/*
 * Copyright (C) 2006 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.graphhopper.coll;

import com.graphhopper.util.Helper;

/**
 * Copied from Android project: android.util.SparseArray.java
 * <p/>
 * SparseArrays map integers to Objects. Unlike a normal array of Objects, there can be gaps in the
 * indices. It is intended to be more efficient than using a HashMap to map Integers to Objects.
 */
public class SparseArray<E> implements Cloneable
{
    private static final Object DELETED = new Object();
    private boolean mGarbage = false;
    private int[] mKeys;
    private Object[] mValues;
    private int mSize;

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

    /**
     * Creates a new SparseArray containing no mappings that will not require any additional memory
     * allocation to store the specified number of mappings.
     */
    public SparseArray( int initialCapacity )
    {
        initialCapacity = Helper.idealIntArraySize(initialCapacity);

        mKeys = new int[initialCapacity];
        mValues = new Object[initialCapacity];
        mSize = 0;
    }

    @Override
    @SuppressWarnings("unchecked")
    public SparseArray<E> clone()
    {
        SparseArray<E> clone = null;
        try
        {
            clone = (SparseArray<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 <code>null</code> if no such mapping has
     * been made.
     */
    public E get( int key )
    {
        return get(key, null);
    }

    /**
     * Gets the Object mapped from the specified key, or the specified Object if no such mapping has
     * been made.
     */
    @SuppressWarnings("unchecked")
    public E get( int key, E valueIfKeyNotFound )
    {
        int i = binarySearch(mKeys, 0, 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.
     */
    public void remove( int key )
    {
        int i = binarySearch(mKeys, 0, mSize, key);
        if (i >= 0)
        {
            if (mValues[i] != DELETED)
            {
                mValues[i] = DELETED;
                mGarbage = true;
            }
        }
    }

    /**
     * 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;
        int[] 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.
     */
    public void put( int key, E value )
    {
        int i = binarySearch(mKeys, 0, 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 = ~binarySearch(mKeys, 0, mSize, key);
            }

            if (mSize >= mKeys.length)
            {
                int n = Helper.idealIntArraySize(mSize + 1);

                int[] nkeys = new int[n];
                Object[] nvalues = new Object[n];

                // Log.e("SparseArray", "grow " + mKeys.length + " to " + n);
                System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length);
                System.arraycopy(mValues, 0, nvalues, 0, mValues.length);

                mKeys = nkeys;
                mValues = nvalues;
            }

            if (mSize - i != 0)
            {
                // Log.e("SparseArray", "move " + (mSize - i));
                System.arraycopy(mKeys, i, mKeys, i + 1, mSize - i);
                System.arraycopy(mValues, i, mValues, i + 1, mSize - i);
            }

            mKeys[i] = key;
            mValues[i] = value;
            mSize++;
        }
    }

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

        return mSize;
    }

    /**
     * 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 SparseArray stores.
     */
    public int keyAt( int index )
    {
        if (mGarbage)
        {
            gc();
        }

        return mKeys[index];
    }

    /**
     * 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 SparseArray stores.
     */
    @SuppressWarnings("unchecked")
    public E valueAt( int index )
    {
        if (mGarbage)
        {
            gc();
        }

        return (E) mValues[index];
    }

    /**
     * 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 SparseArray stores.
     */
    public void setValueAt( int index, E value )
    {
        if (mGarbage)
        {
            gc();
        }

        mValues[index] = value;
    }

    /**
     * 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( int key )
    {
        if (mGarbage)
        {
            gc();
        }

        return binarySearch(mKeys, 0, mSize, key);
    }

    /**
     * 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;
    }

    /**
     * Removes all key-value mappings from this SparseArray.
     */
    public void clear()
    {
        trimTo(0);
    }

    public void trimTo( int size )
    {
        // let the gc do its work
        int max = Math.min(mSize, size);
        for (int i = max; i < mSize; i++)
        {
            mValues[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.
     */
    public void append( int key, E value )
    {
        if (mSize != 0 && key <= mKeys[mSize - 1])
        {
            put(key, value);
            return;
        }

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

        int pos = mSize;
        if (pos >= mKeys.length)
        {
            int n = Helper.idealIntArraySize(pos + 1);

            int[] nkeys = new int[n];
            Object[] nvalues = new Object[n];

            // Log.e("SparseArray", "grow " + mKeys.length + " to " + n);
            System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length);
            System.arraycopy(mValues, 0, nvalues, 0, mValues.length);

            mKeys = nkeys;
            mValues = nvalues;
        }

        mKeys[pos] = key;
        mValues[pos] = value;
        mSize = pos + 1;
    }

    // Warning: returns ~index and not -(index+1) like trove and jdk do
    private static int binarySearch( int[] a, int start, int len, int key )
    {
        int high = start + len, low = start - 1, guess;
        while (high - low > 1)
        {
            guess = (high + low) / 2;

            if (a[guess] < key)
            {
                low = guess;
            } else
            {
                high = guess;
            }
        }

        if (high == start + len)
        {
            return ~(start + len);
        } else if (a[high] == key)
        {
            return high;
        } else
        {
            return ~high;
        }
    }
}
