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/*
* Copyright (C) 2016 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.tv.dvr.ui;
import android.support.annotation.VisibleForTesting;
import android.support.v17.leanback.widget.ArrayObjectAdapter;
import android.support.v17.leanback.widget.PresenterSelector;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/**
* Keeps a set of items sorted
*
* <p>{@code T} must have stable IDs.
*/
public abstract class SortedArrayAdapter<T> extends ArrayObjectAdapter {
private final Comparator<T> mComparator;
private final int mMaxItemCount;
private int mExtraItemCount;
SortedArrayAdapter(PresenterSelector presenterSelector, Comparator<T> comparator) {
this(presenterSelector, comparator, Integer.MAX_VALUE);
}
SortedArrayAdapter(PresenterSelector presenterSelector, Comparator<T> comparator,
int maxItemCount) {
super(presenterSelector);
mComparator = comparator;
mMaxItemCount = maxItemCount;
}
/**
* Sets the objects in the given collection to the adapter keeping the elements sorted.
*
* @param items A {@link Collection} of items to be set.
*/
@VisibleForTesting
final void setInitialItems(List<T> items) {
List<T> itemsCopy = new ArrayList<>(items);
Collections.sort(itemsCopy, mComparator);
addAll(0, itemsCopy.subList(0, Math.min(mMaxItemCount, itemsCopy.size())));
}
/**
* Adds an item in sorted order to the adapter.
*
* @param item The item to add in sorted order to the adapter.
*/
@Override
public final void add(Object item) {
add((T) item, false);
}
public boolean isEmpty() {
return size() == 0;
}
/**
* Adds an item in sorted order to the adapter.
*
* @param item The item to add in sorted order to the adapter.
* @param insertToEnd If items are inserted in a more or less sorted fashion,
* sets this parameter to {@code true} to search insertion position from
* the end to save search time.
*/
public final void add(T item, boolean insertToEnd) {
int i;
if (insertToEnd) {
i = findInsertPosition(item);
} else {
i = findInsertPositionBinary(item);
}
super.add(i, item);
if (size() > mMaxItemCount + mExtraItemCount) {
removeItems(mMaxItemCount, size() - mMaxItemCount - mExtraItemCount);
}
}
/**
* Adds an extra item to the end of the adapter. The items will not be subjected to the sorted
* order or the maximum number of items. One or more extra items can be added to the adapter.
* They will be presented in their insertion order.
*/
public int addExtraItem(T item) {
super.add(item);
return ++mExtraItemCount;
}
/**
* Removes an item which has the same ID as {@code item}.
*/
public boolean removeWithId(T item) {
int index = indexWithTypeAndId(item);
return index >= 0 && index < size() && remove(get(index));
}
/**
* Change an item in the list.
* @param item The item to change.
*/
public final void change(T item) {
int oldIndex = indexWithTypeAndId(item);
if (oldIndex != -1) {
T old = (T) get(oldIndex);
if (mComparator.compare(old, item) == 0) {
replace(oldIndex, item);
return;
}
removeItems(oldIndex, 1);
}
add(item);
}
/**
* Returns the id of the the given {@code item}, which will be used in {@link #change} to
* decide if the given item is already existed in the adapter.
*
* The id must be stable.
*/
abstract long getId(T item);
private int indexWithTypeAndId(T item) {
long id = getId(item);
for (int i = 0; i < size() - mExtraItemCount; i++) {
T r = (T) get(i);
if (r.getClass() == item.getClass() && getId(r) == id) {
return i;
}
}
return -1;
}
/**
* Finds the position that the given item should be inserted to keep the sorted order.
*/
public int findInsertPosition(T item) {
for (int i = size() - mExtraItemCount - 1; i >=0; i--) {
T r = (T) get(i);
if (mComparator.compare(r, item) <= 0) {
return i + 1;
}
}
return 0;
}
private int findInsertPositionBinary(T item) {
int lb = 0;
int ub = size() - mExtraItemCount - 1;
while (lb <= ub) {
int mid = (lb + ub) / 2;
T r = (T) get(mid);
int compareResult = mComparator.compare(item, r);
if (compareResult == 0) {
return mid;
} else if (compareResult > 0) {
lb = mid + 1;
} else {
ub = mid - 1;
}
}
return lb;
}
}
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