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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.ahat;
     18 
     19 import java.util.List;
     20 
     21 /**
     22  * The SubsetSelector is that can be added to a page that lets the
     23  * user select a limited number of elements to show.
     24  * This is used to limit the number of elements shown on a page by default,
     25  * requiring the user to explicitly request more, so users not interested in
     26  * more don't have to wait for everything to render.
     27  */
     28 class SubsetSelector<T> {
     29   private static final int kIncrAmount = 1000;
     30   private static final int kDefaultShown = 1000;
     31 
     32   private Query mQuery;
     33   private String mId;
     34   private int mLimit;
     35   private List<T> mElements;
     36 
     37   /**
     38    * @param id - the name of the query parameter key that should hold
     39    * the limit selectors selected value.
     40    * @param query - The query for the current page. This is required so the
     41    * LimitSelector can add a link to the same page with modified limit
     42    * selection.
     43    * @param elements - the elements to select from. The collection of elements
     44    * should not be modified during the lifetime of the SubsetSelector object.
     45    */
     46   public SubsetSelector(Query query, String id, List<T> elements) {
     47     mQuery = query;
     48     mId = id;
     49     mLimit = getSelectedLimit(query, id, elements.size());
     50     mElements = elements;
     51   }
     52 
     53   // Return the list of elements included in the selected subset.
     54   public List<T> selected() {
     55     return mElements.subList(0, mLimit);
     56   }
     57 
     58   // Return the list of remaining elements not included in the selected subset.
     59   public List<T> remaining() {
     60     return mElements.subList(mLimit, mElements.size());
     61   }
     62 
     63   /**
     64    * Returns the currently selected limit.
     65    * @param query the current page query
     66    * @param size the total number of elements to select from
     67    * @return the number of selected elements
     68    */
     69   private static int getSelectedLimit(Query query, String id, int size) {
     70     String value = query.get(id, null);
     71     try {
     72       int ivalue = Math.min(size, Integer.parseInt(value));
     73       return Math.max(0, ivalue);
     74     } catch (NumberFormatException e) {
     75       // We can't parse the value as a number. Ignore it.
     76     }
     77     return Math.min(kDefaultShown, size);
     78   }
     79 
     80   // Render the limit selector to the given doc.
     81   // It has the form:
     82   //  (showing X of Y - show none - show less - show more - show all)
     83   public void render(Doc doc) {
     84     int all = mElements.size();
     85     if (all > kDefaultShown) {
     86       DocString menu = new DocString();
     87       menu.appendFormat("(%d of %d elements shown - ", mLimit, all);
     88       if (mLimit > 0) {
     89         int less = Math.max(0, mLimit - kIncrAmount);
     90         menu.appendLink(mQuery.with(mId, 0), DocString.text("show none"));
     91         menu.append(" - ");
     92         menu.appendLink(mQuery.with(mId, less), DocString.text("show less"));
     93         menu.append(" - ");
     94       } else {
     95         menu.append("show none - show less - ");
     96       }
     97       if (mLimit < all) {
     98         int more = Math.min(mLimit + kIncrAmount, all);
     99         menu.appendLink(mQuery.with(mId, more), DocString.text("show more"));
    100         menu.append(" - ");
    101         menu.appendLink(mQuery.with(mId, all), DocString.text("show all"));
    102         menu.append(")");
    103       } else {
    104         menu.append("show more - show all)");
    105       }
    106       doc.println(menu);
    107     }
    108   }
    109 }
    110