AnnotationOutput.java

/*
 * Copyright (C) 2014 Google, Inc.
 *
 * 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 retroweibo.processor;

import com.google.common.collect.ImmutableMap;

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

import javax.annotation.processing.ProcessingEnvironment;
import javax.lang.model.element.AnnotationMirror;
import javax.lang.model.element.AnnotationValue;
import javax.lang.model.element.Element;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.VariableElement;
import javax.lang.model.type.TypeMirror;
import javax.lang.model.util.SimpleAnnotationValueVisitor6;
import javax.tools.Diagnostic;

/**
 * Handling of default values for annotation members.
 *
 * @author emcmanus@google.com (Éamonn McManus)
 */
class AnnotationOutput {
  private final TypeSimplifier typeSimplifier;

  AnnotationOutput(TypeSimplifier typeSimplifier) {
    this.typeSimplifier = typeSimplifier;
  }

  /**
   * Visitor that produces a string representation of an annotation value, suitable for inclusion
   * in a Java source file as an annotation member or as the initializer of a variable of the
   * appropriate type. The syntax for the two is the same except for annotation members that are
   * themselves annotations. Within an annotation, an annotation member can be written as
   * {@code @NestedAnnotation(...)}, while in an initializer it must be written as an object,
   * for example the construction of an {@code @AutoAnnotation} class. That's why we have this
   * abstract class and two concrete subclasses.
   */
  private abstract class SourceFormVisitor
      extends SimpleAnnotationValueVisitor6<Void, StringBuilder> {
    @Override
    protected Void defaultAction(Object value, StringBuilder sb) {
      sb.append(value);
      return null;
    }

    @Override
    public Void visitArray(List<? extends AnnotationValue> values, StringBuilder sb) {
      sb.append('{');
      String sep = "";
      for (AnnotationValue value : values) {
        sb.append(sep);
        visit(value, sb);
        sep = ", ";
      }
      sb.append('}');
      return null;
    }

    @Override
    public Void visitChar(char c, StringBuilder sb) {
      appendQuoted(sb, c);
      return null;
    }

    @Override
    public Void visitLong(long i, StringBuilder sb) {
      sb.append(i).append('L');
      return null;
    }

    @Override
    public Void visitDouble(double d, StringBuilder sb) {
      if (Double.isNaN(d)) {
        sb.append("Double.NaN");
      } else if (d == Double.POSITIVE_INFINITY) {
        sb.append("Double.POSITIVE_INFINITY");
      } else if (d == Double.NEGATIVE_INFINITY) {
        sb.append("Double.NEGATIVE_INFINITY");
      } else {
        sb.append(d);
      }
      return null;
    }

    @Override
    public Void visitFloat(float f, StringBuilder sb) {
      if (Float.isNaN(f)) {
        sb.append("Float.NaN");
      } else if (f == Float.POSITIVE_INFINITY) {
        sb.append("Float.POSITIVE_INFINITY");
      } else if (f == Float.NEGATIVE_INFINITY) {
        sb.append("Float.NEGATIVE_INFINITY");
      } else {
        sb.append(f).append('F');
      }
      return null;
    }

    @Override
    public Void visitEnumConstant(VariableElement c, StringBuilder sb) {
      sb.append(typeSimplifier.simplify(c.asType())).append('.').append(c.getSimpleName());
      return null;
    }

    @Override
    public Void visitString(String s, StringBuilder sb) {
      appendQuoted(sb, s);
      return null;
    }

    @Override
    public Void visitType(TypeMirror classConstant, StringBuilder sb) {
      sb.append(typeSimplifier.simplify(classConstant)).append(".class");
      return null;
    }
  }

  private class InitializerSourceFormVisitor extends SourceFormVisitor {
    private final ProcessingEnvironment processingEnv;
    private final String memberName;
    private final Element context;

    InitializerSourceFormVisitor(
        ProcessingEnvironment processingEnv, String memberName, Element context) {
      this.processingEnv = processingEnv;
      this.memberName = memberName;
      this.context = context;
    }

    @Override
    public Void visitAnnotation(AnnotationMirror a, StringBuilder sb) {
      processingEnv.getMessager().printMessage(
          Diagnostic.Kind.ERROR,
          "@AutoAnnotation cannot yet supply a default value for annotation-valued member '"
              + memberName + "'",
          context);
      sb.append("null");
      return null;
    }
  }

  private class AnnotationSourceFormVisitor extends SourceFormVisitor {
    @Override
    public Void visitAnnotation(AnnotationMirror a, StringBuilder sb) {
      sb.append('@').append(typeSimplifier.simplify(a.getAnnotationType()));
      Map<ExecutableElement, AnnotationValue> map = ImmutableMap.copyOf(a.getElementValues());
      if (!map.isEmpty()) {
        sb.append('(');
        String sep = "";
        for (Map.Entry<ExecutableElement, AnnotationValue> entry : map.entrySet()) {
          sb.append(sep).append(entry.getKey().getSimpleName()).append(" = ");
          sep = ", ";
          this.visit(entry.getValue(), sb);
        }
        sb.append(')');
      }
      return null;
    }
  }

  /**
   * Returns a string representation of the given annotation value, suitable for inclusion in a Java
   * source file as the initializer of a variable of the appropriate type.
   */
  String sourceFormForInitializer(
      AnnotationValue annotationValue,
      ProcessingEnvironment processingEnv,
      String memberName,
      Element context) {
    SourceFormVisitor visitor =
        new InitializerSourceFormVisitor(processingEnv, memberName, context);
    StringBuilder sb = new StringBuilder();
    visitor.visit(annotationValue, sb);
    return sb.toString();
  }

  /**
   * Returns a string representation of the given annotation mirror, suitable for inclusion in a
   * Java source file to reproduce the annotation in source form.
   */
  String sourceFormForAnnotation(AnnotationMirror annotationMirror) {
    StringBuilder sb = new StringBuilder();
    new AnnotationSourceFormVisitor().visitAnnotation(annotationMirror, sb);
    return sb.toString();
  }

  private static StringBuilder appendQuoted(StringBuilder sb, String s) {
    sb.append('"');
    for (int i = 0; i < s.length(); i++) {
      appendEscaped(sb, s.charAt(i));
    }
    return sb.append('"');
  }

  private static StringBuilder appendQuoted(StringBuilder sb, char c) {
    sb.append('\'');
    appendEscaped(sb, c);
    return sb.append('\'');
  }

  private static void appendEscaped(StringBuilder sb, char c) {
    switch (c) {
    case '\\':
    case '"':
    case '\'':
      sb.append('\\').append(c);
      break;
    case '\n':
      sb.append("\\n");
      break;
    case '\r':
      sb.append("\\r");
      break;
    case '\t':
      sb.append("\\t");
      break;
    default:
      if (c < 0x20) {
        sb.append(String.format("\\%03o", (int) c));
      } else if (c < 0x7f || Character.isLetter(c)) {
        sb.append(c);
      } else {
        sb.append(String.format("\\u%04x", (int) c));
      }
      break;
    }
  }
}