generator/src/main/java/com/google/autofactory/AutoFactoryDeclaration.java

package com.google.autofactory;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;

import java.util.List;
import java.util.Map;

import javax.lang.model.element.AnnotationMirror;
import javax.lang.model.element.AnnotationValue;
import javax.lang.model.type.DeclaredType;
import javax.lang.model.type.TypeMirror;
import javax.lang.model.util.Elements;
import javax.lang.model.util.SimpleAnnotationValueVisitor6;
import javax.lang.model.util.SimpleTypeVisitor6;

import com.google.common.collect.ImmutableSet;

final class AutoFactoryDeclaration {
  private final String namePattern;
  private final String extendingQualifiedName;
  private final ImmutableSet<String> implementingQualifiedNames;

  AutoFactoryDeclaration(String namePattern, String extendingQualifiedName,
      ImmutableSet<String> implementingQualifiedNames) {
    this.namePattern = namePattern;
    this.extendingQualifiedName = extendingQualifiedName;
    this.implementingQualifiedNames = implementingQualifiedNames;
  }

  String namePattern() {
    return namePattern;
  }

  String extendingQualifiedName() {
    return extendingQualifiedName;
  }

  ImmutableSet<String> implementingQualifiedNames() {
    return implementingQualifiedNames;
  }

  static AutoFactoryDeclaration fromAnnotationMirror(Elements elements, AnnotationMirror mirror) {
    checkNotNull(mirror);
    checkArgument(Mirrors.getQualifiedName(mirror.getAnnotationType()).
        contentEquals(AutoFactory.class.getName()));
    Map<String, AnnotationValue> values =
        Mirrors.simplifyAnnotationValueMap(elements.getElementValuesWithDefaults(mirror));
    checkState(values.size() == 3);

    AnnotationValue namedValue = checkNotNull(values.get("named"));
    // value is a string, so we can just call toString
    String named = namedValue.getValue().toString();
    AnnotationValue extendingValue = checkNotNull(values.get("extending"));
    String extendingQualifiedName = extendingValue.accept(new QualifiedNameValueVisitor(), null);
    AnnotationValue implementingValue = checkNotNull(values.get("implementing"));
    ImmutableSet<String> implementingQualifiedNames =
        implementingValue.accept(new SimpleAnnotationValueVisitor6<ImmutableSet<String>, Void>() {
          @Override
          protected ImmutableSet<String> defaultAction(Object o, Void p) {
            throw new AssertionError();
          }

          @Override
          public ImmutableSet<String> visitArray(List<? extends AnnotationValue> vals, Void p) {
            ImmutableSet.Builder<String> builder = ImmutableSet.builder();
            for (AnnotationValue annotationValue : vals) {
              builder.add(annotationValue.accept(new QualifiedNameValueVisitor(), null));
            }
            return builder.build();
          }
        }, null);
    return new AutoFactoryDeclaration(named, extendingQualifiedName, implementingQualifiedNames);
  }

  private static final class QualifiedNameValueVisitor
      extends SimpleAnnotationValueVisitor6<String, Void> {
    @Override
    protected String defaultAction(Object o, Void p) {
      throw new IllegalStateException();
    }

    @Override
    public String visitType(TypeMirror t, Void p) {
      return t.accept(new SimpleTypeVisitor6<String, Void>() {
        @Override
        protected String defaultAction(TypeMirror e, Void p) {
          throw new AssertionError();
        }

        @Override
        public String visitDeclared(DeclaredType t, Void p) {
          return Mirrors.getQualifiedName(t).toString();
        }
      }, null);
    }
  }
}