/*
 * Copyright (C) 2015 The Dagger 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 dagger.internal.codegen.componentgenerator;

import static com.google.auto.common.MoreElements.getLocalAndInheritedMethods;
import static com.google.auto.common.MoreTypes.asDeclared;
import static com.google.common.base.Preconditions.checkState;
import static com.squareup.javapoet.MethodSpec.constructorBuilder;
import static com.squareup.javapoet.MethodSpec.methodBuilder;
import static dagger.internal.codegen.binding.BindingRequest.bindingRequest;
import static dagger.internal.codegen.binding.ComponentCreatorKind.BUILDER;
import static dagger.internal.codegen.extension.DaggerStreams.toImmutableList;
import static dagger.internal.codegen.javapoet.AnnotationSpecs.Suppression.UNCHECKED;
import static dagger.internal.codegen.javapoet.CodeBlocks.parameterNames;
import static dagger.internal.codegen.writing.ComponentImplementation.MethodSpecKind.BUILDER_METHOD;
import static dagger.internal.codegen.writing.ComponentImplementation.MethodSpecKind.CANCELLATION_LISTENER_METHOD;
import static dagger.internal.codegen.writing.ComponentImplementation.MethodSpecKind.COMPONENT_METHOD;
import static dagger.internal.codegen.writing.ComponentImplementation.MethodSpecKind.CONSTRUCTOR;
import static dagger.internal.codegen.writing.ComponentImplementation.MethodSpecKind.INITIALIZE_METHOD;
import static dagger.internal.codegen.writing.ComponentImplementation.TypeSpecKind.COMPONENT_CREATOR;
import static dagger.internal.codegen.writing.ComponentImplementation.TypeSpecKind.SUBCOMPONENT;
import static dagger.producers.CancellationPolicy.Propagation.PROPAGATE;
import static javax.lang.model.element.Modifier.FINAL;
import static javax.lang.model.element.Modifier.PRIVATE;
import static javax.lang.model.element.Modifier.PUBLIC;
import static javax.lang.model.element.Modifier.STATIC;

import com.google.auto.common.MoreTypes;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableListMultimap;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimaps;
import com.squareup.javapoet.ClassName;
import com.squareup.javapoet.CodeBlock;
import com.squareup.javapoet.MethodSpec;
import com.squareup.javapoet.ParameterSpec;
import com.squareup.javapoet.TypeSpec;
import dagger.internal.Preconditions;
import dagger.internal.codegen.binding.BindingGraph;
import dagger.internal.codegen.binding.ComponentCreatorDescriptor;
import dagger.internal.codegen.binding.ComponentCreatorKind;
import dagger.internal.codegen.binding.ComponentDescriptor.ComponentMethodDescriptor;
import dagger.internal.codegen.binding.ComponentRequirement;
import dagger.internal.codegen.binding.FrameworkType;
import dagger.internal.codegen.javapoet.AnnotationSpecs;
import dagger.internal.codegen.javapoet.CodeBlocks;
import dagger.internal.codegen.kotlin.KotlinMetadataUtil;
import dagger.internal.codegen.langmodel.DaggerElements;
import dagger.internal.codegen.langmodel.DaggerTypes;
import dagger.internal.codegen.writing.ComponentBindingExpressions;
import dagger.internal.codegen.writing.ComponentCreatorImplementation;
import dagger.internal.codegen.writing.ComponentImplementation;
import dagger.internal.codegen.writing.ComponentRequirementExpressions;
import dagger.internal.codegen.writing.ParentComponent;
import dagger.model.Key;
import dagger.producers.internal.CancellationListener;
import dagger.producers.internal.Producers;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.function.Function;
import javax.inject.Inject;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.type.DeclaredType;

/** A builder of {@link ComponentImplementation}s. */
// This only needs to be public because it's referenced in an entry point.
public final class ComponentImplementationBuilder {
  private static final String MAY_INTERRUPT_IF_RUNNING = "mayInterruptIfRunning";

  /**
   * How many statements per {@code initialize()} or {@code onProducerFutureCancelled()} method
   * before they get partitioned.
   */
  private static final int STATEMENTS_PER_METHOD = 100;

  private static final String CANCELLATION_LISTENER_METHOD_NAME = "onProducerFutureCancelled";

  private final Optional<ComponentImplementationBuilder> parent;
  private final BindingGraph graph;
  private final ComponentBindingExpressions bindingExpressions;
  private final ComponentRequirementExpressions componentRequirementExpressions;
  private final ComponentImplementation componentImplementation;
  private final ComponentCreatorImplementationFactory componentCreatorImplementationFactory;
  private final TopLevelImplementationComponent topLevelImplementationComponent;
  private final DaggerTypes types;
  private final DaggerElements elements;
  private final KotlinMetadataUtil metadataUtil;
  private boolean done;

  @Inject
  ComponentImplementationBuilder(
      @ParentComponent Optional<ComponentImplementationBuilder> parent,
      BindingGraph graph,
      ComponentBindingExpressions bindingExpressions,
      ComponentRequirementExpressions componentRequirementExpressions,
      ComponentImplementation componentImplementation,
      ComponentCreatorImplementationFactory componentCreatorImplementationFactory,
      TopLevelImplementationComponent topLevelImplementationComponent,
      DaggerTypes types,
      DaggerElements elements,
      KotlinMetadataUtil metadataUtil) {
    this.parent = parent;
    this.graph = graph;
    this.bindingExpressions = bindingExpressions;
    this.componentRequirementExpressions = componentRequirementExpressions;
    this.componentImplementation = componentImplementation;
    this.componentCreatorImplementationFactory = componentCreatorImplementationFactory;
    this.types = types;
    this.elements = elements;
    this.topLevelImplementationComponent = topLevelImplementationComponent;
    this.metadataUtil = metadataUtil;
  }

  /**
   * Returns a {@link ComponentImplementation} for this component. This is only intended to be
   * called once (and will throw on successive invocations). If the component must be regenerated,
   * use a new instance.
   */
  ComponentImplementation build() {
    checkState(
        !done,
        "ComponentImplementationBuilder has already built the ComponentImplementation for [%s].",
        componentImplementation.name());
    setSupertype();

    componentCreatorImplementationFactory.create()
        .map(ComponentCreatorImplementation::spec)
        .ifPresent(this::addCreatorClass);

    getLocalAndInheritedMethods(graph.componentTypeElement(), types, elements)
        .forEach(method -> componentImplementation.claimMethodName(method.getSimpleName()));

    addFactoryMethods();
    addInterfaceMethods();
    addChildComponents();

    addConstructorAndInitializationMethods();

    if (graph.componentDescriptor().isProduction()) {
      addCancellationListenerImplementation();
    }

    done = true;
    return componentImplementation;
  }

  /** Set the supertype for this generated class. */
  private void setSupertype() {
    componentImplementation.addSupertype(graph.componentTypeElement());
  }

  private void addCreatorClass(TypeSpec creator) {
    if (parent.isPresent()) {
      // In an inner implementation of a subcomponent the creator is a peer class.
      parent.get().componentImplementation.addType(SUBCOMPONENT, creator);
    } else {
      componentImplementation.addType(COMPONENT_CREATOR, creator);
    }
  }

  private void addFactoryMethods() {
    if (parent.isPresent()) {
      graph.factoryMethod().ifPresent(this::createSubcomponentFactoryMethod);
    } else {
      createRootComponentFactoryMethod();
    }
  }

  private void addInterfaceMethods() {
    // Each component method may have been declared by several supertypes. We want to implement
    // only one method for each distinct signature.
    ImmutableListMultimap<MethodSignature, ComponentMethodDescriptor> componentMethodsBySignature =
        Multimaps.index(graph.componentDescriptor().entryPointMethods(), this::getMethodSignature);
    for (List<ComponentMethodDescriptor> methodsWithSameSignature :
        Multimaps.asMap(componentMethodsBySignature).values()) {
      ComponentMethodDescriptor anyOneMethod = methodsWithSameSignature.stream().findAny().get();
      MethodSpec methodSpec = bindingExpressions.getComponentMethod(anyOneMethod);

      componentImplementation.addMethod(COMPONENT_METHOD, methodSpec);
    }
  }

  private void addCancellationListenerImplementation() {
    componentImplementation.addSupertype(elements.getTypeElement(CancellationListener.class));
    componentImplementation.claimMethodName(CANCELLATION_LISTENER_METHOD_NAME);

    ImmutableList<ParameterSpec> parameters =
        ImmutableList.of(ParameterSpec.builder(boolean.class, MAY_INTERRUPT_IF_RUNNING).build());

    MethodSpec.Builder methodBuilder =
        methodBuilder(CANCELLATION_LISTENER_METHOD_NAME)
            .addModifiers(PUBLIC)
            .addAnnotation(Override.class)
            .addParameters(parameters);

    ImmutableList<CodeBlock> cancellationStatements = cancellationStatements();

    if (cancellationStatements.size() < STATEMENTS_PER_METHOD) {
      methodBuilder.addCode(CodeBlocks.concat(cancellationStatements)).build();
    } else {
      ImmutableList<MethodSpec> cancelProducersMethods =
          createPartitionedMethods(
              "cancelProducers",
              parameters,
              cancellationStatements,
              methodName -> methodBuilder(methodName).addModifiers(PRIVATE));
      for (MethodSpec cancelProducersMethod : cancelProducersMethods) {
        methodBuilder.addStatement("$N($L)", cancelProducersMethod, MAY_INTERRUPT_IF_RUNNING);
        componentImplementation.addMethod(CANCELLATION_LISTENER_METHOD, cancelProducersMethod);
      }
    }

    cancelParentStatement().ifPresent(methodBuilder::addCode);

    componentImplementation.addMethod(CANCELLATION_LISTENER_METHOD, methodBuilder.build());
  }

  private ImmutableList<CodeBlock> cancellationStatements() {
    // Reversing should order cancellations starting from entry points and going down to leaves
    // rather than the other way around. This shouldn't really matter but seems *slightly*
    // preferable because:
    // When a future that another future depends on is cancelled, that cancellation will propagate
    // up the future graph toward the entry point. Cancelling in reverse order should ensure that
    // everything that depends on a particular node has already been cancelled when that node is
    // cancelled, so there's no need to propagate. Otherwise, when we cancel a leaf node, it might
    // propagate through most of the graph, making most of the cancel calls that follow in the
    // onProducerFutureCancelled method do nothing.
    ImmutableList<Key> cancellationKeys =
        componentImplementation.getCancellableProducerKeys().reverse();

    ImmutableList.Builder<CodeBlock> cancellationStatements = ImmutableList.builder();
    for (Key cancellationKey : cancellationKeys) {
      cancellationStatements.add(
          CodeBlock.of(
              "$T.cancel($L, $N);",
              Producers.class,
              bindingExpressions
                  .getDependencyExpression(
                      bindingRequest(cancellationKey, FrameworkType.PRODUCER_NODE),
                      componentImplementation.name())
                  .codeBlock(),
              MAY_INTERRUPT_IF_RUNNING));
    }
    return cancellationStatements.build();
  }

  private Optional<CodeBlock> cancelParentStatement() {
    if (!shouldPropagateCancellationToParent()) {
      return Optional.empty();
    }
    return Optional.of(
        CodeBlock.builder()
            .addStatement(
                "$T.this.$N($N)",
                parent.get().componentImplementation.name(),
                CANCELLATION_LISTENER_METHOD_NAME,
                MAY_INTERRUPT_IF_RUNNING)
            .build());
  }

  private boolean shouldPropagateCancellationToParent() {
    return parent.isPresent()
        && parent
            .get()
            .componentImplementation
            .componentDescriptor()
            .cancellationPolicy()
            .map(policy -> policy.fromSubcomponents().equals(PROPAGATE))
            .orElse(false);
  }

  private MethodSignature getMethodSignature(ComponentMethodDescriptor method) {
    return MethodSignature.forComponentMethod(
        method, MoreTypes.asDeclared(graph.componentTypeElement().asType()), types);
  }

  private void addChildComponents() {
    for (BindingGraph subgraph : graph.subgraphs()) {
      componentImplementation.addType(SUBCOMPONENT, childComponent(subgraph));
    }
  }

  private TypeSpec childComponent(BindingGraph childGraph) {
    return topLevelImplementationComponent
        .currentImplementationSubcomponentBuilder()
        .componentImplementation(subcomponent(childGraph))
        .bindingGraph(childGraph)
        .parentBuilder(Optional.of(this))
        .parentBindingExpressions(Optional.of(bindingExpressions))
        .parentRequirementExpressions(Optional.of(componentRequirementExpressions))
        .build()
        .componentImplementationBuilder()
        .build()
        .generate()
        .build();
  }

  /** Creates an inner subcomponent implementation. */
  private ComponentImplementation subcomponent(BindingGraph childGraph) {
    return componentImplementation.childComponentImplementation(childGraph);
  }

  /** Creates and adds the constructor and methods needed for initializing the component. */
  private void addConstructorAndInitializationMethods() {
    MethodSpec.Builder constructor = constructorBuilder().addModifiers(PRIVATE);
    implementInitializationMethod(constructor, initializationParameters());
    componentImplementation.addMethod(CONSTRUCTOR, constructor.build());
  }

  /** Adds parameters and code to the given {@code initializationMethod}. */
  private void implementInitializationMethod(
      MethodSpec.Builder initializationMethod,
      ImmutableMap<ComponentRequirement, ParameterSpec> initializationParameters) {
    initializationMethod.addParameters(initializationParameters.values());
    initializationMethod.addCode(
        CodeBlocks.concat(componentImplementation.getComponentRequirementInitializations()));
    addInitializeMethods(initializationMethod, initializationParameters.values().asList());
  }

  /**
   * Adds any necessary {@code initialize} methods to the component and adds calls to them to the
   * given {@code callingMethod}.
   */
  private void addInitializeMethods(
      MethodSpec.Builder callingMethod, ImmutableList<ParameterSpec> parameters) {
    // TODO(cgdecker): It's not the case that each initialize() method has need for all of the
    // given parameters. In some cases, those parameters may have already been assigned to fields
    // which could be referenced instead. In other cases, an initialize method may just not need
    // some of the parameters because the set of initializations in that partition does not
    // include any reference to them. Right now, the Dagger code has no way of getting that
    // information because, among other things, componentImplementation.getImplementations() just
    // returns a bunch of CodeBlocks with no semantic information. Additionally, we may not know
    // yet whether a field will end up needing to be created for a specific requirement, and we
    // don't want to create a field that ends up only being used during initialization.
    CodeBlock args = parameterNames(parameters);
    ImmutableList<MethodSpec> methods =
        createPartitionedMethods(
            "initialize",
            makeFinal(parameters),
            componentImplementation.getInitializations(),
            methodName ->
                methodBuilder(methodName)
                    .addModifiers(PRIVATE)
                    /* TODO(gak): Strictly speaking, we only need the suppression here if we are
                     * also initializing a raw field in this method, but the structure of this
                     * code makes it awkward to pass that bit through.  This will be cleaned up
                     * when we no longer separate fields and initialization as we do now. */
                    .addAnnotation(AnnotationSpecs.suppressWarnings(UNCHECKED)));
    for (MethodSpec method : methods) {
      callingMethod.addStatement("$N($L)", method, args);
      componentImplementation.addMethod(INITIALIZE_METHOD, method);
    }
  }

  /**
   * Creates one or more methods, all taking the given {@code parameters}, which partition the given
   * list of {@code statements} among themselves such that no method has more than {@code
   * STATEMENTS_PER_METHOD} statements in it and such that the returned methods, if called in order,
   * will execute the {@code statements} in the given order.
   */
  private ImmutableList<MethodSpec> createPartitionedMethods(
      String methodName,
      Iterable<ParameterSpec> parameters,
      List<CodeBlock> statements,
      Function<String, MethodSpec.Builder> methodBuilderCreator) {
    return Lists.partition(statements, STATEMENTS_PER_METHOD).stream()
        .map(
            partition ->
                methodBuilderCreator
                    .apply(componentImplementation.getUniqueMethodName(methodName))
                    .addParameters(parameters)
                    .addCode(CodeBlocks.concat(partition))
                    .build())
        .collect(toImmutableList());
  }

  /** Returns the given parameters with a final modifier added. */
  private final ImmutableList<ParameterSpec> makeFinal(Collection<ParameterSpec> parameters) {
    return parameters.stream()
        .map(param -> param.toBuilder().addModifiers(FINAL).build())
        .collect(toImmutableList());
  }

  /**
   * Returns the parameters for the constructor as a map from the requirement the parameter fulfills
   * to the spec for the parameter.
   */
  private final ImmutableMap<ComponentRequirement, ParameterSpec> initializationParameters() {
    Map<ComponentRequirement, ParameterSpec> parameters;
    if (componentImplementation.componentDescriptor().hasCreator()) {
      parameters = Maps.toMap(graph.componentRequirements(), ComponentRequirement::toParameterSpec);
    } else if (graph.factoryMethod().isPresent()) {
      parameters = getFactoryMethodParameters(graph);
    } else {
      throw new AssertionError(
          "Expected either a component creator or factory method but found neither.");
    }

    return renameParameters(parameters);
  }

  /**
   * Renames the given parameters to guarantee their names do not conflict with fields in the
   * component to ensure that a parameter is never referenced where a reference to a field was
   * intended.
   */
  // TODO(cgdecker): This is a bit kludgy; it would be preferable to either qualify the field
  // references with "this." or "super." when needed to disambiguate between field and parameter,
  // but that would require more context than is currently available when the code referencing a
  // field is generated.
  private ImmutableMap<ComponentRequirement, ParameterSpec> renameParameters(
      Map<ComponentRequirement, ParameterSpec> parameters) {
    return ImmutableMap.copyOf(
        Maps.transformEntries(
            parameters,
            (requirement, parameter) ->
                renameParameter(
                    parameter,
                    componentImplementation.getParameterName(requirement, parameter.name))));
  }

  private ParameterSpec renameParameter(ParameterSpec parameter, String newName) {
    return ParameterSpec.builder(parameter.type, newName)
        .addAnnotations(parameter.annotations)
        .addModifiers(parameter.modifiers)
        .build();
  }

  private void createRootComponentFactoryMethod() {
    checkState(!parent.isPresent());
    // Top-level components have a static method that returns a builder or factory for the
    // component. If the user defined a @Component.Builder or @Component.Factory, an
    // implementation of their type is returned. Otherwise, an autogenerated Builder type is
    // returned.
    // TODO(cgdecker): Replace this abomination with a small class?
    // Better yet, change things so that an autogenerated builder type has a descriptor of sorts
    // just like a user-defined creator type.
    ComponentCreatorKind creatorKind;
    ClassName creatorType;
    String factoryMethodName;
    boolean noArgFactoryMethod;
    Optional<ComponentCreatorDescriptor> creatorDescriptor =
        graph.componentDescriptor().creatorDescriptor();
    if (creatorDescriptor.isPresent()) {
      ComponentCreatorDescriptor descriptor = creatorDescriptor.get();
      creatorKind = descriptor.kind();
      creatorType = ClassName.get(descriptor.typeElement());
      factoryMethodName = descriptor.factoryMethod().getSimpleName().toString();
      noArgFactoryMethod = descriptor.factoryParameters().isEmpty();
    } else {
      creatorKind = BUILDER;
      creatorType = componentImplementation.getCreatorName();
      factoryMethodName = "build";
      noArgFactoryMethod = true;
    }

    MethodSpec creatorFactoryMethod =
        methodBuilder(creatorKind.methodName())
            .addModifiers(PUBLIC, STATIC)
            .returns(creatorType)
            .addStatement("return new $T()", componentImplementation.getCreatorName())
            .build();
    componentImplementation.addMethod(BUILDER_METHOD, creatorFactoryMethod);
    if (noArgFactoryMethod && canInstantiateAllRequirements()) {
      componentImplementation.addMethod(
          BUILDER_METHOD,
          methodBuilder("create")
              .returns(ClassName.get(graph.componentTypeElement()))
              .addModifiers(PUBLIC, STATIC)
              .addStatement("return new $L().$L()", creatorKind.typeName(), factoryMethodName)
              .build());
    }
  }

  /** {@code true} if all of the graph's required dependencies can be automatically constructed */
  private boolean canInstantiateAllRequirements() {
    return !Iterables.any(
        graph.componentRequirements(),
        dependency -> dependency.requiresAPassedInstance(elements, types, metadataUtil));
  }

  private void createSubcomponentFactoryMethod(ExecutableElement factoryMethod) {
    checkState(parent.isPresent());
    Collection<ParameterSpec> params = getFactoryMethodParameters(graph).values();
    MethodSpec.Builder method = MethodSpec.overriding(factoryMethod, parentType(), types);
    params.forEach(
        param -> method.addStatement("$T.checkNotNull($N)", Preconditions.class, param));
    method.addStatement(
        "return new $T($L)", componentImplementation.name(), parameterNames(params));

    parent.get().componentImplementation.addMethod(COMPONENT_METHOD, method.build());
  }

  private DeclaredType parentType() {
    return asDeclared(parent.get().graph.componentTypeElement().asType());
  }
  /**
   * Returns the map of {@link ComponentRequirement}s to {@link ParameterSpec}s for the given
   * graph's factory method.
   */
  private static Map<ComponentRequirement, ParameterSpec> getFactoryMethodParameters(
      BindingGraph graph) {
    return Maps.transformValues(graph.factoryMethodParameters(), ParameterSpec::get);
  }
}