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      1 /*
      2  * Copyright (C) 2014 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.example.android.mediabrowserservice.utils;
     18 
     19 import java.util.Arrays;
     20 
     21 /**
     22  * Utility class to help on queue related tasks.
     23  */
     24 public class MediaIDHelper {
     25 
     26     private static final String TAG = LogHelper.makeLogTag(MediaIDHelper.class);
     27 
     28     // Media IDs used on browseable items of MediaBrowser
     29     public static final String MEDIA_ID_ROOT = "__ROOT__";
     30     public static final String MEDIA_ID_MUSICS_BY_GENRE = "__BY_GENRE__";
     31     public static final String MEDIA_ID_MUSICS_BY_SEARCH = "__BY_SEARCH__";
     32 
     33     private static final char CATEGORY_SEPARATOR = '/';
     34     private static final char LEAF_SEPARATOR = '|';
     35 
     36     public static String createMediaID(String musicID, String... categories) {
     37         // MediaIDs are of the form <categoryType>/<categoryValue>|<musicUniqueId>, to make it easy
     38         // to find the category (like genre) that a music was selected from, so we
     39         // can correctly build the playing queue. This is specially useful when
     40         // one music can appear in more than one list, like "by genre -> genre_1"
     41         // and "by artist -> artist_1".
     42         StringBuilder sb = new StringBuilder();
     43         if (categories != null && categories.length > 0) {
     44             sb.append(categories[0]);
     45             for (int i=1; i < categories.length; i++) {
     46                 sb.append(CATEGORY_SEPARATOR).append(categories[i]);
     47             }
     48         }
     49         if (musicID != null) {
     50             sb.append(LEAF_SEPARATOR).append(musicID);
     51         }
     52         return sb.toString();
     53     }
     54 
     55     public static String createBrowseCategoryMediaID(String categoryType, String categoryValue) {
     56         return categoryType + CATEGORY_SEPARATOR + categoryValue;
     57     }
     58 
     59     /**
     60      * Extracts unique musicID from the mediaID. mediaID is, by this sample's convention, a
     61      * concatenation of category (eg "by_genre"), categoryValue (eg "Classical") and unique
     62      * musicID. This is necessary so we know where the user selected the music from, when the music
     63      * exists in more than one music list, and thus we are able to correctly build the playing queue.
     64      *
     65      * @param mediaID that contains the musicID
     66      * @return musicID
     67      */
     68     public static String extractMusicIDFromMediaID(String mediaID) {
     69         int pos = mediaID.indexOf(LEAF_SEPARATOR);
     70         if (pos >= 0) {
     71             return mediaID.substring(pos+1);
     72         }
     73         return null;
     74     }
     75 
     76     /**
     77      * Extracts category and categoryValue from the mediaID. mediaID is, by this sample's
     78      * convention, a concatenation of category (eg "by_genre"), categoryValue (eg "Classical") and
     79      * mediaID. This is necessary so we know where the user selected the music from, when the music
     80      * exists in more than one music list, and thus we are able to correctly build the playing queue.
     81      *
     82      * @param mediaID that contains a category and categoryValue.
     83      */
     84     public static String[] getHierarchy(String mediaID) {
     85         int pos = mediaID.indexOf(LEAF_SEPARATOR);
     86         if (pos >= 0) {
     87             mediaID = mediaID.substring(0, pos);
     88         }
     89         return mediaID.split(String.valueOf(CATEGORY_SEPARATOR));
     90     }
     91 
     92     public static String extractBrowseCategoryValueFromMediaID(String mediaID) {
     93         String[] hierarchy = getHierarchy(mediaID);
     94         if (hierarchy != null && hierarchy.length == 2) {
     95             return hierarchy[1];
     96         }
     97         return null;
     98     }
     99 
    100     private static boolean isBrowseable(String mediaID) {
    101         return mediaID.indexOf(LEAF_SEPARATOR) < 0;
    102     }
    103 
    104     public static String getParentMediaID(String mediaID) {
    105         String[] hierarchy = getHierarchy(mediaID);
    106         if (!isBrowseable(mediaID)) {
    107             return createMediaID(null, hierarchy);
    108         }
    109         if (hierarchy == null || hierarchy.length <= 1) {
    110             return MEDIA_ID_ROOT;
    111         }
    112         String[] parentHierarchy = Arrays.copyOf(hierarchy, hierarchy.length-1);
    113         return createMediaID(null, parentHierarchy);
    114     }
    115 }
    116