/******************************************************************************
 * Copyright (C) Ultraleap, Inc. 2011-2021.                                   *
 *                                                                            *
 * Use subject to the terms of the Apache License 2.0 available at            *
 * http://www.apache.org/licenses/LICENSE-2.0, or another agreement           *
 * between Ultraleap and you, your company or other organization.             *
 ******************************************************************************/

using System;
using System.Collections.Generic;
using UnityEngine;

namespace Leap.Unity
{

    public static class ArrayPool<T>
    {
        private static Dictionary<int, Stack<T[]>> _bins;

        static ArrayPool()
        {
            _bins = new Dictionary<int, Stack<T[]>>();

            _bins[0] = new Stack<T[]>();
            for (int i = 0; i < 32; i++)
            {
                _bins[1 << i] = new Stack<T[]>();
            }
        }

        /// <summary>
        /// Spawns an array from the ArrayPool given the minimum length.
        /// The actual length of the array may be larger than what is
        /// requested.
        /// 
        /// Arrays can be returned to the array pool with the Recycle
        /// method.
        /// </summary>
        public static T[] Spawn(int minLength)
        {
            int count = Mathf.NextPowerOfTwo(minLength);
            var bin = _bins[count];

            if (bin.Count > 0)
            {
                return bin.Pop();
            }
            else
            {
                return new T[count];
            }
        }

        /// <summary>
        /// Recycles an array into the ArrayPool.  The array does not
        /// need to be an array that was created with Spawn.
        /// </summary>
        public static void Recycle(T[] array)
        {
            Array.Clear(array, 0, array.Length);
            int binKey = Mathf.NextPowerOfTwo(array.Length + 1) / 2;
            _bins[binKey].Push(array);
        }
    }
}