SPT-Server-Build/Libraries/SPTarkov.Reflection/CodeWrapper/CodeGenerator.cs

using System.Reflection.Emit;
using HarmonyLib;

namespace SPTarkov.Reflection.CodeWrapper;

/// <summary>
/// Helper class to generate IL code for transpilers
/// </summary>
public class CodeGenerator
{
    public static List<CodeInstruction> GenerateInstructions(List<Code> codes)
    {
        var list = new List<CodeInstruction>();

        foreach (Code code in codes)
        {
            list.Add(ParseCode(code));
        }

        return list;
    }

    private static CodeInstruction ParseCode(Code code)
    {
        if (!code.HasOperand)
        {
            return new CodeInstruction(code.OpCode) { labels = GetLabelList(code) };
        }

        if (
            code.OpCode == OpCodes.Ldfld
            || code.OpCode == OpCodes.Ldflda
            || code.OpCode == OpCodes.Stfld
        )
        {
            return new CodeInstruction(
                code.OpCode,
                AccessTools.Field(code.CallerType, code.OperandTarget as string)
            )
            {
                labels = GetLabelList(code),
            };
        }

        if (code.OpCode == OpCodes.Call || code.OpCode == OpCodes.Callvirt)
        {
            return new CodeInstruction(
                code.OpCode,
                AccessTools.Method(code.CallerType, code.OperandTarget as string, code.Parameters)
            )
            {
                labels = GetLabelList(code),
            };
        }

        if (code.OpCode == OpCodes.Box)
        {
            return new CodeInstruction(code.OpCode, code.CallerType)
            {
                labels = GetLabelList(code),
            };
        }

        if (
            code.OpCode == OpCodes.Br
            || code.OpCode == OpCodes.Brfalse
            || code.OpCode == OpCodes.Brtrue
            || code.OpCode == OpCodes.Brtrue_S
            || code.OpCode == OpCodes.Brfalse_S
            || code.OpCode == OpCodes.Br_S
        )
        {
            return new CodeInstruction(code.OpCode, code.OperandTarget)
            {
                labels = GetLabelList(code),
            };
        }

        if (code.OpCode == OpCodes.Ldftn)
        {
            return new CodeInstruction(
                code.OpCode,
                AccessTools.Method(code.CallerType, code.OperandTarget as string, code.Parameters)
            )
            {
                labels = GetLabelList(code),
            };
        }

        if (code.OpCode == OpCodes.Newobj)
        {
            return new CodeInstruction(
                code.OpCode,
                code.CallerType.GetConstructors()
                    .FirstOrDefault(x => x.GetParameters().Length == code.Parameters.Length)
            )
            {
                labels = GetLabelList(code),
            };
        }

        throw new ArgumentException($"Code with OpCode {code.OpCode.ToString()} is not supported.");
    }

    private static List<Label> GetLabelList(Code code)
    {
        if (code.GetLabel() == null)
        {
            return [];
        }

        return [(Label)code.GetLabel()];
    }
}