extensions/proto/src/main/java/com/google/common/truth/extensions/proto/AnyUtils.java

/*
 * Copyright (c) 2017 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 com.google.common.truth.extensions.proto;

import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.protobuf.Any;
import com.google.protobuf.ByteString;
import com.google.protobuf.Descriptors.Descriptor;
import com.google.protobuf.Descriptors.FieldDescriptor;
import com.google.protobuf.DynamicMessage;
import com.google.protobuf.ExtensionRegistry;
import com.google.protobuf.InvalidProtocolBufferException;
import com.google.protobuf.Message;
import com.google.protobuf.TypeRegistry;

/** Helper methods for working with Any protos. */
class AnyUtils {
  private static final FieldDescriptor TYPE_URL_FIELD_DESCRIPTOR =
      Any.getDescriptor().findFieldByNumber(Any.TYPE_URL_FIELD_NUMBER);

  static FieldDescriptor typeUrlFieldDescriptor() {
    return TYPE_URL_FIELD_DESCRIPTOR;
  }

  private static final SubScopeId TYPE_URL_SUB_SCOPE_ID = SubScopeId.of(TYPE_URL_FIELD_DESCRIPTOR);

  static SubScopeId typeUrlSubScopeId() {
    return TYPE_URL_SUB_SCOPE_ID;
  }

  private static final FieldDescriptor VALUE_FIELD_DESCRIPTOR =
      Any.getDescriptor().findFieldByNumber(Any.VALUE_FIELD_NUMBER);

  static FieldDescriptor valueFieldDescriptor() {
    return VALUE_FIELD_DESCRIPTOR;
  }

  private static final SubScopeId VALUE_SUB_SCOPE_ID = SubScopeId.of(VALUE_FIELD_DESCRIPTOR);

  static SubScopeId valueSubScopeId() {
    return VALUE_SUB_SCOPE_ID;
  }

  private static final TypeRegistry DEFAULT_TYPE_REGISTRY = TypeRegistry.getEmptyTypeRegistry();

  static TypeRegistry defaultTypeRegistry() {
    return DEFAULT_TYPE_REGISTRY;
  }

  private static final ExtensionRegistry DEFAULT_EXTENSION_REGISTRY =
      ExtensionRegistry.getEmptyRegistry();

  static ExtensionRegistry defaultExtensionRegistry() {
    return DEFAULT_EXTENSION_REGISTRY;
  }

  /** Unpack an `Any` proto using the given TypeRegistry and ExtensionRegistry. */
  static Optional<Message> unpack(
      Message any, TypeRegistry typeRegistry, ExtensionRegistry extensionRegistry) {
    Preconditions.checkArgument(
        any.getDescriptorForType().equals(Any.getDescriptor()),
        "Expected type google.protobuf.Any, but was: %s",
        any.getDescriptorForType().getFullName());

    String typeUrl = (String) any.getField(typeUrlFieldDescriptor());
    ByteString value = (ByteString) any.getField(valueFieldDescriptor());

    try {
      Descriptor descriptor = typeRegistry.getDescriptorForTypeUrl(typeUrl);
      if (descriptor == null) {
        return Optional.absent();
      }

      Message defaultMessage = DynamicMessage.parseFrom(descriptor, value, extensionRegistry);
      return Optional.of(defaultMessage);
    } catch (InvalidProtocolBufferException e) {
      return Optional.absent();
    }
  }

  private AnyUtils() {}
}