/*
 * Copyright 2016 Google Inc. All Rights Reserved.
 *
 * 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.errorprone.bugpatterns.inject.dagger;

import static com.google.errorprone.BugPattern.Category.DAGGER;
import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
import static com.google.errorprone.bugpatterns.inject.dagger.DaggerAnnotations.isBindingDeclarationMethod;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.matchers.Matchers.isStatic;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.isGeneratedConstructor;
import static com.sun.source.tree.Tree.Kind.CLASS;
import static com.sun.source.tree.Tree.Kind.METHOD;

import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.FluentIterable;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker;
import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
import com.google.errorprone.fixes.Fix;
import com.google.errorprone.fixes.SuggestedFixes;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.Tree;

/** @author gak@google.com (Gregory Kick) */
@BugPattern(
  name = "PrivateConstructorForNoninstantiableModuleTest",
  summary = "Add a private constructor to modules that will not be instantiated by Dagger.",
  explanation =
      "Modules that contain abstract binding methods (@Binds, @Multibinds) or only static"
          + " @Provides methods will not be instantiated by Dagger when they are included in a"
          + " component.  Adding a private constructor clearly conveys that the module will not be"
          + " used as an instance.",
  category = DAGGER,
  severity = SUGGESTION
)
public class PrivateConstructorForNoninstantiableModule extends BugChecker
    implements ClassTreeMatcher {
  private static final Predicate<Tree> IS_CONSTRUCTOR =
      new Predicate<Tree>() {
        @Override
        public boolean apply(Tree tree) {
          return getSymbol(tree).isConstructor();
        }
      };

  @Override
  public Description matchClass(ClassTree classTree, VisitorState state) {
    if (!DaggerAnnotations.isAnyModule().matches(classTree, state)) {
      return NO_MATCH;
    }

    // if a module is declared as an interface, skip it
    if (!classTree.getKind().equals(CLASS)) {
      return NO_MATCH;
    }

    FluentIterable<? extends Tree> nonSyntheticMembers =
        FluentIterable.from(classTree.getMembers())
            .filter(
                Predicates.not(
                    new Predicate<Tree>() {
                      @Override
                      public boolean apply(Tree tree) {
                        return tree.getKind().equals(METHOD)
                            && isGeneratedConstructor((MethodTree) tree);
                      }
                    }));

    // ignore empty modules
    if (nonSyntheticMembers.isEmpty()) {
      return NO_MATCH;
    }

    if (nonSyntheticMembers.anyMatch(IS_CONSTRUCTOR)) {
      return NO_MATCH;
    }

    boolean hasBindingDeclarationMethods =
        nonSyntheticMembers.anyMatch(matcherAsPredicate(isBindingDeclarationMethod(), state));

    if (hasBindingDeclarationMethods) {
      return describeMatch(classTree, addPrivateConstructor(classTree, state));
    }

    boolean allStaticMembers = nonSyntheticMembers.allMatch(matcherAsPredicate(isStatic(), state));

    if (allStaticMembers) {
      return describeMatch(classTree, addPrivateConstructor(classTree, state));
    }

    return NO_MATCH;
  }

  private Fix addPrivateConstructor(ClassTree classTree, VisitorState state) {
    return SuggestedFixes.addMembers(
        classTree, state, "private " + classTree.getSimpleName() + "() {}");
  }

  private static <T extends Tree> Predicate<T> matcherAsPredicate(
      final Matcher<? super T> matcher, final VisitorState state) {
    return new Predicate<T>() {
      @Override
      public boolean apply(T t) {
        return matcher.matches(t, state);
      }
    };
  }
}