/*
 * Copyright (C) 2009 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 android.util;

import com.android.internal.util.ArrayUtils;
import com.android.internal.util.GrowingArrayUtils;

import libcore.util.EmptyArray;

SparseArray mapping longs to Objects.  Unlike a normal array of Objects,
there can be gaps in the indices.  It is intended to be more memory efficient
than using a HashMap to map Longs to Objects, both because it avoids
auto-boxing keys and its data structure doesn't rely on an extra entry object
for each mapping.
Note that this container keeps its mappings in an array data structure,
using a binary search to find keys.  The implementation is not intended to be appropriate for
data structures
that may contain large numbers of items.  It is generally slower than a traditional
HashMap, since lookups require a binary search and adds and removes require inserting
and deleting entries in the array.  For containers holding up to hundreds of items,
the performance difference is not significant, less than 50%.
To help with performance, the container includes an optimization when removing
keys: instead of compacting its array immediately, it leaves the removed entry marked
as deleted.  The entry can then be re-used for the same key, or compacted later in
a single garbage collection step of all removed entries.  This garbage collection will
need to be performed at any time the array needs to be grown or the the map size or
entry values are retrieved.
It is possible to iterate over the items in this container using keyAt(int) and valueAt(int). Iterating over the keys using keyAt(int) with ascending values of the index will return the
keys in ascending order, or the values corresponding to the keys in ascending
order in the case of valueAt(int).
/**
 * SparseArray mapping longs to Objects.  Unlike a normal array of Objects,
 * there can be gaps in the indices.  It is intended to be more memory efficient
 * than using a HashMap to map Longs to Objects, both because it avoids
 * auto-boxing keys and its data structure doesn't rely on an extra entry object
 * for each mapping.
 *
 * <p>Note that this container keeps its mappings in an array data structure,
 * using a binary search to find keys.  The implementation is not intended to be appropriate for
 * data structures
 * that may contain large numbers of items.  It is generally slower than a traditional
 * HashMap, since lookups require a binary search and adds and removes require inserting
 * and deleting entries in the array.  For containers holding up to hundreds of items,
 * the performance difference is not significant, less than 50%.</p>
 *
 * <p>To help with performance, the container includes an optimization when removing
 * keys: instead of compacting its array immediately, it leaves the removed entry marked
 * as deleted.  The entry can then be re-used for the same key, or compacted later in
 * a single garbage collection step of all removed entries.  This garbage collection will
 * need to be performed at any time the array needs to be grown or the the map size or
 * entry values are retrieved.</p>
 *
 * <p>It is possible to iterate over the items in this container using
 * {@link #keyAt(int)} and {@link #valueAt(int)}. Iterating over the keys using
 * <code>keyAt(int)</code> with ascending values of the index will return the
 * keys in ascending order, or the values corresponding to the keys in ascending
 * order in the case of <code>valueAt(int)</code>.</p>
 */
public class LongSparseArray<E> implements Cloneable {
    private static final Object DELETED = new Object();
    private boolean mGarbage = false;

    private long[] mKeys;
    private Object[] mValues;
    private int mSize;

    
Creates a new LongSparseArray containing no mappings.
/**
     * Creates a new LongSparseArray containing no mappings.
     */
    public LongSparseArray() {
        this(10);
    }

    
Creates a new LongSparseArray containing no mappings that will not
require any additional memory allocation to store the specified
number of mappings.  If you supply an initial capacity of 0, the
sparse array will be initialized with a light-weight representation
not requiring any additional array allocations.
/**
     * Creates a new LongSparseArray containing no mappings that will not
     * require any additional memory allocation to store the specified
     * number of mappings.  If you supply an initial capacity of 0, the
     * sparse array will be initialized with a light-weight representation
     * not requiring any additional array allocations.
     */
    public LongSparseArray(int initialCapacity) {
        if (initialCapacity == 0) {
            mKeys = EmptyArray.LONG;
            mValues = EmptyArray.OBJECT;
        } else {
            mKeys = ArrayUtils.newUnpaddedLongArray(initialCapacity);
            mValues = ArrayUtils.newUnpaddedObjectArray(initialCapacity);
        }
        mSize = 0;
    }

    @Override
    @SuppressWarnings("unchecked")
    public LongSparseArray<E> clone() {
        LongSparseArray<E> clone = null;
        try {
            clone = (LongSparseArray<E>) super.clone();
            clone.mKeys = mKeys.clone();
            clone.mValues = mValues.clone();
        } catch (CloneNotSupportedException cnse) {
            /* ignore */
        }
        return clone;
    }

    
Gets the Object mapped from the specified key, or null
if no such mapping has been made.
/**
     * Gets the Object mapped from the specified key, or <code>null</code>
     * if no such mapping has been made.
     */
    public E get(long key) {
        return get(key, null);
    }

    
Gets the Object mapped from the specified key, or the specified Object
if no such mapping has been made.
/**
     * Gets the Object mapped from the specified key, or the specified Object
     * if no such mapping has been made.
     */
    @SuppressWarnings("unchecked")
    public E get(long key, E valueIfKeyNotFound) {
        int i = ContainerHelpers.binarySearch(mKeys, mSize, key);

        if (i < 0 || mValues[i] == DELETED) {
            return valueIfKeyNotFound;
        } else {
            return (E) mValues[i];
        }
    }

    
Removes the mapping from the specified key, if there was any.
/**
     * Removes the mapping from the specified key, if there was any.
     */
    public void delete(long key) {
        int i = ContainerHelpers.binarySearch(mKeys, mSize, key);

        if (i >= 0) {
            if (mValues[i] != DELETED) {
                mValues[i] = DELETED;
                mGarbage = true;
            }
        }
    }

    
Alias for delete(long). /**
     * Alias for {@link #delete(long)}.
     */
    public void remove(long key) {
        delete(key);
    }

    
Removes the mapping at the specified index.
/**
     * Removes the mapping at the specified index.
     */
    public void removeAt(int index) {
        if (mValues[index] != DELETED) {
            mValues[index] = DELETED;
            mGarbage = true;
        }
    }

    private void gc() {
        // Log.e("SparseArray", "gc start with " + mSize);

        int n = mSize;
        int o = 0;
        long[] keys = mKeys;
        Object[] values = mValues;

        for (int i = 0; i < n; i++) {
            Object val = values[i];

            if (val != DELETED) {
                if (i != o) {
                    keys[o] = keys[i];
                    values[o] = val;
                    values[i] = null;
                }

                o++;
            }
        }

        mGarbage = false;
        mSize = o;

        // Log.e("SparseArray", "gc end with " + mSize);
    }

    
Adds a mapping from the specified key to the specified value,
replacing the previous mapping from the specified key if there
was one.
/**
     * Adds a mapping from the specified key to the specified value,
     * replacing the previous mapping from the specified key if there
     * was one.
     */
    public void put(long key, E value) {
        int i = ContainerHelpers.binarySearch(mKeys, mSize, key);

        if (i >= 0) {
            mValues[i] = value;
        } else {
            i = ~i;

            if (i < mSize && mValues[i] == DELETED) {
                mKeys[i] = key;
                mValues[i] = value;
                return;
            }

            if (mGarbage && mSize >= mKeys.length) {
                gc();

                // Search again because indices may have changed.
                i = ~ContainerHelpers.binarySearch(mKeys, mSize, key);
            }

            mKeys = GrowingArrayUtils.insert(mKeys, mSize, i, key);
            mValues = GrowingArrayUtils.insert(mValues, mSize, i, value);
            mSize++;
        }
    }

    
Returns the number of key-value mappings that this LongSparseArray
currently stores.
/**
     * Returns the number of key-value mappings that this LongSparseArray
     * currently stores.
     */
    public int size() {
        if (mGarbage) {
            gc();
        }

        return mSize;
    }

    
Given an index in the range 0...size()-1, returns
the key from the indexth key-value mapping that this
LongSparseArray stores.
The keys corresponding to indices in ascending order are guaranteed to
be in ascending order, e.g., keyAt(0) will return the
smallest key and keyAt(size()-1) will return the largest
key.
/**
     * Given an index in the range <code>0...size()-1</code>, returns
     * the key from the <code>index</code>th key-value mapping that this
     * LongSparseArray stores.
     *
     * <p>The keys corresponding to indices in ascending order are guaranteed to
     * be in ascending order, e.g., <code>keyAt(0)</code> will return the
     * smallest key and <code>keyAt(size()-1)</code> will return the largest
     * key.</p>
     */
    public long keyAt(int index) {
        if (mGarbage) {
            gc();
        }

        return mKeys[index];
    }

    
Given an index in the range 0...size()-1, returns
the value from the indexth key-value mapping that this
LongSparseArray stores.
The values corresponding to indices in ascending order are guaranteed
to be associated with keys in ascending order, e.g.,
valueAt(0) will return the value associated with the
smallest key and valueAt(size()-1) will return the value
associated with the largest key.
/**
     * Given an index in the range <code>0...size()-1</code>, returns
     * the value from the <code>index</code>th key-value mapping that this
     * LongSparseArray stores.
     *
     * <p>The values corresponding to indices in ascending order are guaranteed
     * to be associated with keys in ascending order, e.g.,
     * <code>valueAt(0)</code> will return the value associated with the
     * smallest key and <code>valueAt(size()-1)</code> will return the value
     * associated with the largest key.</p>
     */
    @SuppressWarnings("unchecked")
    public E valueAt(int index) {
        if (mGarbage) {
            gc();
        }

        return (E) mValues[index];
    }

    
Given an index in the range 0...size()-1, sets a new
value for the indexth key-value mapping that this
LongSparseArray stores.
/**
     * Given an index in the range <code>0...size()-1</code>, sets a new
     * value for the <code>index</code>th key-value mapping that this
     * LongSparseArray stores.
     */
    public void setValueAt(int index, E value) {
        if (mGarbage) {
            gc();
        }

        mValues[index] = value;
    }

    
Returns the index for which keyAt would return the specified key, or a negative number if the specified key is not mapped. /**
     * Returns the index for which {@link #keyAt} would return the
     * specified key, or a negative number if the specified
     * key is not mapped.
     */
    public int indexOfKey(long key) {
        if (mGarbage) {
            gc();
        }

        return ContainerHelpers.binarySearch(mKeys, mSize, key);
    }

    
Returns an index for which valueAt would return the specified key, or a negative number if no keys map to the specified value. Beware that this is a linear search, unlike lookups by key, and that multiple keys can map to the same value and this will find only one of them. /**
     * Returns an index for which {@link #valueAt} would return the
     * specified key, or a negative number if no keys map to the
     * specified value.
     * Beware that this is a linear search, unlike lookups by key,
     * and that multiple keys can map to the same value and this will
     * find only one of them.
     */
    public int indexOfValue(E value) {
        if (mGarbage) {
            gc();
        }

        for (int i = 0; i < mSize; i++) {
            if (mValues[i] == value) {
                return i;
            }
        }
        return -1;
    }

    
Returns an index for which valueAt would return the specified key, or a negative number if no keys map to the specified value. 
Beware that this is a linear search, unlike lookups by key,
and that multiple keys can map to the same value and this will
find only one of them.
Note also that this method uses equals unlike indexOfValue. 
@hide
/**
     * Returns an index for which {@link #valueAt} would return the
     * specified key, or a negative number if no keys map to the
     * specified value.
     * <p>Beware that this is a linear search, unlike lookups by key,
     * and that multiple keys can map to the same value and this will
     * find only one of them.
     * <p>Note also that this method uses {@code equals} unlike {@code indexOfValue}.
     * @hide
     */
    public int indexOfValueByValue(E value) {
        if (mGarbage) {
            gc();
        }

        for (int i = 0; i < mSize; i++) {
            if (value == null) {
                if (mValues[i] == null) {
                    return i;
                }
            } else {
                if (value.equals(mValues[i])) {
                    return i;
                }
            }
        }
        return -1;
    }

    
Removes all key-value mappings from this LongSparseArray.
/**
     * Removes all key-value mappings from this LongSparseArray.
     */
    public void clear() {
        int n = mSize;
        Object[] values = mValues;

        for (int i = 0; i < n; i++) {
            values[i] = null;
        }

        mSize = 0;
        mGarbage = false;
    }

    
Puts a key/value pair into the array, optimizing for the case where
the key is greater than all existing keys in the array.
/**
     * Puts a key/value pair into the array, optimizing for the case where
     * the key is greater than all existing keys in the array.
     */
    public void append(long key, E value) {
        if (mSize != 0 && key <= mKeys[mSize - 1]) {
            put(key, value);
            return;
        }

        if (mGarbage && mSize >= mKeys.length) {
            gc();
        }

        mKeys = GrowingArrayUtils.append(mKeys, mSize, key);
        mValues = GrowingArrayUtils.append(mValues, mSize, value);
        mSize++;
    }

    
{@inheritDoc}
This implementation composes a string by iterating over its mappings. If
this map contains itself as a value, the string "(this Map)"
will appear in its place.
/**
     * {@inheritDoc}
     *
     * <p>This implementation composes a string by iterating over its mappings. If
     * this map contains itself as a value, the string "(this Map)"
     * will appear in its place.
     */
    @Override
    public String toString() {
        if (size() <= 0) {
            return "{}";
        }

        StringBuilder buffer = new StringBuilder(mSize * 28);
        buffer.append('{');
        for (int i=0; i<mSize; i++) {
            if (i > 0) {
                buffer.append(", ");
            }
            long key = keyAt(i);
            buffer.append(key);
            buffer.append('=');
            Object value = valueAt(i);
            if (value != this) {
                buffer.append(value);
            } else {
                buffer.append("(this Map)");
            }
        }
        buffer.append('}');
        return buffer.toString();
    }
}