//adapted from https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/util/Pools.java

using System;

namespace HandyControl.Tools
{
    public class SimplePool<T> : IPool<T>
    {
        private readonly object[] _pool;

        private int _poolSize;

        public SimplePool(int maxPoolSize)
        {
            if (maxPoolSize <= 0)
            {
                throw new ArgumentException("The max pool size must be > 0");
            }
            _pool = new object[maxPoolSize];
        }

        public virtual T Acquire()
        {
            if (_poolSize > 0)
            {
                var lastPooledIndex = _poolSize - 1;
                var instance = (T) _pool[lastPooledIndex];
                _pool[lastPooledIndex] = null;
                _poolSize--;
                return instance;
            }
            return default;
        }

        public virtual bool Release(T instance)
        {
            if (IsInPool(instance))
            {
                throw new Exception("Already in the pool!");
            }

            if (_poolSize < _pool.Length)
            {
                _pool[_poolSize] = instance;
                _poolSize++;
                return true;
            }

            return false;
        }

        private bool IsInPool(T instance)
        {
            for (var i = 0; i < _poolSize; i++)
            {
                if (Equals(_pool[i], instance))
                {
                    return true;
                }
            }
            return false;
        }
    }
}
