content: /*
   * Copyright (C) 2017 The Android Open Source Project
   *
   * 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 com.android.server.audio;
  
  import android.util.Log;
  
  import java.io.PrintWriter;
  import java.text.SimpleDateFormat;
  import java.util.Date;
  import java.util.LinkedList;
  
  public class AudioEventLogger {
  
      // ring buffer of events to log.
      private final LinkedList<Event> mEvents;
  
      private final String mTitle;
  
      // the maximum number of events to keep in log
      private final int mMemSize;
  
      public static abstract class Event {
          // formatter for timestamps
          private final static SimpleDateFormat sFormat = new SimpleDateFormat("MM-dd HH:mm:ss:SSS");
  
          private final long mTimestamp;
  
          Event() {
              mTimestamp = System.currentTimeMillis();
          }
  
          public String toString() {
              return (new StringBuilder(sFormat.format(new Date(mTimestamp))))
                      .append(" ").append(eventToString()).toString();
          }
  
          /**
           * Causes the string message for the event to appear in the logcat.
           * Here is an example of how to create a new event (a StringEvent), adding it to the logger
           * (an instance of AudioEventLogger) while also making it show in the logcat:
           * <pre>
           *     myLogger.log(
           *         (new StringEvent("something for logcat and logger")).printLog(MyClass.TAG) );
           * </pre>
           * @param tag the tag for the android.util.Log.v
           * @return the same instance of the event
           */
          public Event printLog(String tag) {
              Log.i(tag, eventToString());
              return this;
          }
  
          /**
           * Convert event to String.
           * This method is only called when the logger history is about to the dumped,
           * so this method is where expensive String conversions should be made, not when the Event
           * subclass is created.
           * Timestamp information will be automatically added, do not include it.
           * @return a string representation of the event that occurred.
           */
          abstract public String eventToString();
      }
  
      public static class StringEvent extends Event {
          private final String mMsg;
  
          public StringEvent(String msg) {
              mMsg = msg;
          }
  
          @Override
          public String eventToString() {
              return mMsg;
          }
      }
  
      /**
       * Constructor for logger.
       * @param size the maximum number of events to keep in log
       * @param title the string displayed before the recorded log
       */
      public AudioEventLogger(int size, String title) {
          mEvents = new LinkedList<Event>();
          mMemSize = size;
          mTitle = title;
      }
  
      public synchronized void log(Event evt) {
          if (mEvents.size() >= mMemSize) {
              mEvents.removeFirst();
          }
          mEvents.add(evt);
      }
  
      public synchronized void dump(PrintWriter pw) {
          pw.println("Audio event log: " + mTitle);
          for (Event evt : mEvents) {
              pw.println(evt.toString());
          }
      }
  }
  