using Mono.Cecil;
using Mono.Cecil.Cil;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using UnityEngine;
using UnityEditorInternal;
using UnityEditor;
using UnityEditor.Compilation;
using UnityEngine.Assertions;
using System.Text;

namespace com.bbbirder.injection.editor
{
    public static class InjectHelper
    {

        /// <summary>
        /// inject target assembly
        /// </summary>
        /// <param name="injections"></param>
        /// <param name="inputAssemblyPath"></param>
        /// <param name="outputAssemblyPath"></param>
        /// <returns>is written</returns>
        internal static bool InjectAssembly(InjectionInfo[] injections, string inputAssemblyPath, string outputAssemblyPath, bool isEditor, BuildTarget buildTarget)
        {
            // set up assembly resolver
            var resolver = new DefaultAssemblyResolver();
            var apiCompatibilityLevel = PlayerSettings.GetApiCompatibilityLevel(EditorUserBuildSettings.selectedBuildTargetGroup);
            var assemblySearchFolders = UnityInjectUtils.GetAssemblySearchFolders(isEditor, buildTarget);
            var systemAssemblyDirectories = CompilationPipeline.GetSystemAssemblyDirectories(apiCompatibilityLevel);
            resolver.AddSearchDirectory(Path.GetDirectoryName(outputAssemblyPath));
            foreach (var folder in assemblySearchFolders)
            {
                resolver.AddSearchDirectory(folder);
            }
            foreach (var folder in systemAssemblyDirectories)
            {
                resolver.AddSearchDirectory(folder);
            }

            var IsPlayerAssembly = Path.GetFullPath(inputAssemblyPath).StartsWith(Path.GetFullPath("Library/"))
                                || Path.GetFullPath(inputAssemblyPath).StartsWith(Path.GetFullPath("Temp/"));

            var targetAssembly = AssemblyDefinition.ReadAssembly(inputAssemblyPath, new ReaderParameters()
            {
                AssemblyResolver = resolver,
                ReadingMode = ReadingMode.Immediate,
                ReadSymbols = IsPlayerAssembly,
                InMemory = true,
            });

            foreach(var inj in injections)
            {
                var providerMethod = inj.DryInjectMethod;
                if (providerMethod is null) continue;
                var methodName = inj.DryInjectMethodName;
                var targetType = GetCorrespondingType(targetAssembly.MainModule, inj.DryInjectAssmemble);
                if (targetType == null)
                {
                    throw new($"Cannot find Type `{inj.DryInjectAssmemble}` in target assembly {inputAssemblyPath}");
                }

                var providerAssemblyPath = providerMethod.DeclaringType.Assembly.GetAssemblyPath();
                var providerAssembly = AssemblyDefinition.ReadAssembly(providerAssemblyPath, new ReaderParameters()
                {
                    AssemblyResolver = resolver,
                    ReadingMode = ReadingMode.Immediate,
                    ReadSymbols = IsPlayerAssembly,
                    InMemory = true,
                });
                var providerType = GetCorrespondingType(providerAssembly.MainModule, providerMethod.DeclaringType);
                var targetMethod = providerType.FindMethod(providerMethod.GetSignature()).Resolve();
                if (targetMethod is null)
                {
                    throw new($"Cannot find Method `{methodName}` in Type `{providerMethod.DeclaringType}`");
                }
                //add field
                targetType.AddInjectField(targetMethod, methodName, true);
            }
/*
            //mark check
            var injected = targetAssembly.MainModule.Types.Any(t =>
                Constants.INJECTED_MARK_NAME == t.Name &&
                Constants.INJECTED_MARK_NAMESPACE == t.Namespace);
            if (injected)
            {
                targetAssembly.Release();
                return false;
            }
*/
            foreach (var group in injections.GroupBy(inj => inj.InjectedMethod))
            {
                var injectedMethod = group.Key;
                if (injectedMethod is null) continue;
                var type = injectedMethod.DeclaringType;
                var methodName = injectedMethod.Name;
                var targetType = GetCorrespondingType(targetAssembly.MainModule, type);
                if (targetType is null)
                {
                    throw new($"Cannot find Type `{type}` in target assembly {inputAssemblyPath}");
                }
                var targetMethod = targetType.FindMethod(injectedMethod.GetSignature()).Resolve();
                if (targetMethod is null)
                {
                    throw new($"Cannot find Method `{methodName}` in Type `{type}`");
                }

                //add origin
                var originalMethod = targetType.DuplicateOriginalMethod(targetMethod);
                //add field
                var injectionName = Constants.GetInjectedFieldName(methodName, targetMethod.GetSignature());
                var (field, fieldInvoke) = targetType.AddInjectField(targetMethod, injectionName);
                //add method
                targetType.AddInjectionMethod(targetMethod, originalMethod, field, fieldInvoke, methodName);
            }

            //mark make
            var InjectedMark = new TypeDefinition(
                Constants.INJECTED_MARK_NAMESPACE,
                Constants.INJECTED_MARK_NAME,
                TypeAttributes.Class,
                targetAssembly.MainModule.TypeSystem.Object);
            targetAssembly.MainModule.Types.Add(InjectedMark);


            targetAssembly.Write(outputAssemblyPath, new WriterParameters()
            {
                WriteSymbols = IsPlayerAssembly,
            });
            targetAssembly.Release();
            return true;
            static TypeDefinition GetCorrespondingType(ModuleDefinition module, Type t1)
            {
                var typeDefinition = default(TypeDefinition);
                foreach (var type in GetContainingTypes(t1).Reverse())
                {
                    if (typeDefinition is null)
                    {
                        typeDefinition = module.Types.FirstOrDefault(t => type.FullName == t.FullName);
                    }
                    else
                    {
                        typeDefinition = typeDefinition.NestedTypes.FirstOrDefault(t => t.Name == type.Name);
                    }
                    if (typeDefinition is null) return null;
                }
                return typeDefinition;
                static IEnumerable<Type> GetContainingTypes(Type type)
                {
                    while (type != null)
                    {
                        yield return type;
                        type = type.DeclaringType;
                    }
                }
            }
        }


        static MethodDefinition DuplicateOriginalMethod(this TypeDefinition targetType, MethodDefinition targetMethod)
        {
            var originName = Constants.GetOriginMethodName(targetMethod.Name, targetMethod.GetSignature());
            var duplicatedMethod = targetType.Methods.FirstOrDefault(m => m.Name == originName);
            if (duplicatedMethod is null)
            {
                duplicatedMethod = targetMethod.Clone();
                duplicatedMethod.IsPrivate = true;
                duplicatedMethod.Name = originName;
                targetType.Methods.Add(duplicatedMethod);
            }
            return duplicatedMethod;
        }


        static void Release(this AssemblyDefinition assemblyDefinition)
        {
            if (assemblyDefinition == null) return;
            assemblyDefinition.MainModule.AssemblyResolver?.Dispose();
            assemblyDefinition.MainModule.SymbolReader?.Dispose();
            assemblyDefinition.Dispose();
        }


        static (FieldDefinition field, MethodReference fieldInvokeMethod) AddInjectField(this TypeDefinition targetType, MethodDefinition targetMethod, string injectionName, bool isPublic=false)
        {
            var HasThis = targetMethod.HasThis;
            var Parameters = targetMethod.Parameters;
            var GenericParameters = targetMethod.GenericParameters;
            // var CustomAttributes = targetMethod.CustomAttributes;
            var ReturnType = targetMethod.ReturnType;
            var ReturnVoid = targetMethod.IsReturnVoid();
            //define delegate
            // var delegateParameters = new List<TypeReference>();
            // if(HasThis) delegateParameters.Add(targetType);
            // foreach(var p in Parameters) delegateParameters.Add(p.ParameterType);
            // var delegateType = targetType.Module.CreateDelegateType(Settings.GetDelegateTypeName(methodName),targetType,ReturnType,delegateParameters);
            // targetType.NestedTypes.Add(delegateType);

            var genName = targetMethod.IsReturnVoid() ? "System.Action" : "System.Func";
            var genPCnt = Parameters.Count;
            if (!ReturnVoid) genPCnt++;
            if (HasThis) genPCnt++;
            if (genPCnt > 0)
            {
                genName += "`" + genPCnt;
            }
            var rawGenType = targetType.Module.FindType(Type.GetType(genName));
            var genType = targetType.Module.ImportReference(rawGenType);
            var genInst = new GenericInstanceType(genType);
            if (HasThis)
                genInst.GenericArguments.Add(targetType);
            foreach (var p in Parameters)
                genInst.GenericArguments.Add(p.ParameterType);
            if (!ReturnVoid)
                genInst.GenericArguments.Add(ReturnType);
            //store fields
            var sfldInject = targetType.Fields.FirstOrDefault(f => f.Name == injectionName);
            if (sfldInject is null)
            {
                sfldInject = new FieldDefinition(injectionName,
                    FieldAttributes.Static | (isPublic ? FieldAttributes.Public : FieldAttributes.Private),
                    genInst);
                targetType.Fields.Add(sfldInject);
            }

            // var sfldOrigin = new FieldDefinition(originName,
            //     FieldAttributes.Private|FieldAttributes.Static|FieldAttributes.Assembly,
            //     targetType.Module.ImportReference(typeof(Delegate)));
            // var resMth = genInst.Resolve();
            var genMtd = rawGenType.FindMethodByName("Invoke");
            // genMtd.DeclaringType = genInst;
            var mnlMth = new MethodReference(genMtd.Name, genMtd.ReturnType, genInst)
            {
                ExplicitThis = false,
                HasThis = true,
                CallingConvention = genMtd.CallingConvention
            };
            foreach (var p in genMtd.Parameters)
                mnlMth.Parameters.Add(p);

            return (sfldInject, mnlMth);
        }


        static void AddInjectionMethod(
            this TypeDefinition targetType,
            MethodDefinition targetMethod, MethodDefinition originalMethod,
            FieldDefinition delegateField, MethodReference fieldInvoke, string methodName
        )
        {
            var argidx = 0;
            var HasThis = targetMethod.HasThis;
            var Parameters = targetMethod.Parameters;
            // var GenericParameters = targetMethod.GenericParameters;
            // var CustomAttributes =  targetMethod.CustomAttributes;
            var ReturnType = targetMethod.ReturnType;

            //redirect method
            if (!targetMethod.HasBody)
            {
                throw new ArgumentException($"method {targetMethod.Name} in type {targetType.Name} dont have a body");
            }
            targetMethod.Body.Instructions.Clear();
            var delegateType = delegateField.FieldType.Resolve();
            var ilProcessor = targetMethod.Body.GetILProcessor();
            var tagOp = Instruction.Create(OpCodes.Nop);
            //check null
            ilProcessor.Append(Instruction.Create(OpCodes.Ldsfld, delegateField));
            ilProcessor.Append(Instruction.Create(OpCodes.Brtrue_S, tagOp));

            // //set field
            // if(HasThis)
            //     ilProcessor.Append(Instruction.Create(OpCodes.Ldarg_0));
            // else
            //     ilProcessor.Append(Instruction.Create(OpCodes.Ldnull));
            // ilProcessor.Append(Instruction.Create(OpCodes.Ldftn, originalMethod));
            // ilProcessor.Append(Instruction.Create(OpCodes.Newobj,delegateType.FindMethod(".ctor")));
            // ilProcessor.Append(Instruction.Create(OpCodes.Stsfld,delegateField));

            //invoke origin
            argidx = 0;
            if (HasThis)
                ilProcessor.Append(ilProcessor.createLdarg(argidx++));
            for (var i = 0; i < Parameters.Count; i++)
            {
                var pType = Parameters[i].ParameterType;
                ilProcessor.Append(ilProcessor.createLdarg(argidx++));
                // if(pType.IsValueType)
                //     ilProcessor.Append(Instruction.Create(OpCodes.Box,pType));
            }
            if (HasThis)
                ilProcessor.Append(Instruction.Create(OpCodes.Callvirt, originalMethod));
            else
                ilProcessor.Append(Instruction.Create(OpCodes.Call, originalMethod));
            // if(originalMethod.IsReturnVoid())
            //     ilProcessor.Append(Instruction.Create(OpCodes.Pop));
            ilProcessor.Append(Instruction.Create(OpCodes.Ret));

            //invoke
            ilProcessor.Append(tagOp);
            ilProcessor.Append(Instruction.Create(OpCodes.Ldsfld, delegateField));
            argidx = 0;
            if (HasThis)
                ilProcessor.Append(ilProcessor.createLdarg(argidx++));
            for (var i = 0; i < Parameters.Count; i++)
            {
                var pType = Parameters[i].ParameterType;
                ilProcessor.Append(ilProcessor.createLdarg(argidx++));
                // if(pType.IsValueType)
                //     ilProcessor.Append(Instruction.Create(OpCodes.Box,pType));
            }
            ilProcessor.Append(Instruction.Create(OpCodes.Callvirt,
                (fieldInvoke)));

            // Fixes: conditional boxing here is unnecessary
            // if(ReturnType.IsComplexValueType())
            //     ilProcessor.Append(Instruction.Create(OpCodes.Box,ReturnType));

            ilProcessor.Append(Instruction.Create(OpCodes.Nop));
            ilProcessor.Append(Instruction.Create(OpCodes.Ret));
        }


        static Instruction createLdarg(this ILProcessor ilProcessor, int i)
        {
            if (i < s_ldargs.Length)
            {
                return Instruction.Create(s_ldargs[i]);
            }
            else if (i < 256)
            {
                return ilProcessor.Create(OpCodes.Ldarg_S, (byte)i);
            }
            else
            {
                return ilProcessor.Create(OpCodes.Ldarg, (short)i);
            }
        }


        /// <summary>
        /// Create a clone of the given method definition
        /// </summary>
        public static MethodDefinition Clone(this MethodDefinition source)
        {
            var result = new MethodDefinition(source.Name, source.Attributes, source.ReturnType)
            {
                ImplAttributes = source.ImplAttributes,
                SemanticsAttributes = source.SemanticsAttributes,
                HasThis = source.HasThis,
                ExplicitThis = source.ExplicitThis,
                CallingConvention = source.CallingConvention
            };
            foreach (var p in source.Parameters) result.Parameters.Add(p);
            // foreach (var p in source.CustomAttributes) result.CustomAttributes.Add(p);
            foreach (var p in source.GenericParameters) result.GenericParameters.Add(p);
            if (source.HasBody)
            {
                result.Body = source.Body.Clone(result);
            }
            return result;
        }


        /// <summary>
        /// Create a clone of the given method body
        /// </summary>
        public static MethodBody Clone(this MethodBody source, MethodDefinition target)
        {
            var result = new MethodBody(target) { InitLocals = source.InitLocals, MaxStackSize = source.MaxStackSize };
            var worker = result.GetILProcessor();
            if (source.HasVariables)
            {
                foreach (var v in source.Variables)
                {
                    result.Variables.Add(v);
                }
            }
            foreach (var i in source.Instructions)
            {
                // Poor mans clone, but sufficient for our needs
                var clone = Instruction.Create(OpCodes.Nop);
                clone.OpCode = i.OpCode;
                clone.Operand = i.Operand;
                worker.Append(clone);
            }
            return result;
        }


        internal static bool IsReturnVoid(this MethodDefinition md)
            => md.ReturnType.ToString() == voidType.ToString();
        internal static bool IsReturnValueType(this MethodDefinition md)
            => !md.IsReturnVoid() && md.ReturnType.IsValueType;
        internal static bool IsComplexValueType(this TypeReference td)
            => td.ToString() != voidType.ToString() && !td.IsPrimitive;
        internal static Type GetUnderlyingType(this TypeReference td)
            => td.IsPrimitive ? Type.GetType(td.Name) : objType;

        internal static string GetSignature(this MethodDefinition md)
        {
            var builder = new StringBuilder();
            builder.Append(md.Name);
            if (md.HasGenericParameters)
            {
                builder.Append('`');
                builder.Append(md.GenericParameters.Count);
            }
            builder.Append('(');

            if (md.HasParameters)
            {
                var parameters = md.Parameters;
                for (int i = 0; i < parameters.Count; i++)
                {
                    ParameterDefinition parameterDefinition = parameters[i];
                    if (i > 0)
                    {
                        builder.Append(",");
                    }

                    AppendTypeFullName(builder, parameterDefinition.ParameterType);
                }
            }

            builder.Append(')');
            return builder.ToString();

            static void AppendTypeFullName(StringBuilder builder, TypeReference type)
            {
                if (!string.IsNullOrEmpty(type.Namespace))
                {
                    builder.Append(type.Namespace);
                    builder.Append("::");
                }

                var stack = new Stack<TypeReference>();
                var declaringType = type;
                while (null != declaringType)
                {
                    stack.Push(declaringType);
                    declaringType = declaringType.DeclaringType;
                }
                while (stack.TryPop(out var nestedType)) AppendNestedType(builder, nestedType);
            }
            static void AppendNestedType(StringBuilder builder, TypeReference type)
            {
                builder.Append(type.Name);
                if (type is GenericInstanceType gInst)
                {
                    builder.Append('<');
                    var args = gInst.GenericArguments;
                    for (int i = 0; i < args.Count; i++)
                    {
                        if (i != 0)
                        {
                            builder.Append(',');
                        }
                        AppendTypeFullName(builder, args[i]);
                    }
                    builder.Append('>');
                }
            }
        }

        internal static MethodReference FindMethod(this TypeDefinition td, string methodSignature)
        {
            var method = td.Methods.FirstOrDefault(m => m.GetSignature().Equals(methodSignature));
            if (method is null) return null;
            return td.Module.ImportReference(method);
        }

        internal static MethodReference FindMethodByName(this TypeDefinition td, string methodName)
            => td.Module.ImportReference(td.Methods.FirstOrDefault(m => m.Name.Equals(methodName)));
        internal static TypeDefinition FindType(this ModuleDefinition md, Type type)
        {
            DebugHelper.IsNotNull(type);
            HashSet<string> knownAssemblyNames = new();
            List<ModuleDefinition> modules = new();
            GetModules(md);
            foreach (var m in modules)
            {
                DebugHelper.IsNotNull(m);
                var tp = m.GetType(type.Namespace, type.Name);
                if (null != tp)
                {
                    return tp;
                }
            }
            return null;
            void GetModules(ModuleDefinition md)
            {
                if (knownAssemblyNames.Contains(md.FileName))
                    return;
                var refModules = md.AssemblyReferences
                    .Select(an =>
                    {
                        try
                        {
                            return md.AssemblyResolver.Resolve(an).MainModule;
                        }
                        catch
                        {
                            return null;
                        }
                    })
                    .Where(r => r != null)
                    .ToArray();
                AddModule(md);
                foreach (var m in refModules)
                {
                    GetModules(m);
                }
            }
            void AddModule(ModuleDefinition md)
            {
                var fileName = md.FileName;
                if (!knownAssemblyNames.Contains(fileName))
                    modules.Add(md);
                knownAssemblyNames.Add(fileName);
            }
            // return new TypeReference(type.Namespace,type.Name,md,md.TypeSystem.CoreLibrary);
        }


        internal static TypeReference FindType<T>(this ModuleDefinition md)
        {
            return FindType(md, typeof(T));
            // return new TypeReference(typeof(T).Namespace,typeof(T).Name,md,md.TypeSystem.CoreLibrary);
        }


        internal static TypeDefinition CreateDelegateType(this ModuleDefinition assembly, string name, TypeDefinition declaringType,
                TypeReference returnType, IEnumerable<TypeReference> parameters)
        {
            var voidType = assembly.TypeSystem.Void;
            var objectType = assembly.TypeSystem.Object;
            var nativeIntType = assembly.TypeSystem.IntPtr;
            var asyncResultType = assembly.FindType<IAsyncResult>();
            var asyncCallbackType = assembly.FindType<AsyncCallback>();
            var multicastDelegateType = assembly.FindType<MulticastDelegate>();

            var DelegateTypeAttributes = TypeAttributes.NestedPublic | TypeAttributes.Sealed;
            var dt = new TypeDefinition("", name, DelegateTypeAttributes, multicastDelegateType);
            dt.DeclaringType = declaringType;

            // add constructor
            var ConstructorAttributes = MethodAttributes.Public | MethodAttributes.HideBySig | MethodAttributes.SpecialName | MethodAttributes.RTSpecialName;
            var constructor = new MethodDefinition(".ctor", ConstructorAttributes, voidType);
            constructor.Parameters.Add(new ParameterDefinition("objectInstance", ParameterAttributes.None, objectType));
            constructor.Parameters.Add(new ParameterDefinition("functionPtr", ParameterAttributes.None, nativeIntType));
            constructor.ImplAttributes = MethodImplAttributes.Runtime;
            dt.Methods.Add(constructor);

            // add BeginInvoke
            var DelegateMethodAttributes = MethodAttributes.Public | MethodAttributes.HideBySig | MethodAttributes.Virtual | MethodAttributes.VtableLayoutMask;
            var beginInvoke = new MethodDefinition("BeginInvoke", DelegateMethodAttributes, asyncResultType);
            foreach (var p in parameters)
            {
                beginInvoke.Parameters.Add(new ParameterDefinition(p));
            }
            beginInvoke.Parameters.Add(new ParameterDefinition("callback", ParameterAttributes.None, asyncCallbackType));
            beginInvoke.Parameters.Add(new ParameterDefinition("object", ParameterAttributes.None, objectType));
            beginInvoke.ImplAttributes = MethodImplAttributes.Runtime;
            dt.Methods.Add(beginInvoke);

            // add EndInvoke
            var endInvoke = new MethodDefinition("EndInvoke", DelegateMethodAttributes, returnType);
            endInvoke.Parameters.Add(new ParameterDefinition("result", ParameterAttributes.None, asyncResultType));
            endInvoke.ImplAttributes = MethodImplAttributes.Runtime;
            dt.Methods.Add(endInvoke);

            // add Invoke
            var invoke = new MethodDefinition("Invoke", DelegateMethodAttributes, returnType);
            foreach (var p in parameters)
            {
                // if(!p.IsValueType){
                //     invoke.Parameters.Add(new ParameterDefinition(p.Name,ParameterAttributes.In,objectType));
                // }else{
                invoke.Parameters.Add(new ParameterDefinition(p));
                // }
            }
            invoke.ImplAttributes = MethodImplAttributes.Runtime;
            dt.Methods.Add(invoke);

            return dt;
        }


        static Type voidType = typeof(void);
        static Type objType = typeof(object);
        static OpCode[] s_ldargs = new[] { OpCodes.Ldarg_0, OpCodes.Ldarg_1, OpCodes.Ldarg_2, OpCodes.Ldarg_3 };
    }
}