// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using Internal.TypeSystem;
using static ILCompiler.ObjectWriter.DwarfNative;

namespace ILCompiler.ObjectWriter
{
    internal sealed class DwarfCie
    {
        public readonly byte PointerEncoding;
        public readonly byte LsdaEncoding;
        public readonly byte PersonalityEncoding;
        public readonly string PersonalitySymbolName;
        public readonly uint CodeAlignFactor;
        public readonly int DataAlignFactor;
        public readonly bool IsSignalFrame;
        public readonly bool FdesHaveAugmentationData;
        public readonly byte ReturnAddressRegister;
        public readonly byte[] Instructions;
        public readonly byte InitialCFAOffset;

        public DwarfCie(TargetArchitecture targetArchitecture)
        {
            IsSignalFrame = false;

            // Each FDE has LSDA pointer
            FdesHaveAugmentationData = true;

            // Unused
            PersonalityEncoding = 0;
            PersonalitySymbolName = null;

            // NOTE: Apple linker only knows how to handle DW_EH_PE_pcrel in combination with
            // DW_EH_PE_sdata4 or DW_EH_PE_ptr.
            PointerEncoding = DW_EH_PE_pcrel | DW_EH_PE_sdata4;
            LsdaEncoding = DW_EH_PE_pcrel | DW_EH_PE_sdata4;

            switch (targetArchitecture)
            {
                case TargetArchitecture.ARM:
                    CodeAlignFactor = 1;
                    DataAlignFactor = -4;
                    ReturnAddressRegister = 14; // LR
                    Instructions = new byte[]
                    {
                        DW_CFA_def_cfa,
                        13, // SP
                        0, // Offset from SP
                    };
                    InitialCFAOffset = 0;
                    break;

                case TargetArchitecture.ARM64:
                    CodeAlignFactor = 1;
                    DataAlignFactor = -4;
                    ReturnAddressRegister = 30; // LR
                    Instructions = new byte[]
                    {
                        DW_CFA_def_cfa,
                        31, // SP
                        0, // Offset from SP
                    };
                    InitialCFAOffset = 0;
                    break;

                case TargetArchitecture.X64:
                    CodeAlignFactor = 1;
                    DataAlignFactor = -8;
                    ReturnAddressRegister = 16; // RA
                    Instructions = new byte[]
                    {
                        DW_CFA_def_cfa,
                        7, // RSP
                        8, // Offset from RSP
                        DW_CFA_offset | 16, // RIP
                        1, // RIP is at -8
                    };
                    InitialCFAOffset = 8;
                    break;

                case TargetArchitecture.LoongArch64:
                    CodeAlignFactor = 1;
                    DataAlignFactor = -4;
                    ReturnAddressRegister = 1; // RA
                    Instructions =
                    [
                        DW_CFA_def_cfa,
                        3, // SP
                        0, // Offset from SP
                    ];
                    InitialCFAOffset = 0;
                    break;

                case TargetArchitecture.RiscV64:
                    CodeAlignFactor = 1;
                    DataAlignFactor = -8;
                    ReturnAddressRegister = 1; // RA
                    Instructions = new byte[]
                    {
                        DW_CFA_def_cfa,
                        2, // SP
                        0, // Offset from SP
                    };
                    InitialCFAOffset = 0;
                    break;

                default:
                    throw new NotSupportedException("Unsupported architecture");
            }
        }
    }
}