/*
 * 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.bugpatterns;

import static com.google.errorprone.BugPattern.Category.JDK;
import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.matchers.Matchers.allOf;
import static com.google.errorprone.matchers.Matchers.staticMethod;

import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Iterables;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
import com.google.errorprone.fixes.Fix;
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.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.tools.javac.code.Type;
import com.sun.tools.javac.code.Type.ArrayType;
import java.util.EnumMap;
import java.util.Map;
import javax.lang.model.type.TypeKind;

@BugPattern(
  name = "ArraysAsListPrimitiveArray",
  summary = "Arrays.asList does not autobox primitive arrays, as one might expect.",
  explanation =
      "Arrays.asList does not autobox primitive arrays, as one might expect. "
          + "If you intended to autobox the primitive array, use an asList method "
          + "from Guava that does autobox.  If you intended to create a singleton "
          + "list containing the primitive array, use Collections.singletonList to "
          + "make your intent clearer.",
  category = JDK,
  severity = ERROR
)
public class ArraysAsListPrimitiveArray extends BugChecker implements MethodInvocationTreeMatcher {

  private static final Matcher<MethodInvocationTree> ARRAYS_AS_LIST_SINGLE_ARRAY =
      allOf(
          staticMethod().onClass("java.util.Arrays").named("asList"),
          Matchers.argumentCount(1),
          Matchers.argument(0, Matchers.<ExpressionTree>isArrayType()));

  private static final ImmutableMap<TypeKind, String> GUAVA_UTILS = getGuavaUtils();

  static ImmutableMap<TypeKind, String> getGuavaUtils() {
    Map<TypeKind, String> guavaUtils = new EnumMap<>(TypeKind.class);
    guavaUtils.put(TypeKind.BOOLEAN, "Booleans");
    guavaUtils.put(TypeKind.BYTE, "Bytes");
    guavaUtils.put(TypeKind.SHORT, "Shorts");
    guavaUtils.put(TypeKind.INT, "Ints");
    guavaUtils.put(TypeKind.LONG, "Longs");
    guavaUtils.put(TypeKind.CHAR, "Chars");
    guavaUtils.put(TypeKind.FLOAT, "Floats");
    guavaUtils.put(TypeKind.DOUBLE, "Doubles");
    return ImmutableMap.copyOf(guavaUtils);
  }

  @Override
  public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
    if (!ARRAYS_AS_LIST_SINGLE_ARRAY.matches(tree, state)) {
      return NO_MATCH;
    }
    ExpressionTree array = Iterables.getOnlyElement(tree.getArguments());
    Type componentType = ((ArrayType) ASTHelpers.getType(array)).getComponentType();
    if (!componentType.isPrimitive()) {
      return NO_MATCH;
    }
    String guavaUtils = GUAVA_UTILS.get(componentType.getKind());
    if (guavaUtils == null) {
      return NO_MATCH;
    }
    Fix fix =
        SuggestedFix.builder()
            .addImport("com.google.common.primitives." + guavaUtils)
            .replace(tree.getMethodSelect(), guavaUtils + ".asList")
            .build();
    return describeMatch(tree, fix);
  }
}