ProtoEncoder.java

/*
 * Copyright 2014 Bevbot LLC <info@bevbot.com>
 *
 * This file is part of the Kegtab package from the Kegbot project. For
 * more information on Kegtab or Kegbot, see <http://kegbot.org/>.
 *
 * Kegtab is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free
 * Software Foundation, version 2.
 *
 * Kegtab is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with Kegtab. If not, see <http://www.gnu.org/licenses/>.
 */
package org.kegbot.api;

import com.google.protobuf.Descriptors.Descriptor;
import com.google.protobuf.Descriptors.FieldDescriptor;
import com.google.protobuf.Message.Builder;

import org.codehaus.jackson.JsonNode;

import java.io.IOException;
import java.util.Iterator;

public class ProtoEncoder {

  /**
   * Assigns all fields in {@link JsonNode} instance to a {@link Builder}.
   *
   * @param builder the builder to be populated
   * @param root    the JSON object
   * @return the original builder, populated with any fields that were discovered
   */
  public static Builder toProto(final Builder builder, final JsonNode root) {
    Descriptor type = builder.getDescriptorForType();
    for (final FieldDescriptor fieldDesc : type.getFields()) {
      final String attrName = fieldDesc.getName();
      final JsonNode node = root.get(attrName);

      if (node == null) {
        continue;
      }

      if (node.isNull()) {
        continue;
      }

      if (fieldDesc.isRepeated()) {
        final Iterator<JsonNode> iter = node.getElements();
        while (iter.hasNext()) {
          builder.addRepeatedField(fieldDesc, toJavaObj(builder, fieldDesc, iter.next()));
        }
      } else {
        builder.setField(fieldDesc, toJavaObj(builder, fieldDesc, node));
      }
    }
    return builder;
  }

  private static Object toJavaObj(final Builder builder, final FieldDescriptor fieldDesc,
      final JsonNode node) {
    Object value;
    switch (fieldDesc.getJavaType()) {
      case MESSAGE:
        final Builder subBuilder = builder.newBuilderForField(fieldDesc);
        value = toProto(subBuilder, node).build();
        break;
      case BOOLEAN:
        value = Boolean.valueOf(node.getBooleanValue());
        break;
      case BYTE_STRING:
        try {
          value = node.getBinaryValue();
        } catch (IOException e) {
          throw new RuntimeException(e);
        }
        break;
      case DOUBLE:
        value = Double.valueOf(node.getDoubleValue());
        break;
      case FLOAT:
        value = Float.valueOf(Double.valueOf(node.getDoubleValue()).floatValue());
        break;
      case ENUM:
        value = fieldDesc.getEnumType().findValueByName(node.getTextValue());
        break;
      case INT:
        value = Integer.valueOf(node.getIntValue());
        break;
      case LONG:
        value = Long.valueOf(node.getLongValue());
        break;
      case STRING:
        value = node.getTextValue();
        break;
      default:
        throw new IllegalArgumentException();
    }
    return value;

  }

}