/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.activemq.artemis.cli.commands.messages.perf;

import java.util.concurrent.TimeUnit;

public class MicrosClock {

   // no need for volatile here
   private static long offset = -1;
   private static long NANOS_PER_SECOND = TimeUnit.SECONDS.toNanos(1);

   private static final boolean AVAILABLE = checkAvailable();

   private static boolean checkAvailable() {
      try {
         final long now = now();
         if (now < 0) {
            return false;
         }
         return true;
      } catch (Throwable t) {
         return false;
      }
   }

   public static boolean isAvailable() {
      return AVAILABLE;
   }

   public static long now() {
      long epochSecond = offset;
      long nanoAdjustment = jdk.internal.misc.VM.getNanoTimeAdjustment(epochSecond);

      if (nanoAdjustment == -1) {
         epochSecond = System.currentTimeMillis() / 1000 - 1024;
         nanoAdjustment = jdk.internal.misc.VM.getNanoTimeAdjustment(epochSecond);
         if (nanoAdjustment == -1) {
            throw new InternalError("Offset " + epochSecond + " is not in range");
         } else {
            offset = epochSecond;
         }
      }
      final long secs = Math.addExact(epochSecond, Math.floorDiv(nanoAdjustment, NANOS_PER_SECOND));
      final long secsInUs = TimeUnit.SECONDS.toMicros(secs);
      final long nsOffset = (int) Math.floorMod(nanoAdjustment, NANOS_PER_SECOND);
      final long usOffset = TimeUnit.NANOSECONDS.toMicros(nsOffset);
      return secsInUs + usOffset;
   }

}
