content: /*
   *  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.causeway.commons.internal.base;
  
  import java.io.Serializable;
  import java.util.Locale;
  import java.util.function.Supplier;
  
  import org.apache.logging.log4j.Logger;
  
  import lombok.Getter;
  
  /**
   * <h1>- internal use only -</h1>
   * <p>
   * Time measuring utilities.
   * </p>
   * <p>
   * <b>WARNING</b>: Do <b>NOT</b> use any of the classes provided by this package! <br/>
   * These may be changed or removed without notice!
   * </p>
   *
   * @since 2.0
   */
  public final class _Timing {
  
      private _Timing(){}
  
      /**
       * @return a new 'now' started instance of {@link StopWatch}
       */
      public static StopWatch now() {
          return new StopWatch();
      }
  
      /**
       *
       * @param startedAtSystemNanos
       * @return a new {@code startedAtSystemNanos} instance of {@link StopWatch}
       */
      public static StopWatch atSystemNanos(final long startedAtSystemNanos) {
          return new StopWatch(startedAtSystemNanos);
      }
  
      /**
       * Non thread safe start/stop watch utilizing the currently running
       * JVM's high-resolution time source.
       * @implNote using {@link System#nanoTime()} as this is best suited to measure elapsed time
       */
      public static final class StopWatch implements Serializable {
          private static final long serialVersionUID = 1L;
  
          private long t0 = 0;
          private long t1 = 0;
          @Getter private boolean stopped;
  
          private StopWatch(final long startedAtSystemNanos) {
              t0 = startedAtSystemNanos;
          }
  
          private StopWatch() {
              start();
          }
  
          /** On repeated calls simply restarts the clock. */
          public StopWatch start() {
              t0 = System.nanoTime();
              stopped = false;
              return this;
          }
  
          /** Snapshots a split time.
           * Repeated calls will update the measurement value leaving the starting point unchanged. */
          public StopWatch stop() {
              t1 = System.nanoTime();
              stopped  = true;
              return this;
          }
  
          public double getSeconds() {
              return 0.001 * getMillis();
          }
  
          /**
           * @return elapsed nano seconds since started
           * (or when stopped, the time interval between started and stopped)
           */
          public long getNanos() {
              return stopped ? t1 - t0 : System.nanoTime() - t0 ;
          }
  
          /**
           * @return elapsed micro seconds since started
           * (or when stopped, the time interval between started and stopped)
           */
          public long getMicros() {
              return getNanos()/1000L;
          }
  
          /**
           * @return elapsed milli seconds since started
           * (or when stopped, the time interval between started and stopped)
           */
          public long getMillis() {
              return getNanos()/1000_000L;
          }
  
          @Override
          public String toString() {
              return String.format(Locale.US, "%d ms", getMillis());
          }
  
      }
  
      public static StopWatch run(final Runnable runnable) {
          final StopWatch watch = now();
          runnable.run();
          return watch.stop();
      }
  
      public static void runVerbose(final Logger log, final String label, final Runnable runnable) {
          final StopWatch watch = run(runnable);
          log.info(String.format(Locale.US, "Running '%s' took %d ms", label, watch.getMillis()));
      }
  
      public static <T> T callVerbose(final Logger log, final String label, final Supplier<T> callable) {
          final StopWatch watch = now();
          T result = callable.get();
          watch.stop();
          log.info(String.format(Locale.US, "Calling '%s' took %d ms", label, watch.getMillis()));
          return result;
      }
  
  }
  