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

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

        private static readonly 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 bgMgr = ad.MainModule.GetType("BgMgr");
            var importCM = ad.MainModule.GetType("ImportCM");

            var createAssetBundle = bgMgr.Methods.FirstOrDefault(m => m.Name == "CreateAssetBundle");
            PatchPostfix(createAssetBundle,
                         hooks.Methods.FirstOrDefault(m => m.Name == nameof(Hooks.PostCreateAssetBundle)));

            var readMaterial = importCM.Methods.FirstOrDefault(m => m.Name == "ReadMaterial");
            PatchPostfix(readMaterial, hooks.Methods.FirstOrDefault(m => m.Name == nameof(Hooks.PostReadMaterial)));
        }

        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 replacement;

        public static Material PostReadMaterial(Material result)
        {
            if (result.shader?.name.ToLowerInvariant().Contains("mosaic") ?? false)
            {
                if (replacement == null)
                    replacement = Shader.Find("Unlit/Transparent");
                result.shader = (Shader)replacement;
                result.renderQueue = 0;
            }

            return result;
        }

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

        public static Object OnResourceLoad(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)
                PostReadMaterial(mm);
        }
    }
}