using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using Mono.Cecil;
using Mono.Cecil.Cil;
using UnityEngine;

namespace COM3D2.NeighUncensor.Patcher
{
    public static class NeighUncensorPatcher
    {
        public static readonly string[] TargetAssemblyNames = { "Assembly-CSharp.dll", "UnityEngine.dll" };

        private static Dictionary<string, Action<AssemblyDefinition, TypeDefinition>> patches = new Dictionary<string, Action<AssemblyDefinition, TypeDefinition>>
        {
            ["Assembly-CSharp"] = PatchAssemblyCSharp,
            ["UnityEngine"] = PatchUnityEngine
        };

        public static void Patch(AssemblyDefinition ad)
        {
            var hookAd = AssemblyDefinition.ReadAssembly(Assembly.GetExecutingAssembly().Location);
            var hooks = hookAd.MainModule.GetType("COM3D2.NeighUncensor.Patcher.Hooks");

            if (patches.TryGetValue(ad.Name.Name, out var patch))
                patch(ad, hooks);
        }

        private static void PatchPostfix(MethodDefinition method, MethodReference postfix, bool passInstance = false)
        {
            var il = method.Body.GetILProcessor();
            var mRef = method.Module.ImportReference(postfix);
            foreach (var ins in method.Body.Instructions.ToList())
            {
                if (ins.OpCode != OpCodes.Ret)
                    continue;

                ins.OpCode = OpCodes.Nop;
                il.InsertAfter(ins, il.Create(OpCodes.Ret));
                il.InsertAfter(ins, il.Create(OpCodes.Call, mRef));
                if(passInstance)
                    il.InsertAfter(ins, il.Create(OpCodes.Ldarg_0));
            }
        }

        private static void PatchAssemblyCSharp(AssemblyDefinition ad, TypeDefinition hooks)
        {
            var tBody = ad.MainModule.GetType("TBody");
            var importCM = ad.MainModule.GetType("ImportCM");

            var fixMaskFlag = tBody.Methods.FirstOrDefault(m => m.Name == "FixMaskFlag");
            PatchPostfix(fixMaskFlag, hooks.Methods.FirstOrDefault(m => m.Name == nameof(Hooks.PostFixMaskFlag)), true);

            var loadSkinMeshR = importCM.Methods.FirstOrDefault(m => m.Name == "LoadSkinMesh_R");
            PatchPostfix(loadSkinMeshR, hooks.Methods.FirstOrDefault(m => m.Name == nameof(Hooks.PostLoadMesh)));
        }

        private static void PatchUnityEngine(AssemblyDefinition ad, TypeDefinition hooks)
        {
            var resources = ad.MainModule.GetType("UnityEngine.Resources");

            var load = resources.Methods.FirstOrDefault(
                m => m.Name == "Load" && m.Parameters.Count == 1 &&
                     m.ReturnType.FullName == "UnityEngine.Object");

            PatchPostfix(load, hooks.Methods.FirstOrDefault(m => m.Name == nameof(Hooks.OnResourceLoad)));
        }
    }

    public static class Hooks
    {
        private static object diffuse;

        public static void PostFixMaskFlag(TBody tbody)
        {
            tbody.goSlot[(int)TBody.hashSlotName["moza"]].boVisible = false;
        }

        public static GameObject PostLoadMesh(GameObject result)
        {
            TryUncensor(result);
            return result;
        }

        public static UnityEngine.Object OnResourceLoad(UnityEngine.Object result)
        {
            if (result is GameObject go)
                TryUncensor(go);
            return result;
        }

        private static void TryUncensor(GameObject go)
        {
            if (go == null)
                return;

            var smr = go.GetComponentInChildren<Renderer>();
            if (smr == null || smr.materials == null)
                return;
            foreach (var mm in smr.materials)
            {
                if (mm.shader?.name.ToLowerInvariant().Contains("mosaic") ?? false)
                {
                    if (diffuse == null)
                        diffuse = Shader.Find("CM3D2/Toony_Lighted_Trans");

                    mm.shader = diffuse as Shader;
                    mm.color += new Color(0f, 0f, 0f, -1f);
                }
            }
        }
    }
}