luticate2-api/Luticate2.Auth/Utils/Business/ExpressionConverter/LuExpressionConverterVisito...

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using Luticate2.Auth.Utils.Dbo;
using Luticate2.Auth.Utils.Dbo.Result;
using Luticate2.Auth.Utils.Exceptions;
using Luticate2.Auth.Utils.Interfaces;

namespace Luticate2.Auth.Utils.Business.ExpressionConverter
{
    public class LuExpressionConverterVisitor : ExpressionVisitor
    {
        public LuExpressionConverterOptions Options { get; }

        protected IServiceProvider ServiceProvider { get; }

        public LuExpressionConverterVisitor(LuExpressionConverterOptions options, IServiceProvider serviceProvider)
        {
            Options = options;
            ServiceProvider = serviceProvider;
        }

        protected LuResult<Stack<Expression>> StackSimpleExpression(Expression expression, Stack<Expression> stack)
        {
            stack.Push(expression);
            if (expression is MemberExpression memberExpression)
            {
                if (memberExpression.Expression != null)
                {
                    var result = StackSimpleExpression(memberExpression.Expression, stack);
                    return result;
                }
                return LuResult<Stack<Expression>>.Ok(stack);
            }
            else if (expression is MethodCallExpression methodCallExpression)
            {
                if (methodCallExpression.Object != null)
                {
                    var result = StackSimpleExpression(methodCallExpression.Object, stack);
                    return result;
                }
                return LuResult<Stack<Expression>>.Ok(stack);
            }
            else
            {
                return LuResult<Stack<Expression>>.Ok(stack);
            }
        }

        protected ILuObjectConverterDescriptor GetConverterDescriptor(Type typeFrom, Type typeTo)
        {
            var type = typeof(ILuObjectConverterDescriptor<,>);
            var gtype = type.MakeGenericType(typeFrom, typeTo);
            var descriptor = (ILuObjectConverterDescriptor) ServiceProvider.GetService(gtype);
            if (descriptor == null && typeFrom == typeTo)
            {
                descriptor = (ILuObjectConverterDescriptor) ServiceProvider.GetService(typeof(ILuObjectConverterDescriptorIdentity));
            }
            return descriptor;
        }

        protected LuResult<Expression> ConvertMemberExpression(MemberExpression memberExpression, Expression newExpression, Type typeTo)
        {
            var typeFrom = memberExpression.Expression == null ? memberExpression.Member.DeclaringType : memberExpression.Expression.Type;
            var descriptor = GetConverterDescriptor(typeFrom, typeTo);
            if (descriptor == null)
            {
                return LuResult<Expression>.Error(LuStatus.InternalError.ToInt(),
                    $"Could not find converter descriptor for {typeFrom} => {typeTo}");
            }

            var valueExpression = descriptor.GetMemberValueExpression(memberExpression.Member, Options.Types);
            if (valueExpression == null)
            {
                return LuResult<Expression>.Error(LuStatus.InternalError.ToInt(),
                    $"Could not find converter descriptor lambda for {typeFrom} => {typeTo} => {memberExpression.Member}");
            }
            if (valueExpression.Parameters[0].Type != typeTo)
            {
                return LuResult<Expression>.Error(LuStatus.InternalError.ToInt(),
                    $"Invalid conversion lambda for {typeFrom} => {typeTo}");
            }

            if (newExpression != null)
            {
                Options.Parameters.Add(valueExpression.Parameters[0], newExpression);
            }

            var visitor = new LuExpressionParamReplaceVisitor(Options);
            var replacedExpression = visitor.Visit(valueExpression.Body);
            newExpression = LuExpressionUtils.GetFromConvert(replacedExpression);

            if (newExpression != null)
            {
                Options.Parameters.Remove(valueExpression.Parameters[0]);
            }

            return LuResult<Expression>.Ok(newExpression);
        }

        protected LuResult<Expression> ConvertMethodCallExpression(MethodCallExpression methodCallExpression, Expression newExpression, Type typeTo)
        {
            var typeFrom = methodCallExpression.Object == null ? methodCallExpression.Method.DeclaringType : methodCallExpression.Object.Type;
            var descriptor = GetConverterDescriptor(typeFrom, typeTo);
            if (descriptor == null)
            {
                return LuResult<Expression>.Error(LuStatus.InternalError.ToInt(),
                    $"Could not find converter descriptor for {typeFrom} => {typeTo}");
            }

            var valueExpression = descriptor.GetMethodValueExpression(methodCallExpression.Method, Options.Types);
            if (valueExpression == null)
            {
                return LuResult<Expression>.Error(LuStatus.InternalError.ToInt(),
                    $"Could not find converter descriptor lambda for {typeFrom} => {typeTo} => {methodCallExpression.Method}");
            }
            if (valueExpression.Parameters.Count != methodCallExpression.Arguments.Count + 1)
            {
                return LuResult<Expression>.Error(LuStatus.InternalError.ToInt(),
                    $"Converter descriptor lambda has incorrect number of arguments for {typeFrom} => {typeTo} => {methodCallExpression.Method}");
            }
            if (valueExpression.Parameters[0].Type != typeTo)
            {
                return LuResult<Expression>.Error(LuStatus.InternalError.ToInt(),
                    $"Invalid conversion lambda for {typeFrom} => {typeTo}");
            }

            var visitorConverter = new LuExpressionConverterVisitor(Options, ServiceProvider);
            for (var i = 0; i < methodCallExpression.Arguments.Count; ++i)
            {
                var convertedArgument = visitorConverter.Visit(methodCallExpression.Arguments[i]);
                Options.Parameters.Add(valueExpression.Parameters[i + 1], convertedArgument);
            }
            Options.Parameters.Add(valueExpression.Parameters[0], newExpression);
            var visitor = new LuExpressionParamReplaceVisitor(Options);
            var replacedExpression = visitor.Visit(valueExpression.Body);
            newExpression = LuExpressionUtils.GetFromConvert(replacedExpression);
            Options.Parameters.Remove(valueExpression.Parameters[0]);

            return LuResult<Expression>.Ok(newExpression);
        }

        protected LuResult<Expression> ReplaceExpression(Expression expression)
        {
            var stackResult = StackSimpleExpression(expression, new Stack<Expression>());
            if (!stackResult)
            {
                return stackResult.To<Expression>();
            }

            Expression newExpression;
            var currentExp = stackResult.Data.Pop();

            if (currentExp is ParameterExpression parameterExpression)
            {
                if (!Options.Parameters.ContainsKey(parameterExpression))
                {
                    return LuResult<Expression>.Error(LuStatus.InternalError.ToInt(),
                        $"Could not find a conversion for parameter {parameterExpression}");
                }
                newExpression = Options.Parameters[parameterExpression];
            }
            else if (currentExp is MemberExpression memberExpression)
            {
                var typeFrom = memberExpression.Member.DeclaringType;
                var typeTo = Options.Types.ContainsKey(typeFrom) ? Options.Types[typeFrom] : typeFrom;

                var convertResult = ConvertMemberExpression(memberExpression, null, typeTo);
                if (!convertResult)
                {
                    return convertResult;
                }

                newExpression = convertResult.Data;
            }
            else if (currentExp is MethodCallExpression methodCallExpression)
            {
                var typeFrom = methodCallExpression.Method.DeclaringType;
                var typeTo = Options.Types.ContainsKey(typeFrom) ? Options.Types[typeFrom] : typeFrom;

                var convertResult = ConvertMethodCallExpression(methodCallExpression, null, typeTo);
                if (!convertResult)
                {
                    return convertResult;
                }

                newExpression = convertResult.Data;
            }
            else
            {
                var visitor = new LuExpressionConverterVisitor(Options, ServiceProvider);
                newExpression = visitor.Visit(currentExp);
            }

            if (newExpression == null)
            {
                return LuResult<Expression>.Error(LuStatus.InternalError.ToInt(),
                    $"Invalid simple expression first member: {currentExp}", "");
            }

            while (stackResult.Data.Any())
            {
                currentExp = stackResult.Data.Pop();

                if (currentExp is MemberExpression memberExpression)
                {
                    var typeTo = newExpression.Type;

                    var convertResult = ConvertMemberExpression(memberExpression, newExpression, typeTo);
                    if (!convertResult)
                    {
                        return convertResult;
                    }

                    newExpression = convertResult.Data;
                }
                else if (currentExp is MethodCallExpression methodCallExpression)
                {
                    var typeTo = newExpression.Type;

                    var convertResult = ConvertMethodCallExpression(methodCallExpression, newExpression, typeTo);
                    if (!convertResult)
                    {
                        return convertResult;
                    }

                    newExpression = convertResult.Data;
                }
                else
                {
                    return LuResult<Expression>.Error(LuStatus.InternalError.ToInt(),
                        $"Unknown expression type (should not happen) {currentExp}");
                }
            }

            return LuResult<Expression>.Ok(newExpression);
        }

        protected override Expression VisitMember(MemberExpression node)
        {
            return ReplaceExpression(node).ThrowIfNotSuccess().Data;
        }

        protected override Expression VisitMethodCall(MethodCallExpression node)
        {
            return ReplaceExpression(node).ThrowIfNotSuccess().Data;
        }

        protected override Expression VisitParameter(ParameterExpression node)
        {
            if (!Options.Parameters.ContainsKey(node))
            {
                LuResult<Expression>.Error(LuStatus.InternalError.ToInt(),
                    $"Could not find a conversion for parameter {node}").Throw();
            }
            return Options.Parameters[node];
        }

        protected override Expression VisitLambda<T>(Expression<T> node)
        {
            var convertedParams = new List<ParameterExpression>();
            foreach (var parameter in node.Parameters)
            {
                // TODO check Options.Types[parameter.Type] access
                var convertedParam = Expression.Parameter(Options.Types[parameter.Type]);
                Options.Parameters.Add(parameter, convertedParam);
                convertedParams.Add(convertedParam);
            }
            var convertedBody = Visit(node.Body);
            foreach (var parameter in node.Parameters)
            {
                Options.Parameters.Remove(parameter);
            }

            var convertedLambda = Expression.Lambda(convertedBody, convertedParams);
            return convertedLambda;
        }
    }
}