modules/project/SPT.SinglePlayer/Patches/ScavMode/ScavPrefabLoadPatch.cs

using SPT.Reflection.CodeWrapper;
using SPT.Reflection.Patching;
using SPT.Reflection.Utils;
using EFT;
using HarmonyLib;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;

namespace SPT.SinglePlayer.Patches.ScavMode
{
    public class ScavPrefabLoadPatch : ModulePatch
    {
        /// <summary>
        /// Aim of this patch is to check what Side we are loading into the raid as.
        /// then if we are Scav, the game will load the bundles for that
        /// else it will load the bundles for PMC
        /// </summary>
        /// <returns></returns>
        protected override MethodBase GetTargetMethod()
        {
            // Struct324 - 3.10.0
            var desiredType = typeof(TarkovApplication)
                .GetNestedTypes(PatchConstants.PublicDeclaredFlags)
                .SingleCustom(x => x.GetField("timeAndWeather") != null
                                   && x.GetField("tarkovApplication_0") != null
                                   && x.GetField("inTransition") != null
                                   && x.Name.Contains("Struct"));

            var desiredMethod = desiredType.GetMethods(PatchConstants.PublicDeclaredFlags)
                .FirstOrDefault(x => x.Name == "MoveNext");

            Logger.LogDebug($"{this.GetType().Name} Type: {desiredType?.Name}");
            Logger.LogDebug($"{this.GetType().Name} Method: {desiredMethod?.Name}");

            return desiredMethod;
        }

        [PatchTranspiler]
        public static IEnumerable<CodeInstruction> PatchTranspile(ILGenerator generator, IEnumerable<CodeInstruction> instructions)
        {
            var codes = new List<CodeInstruction>(instructions);

            // Search for code where backend.Session.getProfile() is called.
            var searchCode = new CodeInstruction(OpCodes.Callvirt, AccessTools.Method(PatchConstants.BackendProfileInterfaceType, "get_Profile"));
            var searchIndex = -1;

            for (var i = 0; i < codes.Count; i++)
            {
                if (codes[i].opcode == searchCode.opcode && codes[i].operand == searchCode.operand)
                {
                    searchIndex = i;
                    break;
                }
            }

            // Patch failed.
            if (searchIndex == -1)
            {
                Logger.LogError($"Patch {MethodBase.GetCurrentMethod()} failed: Could not find reference code.");
                return instructions;
            }

            // Move back by 2. This is the start of IL chain that we're interested in.
            searchIndex -= 2;

            var brFalseLabel = generator.DefineLabel();
            var brLabel = generator.DefineLabel();

            var newCodes = CodeGenerator.GenerateInstructions(new List<Code>()
            {
                new Code(OpCodes.Ldloc_1),
                new Code(OpCodes.Call, typeof(ClientApplication<ISession>), "get_Session"),
                new Code(OpCodes.Ldloc_1),
                new Code(OpCodes.Ldfld, typeof(TarkovApplication), "_raidSettings"),
                new Code(OpCodes.Callvirt, typeof(RaidSettings), "get_IsPmc"),
                new Code(OpCodes.Brfalse, brFalseLabel),
                new Code(OpCodes.Callvirt, PatchConstants.BackendProfileInterfaceType, "get_Profile"),
                new Code(OpCodes.Br, brLabel),
                new CodeWithLabel(OpCodes.Callvirt, brFalseLabel, PatchConstants.BackendProfileInterfaceType, "get_ProfileOfPet"),
                new CodeWithLabel(OpCodes.Ldc_I4_1, brLabel)
            });

            codes.RemoveRange(searchIndex, 4);
            codes.InsertRange(searchIndex, newCodes);

            return codes.AsEnumerable();
        }
    }
}