/*
 * Copyright (c) 2012, the Dart project authors.
 * 
 * Licensed under the Eclipse Public License v1.0 (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.eclipse.org/legal/epl-v10.html
 * 
 * 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 com.github.sdbg.debug.core.internal.util;

import com.github.sdbg.debug.core.util.Trace;

import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.List;

/**
 * A simple class to measure timings in the debugger.
 */
public class LogTimer {
  public static interface LogListener {
    /**
     * Handle a log event w/ the given action name and duration (in milliseconds).
     * 
     * @param actionName
     * @param durationMs
     */
    public void timerLog(String actionName, long durationMs);
  }

  private static List<LogListener> listeners = new ArrayList<LogTimer.LogListener>();

  private String name;

  private long startTime;

  private String taskName;
  private long taskStart;

  /**
   * This formatter always shows the thousandths position (0.000).
   */
  private static final NumberFormat numberFormat = new DecimalFormat("#.###");

  public static void addLogListener(LogListener listener) {
    listeners.add(listener);
  }

  public static void removeLogListener(LogListener listener) {
    listeners.remove(listener);
  }

  /**
   * Create a new LogTimer.
   * 
   * @param name
   */
  public LogTimer(String name) {
    this.name = name;
    this.startTime = System.currentTimeMillis();
  }

  /**
   * Start a sub-task timer. This does not interfere with the main timer.
   * 
   * @param taskName
   */
  public void startTask(String taskName) {
    this.taskName = taskName;
    this.taskStart = System.currentTimeMillis();
  }

  /**
   * Stop a sub-task timer. This does not interfere with the main timer.
   */
  public void stopTask() {
    long duration = System.currentTimeMillis() - taskStart;

    if (isTracing()) {
      trace(taskName + " time: " + duration + "ms");
    }

    taskName = null;
  }

  /**
   * Stop the timer, and log the duration to the Eclipse .log.
   */
  public void stopTimer() {
    long duration = System.currentTimeMillis() - startTime;

    if (isTracing()) {
      trace(name + " total time: " + getSeconds(duration) + " sec");
    }

    for (LogListener listener : listeners) {
      listener.timerLog(name, duration);
    }
  }

  private String getSeconds(long durationMs) {
    return numberFormat.format(durationMs / 1000.0);
  }

  private boolean isTracing() {
    return Trace.isTracing(Trace.TIMER);
  }

  private void trace(String message) {
    Trace.trace(Trace.TIMER, message);
  }
}