// Copyright (C) 2019 The Android Open Source Project
//
// 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.googlesource.gerrit.plugins.kafka.subscribe;

import static java.util.Objects.requireNonNull;

import com.gerritforge.gerrit.eventbroker.EventMessage;
import com.gerritforge.gerrit.eventbroker.EventMessage.Header;
import com.google.gerrit.server.events.Event;
import com.google.gson.Gson;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import java.util.Map;
import java.util.UUID;
import org.apache.kafka.common.serialization.Deserializer;
import org.apache.kafka.common.serialization.StringDeserializer;

@Singleton
public class KafkaEventDeserializer implements Deserializer<EventMessage> {

  private final StringDeserializer stringDeserializer = new StringDeserializer();
  private Gson gson;

  // To be used when providing this deserializer with class name (then need to add a configuration
  // entry to set the gson.provider
  public KafkaEventDeserializer() {}

  @Inject
  public KafkaEventDeserializer(Gson gson) {
    this.gson = gson;
  }

  @Override
  public void configure(Map<String, ?> configs, boolean isKey) {}

  @Override
  public EventMessage deserialize(String topic, byte[] data) {
    String json = stringDeserializer.deserialize(topic, data);
    EventMessage result = gson.fromJson(json, EventMessage.class);
    if (result.getEvent() == null && result.getHeader() == null) {
      Event event = deserialiseEvent(json);
      result = new EventMessage(new Header(UUID.randomUUID(), event.instanceId), event);
    }
    result.validate();
    return result;
  }

  private Event deserialiseEvent(String json) {
    Event event = gson.fromJson(json, Event.class);
    requireNonNull(event.type, "Event type cannot be null");
    requireNonNull(event.instanceId, "Event instance id cannot be null");
    return event;
  }

  @Override
  public void close() {}
}