/*
 * Copyright 2018, OpenCensus Authors
 *
 * 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 io.opencensus.exporter.metrics.ocagent;

import com.google.common.annotations.VisibleForTesting;
import io.opencensus.common.OpenCensusLibraryInformation;
import io.opencensus.common.Timestamp;
import io.opencensus.contrib.resource.util.ResourceUtils;
import io.opencensus.proto.agent.common.v1.LibraryInfo;
import io.opencensus.proto.agent.common.v1.LibraryInfo.Language;
import io.opencensus.proto.agent.common.v1.Node;
import io.opencensus.proto.agent.common.v1.ProcessIdentifier;
import io.opencensus.proto.agent.common.v1.ServiceInfo;
import io.opencensus.proto.resource.v1.Resource;
import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.SecureRandom;
import java.util.Map.Entry;
import javax.annotation.Nullable;

/** Utilities for detecting and creating {@link Node}. */
// TODO(songya): extract the utilities to a common artifact.
final class OcAgentNodeUtils {

  // The current version of the OpenCensus OC-Agent Exporter.
  @VisibleForTesting
  static final String OC_AGENT_EXPORTER_VERSION = "0.18.0-SNAPSHOT"; // CURRENT_OPENCENSUS_VERSION

  @Nullable
  private static final io.opencensus.resource.Resource AUTO_DETECTED_RESOURCE =
      ResourceUtils.detectResource();

  // Creates a Node with information from the OpenCensus library and environment variables.
  static Node getNodeInfo(String serviceName) {
    String jvmName = ManagementFactory.getRuntimeMXBean().getName();
    Timestamp censusTimestamp = Timestamp.fromMillis(System.currentTimeMillis());
    return Node.newBuilder()
        .setIdentifier(getProcessIdentifier(jvmName, censusTimestamp))
        .setLibraryInfo(getLibraryInfo(OpenCensusLibraryInformation.VERSION))
        .setServiceInfo(getServiceInfo(serviceName))
        .build();
  }

  // Creates process identifier with the given JVM name and start time.
  @VisibleForTesting
  static ProcessIdentifier getProcessIdentifier(String jvmName, Timestamp censusTimestamp) {
    String hostname;
    int pid;
    // jvmName should be something like '<pid>@<hostname>', at least in Oracle and OpenJdk JVMs
    int delimiterIndex = jvmName.indexOf('@');
    if (delimiterIndex < 1) {
      // Not the expected format, generate a random number.
      try {
        hostname = InetAddress.getLocalHost().getHostName();
      } catch (UnknownHostException e) {
        hostname = "localhost";
      }
      // Generate a random number as the PID.
      pid = new SecureRandom().nextInt();
    } else {
      hostname = jvmName.substring(delimiterIndex + 1, jvmName.length());
      try {
        pid = Integer.parseInt(jvmName.substring(0, delimiterIndex));
      } catch (NumberFormatException e) {
        // Generate a random number as the PID if format is unexpected.
        pid = new SecureRandom().nextInt();
      }
    }

    return ProcessIdentifier.newBuilder()
        .setHostName(hostname)
        .setPid(pid)
        .setStartTimestamp(MetricsProtoUtils.toTimestampProto(censusTimestamp))
        .build();
  }

  // Creates library info with the given OpenCensus Java version.
  @VisibleForTesting
  static LibraryInfo getLibraryInfo(String currentOcJavaVersion) {
    return LibraryInfo.newBuilder()
        .setLanguage(Language.JAVA)
        .setCoreLibraryVersion(currentOcJavaVersion)
        .setExporterVersion(OC_AGENT_EXPORTER_VERSION)
        .build();
  }

  // Creates service info with the given service name.
  @VisibleForTesting
  static ServiceInfo getServiceInfo(String serviceName) {
    return ServiceInfo.newBuilder().setName(serviceName).build();
  }

  @Nullable
  static Resource getAutoDetectedResourceProto() {
    return toResourceProto(AUTO_DETECTED_RESOURCE);
  }

  // Converts a Java Resource object to a Resource proto.
  @Nullable
  @VisibleForTesting
  static Resource toResourceProto(@Nullable io.opencensus.resource.Resource resource) {
    if (resource == null || resource.getType() == null) {
      return null;
    } else {
      Resource.Builder resourceProtoBuilder = Resource.newBuilder();
      resourceProtoBuilder.setType(resource.getType());
      for (Entry<String, String> keyValuePairs : resource.getLabels().entrySet()) {
        resourceProtoBuilder.putLabels(keyValuePairs.getKey(), keyValuePairs.getValue());
      }
      return resourceProtoBuilder.build();
    }
  }

  private OcAgentNodeUtils() {}
}
