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A fast dependency injector for Android and Java.
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/*
 * Copyright (C) 2013 The Dagger Authors.
 *
 * 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 dagger.internal.codegen.base;

import static com.google.auto.common.AnnotationMirrors.getAnnotationValue;
import static com.google.auto.common.AnnotationMirrors.getAnnotationValuesWithDefaults;

import com.google.common.collect.ImmutableList;
import java.util.List;
import java.util.Optional;
import javax.lang.model.element.AnnotationMirror;
import javax.lang.model.element.AnnotationValue;
import javax.lang.model.element.AnnotationValueVisitor;
import javax.lang.model.type.TypeMirror;
import javax.lang.model.util.SimpleAnnotationValueVisitor8;

/** Utility methods for working with {@link AnnotationValue} instances. */
public final class MoreAnnotationValues {
  /**
   * Returns the list of values represented by an array annotation value.
   *
   * @throws IllegalArgumentException unless {@code annotationValue} represents an array
   */
  public static ImmutableList asAnnotationValues(AnnotationValue annotationValue) {
    return annotationValue.accept(AS_ANNOTATION_VALUES, null);
  }

  private static final AnnotationValueVisitor, String>
      AS_ANNOTATION_VALUES =
          new SimpleAnnotationValueVisitor8, String>() {
            @Override
            public ImmutableList visitArray(
                List vals, String elementName) {
              return ImmutableList.copyOf(vals);
            }

            @Override
            protected ImmutableList defaultAction(Object o, String elementName) {
              throw new IllegalArgumentException(elementName + " is not an array: " + o);
            }
          };

  /**
   * Returns the type represented by an annotation value.
   *
   * @throws IllegalArgumentException unless {@code annotationValue} represents a single type
   */
  public static TypeMirror asType(AnnotationValue annotationValue) {
    return AS_TYPE.visit(annotationValue);
  }

  private static final AnnotationValueVisitor AS_TYPE =
      new SimpleAnnotationValueVisitor8() {
        @Override
        public TypeMirror visitType(TypeMirror t, Void p) {
          return t;
        }

        @Override
        protected TypeMirror defaultAction(Object o, Void p) {
          throw new TypeNotPresentException(o.toString(), null);
        }
      };

  /** Returns the int value of an annotation */
  public static int getIntValue(AnnotationMirror annotation, String valueName) {
    return (int) getAnnotationValue(annotation, valueName).getValue();
  }

  /** Returns an optional int value of an annotation if the value name is present */
  public static Optional getOptionalIntValue(
      AnnotationMirror annotation, String valueName) {
    return isValuePresent(annotation, valueName)
        ? Optional.of(getIntValue(annotation, valueName))
        : Optional.empty();
  }

  /** Returns the String value of an annotation */
  public static String getStringValue(AnnotationMirror annotation, String valueName) {
    return (String) getAnnotationValue(annotation, valueName).getValue();
  }

  /** Returns an optional String value of an annotation if the value name is present */
  public static Optional getOptionalStringValue(
      AnnotationMirror annotation, String valueName) {
    return isValuePresent(annotation, valueName)
        ? Optional.of(getStringValue(annotation, valueName))
        : Optional.empty();
  }

  /** Returns the int array value of an annotation */
  public static int[] getIntArrayValue(AnnotationMirror annotation, String valueName) {
    return asAnnotationValues(getAnnotationValue(annotation, valueName)).stream()
        .mapToInt(it -> (int) it.getValue())
        .toArray();
  }

  /** Returns the String array value of an annotation */
  public static String[] getStringArrayValue(AnnotationMirror annotation, String valueName) {
    return asAnnotationValues(getAnnotationValue(annotation, valueName)).stream()
        .map(it -> (String) it.getValue())
        .toArray(String[]::new);
  }

  private static boolean isValuePresent(AnnotationMirror annotation, String valueName) {
    return getAnnotationValuesWithDefaults(annotation).keySet().stream()
        .anyMatch(member -> member.getSimpleName().contentEquals(valueName));
  }

  private MoreAnnotationValues() {}
}