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      1 /*
      2  * Copyright (C) 2015 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.tv.recommendation;
     18 
     19 import java.util.concurrent.TimeUnit;
     20 
     21 public class RecentChannelEvaluator extends Recommender.Evaluator {
     22     private static final long WATCH_DURATION_MS_LOWER_BOUND = TimeUnit.MINUTES.toMillis(3);
     23     private static final long WATCH_DURATION_MS_UPPER_BOUND = TimeUnit.MINUTES.toMillis(7);
     24 
     25     private static final double MAX_SCORE_FOR_LOWER_BOUND = 0.1;
     26 
     27     private long mLastWatchLogUpdateTimeMs;
     28 
     29     public RecentChannelEvaluator() {
     30         mLastWatchLogUpdateTimeMs = System.currentTimeMillis();
     31     }
     32 
     33     @Override
     34     public void onNewWatchLog(ChannelRecord channelRecord) {
     35         mLastWatchLogUpdateTimeMs = System.currentTimeMillis();
     36     }
     37 
     38     @Override
     39     public double evaluateChannel(long channelId) {
     40         ChannelRecord cr = getRecommender().getChannelRecord(channelId);
     41         if (cr == null) {
     42             return NOT_RECOMMENDED;
     43         }
     44         WatchedProgram[] watchHistory = cr.getWatchHistory();
     45         double maxScore = 0.0;
     46         for (int i = watchHistory.length - 1; i >= 0; --i) {
     47             double recentWatchScore =
     48                     (double) watchHistory[i].getWatchEndTimeMs() / mLastWatchLogUpdateTimeMs;
     49             double watchDurationScore;
     50             double watchDuration = watchHistory[i].getWatchedDurationMs();
     51             if (watchDuration < WATCH_DURATION_MS_LOWER_BOUND) {
     52                 watchDurationScore = MAX_SCORE_FOR_LOWER_BOUND;
     53             } else if (watchDuration < WATCH_DURATION_MS_UPPER_BOUND) {
     54                 watchDurationScore = (watchDuration - WATCH_DURATION_MS_LOWER_BOUND)
     55                         / (WATCH_DURATION_MS_UPPER_BOUND - WATCH_DURATION_MS_LOWER_BOUND)
     56                         * (1 - MAX_SCORE_FOR_LOWER_BOUND) + MAX_SCORE_FOR_LOWER_BOUND;
     57             } else {
     58                 watchDurationScore = 1.0;
     59             }
     60             maxScore = Math.max(maxScore, watchDurationScore * recentWatchScore);
     61         }
     62         return (maxScore > 0.0) ? maxScore : NOT_RECOMMENDED;
     63     }
     64 }