Deep North Compat

// BepInEx preloader patcher: restores API overloads that Valheim 1.0 (Deep North) removed by ADDING trailing
// parameters, so mods built for the older game keep working without modifying their DLLs. Own code; does not
// redistribute any mod. Each restored overload forwards to the new method, filling the new trailing parameters
// with their declared defaults (or default(T)). Only the whitelisted methods below are touched.
// CAUTION: every added overload makes name-only reflection/Harmony lookups of that method ambiguous.
using System;
using System.Collections.Generic;
using System.Linq;
using Mono.Cecil;
using Mono.Cecil.Cil;

public static class MistookenCompatPatcher
{
    // Type, method, old parameter types (full names) that mods still call.
    static readonly string[][] Shims = new string[][]
    {
        new string[] { "Character", "Message", "MessageHud/MessageType", "System.String", "System.Int32", "UnityEngine.Sprite" },
        new string[] { "SEMan", "AddStatusEffect", "System.Int32", "System.Boolean", "System.Int32", "System.Single" },
        // Not shimmed on purpose: Piece.SetCreator, EffectList.Create, PlayerProfile.IncrementStat. Up-to-date mods
        // (e.g. PlantEverything) patch those BY NAME; a second overload makes Harmony's lookup ambiguous and breaks them.
    };

    public static IEnumerable<string> TargetDLLs
    {
        get { yield return "assembly_valheim.dll"; }
    }

    public static void Patch(AssemblyDefinition assembly)
    {
        foreach (string[] s in Shims)
        {
            try { AddForwardingOverload(assembly.MainModule, s[0], s[1], s.Skip(2).ToArray()); }
            catch (Exception) { /* a failed shim must never stop the game from starting */ }
        }
    }

    static bool ParamsMatch(MethodDefinition m, string[] oldTypes, int count)
    {
        if (m.Parameters.Count != count) return false;
        for (int i = 0; i < oldTypes.Length && i < count; i++)
            if (m.Parameters[i].ParameterType.FullName != oldTypes[i]) return false;
        return true;
    }

    static void AddForwardingOverload(ModuleDefinition module, string typeName, string methodName, string[] oldTypes)
    {
        TypeDefinition type = module.GetType(typeName);
        if (type == null) return;
        if (type.Methods.Any(m => m.Name == methodName && ParamsMatch(m, oldTypes, oldTypes.Length))) return; // already there

        MethodDefinition target = type.Methods.FirstOrDefault(m =>
            m.Name == methodName && m.Parameters.Count > oldTypes.Length && ParamsMatch(m, oldTypes, m.Parameters.Count));
        if (target == null) return;

        MethodAttributes attrs = MethodAttributes.Public | MethodAttributes.HideBySig;
        if (target.IsStatic) attrs |= MethodAttributes.Static;
        MethodDefinition shim = new MethodDefinition(methodName, attrs, target.ReturnType);
        shim.HasThis = !target.IsStatic;
        for (int i = 0; i < oldTypes.Length; i++)
            shim.Parameters.Add(new ParameterDefinition(target.Parameters[i].Name, ParameterAttributes.None, target.Parameters[i].ParameterType));

        shim.Body.InitLocals = true;
        ILProcessor il = shim.Body.GetILProcessor();
        if (!target.IsStatic) il.Emit(OpCodes.Ldarg_0);
        for (int i = 0; i < oldTypes.Length; i++) il.Emit(OpCodes.Ldarg, shim.Parameters[i]);
        for (int i = oldTypes.Length; i < target.Parameters.Count; i++) EmitDefault(shim, il, target.Parameters[i]);
        il.Emit(target.IsStatic || !target.IsVirtual ? OpCodes.Call : OpCodes.Callvirt, target);
        il.Emit(OpCodes.Ret);
        type.Methods.Add(shim);
    }

    static void EmitDefault(MethodDefinition shim, ILProcessor il, ParameterDefinition p)
    {
        if (p.HasConstant && p.Constant != null)
        {
            object c = p.Constant;
            if (c is bool) { il.Emit(((bool)c) ? OpCodes.Ldc_I4_1 : OpCodes.Ldc_I4_0); return; }
            if (c is int) { il.Emit(OpCodes.Ldc_I4, (int)c); return; }
            if (c is short) { il.Emit(OpCodes.Ldc_I4, (int)(short)c); return; }
            if (c is byte) { il.Emit(OpCodes.Ldc_I4, (int)(byte)c); return; }
            if (c is float) { il.Emit(OpCodes.Ldc_R4, (float)c); return; }
        }
        TypeDefinition def = p.ParameterType.Resolve();
        if (def != null && def.IsValueType)
        {
            VariableDefinition loc = new VariableDefinition(p.ParameterType);
            shim.Body.Variables.Add(loc);
            il.Emit(OpCodes.Ldloca, loc);
            il.Emit(OpCodes.Initobj, p.ParameterType);
            il.Emit(OpCodes.Ldloc, loc);
        }
        else il.Emit(OpCodes.Ldnull);
    }
}