using System;
using System.Runtime.InteropServices;

using BizHawk.Emulation.Common;
using BizHawk.Common;

namespace BizHawk.Emulation.Cores.Nintendo.SNES
{
	public unsafe partial class LibsnesCore : ISaveRam
	{
		public bool SaveRamModified =>
			Api.QUERY_get_memory_size(LibsnesApi.SNES_MEMORY.CARTRIDGE_RAM) != 0
			|| Api.QUERY_get_memory_size(LibsnesApi.SNES_MEMORY.SGB_CARTRAM) != 0;

		public byte[] CloneSaveRam()
		{
			using (Api.EnterExit())
			{
				byte* buf = Api.QUERY_get_memory_data(LibsnesApi.SNES_MEMORY.CARTRIDGE_RAM);
				var size = Api.QUERY_get_memory_size(LibsnesApi.SNES_MEMORY.CARTRIDGE_RAM);
				if (buf == null && Api.QUERY_get_memory_size(LibsnesApi.SNES_MEMORY.SGB_CARTRAM) > 0)
				{
					buf = Api.QUERY_get_memory_data(LibsnesApi.SNES_MEMORY.SGB_CARTRAM);
					size = Api.QUERY_get_memory_size(LibsnesApi.SNES_MEMORY.SGB_CARTRAM);
				}

				if (buf == null)
				{
					return null;
				}

				var ret = new byte[size];
				Marshal.Copy((IntPtr)buf, ret, 0, size);
				return ret;
			}
		}

		public void StoreSaveRam(byte[] data)
		{
			using (Api.EnterExit())
			{
				byte* buf = Api.QUERY_get_memory_data(LibsnesApi.SNES_MEMORY.CARTRIDGE_RAM);
				var size = Api.QUERY_get_memory_size(LibsnesApi.SNES_MEMORY.CARTRIDGE_RAM);
				if (buf == null)
				{
					buf = Api.QUERY_get_memory_data(LibsnesApi.SNES_MEMORY.SGB_CARTRAM);
					size = Api.QUERY_get_memory_size(LibsnesApi.SNES_MEMORY.SGB_CARTRAM);
				}

				if (size == 0)
				{
					return;
				}

				if (size != data.Length)
				{
					throw new InvalidOperationException("Somehow, we got a mismatch between saveram size and what bsnes says the saveram size is");
				}

				Marshal.Copy(data, 0, (IntPtr)buf, size);
			}
		}
	}
}