/*
 * Copyright 2012 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;

import static com.google.errorprone.BugPattern.Category.GUAVA;
import static com.google.errorprone.BugPattern.MaturityLevel.MATURE;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
import static com.google.errorprone.matchers.Matchers.*;

import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.matchers.Matchers;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.LiteralTree;
import com.sun.source.tree.MemberSelectTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.source.tree.Tree.Kind;

import java.util.List;
import java.util.regex.Pattern;

/**
 * Error checker for calls to the Preconditions class in Guava which use
 * 'expensive' methods of producing the error string. In most cases, users are
 * better off using the equivalent methods which defer the computation of the
 * string until the test actually fails.
 *
 * @author sjnickerson@google.com (Simon Nickerson)
 */
@BugPattern(name = "PreconditionsErrorMessageEagerEvaluation",
    summary = "Second argument to Preconditions.* is a call to String.format(), which " +
    		"can be unwrapped",
    explanation =
        "Preconditions checks take an error message to display if the check fails. " +
        "The error message is rarely needed, so it should either be cheap to construct " +
        "or constructed only when needed. This check ensures that these error messages " +
        "are not constructed using expensive methods that are evaluated eagerly.",
    category = GUAVA, severity = WARNING, maturity = MATURE)
public class PreconditionsExpensiveString
    extends BugChecker implements MethodInvocationTreeMatcher {

  @SuppressWarnings({"vararg", "unchecked"})
  private static final Matcher<MethodInvocationTree> matcher = allOf(
      anyOf(
          methodSelect(staticMethod(
              "com.google.common.base.Preconditions", "checkNotNull")),
          methodSelect(staticMethod(
              "com.google.common.base.Preconditions", "checkState")),
          methodSelect(staticMethod(
              "com.google.common.base.Preconditions", "checkArgument"))),
      argument(1, Matchers.<ExpressionTree>allOf(
          Matchers.<ExpressionTree>kindIs(Kind.METHOD_INVOCATION),
          expressionMethodSelect(staticMethod("java.lang.String", "format")),
          new StringFormatCallContainsNoSpecialFormattingMatcher(
              Pattern.compile("%[^%s]"))
      ))
  );

  @Override
  public Description matchMethodInvocation(MethodInvocationTree methodInvocationTree, VisitorState state) {
    if (!matcher.matches(methodInvocationTree, state)) {
      return Description.NO_MATCH;
    }

    MemberSelectTree method =
        (MemberSelectTree) methodInvocationTree.getMethodSelect();

    List<? extends ExpressionTree> arguments =
        methodInvocationTree.getArguments();
    MethodInvocationTree stringFormat = (MethodInvocationTree) arguments.get(1);

    // TODO(sjnickerson): Figure out how to get a suggested fix. Basically we
    // remove the String.format() wrapper, but I don't know how to express
    // this. This current one is not correct!
    SuggestedFix fix = null;

    return describeMatch(arguments.get(1), fix);
  }

  private static class StringFormatCallContainsNoSpecialFormattingMatcher
      implements Matcher<ExpressionTree> {

    private final Pattern invalidFormatCharacters;

    StringFormatCallContainsNoSpecialFormattingMatcher(
        Pattern invalidFormatCharacters) {
      this.invalidFormatCharacters = invalidFormatCharacters;
    }

    @Override
    public boolean matches(ExpressionTree t, VisitorState state) {
      if (!(t instanceof MethodInvocationTree)) {
        return false;
      }
      MethodInvocationTree stringFormatInvocation = (MethodInvocationTree) t;
      if (!(stringFormatInvocation.getArguments().get(0)
          instanceof LiteralTree)) {
        return false;
      }
      LiteralTree firstArg = (LiteralTree)
          stringFormatInvocation.getArguments().get(0);
      String literal = firstArg.getValue().toString();
      return !invalidFormatCharacters.matcher(literal).find();
    }
  }
}

@@ -778,22 +778,28 @@
 tyLevel.
-MATURE
+EXPERIMENTAL
 ;%0Aimport
@@ -2499,14 +2499,20 @@
 y = 
-MATURE
+EXPERIMENTAL
 )%0Apu

Disable the PreconditionsExpensiveString check, since it has a bug. Update issue 173