/*
    * Copyright 2016 Function1, Inc. All Rights Reserved.
    *
    * 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 tools.gsf.time;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Stopwatch that records records into a logger. If the logger specified is not enabled at the debug level,
   * this timer does nothing. Designed for performance measurements.
   *
   * Very lightweight object. Upon instantiation, the current time is measured once.
   *
   * @author Tony Field
   * @since 2016-07-17
   */
  public final class LoggerStopwatch implements Stopwatch {
  
      /**
       * Default logger name used by this timer if no other logger is named.
       */
      public static final String DEFAULT_LOGGER_NAME = "tools.gsf.time";
  
      /**
       * Stopwatch message format string. This format will be used for all split measurements.
       * The first {} marker will be replaced by the time in microseconds. The second marker will be replaced
       * by the human-readable version of the time. The provided message will be appended to the end.
       */
      public static final String MESSAGE_FORMAT_SPLIT = "Split timer measurement: {}us ({}) for: ";
  
      /**
       * Stopwatch message format string. This format will be used for all cumulative measurements.
       * The first {} marker will be replaced by the time in microseconds. The second marker will be replaced
       * by the human-readable version of the time. The provided message will be appended to the end.
       */
      public static final String MESSAGE_FORMAT_ELAPSED = "Elapsed timer measurement: {}us ({}) for: ";
  
      private final Logger logger;
      private long startTimeNanos;
      private long lastIntervalTimeNanos;
  
      /**
       * Create a logger stopwatch using the logger specified. If debug is not enabled, the NoopStopwatch is returned
       * @param logger logger instance
       * @return the stopwatch or the NoopStopwatch if debug is not enabled
       * @see NoopStopwatch
       */
      public static Stopwatch getInstance(Logger logger) {
          return logger.isDebugEnabled() ? new LoggerStopwatch(logger) : NoopStopwatch.INSTANCE;
      }
  
      /**
       * Create a logger stopwatch using the logger specified. If debug is not enabled, the NoopStopwatch is returned
       * @param logger logger instance
       * @return the stopwatch or the NoopStopwatch if debug is not enabled
       * @see NoopStopwatch
       */
      public static Stopwatch getInstance(String logger) {
          return getInstance(LoggerFactory.getLogger(logger));
      }
  
      /**
       * Create a stopwatch using the default logger, if debug is enabled. If debug is not enabled, the NoopStopwatch
       * is returned.
       * @return the stopwatch or the NoopStopwatch if debug is not enabled
       * @see NoopStopwatch
       * @see #DEFAULT_LOGGER_NAME
       */
      public static Stopwatch getInstance() {
          return getInstance(DEFAULT_LOGGER_NAME);
      }
  
      private LoggerStopwatch(Logger logger) {
          this.logger = logger;
          this.startTimeNanos = 0L;
          this.lastIntervalTimeNanos = 0L;
      }
  
      @Override
      public void start() {
          startTimeNanos = System.nanoTime();
          lastIntervalTimeNanos = startTimeNanos;
      }
  
      public void split(String msg) {
          if (startTimeNanos == 0L) throw new IllegalStateException("Not yet started. Call start() first.");
         long now = System.nanoTime();
         _log(lastIntervalTimeNanos, now, true, msg);
         lastIntervalTimeNanos = now;
     }
 
     public void split(String msg, Object... args) {
         if (startTimeNanos == 0L) throw new IllegalStateException("Not yet started. Call start() first.");
         long now = System.nanoTime();
         _log(lastIntervalTimeNanos, now, true, msg, args);
         lastIntervalTimeNanos = now;
     }
 
     public void elapsed(String msg) {
         if (startTimeNanos == 0L) throw new IllegalStateException("Not yet started. Call start() first.");
         long now = System.nanoTime();
         _log(startTimeNanos, now, false, msg);
     }
 
     public void elapsed(String msg, Object... args) {
         if (startTimeNanos == 0L) throw new IllegalStateException("Not yet started. Call start() first.");
         long now = System.nanoTime();
         _log(startTimeNanos, now, false, msg, args);
     }
 
     private void _log(long startNanos, long endNanos, boolean split, String msg, Object... args) {
 
         long micros = (endNanos - startNanos) / 1000;
         String sMicros = Long.toString(micros);
         String human = _humanFormat(micros);
 
         String logmsg = split ? MESSAGE_FORMAT_SPLIT : MESSAGE_FORMAT_ELAPSED;
         logmsg += msg;
 
         if (args == null || args.length == 0) {
             logger.debug(logmsg, sMicros, human);
         } else {
             Object[] arguments = new Object[args.length + 2];
             arguments[0] = sMicros;
             arguments[1] = human;
             System.arraycopy(args, 0, arguments, 2, args.length);
             logger.debug(logmsg, arguments);
         }
     }
 
     private String _humanFormat(long micros) {
         String human;
         if (micros > 1000000) {
             final long millis = micros / 1000;
             human = Long.toString(millis / 1000) + "." + String.format("%03d", (millis % 1000)) + "s";
         } else if (micros > 1000) {
             human = Long.toString(micros / 1000) + "." + String.format("%03d", (micros % 1000)) + "ms";
         } else {
             human = Long.toString(micros) + "us";
         }
         return human;
     }
 }