using Ryujinx.HLE.Exceptions;

namespace Ryujinx.HLE.HOS.Tamper.CodeEmitters
{
    /// <summary>
    /// Code type 5 allows loading a value from memory into a register, either using a fixed address or by
    /// dereferencing the destination register.
    /// </summary>
    class LoadRegisterWithMemory
    {
        private const int OperationWidthIndex = 1;
        private const int MemoryRegionIndex = 2;
        private const int DestinationRegisterIndex = 3;
        private const int UseDestinationAsSourceIndex = 4;
        private const int OffsetImmediateIndex = 6;

        private const int OffsetImmediateSize = 10;

        public static void Emit(byte[] instruction, CompilationContext context)
        {
            // 5TMR00AA AAAAAAAA
            // T: Width of memory read (1, 2, 4, or 8 bytes).
            // M: Memory region to write to (0 = Main NSO, 1 = Heap).
            // R: Register to load value into.
            // A: Immediate offset to use from memory region base.

            // 5TMR10AA AAAAAAAA
            // T: Width of memory read(1, 2, 4, or 8 bytes).
            // M: Ignored.
            // R: Register to use as base address and to load value into.
            // A: Immediate offset to use from register R.

            byte operationWidth = instruction[OperationWidthIndex];
            MemoryRegion memoryRegion = (MemoryRegion)instruction[MemoryRegionIndex];
            Register destinationRegister = context.GetRegister(instruction[DestinationRegisterIndex]);
            byte useDestinationAsSourceIndex = instruction[UseDestinationAsSourceIndex];
            ulong address = InstructionHelper.GetImmediate(instruction, OffsetImmediateIndex, OffsetImmediateSize);

            Pointer sourceMemory;

            switch (useDestinationAsSourceIndex)
            {
                case 0:
                    // Don't use the source register as an additional address offset.
                    sourceMemory = MemoryHelper.EmitPointer(memoryRegion, address, context);
                    break;
                case 1:
                    // Use the source register as the base address.
                    sourceMemory = MemoryHelper.EmitPointer(destinationRegister, address, context);
                    break;
                default:
                    throw new TamperCompilationException($"Invalid source mode {useDestinationAsSourceIndex} in Atmosphere cheat");
            }

            InstructionHelper.EmitMov(operationWidth, context, destinationRegister, sourceMemory);
        }
    }
}