using System.Runtime.InteropServices;
using System;

namespace DCFApixels.DragonECS
{
    internal static class ArrayUtility
    {
        public static void Fill<T>(T[] array, T value, int startIndex = 0, int length = -1)
        {
            if (length < 0)
            {
                length = array.Length;
            }
            else
            {
                length = startIndex + length;
            }
            for (int i = startIndex; i < length; i++)
            {
                array[i] = value;
            }
        }
    }

    internal static unsafe class UnmanagedArray
    {
        public static void* New<T>(int elementCount)
            where T : struct
        {
            return Marshal.AllocHGlobal(Marshal.SizeOf(typeof(T)) * elementCount).ToPointer();
        }

        public static void* NewAndInit<T>(int elementCount)
            where T : struct
        {
            int newSizeInBytes = Marshal.SizeOf(typeof(T)) * elementCount;
            byte* newArrayPointer = (byte*)Marshal.AllocHGlobal(newSizeInBytes).ToPointer();

            for (int i = 0; i < newSizeInBytes; i++)
                *(newArrayPointer + i) = 0;

            return (void*)newArrayPointer;
        }

        public static void Free(void* pointerToUnmanagedMemory)
        {
            Marshal.FreeHGlobal(new IntPtr(pointerToUnmanagedMemory));
        }

        public static void* Resize<T>(void* oldPointer, int newElementCount)
            where T : struct
        {
            return (Marshal.ReAllocHGlobal(new IntPtr(oldPointer),
                new IntPtr(Marshal.SizeOf(typeof(T)) * newElementCount))).ToPointer();
        }
    }
}