/*
 * Copyright 2014 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.errorprone.BugPattern.SeverityLevel;
import com.google.errorprone.DescriptionListener;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.DoWhileLoopTree;
import com.sun.source.tree.IfTree;
import com.sun.source.tree.ParenthesizedTree;
import com.sun.source.tree.SynchronizedTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.WhileLoopTree;
import com.sun.source.util.SimpleTreeVisitor;
import com.sun.source.util.TreeScanner;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.parser.JavaTokenizer;
import com.sun.tools.javac.parser.ScannerFactory;
import com.sun.tools.javac.parser.Tokens.Token;
import com.sun.tools.javac.parser.Tokens.TokenKind;
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
import com.sun.tools.javac.tree.JCTree.JCStatement;
import com.sun.tools.javac.tree.TreeMaker;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.ListBuffer;
import java.nio.CharBuffer;

/**
 * Scanner that outputs suggested fixes generated by a {@code RefasterMatcher}.
 * 
 * @author lowasser@google.com (Louis Wasserman)
 */
@AutoValue
abstract class RefasterScanner<M extends TemplateMatch, T extends Template<M>> 
    extends TreeScanner<Void, Context> {
  static <M extends TemplateMatch, T extends Template<M>> RefasterScanner<M, T> create(
      RefasterRule<M, T> rule, DescriptionListener listener) {
    return new AutoValue_RefasterScanner<>(rule, listener);
  }
  
  abstract RefasterRule<M, T> rule();

  abstract DescriptionListener listener();
  
  @Override
  public Void visitClass(ClassTree node, Context context) {
    Symbol sym = ASTHelpers.getSymbol(node);
    if (sym == null || !sym.getQualifiedName().contentEquals(rule().qualifiedTemplateClass())) {
      ListBuffer<JCStatement> statements = new ListBuffer<>();
      for (Tree tree : node.getMembers()) {
        if (tree instanceof JCStatement) {
          statements.append((JCStatement) tree);
        } else {
          tree.accept(this, context);
        }
      }
      scan(TreeMaker.instance(context).Block(0, statements.toList()), context);
    }
    return null;
  }

  @Override
  public Void scan(Tree tree, Context context) {
    if (tree == null) {
      return null;
    }
    JCCompilationUnit compilationUnit = context.get(JCCompilationUnit.class);
    for (T beforeTemplate : rule().beforeTemplates()) {
      matchLoop: for (M match : beforeTemplate.match((JCTree) tree, context)) {
        if (rule().rejectMatchesWithComments()) {
          String matchContents = match.getRange(compilationUnit);
          JavaTokenizer tokenizer = new JavaTokenizer(ScannerFactory.instance(context), 
              CharBuffer.wrap(matchContents)) {};
          for (Token token = tokenizer.readToken(); token.kind != TokenKind.EOF;
              token = tokenizer.readToken()) {
            if (token.comments != null && !token.comments.isEmpty()) {
              continue matchLoop;
            }
          }
        }
        Description.Builder builder = Description.builder(match.getLocation(),
            rule().qualifiedTemplateClass(), "", SeverityLevel.WARNING, "");
            
        if (rule().afterTemplates().isEmpty()) {
          builder.addFix(SuggestedFix.prefixWith(match.getLocation(), "/* match found */ "));
        } else {
          for (T afterTemplate : rule().afterTemplates()) {
            builder.addFix(afterTemplate.replace(match));
          }
        }
        listener().onDescribed(builder.build());
      }
    }
    return super.scan(tree, context);
  }
  
  private static final SimpleTreeVisitor<Tree, Void> SKIP_PARENS =
      new SimpleTreeVisitor<Tree, Void>() {
        @Override
        public Tree visitParenthesized(ParenthesizedTree node, Void v) {
          return node.getExpression().accept(this, null);
        }

        @Override
        protected Tree defaultAction(Tree node, Void v) {
          return node;
        }
      };

  /* 
   * Matching on the parentheses surrounding the condition of an if, while, or do-while
   * is nonsensical, as those parentheses are obligatory and should never be changed.
   */

  @Override
  public Void visitDoWhileLoop(DoWhileLoopTree node, Context context) {
    scan(node.getStatement(), context);
    scan(SKIP_PARENS.visit(node.getCondition(), null), context);
    return null;
  }

  @Override
  public Void visitWhileLoop(WhileLoopTree node, Context context) {
    scan(SKIP_PARENS.visit(node.getCondition(), null), context);
    scan(node.getStatement(), context);
    return null;
  }

  @Override
  public Void visitSynchronized(SynchronizedTree node, Context context) {
    scan(SKIP_PARENS.visit(node.getExpression(), null), context);
    scan(node.getBlock(), context);
    return null;
  }

  @Override
  public Void visitIf(IfTree node, Context context) {
    scan(SKIP_PARENS.visit(node.getCondition(), null), context);
    scan(node.getThenStatement(), context);
    scan(node.getElseStatement(), context);
    return null;
  }
}