements Injector {
    private final Injector delegateInjector;

    ToolStageInjector(Injector delegateInjector) {
      this.delegateInjector = delegateInjector;
    }

    @Override
    public void injectMembers(Object o) {
      throw new UnsupportedOperationException(
          "Injector.injectMembers(Object) is not supported in Stage.TOOL");
    }

    @Override
    public Map<Key<?>, Binding<?>> getBindings() {
      return this.delegateInjector.getBindings();
    }

    @Override
    public Map<Key<?>, Binding<?>> getAllBindings() {
      return this.delegateInjector.getAllBindings();
    }

    @Override
    public <T> Binding<T> getBinding(Key<T> key) {
      return this.delegateInjector.getBinding(key);
    }

    @Override
    public <T> Binding<T> getBinding(Class<T> type) {
      return this.delegateInjector.getBinding(type);
    }

    @Override
    public <T> Binding<T> getExistingBinding(Key<T> key) {
      return this.delegateInjector.getExistingBinding(key);
    }

    @Override
    public <T> List<Binding<T>> findBindingsByType(TypeLiteral<T> type) {
      return this.delegateInjector.findBindingsByType(type);
    }

    @Override
    public Injector getParent() {
      return delegateInjector.getParent();
    }

    @Override
    public Injector createChildInjector(Iterable<? extends Module> modules) {
      return delegateInjector.createChildInjector(modules);
    }

    @Override
    public Injector createChildInjector(Module... modules) {
      return delegateInjector.createChildInjector(modules);
    }

    @Override
    public Map<Class<? extends Annotation>, Scope> getScopeBindings() {
      return delegateInjector.getScopeBindings();
    }

    @Override
    public Set<TypeConverterBinding> getTypeConverterBindings() {
      return delegateInjector.getTypeConverterBindings();
    }

    @Override
    public <T> Provider<T> getProvider(Key<T> key) {
      throw new UnsupportedOperationException(
          "Injector.getProvider(Key<T>) is not supported in Stage.TOOL");
    }

    @Override
    public <T> Provider<T> getProvider(Class<T> type) {
      throw new UnsupportedOperationException(
          "Injector.getProvider(Class<T>) is not supported in Stage.TOOL");
    }

    @Override
    public <T> MembersInjector<T> getMembersInjector(TypeLiteral<T> typeLiteral) {
      throw new UnsupportedOperationException(
          "Injector.getMembersInjector(TypeLiteral<T>) is not supported in Stage.TOOL");
    }

    @Override
    public <T> MembersInjector<T> getMembersInjector(Class<T> type) {
      throw new UnsupportedOperationException(
          "Injector.getMembersInjector(Class<T>) is not supported in Stage.TOOL");
    }

    @Override
    public <T> T getInstance(Key<T> key) {
      throw new UnsupportedOperationException(
          "Injector.getInstance(Key<T>) is not supported in Stage.TOOL");
    }

    @Override
    public <T> T getInstance(Class<T> type) {
      throw new UnsupportedOperationException(
          "Injector.getInstance(Class<T>) is not supported in Stage.TOOL");
    }
  }
}