using ARMeilleure.Decoders;
using ARMeilleure.IntermediateRepresentation;
using ARMeilleure.Translation;
using ARMeilleure.Translation.PTC;
using System;
using System.Reflection;

using static ARMeilleure.Instructions.InstEmitHelper;
using static ARMeilleure.IntermediateRepresentation.OperandHelper;

namespace ARMeilleure.Instructions
{
    static class InstEmitMemoryHelper
    {
        private const int PageBits = 12;
        private const int PageMask = (1 << PageBits) - 1;

        private enum Extension
        {
            Zx,
            Sx32,
            Sx64
        }

        public static void EmitLoadZx(ArmEmitterContext context, Operand address, int rt, int size)
        {
            EmitLoad(context, address, Extension.Zx, rt, size);
        }

        public static void EmitLoadSx32(ArmEmitterContext context, Operand address, int rt, int size)
        {
            EmitLoad(context, address, Extension.Sx32, rt, size);
        }

        public static void EmitLoadSx64(ArmEmitterContext context, Operand address, int rt, int size)
        {
            EmitLoad(context, address, Extension.Sx64, rt, size);
        }

        private static void EmitLoad(ArmEmitterContext context, Operand address, Extension ext, int rt, int size)
        {
            bool isSimd = IsSimd(context);

            if ((uint)size > (isSimd ? 4 : 3))
            {
                throw new ArgumentOutOfRangeException(nameof(size));
            }

            if (isSimd)
            {
                EmitReadVector(context, address, context.VectorZero(), rt, 0, size);
            }
            else
            {
                EmitReadInt(context, address, rt, size);
            }

            if (!isSimd && !(context.CurrOp is OpCode32 && rt == State.RegisterAlias.Aarch32Pc))
            {
                Operand value = GetInt(context, rt);

                if (ext == Extension.Sx32 || ext == Extension.Sx64)
                {
                    OperandType destType = ext == Extension.Sx64 ? OperandType.I64 : OperandType.I32;

                    switch (size)
                    {
                        case 0: value = context.SignExtend8 (destType, value); break;
                        case 1: value = context.SignExtend16(destType, value); break;
                        case 2: value = context.SignExtend32(destType, value); break;
                    }
                }

                SetInt(context, rt, value);
            }
        }

        public static void EmitLoadSimd(
            ArmEmitterContext context,
            Operand address,
            Operand vector,
            int rt,
            int elem,
            int size)
        {
            EmitReadVector(context, address, vector, rt, elem, size);
        }

        public static void EmitStore(ArmEmitterContext context, Operand address, int rt, int size)
        {
            bool isSimd = IsSimd(context);

            if ((uint)size > (isSimd ? 4 : 3))
            {
                throw new ArgumentOutOfRangeException(nameof(size));
            }

            if (isSimd)
            {
                EmitWriteVector(context, address, rt, 0, size);
            }
            else
            {
                EmitWriteInt(context, address, rt, size);
            }
        }

        public static void EmitStoreSimd(
            ArmEmitterContext context,
            Operand address,
            int rt,
            int elem,
            int size)
        {
            EmitWriteVector(context, address, rt, elem, size);
        }

        private static bool IsSimd(ArmEmitterContext context)
        {
            return context.CurrOp is IOpCodeSimd &&
                 !(context.CurrOp is OpCodeSimdMemMs ||
                   context.CurrOp is OpCodeSimdMemSs);
        }

        private static void EmitReadInt(ArmEmitterContext context, Operand address, int rt, int size)
        {
            Operand lblSlowPath = Label();
            Operand lblEnd      = Label();

            Operand isUnalignedAddr = EmitAddressCheck(context, address, size);

            context.BranchIfTrue(lblSlowPath, isUnalignedAddr);

            Operand physAddr = EmitPtPointerLoad(context, address, lblSlowPath, write: false);

            Operand value = null;

            switch (size)
            {
                case 0: value = context.Load8 (physAddr);                  break;
                case 1: value = context.Load16(physAddr);                  break;
                case 2: value = context.Load  (OperandType.I32, physAddr); break;
                case 3: value = context.Load  (OperandType.I64, physAddr); break;
            }

            SetInt(context, rt, value);

            context.Branch(lblEnd);

            context.MarkLabel(lblSlowPath, BasicBlockFrequency.Cold);

            EmitReadIntFallback(context, address, rt, size);

            context.MarkLabel(lblEnd);
        }

        public static Operand EmitReadIntAligned(ArmEmitterContext context, Operand address, int size)
        {
            if ((uint)size > 4)
            {
                throw new ArgumentOutOfRangeException(nameof(size));
            }

            Operand isUnalignedAddr = EmitAddressCheck(context, address, size);

            Operand lblFastPath = Label();

            context.BranchIfFalse(lblFastPath, isUnalignedAddr, BasicBlockFrequency.Cold);

            // The call is not expected to return (it should throw).
            context.Call(typeof(NativeInterface).GetMethod(nameof(NativeInterface.ThrowInvalidMemoryAccess)), address);

            context.MarkLabel(lblFastPath);

            Operand physAddr = EmitPtPointerLoad(context, address, null, write: false);

            return size switch
            {
                0 => context.Load8(physAddr),
                1 => context.Load16(physAddr),
                2 => context.Load(OperandType.I32, physAddr),
                3 => context.Load(OperandType.I64, physAddr),
                _ => context.Load(OperandType.V128, physAddr)
            };
        }

        private static void EmitReadVector(
            ArmEmitterContext context,
            Operand address,
            Operand vector,
            int rt,
            int elem,
            int size)
        {
            Operand lblSlowPath = Label();
            Operand lblEnd      = Label();

            Operand isUnalignedAddr = EmitAddressCheck(context, address, size);

            context.BranchIfTrue(lblSlowPath, isUnalignedAddr);

            Operand physAddr = EmitPtPointerLoad(context, address, lblSlowPath, write: false);

            Operand value = null;

            switch (size)
            {
                case 0: value = context.VectorInsert8 (vector, context.Load8(physAddr), elem);                 break;
                case 1: value = context.VectorInsert16(vector, context.Load16(physAddr), elem);                break;
                case 2: value = context.VectorInsert  (vector, context.Load(OperandType.I32, physAddr), elem); break;
                case 3: value = context.VectorInsert  (vector, context.Load(OperandType.I64, physAddr), elem); break;
                case 4: value = context.Load          (OperandType.V128, physAddr);                            break;
            }

            context.Copy(GetVec(rt), value);

            context.Branch(lblEnd);

            context.MarkLabel(lblSlowPath, BasicBlockFrequency.Cold);

            EmitReadVectorFallback(context, address, vector, rt, elem, size);

            context.MarkLabel(lblEnd);
        }

        private static Operand VectorCreate(ArmEmitterContext context, Operand value)
        {
            return context.VectorInsert(context.VectorZero(), value, 0);
        }

        private static void EmitWriteInt(ArmEmitterContext context, Operand address, int rt, int size)
        {
            Operand lblSlowPath = Label();
            Operand lblEnd      = Label();

            Operand isUnalignedAddr = EmitAddressCheck(context, address, size);

            context.BranchIfTrue(lblSlowPath, isUnalignedAddr);

            Operand physAddr = EmitPtPointerLoad(context, address, lblSlowPath, write: true);

            Operand value = GetInt(context, rt);

            if (size < 3 && value.Type == OperandType.I64)
            {
                value = context.ConvertI64ToI32(value);
            }

            switch (size)
            {
                case 0: context.Store8 (physAddr, value); break;
                case 1: context.Store16(physAddr, value); break;
                case 2: context.Store  (physAddr, value); break;
                case 3: context.Store  (physAddr, value); break;
            }

            context.Branch(lblEnd);

            context.MarkLabel(lblSlowPath, BasicBlockFrequency.Cold);

            EmitWriteIntFallback(context, address, rt, size);

            context.MarkLabel(lblEnd);
        }

        public static void EmitWriteIntAligned(ArmEmitterContext context, Operand address, Operand value, int size)
        {
            if ((uint)size > 4)
            {
                throw new ArgumentOutOfRangeException(nameof(size));
            }

            Operand isUnalignedAddr = EmitAddressCheck(context, address, size);

            Operand lblFastPath = Label();

            context.BranchIfFalse(lblFastPath, isUnalignedAddr, BasicBlockFrequency.Cold);

            // The call is not expected to return (it should throw).
            context.Call(typeof(NativeInterface).GetMethod(nameof(NativeInterface.ThrowInvalidMemoryAccess)), address);

            context.MarkLabel(lblFastPath);

            Operand physAddr = EmitPtPointerLoad(context, address, null, write: true);

            if (size < 3 && value.Type == OperandType.I64)
            {
                value = context.ConvertI64ToI32(value);
            }

            if (size == 0)
            {
                context.Store8(physAddr, value);
            }
            else if (size == 1)
            {
                context.Store16(physAddr, value);
            }
            else
            {
                context.Store(physAddr, value);
            }
        }

        private static void EmitWriteVector(
            ArmEmitterContext context,
            Operand address,
            int rt,
            int elem,
            int size)
        {
            Operand lblSlowPath = Label();
            Operand lblEnd      = Label();

            Operand isUnalignedAddr = EmitAddressCheck(context, address, size);

            context.BranchIfTrue(lblSlowPath, isUnalignedAddr);

            Operand physAddr = EmitPtPointerLoad(context, address, lblSlowPath, write: true);

            Operand value = GetVec(rt);

            switch (size)
            {
                case 0: context.Store8 (physAddr, context.VectorExtract8(value, elem));                 break;
                case 1: context.Store16(physAddr, context.VectorExtract16(value, elem));                break;
                case 2: context.Store  (physAddr, context.VectorExtract(OperandType.I32, value, elem)); break;
                case 3: context.Store  (physAddr, context.VectorExtract(OperandType.I64, value, elem)); break;
                case 4: context.Store  (physAddr, value);                                               break;
            }

            context.Branch(lblEnd);

            context.MarkLabel(lblSlowPath, BasicBlockFrequency.Cold);

            EmitWriteVectorFallback(context, address, rt, elem, size);

            context.MarkLabel(lblEnd);
        }

        public static Operand EmitAddressCheck(ArmEmitterContext context, Operand address, int size)
        {
            ulong addressCheckMask = ~((1UL << context.Memory.AddressSpaceBits) - 1);

            addressCheckMask |= (1u << size) - 1;

            return context.BitwiseAnd(address, Const(address.Type, (long)addressCheckMask));
        }

        public static Operand EmitPtPointerLoad(ArmEmitterContext context, Operand address, Operand lblSlowPath, bool write)
        {
            int ptLevelBits = context.Memory.AddressSpaceBits - 12; // 12 = Number of page bits.
            int ptLevelSize = 1 << ptLevelBits;
            int ptLevelMask = ptLevelSize - 1;

            Operand pte = Ptc.State == PtcState.Disabled
                ? Const(context.Memory.PageTablePointer.ToInt64())
                : Const(context.Memory.PageTablePointer.ToInt64(), true, Ptc.PageTablePointerIndex);

            int bit = PageBits;

            // Load page table entry from the page table.
            // This was designed to support multi-level page tables of any size, however right
            // now we only use flat page tables (so there's only one level).
            // The page table entry contains the host address where the page is located.
            // Additionally, the higher 16-bits of the host address may contain extra information
            // used for write tracking, so this must be handled here aswell.
            do
            {
                Operand addrPart = context.ShiftRightUI(address, Const(bit));

                bit += ptLevelBits;

                if (bit < context.Memory.AddressSpaceBits)
                {
                    addrPart = context.BitwiseAnd(addrPart, Const(addrPart.Type, ptLevelMask));
                }

                Operand pteOffset = context.ShiftLeft(addrPart, Const(3));

                if (pteOffset.Type == OperandType.I32)
                {
                    pteOffset = context.ZeroExtend32(OperandType.I64, pteOffset);
                }

                Operand pteAddress = context.Add(pte, pteOffset);

                pte = context.Load(OperandType.I64, pteAddress);
            }
            while (bit < context.Memory.AddressSpaceBits);

            if (lblSlowPath != null)
            {
                ulong protection = (write ? 3UL : 1UL) << 48;
                context.BranchIfTrue(lblSlowPath, context.BitwiseAnd(pte, Const(protection)));
            }
            else
            {
                // When no label is provided to jump to a slow path if the address is invalid,
                // we do the validation ourselves, and throw if needed.

                Operand lblNotWatched = Label();

                // Is the page currently being tracked for read/write? If so we need to call MarkRegionAsModified.
                context.BranchIf(lblNotWatched, pte, Const(0L), Comparison.GreaterOrEqual, BasicBlockFrequency.Cold);

                // Mark the region as modified. Size here doesn't matter as address is assumed to be size aligned here.
                context.Call(typeof(NativeInterface).GetMethod(nameof(NativeInterface.SignalMemoryTracking)), address, Const(1UL), Const(write ? 1 : 0));
                context.MarkLabel(lblNotWatched);

                Operand lblNonNull = Label();

                // Skip exception if the PTE address is non-null (not zero).
                context.BranchIfTrue(lblNonNull, pte, BasicBlockFrequency.Cold);

                // The call is not expected to return (it should throw).
                context.Call(typeof(NativeInterface).GetMethod(nameof(NativeInterface.ThrowInvalidMemoryAccess)), address);
                context.MarkLabel(lblNonNull);
            }

            pte = context.BitwiseAnd(pte, Const(0xffffffffffffUL)); // Ignore any software protection bits. (they are still used by c# memory access)

            Operand pageOffset = context.BitwiseAnd(address, Const(address.Type, PageMask));

            if (pageOffset.Type == OperandType.I32)
            {
                pageOffset = context.ZeroExtend32(OperandType.I64, pageOffset);
            }

            return context.Add(pte, pageOffset);
        }

        private static void EmitReadIntFallback(ArmEmitterContext context, Operand address, int rt, int size)
        {
            MethodInfo info = null;

            switch (size)
            {
                case 0: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.ReadByte));   break;
                case 1: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.ReadUInt16)); break;
                case 2: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.ReadUInt32)); break;
                case 3: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.ReadUInt64)); break;
            }

            SetInt(context, rt, context.Call(info, address));
        }

        private static void EmitReadVectorFallback(
            ArmEmitterContext context,
            Operand address,
            Operand vector,
            int rt,
            int elem,
            int size)
        {
            MethodInfo info = null;

            switch (size)
            {
                case 0: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.ReadByte));      break;
                case 1: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.ReadUInt16));    break;
                case 2: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.ReadUInt32));    break;
                case 3: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.ReadUInt64));    break;
                case 4: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.ReadVector128)); break;
            }

            Operand value = context.Call(info, address);

            switch (size)
            {
                case 0: value = context.VectorInsert8 (vector, value, elem); break;
                case 1: value = context.VectorInsert16(vector, value, elem); break;
                case 2: value = context.VectorInsert  (vector, value, elem); break;
                case 3: value = context.VectorInsert  (vector, value, elem); break;
            }

            context.Copy(GetVec(rt), value);
        }

        private static void EmitWriteIntFallback(ArmEmitterContext context, Operand address, int rt, int size)
        {
            MethodInfo info = null;

            switch (size)
            {
                case 0: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.WriteByte));   break;
                case 1: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.WriteUInt16)); break;
                case 2: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.WriteUInt32)); break;
                case 3: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.WriteUInt64)); break;
            }

            Operand value = GetInt(context, rt);

            if (size < 3 && value.Type == OperandType.I64)
            {
                value = context.ConvertI64ToI32(value);
            }

            context.Call(info, address, value);
        }

        private static void EmitWriteVectorFallback(
            ArmEmitterContext context,
            Operand address,
            int rt,
            int elem,
            int size)
        {
            MethodInfo info = null;

            switch (size)
            {
                case 0: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.WriteByte));      break;
                case 1: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.WriteUInt16));    break;
                case 2: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.WriteUInt32));    break;
                case 3: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.WriteUInt64));    break;
                case 4: info = typeof(NativeInterface).GetMethod(nameof(NativeInterface.WriteVector128)); break;
            }

            Operand value = null;

            if (size < 4)
            {
                switch (size)
                {
                    case 0: value = context.VectorExtract8 (GetVec(rt), elem);                  break;
                    case 1: value = context.VectorExtract16(GetVec(rt), elem);                  break;
                    case 2: value = context.VectorExtract  (OperandType.I32, GetVec(rt), elem); break;
                    case 3: value = context.VectorExtract  (OperandType.I64, GetVec(rt), elem); break;
                }
            }
            else
            {
                value = GetVec(rt);
            }

            context.Call(info, address, value);
        }

        private static Operand GetInt(ArmEmitterContext context, int rt)
        {
            return context.CurrOp is OpCode32 ? GetIntA32(context, rt) : GetIntOrZR(context, rt);
        }

        private static void SetInt(ArmEmitterContext context, int rt, Operand value)
        {
            if (context.CurrOp is OpCode32)
            {
                SetIntA32(context, rt, value);
            }
            else
            {
                SetIntOrZR(context, rt, value);
            }
        }

        // ARM32 helpers.
        public static Operand GetMemM(ArmEmitterContext context, bool setCarry = true)
        {
            switch (context.CurrOp)
            {
                case OpCode32MemRsImm op: return GetMShiftedByImmediate(context, op, setCarry);

                case OpCode32MemReg op: return GetIntA32(context, op.Rm);

                case OpCode32Mem op: return Const(op.Immediate);

                case OpCode32SimdMemImm op: return Const(op.Immediate);

                default: throw InvalidOpCodeType(context.CurrOp);
            }
        }

        private static Exception InvalidOpCodeType(OpCode opCode)
        {
            return new InvalidOperationException($"Invalid OpCode type \"{opCode?.GetType().Name ?? "null"}\".");
        }

        public static Operand GetMShiftedByImmediate(ArmEmitterContext context, OpCode32MemRsImm op, bool setCarry)
        {
            Operand m = GetIntA32(context, op.Rm);

            int shift = op.Immediate;

            if (shift == 0)
            {
                switch (op.ShiftType)
                {
                    case ShiftType.Lsr: shift = 32; break;
                    case ShiftType.Asr: shift = 32; break;
                    case ShiftType.Ror: shift = 1; break;
                }
            }

            if (shift != 0)
            {
                setCarry &= false;

                switch (op.ShiftType)
                {
                    case ShiftType.Lsl: m = InstEmitAluHelper.GetLslC(context, m, setCarry, shift); break;
                    case ShiftType.Lsr: m = InstEmitAluHelper.GetLsrC(context, m, setCarry, shift); break;
                    case ShiftType.Asr: m = InstEmitAluHelper.GetAsrC(context, m, setCarry, shift); break;
                    case ShiftType.Ror:
                        if (op.Immediate != 0)
                        {
                            m = InstEmitAluHelper.GetRorC(context, m, setCarry, shift);
                        }
                        else
                        {
                            m = InstEmitAluHelper.GetRrxC(context, m, setCarry);
                        }
                        break;
                }
            }

            return m;
        }
    }
}
