using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Reflection.Emit;

namespace Umbraco.Core
{
    /// <summary>
    /// Provides utilities to simplify reflection.
    /// </summary>
    public static class ReflectionUtilities
    {
        public const AssemblyBuilderAccess DefaultAssemblyBuilderAccess = AssemblyBuilderAccess.Run;
        public const AssemblyBuilderAccess NoAssembly = 0;

        public static Func<TInstance, TValue> GetPropertyGetter<TInstance, TValue>(string propertyName)
        {
            var type = typeof (TInstance);
            var type0 = typeof (TValue);
            var property = type.GetProperty(propertyName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
            if (property == null || property.PropertyType != type0)
                throw new InvalidOperationException($"Could not get property {type}.{propertyName} : {type0}.");
            return GetPropertyGetter<TInstance, TValue>(property);
        }

        public static Action<TInstance, TValue> GetPropertySetter<TInstance, TValue>(string propertyName)
        {
            var type = typeof (TInstance);
            var type0 = typeof (TValue);
            var property = type.GetProperty(propertyName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
            if (property == null || property.PropertyType != type0)
                throw new InvalidOperationException($"Could not get property {type}.{propertyName} : {type0}.");
            return GetPropertySetter<TInstance, TValue>(property);
        }

        public static void GetPropertyGetterSetter<TInstance, TValue>(string propertyName, out Func<TInstance, TValue> getter, out Action<TInstance, TValue> setter)
        {
            var type = typeof (TInstance);
            var type0 = typeof (TValue);
            var property = type.GetProperty(propertyName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
            if (property == null || property.PropertyType != type0)
                throw new InvalidOperationException($"Could not get property {type}.{propertyName} : {type0}.");
            getter = GetPropertyGetter<TInstance, TValue>(property);
            setter = GetPropertySetter<TInstance, TValue>(property);
        }

        public static Expression<Func<TInstance>> GetCtorExpr<TInstance>(bool mustExist = true)
        {
            var type = typeof (TInstance);

            // get the constructor infos
            var ctor = type.GetConstructor(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance,
                null, Type.EmptyTypes, null);

            if (ctor == null)
            {
                if (!mustExist) return null;
                throw new InvalidOperationException($"Could not find constructor {type}.ctor().");                
            }

            var exprNew = Expression.New(ctor);
            return Expression.Lambda<Func<TInstance>>(exprNew);
        }

        public static Expression<TLambda> GetCtorExpr<TLambda>(Type type, bool mustExist = true)
        {
            // get the constructor infos
            var ctor = type.GetConstructor(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance,
                null, Type.EmptyTypes, null);

            if (ctor == null)
            {
                if (!mustExist) return null;
                throw new InvalidOperationException($"Could not find constructor {type}.ctor().");
            }

            var exprNew = Expression.New(ctor);
            return Expression.Lambda<TLambda>(exprNew);
        }

        public static Func<TInstance> GetCtor<TInstance>(bool mustExist = true, AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            var expr = GetCtorExpr<TInstance>(mustExist);
            if (expr == null) return null;
            return access == NoAssembly ? expr.Compile() : CompileToDelegate(expr, access);
        }

        public static TLambda GetCtor<TLambda>(Type type, bool mustExist = true, AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            var expr = GetCtorExpr<TLambda>(type, mustExist);
            if (expr == null) return default(TLambda);
            return access == NoAssembly ? expr.Compile() : CompileToDelegate(expr, access);
        }

        public static Func<TInstance> EmitCtor<TInstance>(bool mustExist = true)
        {
            var type = typeof (TInstance);

            // get the constructor infos
            var ctor = type.GetConstructor(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance,
                null, Type.EmptyTypes, null);

            if (ctor == null)
            {
                if (!mustExist) return null;
                throw new InvalidOperationException($"Could not find constructor {type}.ctor().");
            }

            var dm = new DynamicMethod(string.Empty, type, Array.Empty<Type>(), type.Module, true);
            var gen = dm.GetILGenerator();
            gen.Emit(OpCodes.Newobj, ctor);
            gen.Emit(OpCodes.Ret);
            return (Func<TInstance>) dm.CreateDelegate(typeof (Func<TInstance>));
        }

        public static Func<TArg0, TInstance> EmitCtor<TInstance, TArg0>(bool mustExist = true)
        {
            var type = typeof (TInstance);
            var type0 = typeof (TArg0);

            // get the constructor infos
            var ctor = type.GetConstructor(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance,
                null, new[] { type0 }, null);

            if (ctor == null)
            {
                if (!mustExist) return null;
                throw new InvalidOperationException($"Could not find constructor {type}.ctor().");
            }

            var dm = new DynamicMethod(string.Empty, type, new[] { type0 }, type.Module, true);
            var gen = dm.GetILGenerator();
            gen.Emit(OpCodes.Ldarg_0);
            gen.Emit(OpCodes.Newobj, ctor);
            gen.Emit(OpCodes.Ret);
            return (Func<TArg0, TInstance>) dm.CreateDelegate(typeof (Func<TArg0, TInstance>));
        }

        public static Func<TArg0, TInstance> EmitCtor<TArg0, TInstance>(Type type, bool mustExist = true)
        {
            var type0 = typeof (TArg0);

            // get the constructor infos
            var ctor = type.GetConstructor(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance,
                null, new[] { type0 }, null);

            if (ctor == null)
            {
                if (!mustExist) return null;
                throw new InvalidOperationException($"Could not find constructor {type}.ctor().");
            }

            var dm = new DynamicMethod(string.Empty, type, new[] { type0 }, type.Module, true);
            var gen = dm.GetILGenerator();
            gen.Emit(OpCodes.Ldarg_0);
            gen.Emit(OpCodes.Newobj, ctor);
            gen.Emit(OpCodes.Ret);
            return (Func<TArg0, TInstance>) dm.CreateDelegate(typeof (Func<TArg0, TInstance>));
        }

        public static TLambda EmitCtor<TLambda>(ConstructorInfo constructorInfo)
        {
            var type = constructorInfo.DeclaringType;
            var args = constructorInfo.GetParameters().Select(x => x.ParameterType).ToArray();

            var dm = new DynamicMethod(string.Empty, type, args, type.Module, true);
            var gen = dm.GetILGenerator();

            if (args.Length < 5)
            {
                if (args.Length > 0)
                    gen.Emit(OpCodes.Ldarg_0);
                if (args.Length > 1)
                    gen.Emit(OpCodes.Ldarg_1);
                if (args.Length > 2)
                    gen.Emit(OpCodes.Ldarg_2);
                if (args.Length > 3)
                    gen.Emit(OpCodes.Ldarg_3);
            }
            else
            {
                for (var i = 0; i < args.Length; i++)
                    gen.Emit(OpCodes.Ldarg, i);
            }
            gen.Emit(OpCodes.Newobj, constructorInfo);
            gen.Emit(OpCodes.Ret);
            return (TLambda) (object) dm.CreateDelegate(typeof (TLambda));
        }

        // fixme others need it too?

        public static Func<TArg0, TInstance> GetCtor<TInstance, TArg0>()
        {
            var type = typeof (TInstance);
            var type0 = typeof (TArg0);

            // get the constructor infos
            var ctor = type.GetConstructor(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance,
                null, new[] { type0 }, null);

            if (ctor == null)
                throw new InvalidOperationException($"Could not find constructor {type}.ctor({type0}).");

            var exprArgs = ctor.GetParameters().Select(x => Expression.Parameter(x.ParameterType, x.Name)).ToArray();
            // ReSharper disable once CoVariantArrayConversion
            var exprNew = Expression.New(ctor, exprArgs);
            var expr = Expression.Lambda<Func<TArg0, TInstance>>(exprNew, exprArgs);
            return expr.CompileToDelegate();
        }

        public static Func<TArg0, TArg1, TInstance> GetCtor<TInstance, TArg0, TArg1>()
        {
            var type = typeof (TInstance);
            var type0 = typeof (TArg0);
            var type1 = typeof (TArg1);

            // get the constructor infos
            var ctor = type.GetConstructor(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance,
                null, new[] { type0, type1 }, null);

            if (ctor == null)
                throw new InvalidOperationException($"Could not find constructor {type}.ctor({type0}, {type1}).");

            var exprArgs = ctor.GetParameters().Select(x => Expression.Parameter(x.ParameterType, x.Name)).ToArray();
            // ReSharper disable once CoVariantArrayConversion
            var exprNew = Expression.New(ctor, exprArgs);
            var expr = Expression.Lambda<Func<TArg0, TArg1, TInstance>>(exprNew, exprArgs);
            return expr.CompileToDelegate();
        }

        public static TMethod GetMethod<TMethod>(MethodInfo method)
        {
            var type = method.DeclaringType;

            GetMethodParms<TMethod>(out var parameterTypes, out var returnType);
            return GetStaticMethod<TMethod>(method, method.Name, type, parameterTypes, returnType);
        }

        public static TMethod GetMethod<TInstance, TMethod>(MethodInfo method)
        {
            var type = method.DeclaringType;

            GetMethodParms<TInstance, TMethod>(out var parameterTypes, out var returnType);
            return GetMethod<TMethod>(method, method.Name, type, parameterTypes, returnType);
        }

        public static TMethod GetMethod<TInstance, TMethod>(string methodName)
        {
            var type = typeof (TInstance);

            GetMethodParms<TInstance, TMethod>(out var parameterTypes, out var returnType);

            var method = type.GetMethod(methodName, BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance,
                null, parameterTypes, null);

            return GetMethod<TMethod>(method, methodName, type, parameterTypes, returnType);
        }

        private static Func<TInstance, TValue> GetPropertyGetter<TInstance, TValue>(PropertyInfo property)
        {
            var type = typeof (TInstance);

            var getMethod = property.GetMethod;
            if (getMethod == null)
                throw new InvalidOperationException($"Property {type}.{property.Name} : {property.PropertyType} does not have a getter.");

            var exprThis = Expression.Parameter(type, "this");
            var exprCall = Expression.Call(exprThis, getMethod);
            var expr = Expression.Lambda<Func<TInstance, TValue>>(exprCall, exprThis);
            return expr.CompileToDelegate();
        }

        private static Action<TInstance, TValue> GetPropertySetter<TInstance, TValue>(PropertyInfo property)
        {
            var type = typeof (TInstance);

            var setMethod = property.SetMethod;
            if (setMethod == null)
                throw new InvalidOperationException($"Property {type}.{property.Name} : {property.PropertyType} does not have a setter.");

            var exprThis = Expression.Parameter(type, "this");
            var exprArg0 = Expression.Parameter(typeof (TValue), "value");
            var exprCall = Expression.Call(exprThis, setMethod, exprArg0);
            var expr = Expression.Lambda<Action<TInstance, TValue>>(exprCall, exprThis, exprArg0);
            return expr.CompileToDelegate();
        }

        private static void GetMethodParms<TMethod>(out Type[] parameterTypes, out Type returnType)
        {
            var typeM = typeof (TMethod);
            var typeList = new List<Type>();
            returnType = typeof (void);

            if (!typeof (MulticastDelegate).IsAssignableFrom(typeM) || typeM == typeof (MulticastDelegate))
                throw new InvalidOperationException("Invalid TMethod, must be a Func or Action.");

            var typeName = typeM.FullName;
            if (typeName == null)
                throw new InvalidOperationException($"Could not get {typeM} type name.");
            if (typeName.StartsWith("System.Func`"))
            {
                var i = 0;
                while (i < typeM.GenericTypeArguments.Length - 1)
                    typeList.Add(typeM.GenericTypeArguments[i++]);
                returnType = typeM.GenericTypeArguments[i];
            }
            else if (typeName.StartsWith("System.Action`"))
            {
                var i = 0;
                while (i < typeM.GenericTypeArguments.Length)
                    typeList.Add(typeM.GenericTypeArguments[i++]);
            }
            else if (typeName == "System.Action")
            {
                // no args
            }
            else
                throw new InvalidOperationException(typeName);

            parameterTypes = typeList.ToArray();
        }

        private static void GetMethodParms<TInstance, TMethod>(out Type[] parameterTypes, out Type returnType)
        {
            var type = typeof (TInstance);

            var typeM = typeof (TMethod);
            var typeList = new List<Type>();
            returnType = typeof (void);

            if (!typeof (MulticastDelegate).IsAssignableFrom(typeM) || typeM == typeof (MulticastDelegate))
                throw new InvalidOperationException("Invalid TMethod, must be a Func or Action.");

            var typeName = typeM.FullName;
            if (typeName == null)
                throw new InvalidOperationException($"Could not get {typeM} type name.");
            if (!typeM.IsGenericType)
                throw new InvalidOperationException($"Type {typeName} is not generic.");
            if (typeM.GenericTypeArguments[0] != type)
                throw new InvalidOperationException($"Invalid type {typeName}, the first generic argument must be {type.FullName}.");
            if (typeName.StartsWith("System.Func`"))
            {
                var i = 1;
                while (i < typeM.GenericTypeArguments.Length - 1)
                    typeList.Add(typeM.GenericTypeArguments[i++]);
                returnType = typeM.GenericTypeArguments[i];
            }
            else if (typeName.StartsWith("System.Action`"))
            {
                var i = 1;
                while (i < typeM.GenericTypeArguments.Length)
                    typeList.Add(typeM.GenericTypeArguments[i++]);
            }
            else
                throw new InvalidOperationException(typeName);

            parameterTypes = typeList.ToArray();
        }

        private static TMethod GetStaticMethod<TMethod>(MethodInfo method, string methodName, Type type, Type[] parameterTypes, Type returnType)
        {
            if (method == null || method.ReturnType != returnType)
                throw new InvalidOperationException($"Could not find static method {type}.{methodName}({string.Join(",", parameterTypes.Select(x => x.ToString()))}) : {returnType}");

            var e = new List<ParameterExpression>();
            foreach (var p in method.GetParameters())
                e.Add(Expression.Parameter(p.ParameterType, p.Name));
            var exprCallArgs = e.ToArray();
            var exprLambdaArgs = exprCallArgs;

            // ReSharper disable once CoVariantArrayConversion
            var exprCall = Expression.Call(method, exprCallArgs);
            var expr = Expression.Lambda<TMethod>(exprCall, exprLambdaArgs);
            return expr.CompileToDelegate();
        }

        private static TMethod GetMethod<TMethod>(MethodInfo method, string methodName, Type type, Type[] parameterTypes, Type returnType)
        {
            if (method == null || method.ReturnType != returnType)
                throw new InvalidOperationException($"Could not find method {type}.{methodName}({string.Join(",", parameterTypes.Select(x => x.ToString()))}) : {returnType}");

            var e = new List<ParameterExpression>();
            foreach (var p in method.GetParameters())
                e.Add(Expression.Parameter(p.ParameterType, p.Name));
            var exprCallArgs = e.ToArray();

            var exprThis = Expression.Parameter(type, "this");
            e.Insert(0, exprThis);
            var exprLambdaArgs = e.ToArray();

            // ReSharper disable once CoVariantArrayConversion
            var exprCall = Expression.Call(exprThis, method, exprCallArgs);
            var expr = Expression.Lambda<TMethod>(exprCall, exprLambdaArgs);
            return expr.Compile();
        }

        // not sure we want this at all?

        /*
        public static object GetStaticProperty(this Type type, string propertyName, Func<IEnumerable<PropertyInfo>, PropertyInfo> filter = null)
        {
            var propertyInfo = GetPropertyInfo(type, propertyName, filter);
            if (propertyInfo == null)
                throw new ArgumentOutOfRangeException(nameof(propertyName),
                    $"Couldn't find property {propertyName} in type {type.FullName}");
            return propertyInfo.GetValue(null, null);
        }

        public static object CallStaticMethod(this Type type, string methodName, params object[] parameters)
        {
            var methodInfo = GetMethodInfo(type, methodName);
            if (methodInfo == null)
                throw new ArgumentOutOfRangeException(nameof(methodName),
                    $"Couldn't find method {methodName} in type {type.FullName}");
            return methodInfo.Invoke(null, parameters);
        }

        public static object CallMethod(this object obj, string methodName, params object[] parameters)
        {
            if (obj == null)
                throw new ArgumentNullException(nameof(obj));
            Type type = obj.GetType();
            var methodInfo = GetMethodInfo(type, methodName);
            if (methodInfo == null)
                throw new ArgumentOutOfRangeException(nameof(methodName),
                    $"Couldn't find method {methodName} in type {type.FullName}");
            return methodInfo.Invoke(obj, parameters);
        }

        public static object CallMethod(this object obj, string methodName, Func<IEnumerable<MethodInfo>, MethodInfo> filter = null, params object[] parameters)
        {
            if (obj == null)
                throw new ArgumentNullException(nameof(obj));
            Type type = obj.GetType();
            var methodInfo = GetMethodInfo(type, methodName, filter);
            if (methodInfo == null)
                throw new ArgumentOutOfRangeException(nameof(methodName),
                    $"Couldn't find method {methodName} in type {type.FullName}");
            return methodInfo.Invoke(obj, parameters);
        }

        private static MethodInfo GetMethodInfo(Type type, string methodName, Func<IEnumerable<MethodInfo>, MethodInfo> filter = null)
        {
            MethodInfo methodInfo;
            do
            {
                try
                {
                    methodInfo = type.GetMethod(methodName,
                        BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static);
                }
                catch (AmbiguousMatchException)
                {
                    if (filter == null) throw;

                    methodInfo = filter(
                        type.GetMethods(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static)
                            .Where(x => x.Name == methodName));
                }
                type = type.BaseType;
            }
            while (methodInfo == null && type != null);
            return methodInfo;
        }

        private static PropertyInfo GetPropertyInfo(Type type, string propertyName, Func<IEnumerable<PropertyInfo>, PropertyInfo> filter = null)
        {
            PropertyInfo propInfo;
            do
            {
                try
                {
                    propInfo = type.GetProperty(propertyName,
                        BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static);
                }
                catch (AmbiguousMatchException)
                {
                    if (filter == null) throw;

                    propInfo = filter(type.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static)
                        .Where(x => x.Name == propertyName));
                }
                type = type.BaseType;
            }
            while (propInfo == null && type != null);
            return propInfo;
        }

        public static object GetPropertyValue(this object obj, string propertyName)
        {
            if (obj == null)
                throw new ArgumentNullException(nameof(obj));
            Type objType = obj.GetType();
            PropertyInfo propInfo = GetPropertyInfo(objType, propertyName);
            if (propInfo == null)
                throw new ArgumentOutOfRangeException(nameof(propertyName),
                    $"Couldn't find property {propertyName} in type {objType.FullName}");
            return propInfo.GetValue(obj, null);
        }

        public static object GetPropertyValue(this object obj, string propertyName, IDictionary<string, PropertyInfo> propCache)
        {
            if (obj == null)
                throw new ArgumentNullException(nameof(obj));
            Type objType = obj.GetType();
            PropertyInfo propInfo;
            if (propCache.ContainsKey(propertyName))
            {
                propInfo = propCache[propertyName];
            }
            else
            {
                propInfo = GetPropertyInfo(objType, propertyName);
                if (propInfo == null)
                    throw new ArgumentOutOfRangeException(nameof(propertyName),
                        $"Couldn't find property {propertyName} in type {objType.FullName}");

                propCache[propertyName] = propInfo;
            }
            return propInfo.GetValue(obj, null);
        }

        public static void SetPropertyValue(this object obj, string propertyName, object val)
        {
            if (obj == null)
                throw new ArgumentNullException(nameof(obj));
            Type objType = obj.GetType();
            PropertyInfo propInfo = GetPropertyInfo(objType, propertyName);
            if (propInfo == null)
                throw new ArgumentOutOfRangeException(nameof(propertyName),
                    $"Couldn't find property {propertyName} in type {objType.FullName}");
            propInfo.SetValue(obj, val, null);
        }

        public static void SetPropertyValue(this object obj, string propertyName, object val, IDictionary<string, PropertyInfo> propCache)
        {
            if (obj == null) throw new ArgumentNullException(nameof(obj));
            if (propCache == null) throw new ArgumentNullException(nameof(propCache));

            Type objType = obj.GetType();
            PropertyInfo propInfo;
            if (propCache.ContainsKey(propertyName))
            {
                propInfo = propCache[propertyName];
            }
            else
            {
                propInfo = GetPropertyInfo(objType, propertyName);
                if (propInfo == null)
                    throw new ArgumentOutOfRangeException(nameof(propertyName),
                        $"Couldn't find property {propertyName} in type {objType.FullName}");

                propCache[propertyName] = propInfo;
            }

            propInfo.SetValue(obj, val, null);
        }
        */

        // fixme dont think this can work at all
        public static TLambda Compile<TLambda>(Expression<TLambda> expr, AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            return access == NoAssembly
                ? expr.Compile()
                : CompileToDelegate(expr, access);
        }

        public static Action CompileToDelegate(Expression<Action> expr, AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            var typeBuilder = CreateTypeBuilder(access);

            var builder = typeBuilder.DefineMethod("Method",
                MethodAttributes.Public | MethodAttributes.Static); // CompileToMethod requires a static method

            expr.CompileToMethod(builder);

            return (Action) Delegate.CreateDelegate(typeof (Action), typeBuilder.CreateType().GetMethod("Method"));
        }

        public static Action<T1> CompileToDelegate<T1>(Expression<Action<T1>> expr, AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            var typeBuilder = CreateTypeBuilder(access);

            var builder = typeBuilder.DefineMethod("Method",
                MethodAttributes.Public | MethodAttributes.Static, // CompileToMethod requires a static method
                typeof (void), new[] { typeof (T1) });

            expr.CompileToMethod(builder);

            return (Action<T1>) Delegate.CreateDelegate(typeof (Action<T1>), typeBuilder.CreateType().GetMethod("Method"));
        }

        public static Action<T1, T2> CompileToDelegate<T1, T2>(Expression<Action<T1, T2>> expr, AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            var typeBuilder = CreateTypeBuilder(access);

            var builder = typeBuilder.DefineMethod("Method",
                MethodAttributes.Public | MethodAttributes.Static, // CompileToMethod requires a static method
                typeof (void), new[] { typeof (T1), typeof (T2) });

            expr.CompileToMethod(builder);

            return (Action<T1, T2>) Delegate.CreateDelegate(typeof (Action<T1, T2>), typeBuilder.CreateType().GetMethod("Method"));
        }

        public static Action<T1, T2, T3> CompileToDelegate<T1, T2, T3>(Expression<Action<T1, T2, T3>> expr, AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            var typeBuilder = CreateTypeBuilder(access);

            var builder = typeBuilder.DefineMethod("Method",
                MethodAttributes.Public | MethodAttributes.Static, // CompileToMethod requires a static method
                typeof (void), new[] { typeof (T1), typeof (T2), typeof (T3) });

            expr.CompileToMethod(builder);

            return (Action<T1, T2, T3>) Delegate.CreateDelegate(typeof (Action<T1, T2, T3>), typeBuilder.CreateType().GetMethod("Method"));
        }

        public static Func<TResult> CompileToDelegate<TResult>(Expression<Func<TResult>> expr, AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            var typeBuilder = CreateTypeBuilder(access);

            var builder = typeBuilder.DefineMethod("Method",
                MethodAttributes.Public | MethodAttributes.Static,
                typeof (TResult), Array.Empty<Type>()); // CompileToMethod requires a static method

            expr.CompileToMethod(builder);

            return (Func<TResult>) Delegate.CreateDelegate(typeof (Func<TResult>), typeBuilder.CreateType().GetMethod("Method"));
        }

        public static Func<T1, TResult> CompileToDelegate<T1, TResult>(Expression<Func<T1, TResult>> expr, AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            var typeBuilder = CreateTypeBuilder(access);

            var builder = typeBuilder.DefineMethod("Method",
                MethodAttributes.Public | MethodAttributes.Static, // CompileToMethod requires a static method
                typeof (TResult), new[] { typeof (T1) });

            expr.CompileToMethod(builder);

            return (Func<T1, TResult>) Delegate.CreateDelegate(typeof (Func<T1, TResult>), typeBuilder.CreateType().GetMethod("Method"));
        }

        public static Func<T1, T2, TResult> CompileToDelegate<T1, T2, TResult>(Expression<Func<T1, T2, TResult>> expr, AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            var typeBuilder = CreateTypeBuilder(access);

            var builder = typeBuilder.DefineMethod("Method",
                MethodAttributes.Public | MethodAttributes.Static, // CompileToMethod requires a static method
                typeof (TResult), new[] { typeof (T1), typeof (T2) });

            expr.CompileToMethod(builder);

            return (Func<T1, T2, TResult>) Delegate.CreateDelegate(typeof (Func<T1, T2, TResult>), typeBuilder.CreateType().GetMethod("Method"));
        }

        public static Func<T1, T2, T3, TResult> CompileToDelegate<T1, T2, T3, TResult>(Expression<Func<T1, T2, T3, TResult>> expr, AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            var typeBuilder = CreateTypeBuilder(access);

            var builder = typeBuilder.DefineMethod("Method",
                MethodAttributes.Public | MethodAttributes.Static, // CompileToMethod requires a static method
                typeof (TResult), new[] { typeof (T1), typeof (T2), typeof (T3) });

            expr.CompileToMethod(builder);

            return (Func<T1, T2, T3, TResult>) Delegate.CreateDelegate(typeof (Func<T1, T2, T3, TResult>), typeBuilder.CreateType().GetMethod("Method"));
        }

        public static TMethod CompileToDelegate<TMethod>(Expression<TMethod> expr, AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            var typeBuilder = CreateTypeBuilder(access);

            GetMethodParms<TMethod>(out var parameterTypes, out var returnType);

            var builder = typeBuilder.DefineMethod("Method",
                MethodAttributes.Public | MethodAttributes.Static, // CompileToMethod requires a static method
                returnType, parameterTypes);

            expr.CompileToMethod(builder);

            return (TMethod) (object) Delegate.CreateDelegate(typeof (TMethod), typeBuilder.CreateType().GetMethod("Method"));
        }

        public static TMethod[] CompileToDelegates<TMethod>(params Expression<TMethod>[] exprs)
            => CompileToDelegates(AssemblyBuilderAccess.RunAndCollect, exprs);

        public static TMethod[] CompileToDelegates<TMethod>(AssemblyBuilderAccess access, params Expression<TMethod>[] exprs)
        {
            var typeBuilder = CreateTypeBuilder(access);

            GetMethodParms<TMethod>(out var parameterTypes, out var returnType);

            var i = 0;
            foreach (var expr in exprs)
            {
                var builder = typeBuilder.DefineMethod($"Method_{i++}",
                    MethodAttributes.Public | MethodAttributes.Static, // CompileToMethod requires a static method
                    returnType, parameterTypes);

                expr.CompileToMethod(builder);
            }

            var type = typeBuilder.CreateType();

            var methods = new TMethod[exprs.Length];
            for (i = 0; i < exprs.Length; i++)
                methods[i] = (TMethod) (object) Delegate.CreateDelegate(typeof (TMethod), type.GetMethod($"Method_{i++}"));
            return methods;
        }

        private static TypeBuilder CreateTypeBuilder(AssemblyBuilderAccess access = DefaultAssemblyBuilderAccess)
        {
            var assemblyName = new AssemblyName("Umbraco.Core.DynamicAssemblies." + Guid.NewGuid().ToString("N"));
            var assembly = AppDomain.CurrentDomain.DefineDynamicAssembly(assemblyName, access);

            var module = (access & AssemblyBuilderAccess.Save) > 0
                ? assembly.DefineDynamicModule(assemblyName.Name, assemblyName.Name + ".dll")
                : assembly.DefineDynamicModule(assemblyName.Name); // has to be transient

            return module.DefineType("Class", TypeAttributes.Public | TypeAttributes.Abstract);
        }
    }
}