NejCommon.NET/Models/Api/ModelBinder.cs

using AngleSharp.Dom;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Abstractions;
using Microsoft.AspNetCore.Mvc.ApiExplorer;
using Microsoft.AspNetCore.Mvc.Controllers;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.ModelBinding.Binders;
using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
using Microsoft.AspNetCore.Mvc.Routing;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using Microsoft.OpenApi.Models;
using Swashbuckle.AspNetCore.SwaggerGen;
using System.Linq.Expressions;
using System.Reflection;
using System.Reflection.Emit;
using System.Runtime.CompilerServices;

namespace NejCommon.Models
{
    public abstract class RouteValue
    {
        public string Name { get; }
        public bool Primary { get; } = false;

        public RouteValue(string name, bool primary = false)
        {
            Name = name;
            Primary = primary;
        }
    }

    public class RouteValue<TEntity> : RouteValue where TEntity : class
    {
        public Expression<Func<TEntity, string, bool>> Expression { get; }

        public RouteValue(string name, Expression<Func<TEntity, string, bool>> expression) : base(name)
        {
            Expression = expression;
        }
        public RouteValue(string name, bool primary, Expression<Func<TEntity, string, bool>> expression) : base(name, primary)
        {
            Expression = expression;
        }
    }


    public abstract class EntityBinder
    {
    }

    public abstract class EntityBinder<TEntity> : EntityBinder<TEntity, string> where TEntity : class
    {
        public EntityBinder(DbContext db, RouteValue<TEntity>[] routeValues) : base(db, routeValues)
        {
        }
    }


    //id should be Guid, int, string, etc.
    public abstract class EntityBinder<TEntity, TIdType> : EntityBinder, IModelBinder, IScopedService
        where TEntity : class
        where TIdType : IEquatable<TIdType>
    {
        private readonly DbContext _db;
        private readonly RouteValue<TEntity>[] _routeValues;

        public RouteValue<TEntity>[] RouteValues => _routeValues;


        public EntityBinder(DbContext db, RouteValue<TEntity>[] routeValues)
        {
            _db = db;
            _routeValues = routeValues;
        }

        public async Task BindModelAsync(ModelBindingContext bindingContext)
        {
            if (bindingContext == null)
            {
                throw new ArgumentNullException(nameof(bindingContext));
            }

            //get the binding parameter attributes

            // Fetch the route values from the route data
            var capturedRouteData = new Dictionary<string, object>();
            foreach (var routeValue in _routeValues)
            {
                var name = routeValue.Name;
                if (routeValue.Primary && !string.IsNullOrWhiteSpace(bindingContext.ModelName))
                {
                    name = bindingContext.ModelName;
                }

                /*
                                Console.WriteLine("Route value: " + name);
                                Console.WriteLine();
                                Console.WriteLine(bindingContext.ActionContext.RouteData.Values[name]);
                                */

                var value = bindingContext.ValueProvider.GetValue(name).FirstOrDefault();//bindingContext.ActionContext.RouteData.Values[name];

                if (value is null)
                {
                    bindingContext.ModelState.AddModelError(name, "Route value not found");
                }
                else
                {
                    capturedRouteData[routeValue.Name] = value;
                }
            }

            // Check if all the required route values are present
            if (!bindingContext.ModelState.IsValid)
            {
                bindingContext.Result = ModelBindingResult.Failed();
                return;
            }

            // Find the entity with the specified route values
            var query = _db.Set<TEntity>().AsQueryable();
            foreach (var routeValue in _routeValues)
            {
                var value = capturedRouteData[routeValue.Name];

                var par = Expression.Parameter(typeof(TEntity));
                var exp = Expression.Invoke(routeValue.Expression, par, Expression.Constant((string)value));
                var redExp = exp.Reduce();
                var compiledExp = Expression.Lambda<Func<TEntity, bool>>(redExp, par);

                query = query.Where(compiledExp);
            }

            var model = await query.FirstOrDefaultAsync();

            if (model == null)
            {
                bindingContext.HttpContext.Response.StatusCode = 404;
                bindingContext.ModelState.AddModelError(bindingContext.FieldName, "Not found in DB");
                bindingContext.Result = ModelBindingResult.Failed();
                return;
            }
            bindingContext.Result = ModelBindingResult.Success(model);
            bindingContext.ValidationState[bindingContext.Result] = new ValidationStateEntry
            {
                SuppressValidation = true
            };
        }
    }

    public class EntityBinderOperationFilter : IOperationFilter
    {
        public object CreateDummyInstance(Type entityBinderType)
        {
            var constructors = entityBinderType.GetConstructors();
            var constructor = constructors.OrderBy(x => x.GetParameters().Count()).First();
            var constructorParameters = constructor.GetParameters();

            var entityBinder = (EntityBinder)constructor.Invoke(constructorParameters.Select(x => (object?)null).ToArray());
            return entityBinder;
        }

        public void Apply(OpenApiOperation operation, OperationFilterContext context)
        {
            var actionDescriptor = context.ApiDescription.ActionDescriptor;

            // Get the action parameters with a ModelBinder attribute
            var modelBinderParameters = actionDescriptor.Parameters
                .Where(p => p.BindingInfo?.BinderType != null && typeof(EntityBinder).IsAssignableFrom(p.BindingInfo.BinderType))
                .Where(x => x != null)
                .ToList();
            if (modelBinderParameters.Count == 0)
            {
                return;
            }

            //Console.WriteLine("Applying EntityBinderOperationFilter to: " + actionDescriptor.DisplayName);

            operation.Parameters = operation.Parameters.Where(p => !modelBinderParameters.Any(mp => mp.Name == p.Name)).ToList();

            /*
            // Get the EntityBinder RouteValues
            foreach (var parameter in modelBinderParameters)
            {
                var entityBinderType = parameter.BindingInfo!.BinderType;
                var routeValuesProperty = entityBinderType!.GetProperty("RouteValues");
                if (routeValuesProperty == null)
                {
                    continue;
                }

                var routeValues = (IEnumerable<RouteValue>?)routeValuesProperty.GetValue(CreateDummyInstance(entityBinderType));
                if (routeValues == null)
                {
                    continue;
                }
                foreach (var routeValue in routeValues)
                {
                    operation.Parameters.Add(new OpenApiParameter
                    {
                        Name = routeValue.Name,
                        In = ParameterLocation.Path,
                        Required = true,
                        Schema = new OpenApiSchema
                        {
                            Type = "string"
                        }
                    });

                }
            }*/

            // Exclude the EntityBinder parameter types from the document schemas
            var schemaRep = context.SchemaRepository;
            foreach (var parameter in modelBinderParameters)
            {
                var entityBinderType = parameter.BindingInfo?.BinderType;

                // Get the EntityBinder generic type argument
                var entityType = GetBinderEntityType(entityBinderType);
                if (entityType == null)
                {
                    Console.WriteLine("Couldn't find entityType of: " + entityBinderType);
                    continue;
                }

                if (schemaRep.Schemas.ContainsKey(entityType.Name))
                {
                    //Console.WriteLine("Removing schema: " + entityType.Name);
                    schemaRep.Schemas.Remove(entityType.Name);
                }
            }
        }

        private Type? GetBinderEntityType(Type? binderType)
        {
            if (binderType == null)
                return null;
            if (binderType.IsGenericType && binderType.GetGenericTypeDefinition() == typeof(EntityBinder<>))
            {
                return binderType.GetTypeInfo().GetGenericArguments().FirstOrDefault();
            }
            return GetBinderEntityType(binderType.BaseType);
        }
    }


    [AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = true)]
    public sealed class EntityAttribute<TEntityBinder, TEntity> : Attribute, IPropertyValidationFilter, IApiDescriptionVisibilityProvider, IBinderTypeProviderMetadata where TEntityBinder : EntityBinder<TEntity> where TEntity : class
    {
        /// <inheritdoc />
        public bool ShouldValidateEntry(ValidationEntry entry, ValidationEntry parentEntry)
        {
            return false;
        }

        /// <inheritdoc />
        public Type? BinderType => typeof(TEntityBinder);

        /// <inheritdoc />
        public BindingSource? BindingSource => BindingSource.Custom;

        public bool IgnoreApi => true;
    }
}