#strict 3

global func SortNumeric(int a, int b)
{
	return a - b;
}

global func SortNumericInverse(int a, int b)
{
	return -SortNumeric(a, b);
}

global func QSort(array& data, callback, callbackArgs)
{
	if(callback == true)
	{
		callback = GlobalCallback("SortNumericInverse");
	}
	else
	{
		callback ??= GlobalCallback("SortNumeric");
	}
	
	// start of flattened recursive part
	var stack = [[0, GetLength(data) - 1]];
	
	// stack pointer points to next empty slot
	for(var stackPointer = 1; stackPointer > 0; )
	{
		var frame = stack[--stackPointer];
		var left = frame[0];
		var right = frame[1];
		
		if(left < right)
		{
			// Partitioning
			var pPos = RandomX(left, right);
			var p = data[pPos];
			var tmp;
			
			tmp = data[pPos];
			data[pPos] = data[right];
			data[right] = tmp;
			pPos = right;
			
			var i = left - 1;
			for(var j = left; j <= right; ++j)
			{
				if(Call(callback, data[j],  p, callbackArgs) < 0)
				{
					++i;
					tmp = data[i];
					data[i] = data[j];
					data[j] = tmp;
				}
			}
			
			++i;
			
			tmp = data[i];
			data[i] = data[pPos];
			data[pPos] = tmp;
			// -----
			
			stack[stackPointer++] = [left, i - 1];
			stack[stackPointer++] = [i + 1, right];
		}
	}
	// end of recursive part
	
	return data;
}