/*
 * Copyright 2013 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.refaster;

import com.google.auto.value.AutoValue;
import com.google.common.base.Function;
import com.google.common.base.Optional;
import com.google.common.collect.ContiguousSet;
import com.google.common.collect.DiscreteDomain;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Range;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.ModifiersTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.TreeVisitor;
import com.sun.source.tree.TypeParameterTree;
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.tree.JCTree.JCClassDecl;
import com.sun.tools.javac.util.List;
import javax.lang.model.element.Name;

/**
 * {@code UTree} representation of a {@code ClassTree} for anonymous inner class matching.
 * 
 * @author lowasser@google.com (Louis Wasserman)
 */
@AutoValue
abstract class UClassDecl extends USimpleStatement implements ClassTree {
  public static UClassDecl create(UMethodDecl... members) {
    return create(ImmutableList.copyOf(members));
  }
  
  public static UClassDecl create(Iterable<UMethodDecl> members) {
    return new AutoValue_UClassDecl(ImmutableList.copyOf(members));
  }
  
  @AutoValue
  abstract static class UnifierWithRemainingMembers {
    static UnifierWithRemainingMembers create(
        Unifier unifier, Iterable<UMethodDecl> remainingMembers) {
      return new AutoValue_UClassDecl_UnifierWithRemainingMembers(unifier,
          ImmutableList.copyOf(remainingMembers));
    }
    
    abstract Unifier unifier();
    abstract ImmutableList<UMethodDecl> remainingMembers();
    
    static final Function<Unifier, UnifierWithRemainingMembers> withRemaining(
        final Iterable<UMethodDecl> remainingMembers) {
      return new Function<Unifier, UnifierWithRemainingMembers>() {
        @Override
        public UnifierWithRemainingMembers apply(Unifier unifier) {
          return create(unifier, remainingMembers);
        }
      };
    }
  }
  
  private static Function<UnifierWithRemainingMembers, Choice<UnifierWithRemainingMembers>>
      match(final Tree tree) {
    return new Function<UnifierWithRemainingMembers, Choice<UnifierWithRemainingMembers>>() {
      @Override
      public Choice<UnifierWithRemainingMembers> apply(final UnifierWithRemainingMembers state) {
        final ImmutableList<UMethodDecl> currentMembers = state.remainingMembers();
        Choice<Integer> methodChoice = Choice.from(ContiguousSet.create(
            Range.closedOpen(0, currentMembers.size()), DiscreteDomain.integers()));
        return methodChoice.thenChoose(
            new Function<Integer, Choice<UnifierWithRemainingMembers>>() {
              @Override
              public Choice<UnifierWithRemainingMembers> apply(Integer i) {
                ImmutableList<UMethodDecl> remainingMembers = 
                    new ImmutableList.Builder<UMethodDecl>()
                        .addAll(currentMembers.subList(0, i))
                        .addAll(currentMembers.subList(i + 1, currentMembers.size()))
                        .build();
                UMethodDecl chosenMethod = currentMembers.get(i);
                Unifier unifier = state.unifier().fork();
                /* 
                 * If multiple methods use the same parameter name, preserve the last parameter
                 * name from the target code.  For example, given a @BeforeTemplate with
                 * 
                 *    int get(int index) {...}
                 *    int set(int index, int value) {...}
                 *    
                 * and target code with the lines
                 * 
                 *    int get(int i) {...}
                 *    int set(int j) {...}
                 *    
                 * then use "j" in place of index in the @AfterTemplates.
                 */
                for (UVariableDecl param : chosenMethod.getParameters()) {
                  unifier.clearBinding(param.key());
                }
                return chosenMethod.unify(tree, unifier)
                    .transform(UnifierWithRemainingMembers.withRemaining(remainingMembers));
              }
            });
      }
    };
  }

  @Override
  public Choice<Unifier> visitClass(ClassTree node, Unifier unifier) {
    Choice<UnifierWithRemainingMembers> path = Choice.of(
        UnifierWithRemainingMembers.create(unifier, getMembers()));
    for (Tree targetMember : node.getMembers()) {
      if (!(targetMember instanceof MethodTree)
          || ((MethodTree) targetMember).getReturnType() != null) {
        // skip synthetic constructors
        path = path.thenChoose(match(targetMember));
      }
    }
    return path.thenOption(new Function<UnifierWithRemainingMembers, Optional<Unifier>>() {
      @Override
      public Optional<Unifier> apply(UnifierWithRemainingMembers state) {
        if (state.remainingMembers().isEmpty()) {
          return Optional.of(state.unifier());
        } else {
          return Optional.absent();
        }
      }});
  }

  @Override
  public JCClassDecl inline(Inliner inliner) throws CouldNotResolveImportException {
    return inliner.maker().AnonymousClassDef(
        inliner.maker().Modifiers(0L),
        List.convert(JCTree.class, inliner.inlineList(getMembers())));
  }
  
  @Override
  public <R, D> R accept(TreeVisitor<R, D> visitor, D data) {
    return visitor.visitClass(this, data);
  }

  @Override
  public Kind getKind() {
    return Kind.CLASS;
  }

  @Override
  public UTree<?> getExtendsClause() {
    return null;
  }

  @Override
  public ImmutableList<UTree<?>> getImplementsClause() {
    return ImmutableList.of();
  }

  @Override
  public abstract ImmutableList<UMethodDecl> getMembers();

  @Override
  public ModifiersTree getModifiers() {
    return null;
  }

  @Override
  public Name getSimpleName() {
    return null;
  }

  @Override
  public ImmutableList<TypeParameterTree> getTypeParameters() {
    return ImmutableList.of();
  }

}