/*
 * Copyright (C) 2016 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.validation;

import static com.google.auto.common.MoreElements.asType;
import static dagger.internal.codegen.langmodel.DaggerElements.isAnyAnnotationPresent;
import static java.util.stream.Collectors.joining;
import static javax.lang.model.element.Modifier.ABSTRACT;
import static javax.lang.model.element.Modifier.PRIVATE;

import com.google.common.collect.ImmutableSet;
import com.google.errorprone.annotations.FormatMethod;
import dagger.internal.codegen.binding.InjectionAnnotations;
import dagger.internal.codegen.kotlin.KotlinMetadataUtil;
import dagger.internal.codegen.langmodel.DaggerElements;
import dagger.internal.codegen.langmodel.DaggerTypes;
import java.lang.annotation.Annotation;
import java.util.Optional;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.TypeElement;
import javax.lang.model.element.VariableElement;
import javax.lang.model.type.TypeMirror;

/** A validator for methods that represent binding declarations. */
abstract class BindingMethodValidator extends BindingElementValidator<ExecutableElement> {

  private final DaggerElements elements;
  private final DaggerTypes types;
  private final KotlinMetadataUtil metadataUtil;
  private final DependencyRequestValidator dependencyRequestValidator;
  private final Class<? extends Annotation> methodAnnotation;
  private final ImmutableSet<? extends Class<? extends Annotation>> enclosingElementAnnotations;
  private final Abstractness abstractness;
  private final ExceptionSuperclass exceptionSuperclass;

  /**
   * Creates a validator object.
   *
   * @param methodAnnotation the annotation on a method that identifies it as a binding method
   * @param enclosingElementAnnotation the method must be declared in a class or interface annotated
   *     with this annotation
   */
  protected BindingMethodValidator(
      DaggerElements elements,
      DaggerTypes types,
      KotlinMetadataUtil metadataUtil,
      DependencyRequestValidator dependencyRequestValidator,
      Class<? extends Annotation> methodAnnotation,
      Class<? extends Annotation> enclosingElementAnnotation,
      Abstractness abstractness,
      ExceptionSuperclass exceptionSuperclass,
      AllowsMultibindings allowsMultibindings,
      AllowsScoping allowsScoping,
      InjectionAnnotations injectionAnnotations) {
    this(
        elements,
        types,
        metadataUtil,
        methodAnnotation,
        ImmutableSet.of(enclosingElementAnnotation),
        dependencyRequestValidator,
        abstractness,
        exceptionSuperclass,
        allowsMultibindings,
        allowsScoping,
        injectionAnnotations);
  }

  /**
   * Creates a validator object.
   *
   * @param methodAnnotation the annotation on a method that identifies it as a binding method
   * @param enclosingElementAnnotations the method must be declared in a class or interface
   *     annotated with one of these annotations
   */
  protected BindingMethodValidator(
      DaggerElements elements,
      DaggerTypes types,
      KotlinMetadataUtil metadataUtil,
      Class<? extends Annotation> methodAnnotation,
      Iterable<? extends Class<? extends Annotation>> enclosingElementAnnotations,
      DependencyRequestValidator dependencyRequestValidator,
      Abstractness abstractness,
      ExceptionSuperclass exceptionSuperclass,
      AllowsMultibindings allowsMultibindings,
      AllowsScoping allowsScoping,
      InjectionAnnotations injectionAnnotations) {
    super(methodAnnotation, allowsMultibindings, allowsScoping, injectionAnnotations);
    this.elements = elements;
    this.types = types;
    this.metadataUtil = metadataUtil;
    this.methodAnnotation = methodAnnotation;
    this.enclosingElementAnnotations = ImmutableSet.copyOf(enclosingElementAnnotations);
    this.dependencyRequestValidator = dependencyRequestValidator;
    this.abstractness = abstractness;
    this.exceptionSuperclass = exceptionSuperclass;
  }

  /** The annotation that identifies binding methods validated by this object. */
  final Class<? extends Annotation> methodAnnotation() {
    return methodAnnotation;
  }

  /**
   * Returns an error message of the form "@<i>annotation</i> methods <i>rule</i>", where
   * <i>rule</i> comes from calling {@link String#format(String, Object...)} on {@code ruleFormat}
   * and the other arguments.
   */
  @FormatMethod
  protected final String bindingMethods(String ruleFormat, Object... args) {
    return bindingElements(ruleFormat, args);
  }

  @Override
  protected final String bindingElements() {
    return String.format("@%s methods", methodAnnotation.getSimpleName());
  }

  @Override
  protected final String bindingElementTypeVerb() {
    return "return";
  }

  /** Abstract validator for individual binding method elements. */
  protected abstract class MethodValidator extends ElementValidator {
    protected MethodValidator(ExecutableElement element) {
      super(element);
    }

    @Override
    protected final Optional<TypeMirror> bindingElementType() {
      return Optional.of(element.getReturnType());
    }

    @Override
    protected final void checkAdditionalProperties() {
      checkEnclosingElement();
      checkTypeParameters();
      checkNotPrivate();
      checkAbstractness();
      checkThrows();
      checkParameters();
      checkAdditionalMethodProperties();
    }

    /** Checks additional properties of the binding method. */
    protected void checkAdditionalMethodProperties() {}

    /**
     * Adds an error if the method is not declared in a class or interface annotated with one of the
     * {@link #enclosingElementAnnotations}.
     */
    private void checkEnclosingElement() {
      TypeElement enclosingElement = asType(element.getEnclosingElement());
      if (metadataUtil.isCompanionObjectClass(enclosingElement)) {
        // Binding method is in companion object, use companion object's enclosing class instead.
        enclosingElement = asType(enclosingElement.getEnclosingElement());
      }
      if (!isAnyAnnotationPresent(enclosingElement, enclosingElementAnnotations)) {
        report.addError(
            bindingMethods(
                "can only be present within a @%s",
                enclosingElementAnnotations.stream()
                    .map(Class::getSimpleName)
                    .collect(joining(" or @"))));
      }
    }

    /** Adds an error if the method is generic. */
    private void checkTypeParameters() {
      if (!element.getTypeParameters().isEmpty()) {
        report.addError(bindingMethods("may not have type parameters"));
      }
    }

    /** Adds an error if the method is private. */
    private void checkNotPrivate() {
      if (element.getModifiers().contains(PRIVATE)) {
        report.addError(bindingMethods("cannot be private"));
      }
    }

    /** Adds an error if the method is abstract but must not be, or is not and must be. */
    private void checkAbstractness() {
      boolean isAbstract = element.getModifiers().contains(ABSTRACT);
      switch (abstractness) {
        case MUST_BE_ABSTRACT:
          if (!isAbstract) {
            report.addError(bindingMethods("must be abstract"));
          }
          break;

        case MUST_BE_CONCRETE:
          if (isAbstract) {
            report.addError(bindingMethods("cannot be abstract"));
          }
      }
    }

    /**
     * Adds an error if the method declares throws anything but an {@link Error} or an appropriate
     * subtype of {@link Exception}.
     */
    private void checkThrows() {
      exceptionSuperclass.checkThrows(BindingMethodValidator.this, element, report);
    }

    /** Adds errors for the method parameters. */
    protected void checkParameters() {
      for (VariableElement parameter : element.getParameters()) {
        checkParameter(parameter);
      }
    }

    /**
     * Adds errors for a method parameter. This implementation reports an error if the parameter has
     * more than one qualifier.
     */
    protected void checkParameter(VariableElement parameter) {
      dependencyRequestValidator.validateDependencyRequest(report, parameter, parameter.asType());
    }
  }

  /** An abstract/concrete restriction on methods. */
  protected enum Abstractness {
    MUST_BE_ABSTRACT,
    MUST_BE_CONCRETE
  }

  /**
   * The exception class that all {@code throws}-declared throwables must extend, other than {@link
   * Error}.
   */
  protected enum ExceptionSuperclass {
    /** Methods may not declare any throwable types. */
    NO_EXCEPTIONS {
      @Override
      protected String errorMessage(BindingMethodValidator validator) {
        return validator.bindingMethods("may not throw");
      }

      @Override
      protected void checkThrows(
          BindingMethodValidator validator,
          ExecutableElement element,
          ValidationReport.Builder<ExecutableElement> report) {
        if (!element.getThrownTypes().isEmpty()) {
          report.addError(validator.bindingMethods("may not throw"));
          return;
        }
      }
    },

    /** Methods may throw checked or unchecked exceptions or errors. */
    EXCEPTION(Exception.class) {
      @Override
      protected String errorMessage(BindingMethodValidator validator) {
        return validator.bindingMethods(
            "may only throw unchecked exceptions or exceptions subclassing Exception");
      }
    },

    /** Methods may throw unchecked exceptions or errors. */
    RUNTIME_EXCEPTION(RuntimeException.class) {
      @Override
      protected String errorMessage(BindingMethodValidator validator) {
        return validator.bindingMethods("may only throw unchecked exceptions");
      }
    },
    ;

    private final Class<? extends Exception> superclass;

    ExceptionSuperclass() {
      this(null);
    }

    ExceptionSuperclass(Class<? extends Exception> superclass) {
      this.superclass = superclass;
    }

    /**
     * Adds an error if the method declares throws anything but an {@link Error} or an appropriate
     * subtype of {@link Exception}.
     *
     * <p>This method is overridden in {@link #NO_EXCEPTIONS}.
     */
    protected void checkThrows(
        BindingMethodValidator validator,
        ExecutableElement element,
        ValidationReport.Builder<ExecutableElement> report) {
      TypeMirror exceptionSupertype = validator.elements.getTypeElement(superclass).asType();
      TypeMirror errorType = validator.elements.getTypeElement(Error.class).asType();
      for (TypeMirror thrownType : element.getThrownTypes()) {
        if (!validator.types.isSubtype(thrownType, exceptionSupertype)
            && !validator.types.isSubtype(thrownType, errorType)) {
          report.addError(errorMessage(validator));
          break;
        }
      }
    }

    protected abstract String errorMessage(BindingMethodValidator validator);
  }
}