/*
    * Copyright 2021 TiKV Project 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 org.tikv.common.log;
  
  import com.google.gson.JsonElement;
  import com.google.gson.JsonObject;
  import java.text.SimpleDateFormat;
  import java.util.HashMap;
  import java.util.Map;
  
  public class SlowLogSpanImpl implements SlowLogSpan {
    private final String name;
    private final long requestStartInstantNS;
    private final long requestStartUnixNS;
  
    /** Key-Value pairs which will be logged, e.g. function name, key, region, etc. */
    private final Map<String, String> properties;
  
    /**
     * use System.nanoTime() to calculate duration, cause System.currentTimeMillis() is not monotonic
     */
    private long startInstantNS;
  
    private long endInstantNS;
  
    public SlowLogSpanImpl(String name, long requestStartMS, long requestStartInstantNS) {
      this.name = name;
      this.requestStartUnixNS = requestStartMS * 1_000_000;
      this.requestStartInstantNS = requestStartInstantNS;
      this.properties = new HashMap<>();
      this.startInstantNS = 0;
      this.endInstantNS = 0;
    }
  
    @Override
    public void addProperty(String key, String value) {
      properties.put(key, value);
    }
  
    @Override
    public void start() {
      startInstantNS = System.nanoTime();
    }
  
    @Override
    public void end() {
      endInstantNS = System.nanoTime();
    }
  
    @Override
    public JsonElement toJsonElement() {
      SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss.SSS");
      JsonObject jsonObject = new JsonObject();
      jsonObject.addProperty("event", name);
      jsonObject.addProperty("begin", dateFormat.format(getStartUnixNS() / 1_000_000));
      jsonObject.addProperty("duration_ms", getDurationNS() / 1_000_000);
  
      if (!properties.isEmpty()) {
        JsonObject propertiesObject = new JsonObject();
        for (Map.Entry<String, String> entry : properties.entrySet()) {
          propertiesObject.addProperty(entry.getKey(), entry.getValue());
        }
        jsonObject.add("properties", propertiesObject);
      }
  
      return jsonObject;
    }
  
    private long getStartUnixNS() {
      return requestStartUnixNS + (startInstantNS - requestStartInstantNS);
    }
  
    private long getDurationNS() {
      if (startInstantNS == 0 || endInstantNS == 0) {
        return -1;
      }
      return endInstantNS - startInstantNS;
    }
  }