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/*
 * SonarQube Java
 * Copyright (C) 2012 SonarSource
 * [email protected]
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02
 */
package org.sonar.java.checks;

import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.collect.Lists;
import org.sonar.api.server.rule.RulesDefinition;
import org.sonar.check.Priority;
import org.sonar.check.Rule;
import org.sonar.plugins.java.api.JavaFileScanner;
import org.sonar.plugins.java.api.JavaFileScannerContext;
import org.sonar.plugins.java.api.semantic.Symbol.TypeSymbol;
import org.sonar.plugins.java.api.semantic.Type;
import org.sonar.plugins.java.api.tree.AnnotationTree;
import org.sonar.plugins.java.api.tree.BaseTreeVisitor;
import org.sonar.plugins.java.api.tree.ClassTree;
import org.sonar.plugins.java.api.tree.IdentifierTree;
import org.sonar.plugins.java.api.tree.MethodTree;
import org.sonar.plugins.java.api.tree.Modifier;
import org.sonar.plugins.java.api.tree.Tree;
import org.sonar.plugins.java.api.tree.VariableTree;
import org.sonar.squidbridge.annotations.SqaleConstantRemediation;
import org.sonar.squidbridge.annotations.SqaleSubCharacteristic;

import java.util.List;

@Rule(
  key = "S1609",
  name = "@FunctionalInterface annotation should be used to flag Single Abstract Method interfaces",
  tags = {"java8"},
  priority = Priority.MAJOR)
@SqaleSubCharacteristic(RulesDefinition.SubCharacteristics.UNDERSTANDABILITY)
@SqaleConstantRemediation("2min")
public class SAMAnnotatedCheck extends BaseTreeVisitor implements JavaFileScanner {

  private static final ImmutableMultimap> OBJECT_METHODS = new ImmutableMultimap.Builder>().
      put("equals", ImmutableList.of("Object")).
      put("getClass", ImmutableList.of()).
      put("hashcode", ImmutableList.of()).
      put("notify", ImmutableList.of()).
      put("notifyAll", ImmutableList.of()).
      put("toString", ImmutableList.of()).
      put("wait", ImmutableList.of()).
      put("wait", ImmutableList.of("long")).
      put("wait", ImmutableList.of("long", "int")).
      build();

  private JavaFileScannerContext context;


  @Override
  public void scanFile(JavaFileScannerContext context) {
    this.context = context;
    scan(context.getTree());
  }

  @Override
  public void visitClass(ClassTree tree) {
    if (isSAM(tree) && !isAnnotated(tree)) {
      context.addIssue(tree, this, "Annotate the \"" + tree.simpleName().name() + "\" interface with the @FunctionInterface annotation");
    }
    super.visitClass(tree);
  }

  private boolean isAnnotated(ClassTree tree) {
    for (AnnotationTree annotationTree : tree.modifiers().annotations()) {
      Tree annotationType = annotationTree.annotationType();
      if (annotationType.is(Tree.Kind.IDENTIFIER) && "FunctionalInterface".equals(((IdentifierTree) annotationType).name())) {
        return true;
      }
    }
    return false;
  }

  //JLS8 9.8
  private boolean isSAM(ClassTree tree) {
    return tree.is(Tree.Kind.INTERFACE) && hasOneAbstractMethod(tree);
  }

  private boolean hasOneAbstractMethod(ClassTree classTree) {
    TypeSymbol symbol = classTree.symbol();
    if (symbol != null) {
      List types = symbol.interfaces();
      for (Type type : types) {
        if (!type.symbol().memberSymbols().isEmpty()) {
          return false;
        }
      }
    }
    int methods = 0;
    for (Tree member : classTree.members()) {
      boolean isMethod = member.is(Tree.Kind.METHOD);
      if (!isMethod) {
        return false;
      }
      if (isNotObjectMethod((MethodTree) member) && isNonStaticNonDefaultMethod(member)) {
        methods++;
      }
    }
    return methods == 1;
  }

  private boolean isNotObjectMethod(MethodTree method) {
    ImmutableCollection> methods = OBJECT_METHODS.get(method.simpleName().name());
    if (methods != null) {
      for (List arguments : methods) {
        List args = Lists.newArrayList(arguments);
        if (method.parameters().size() == args.size()) {
          for (VariableTree var : method.parameters()) {
            args.remove(var.type().symbolType().name());
          }
          if (args.isEmpty()) {
            return false;
          }
        }
      }
    }
    return true;
  }

  private boolean isNonStaticNonDefaultMethod(Tree memberTree) {
    boolean result = memberTree.is(Tree.Kind.METHOD);
    if (result) {
      MethodTree methodTree = (MethodTree) memberTree;
      List modifiers = methodTree.modifiers().modifiers();
      result = !modifiers.contains(Modifier.STATIC) && !modifiers.contains(Modifier.DEFAULT);
    }
    return result;
  }
}