laatzen/LaaProductionWeb/LaaProductionWeb.API/Models/ModelResult[T].cs

namespace LaaProductionWeb.API.Models
{
    using Microsoft.AspNetCore.Mvc;
    using Microsoft.AspNetCore.Mvc.ModelBinding;

    using System.Collections.Generic;
    using System.Linq;

    public class ModelResult<T>
    {
        private readonly Dictionary<string, string> errors;

        private ModelResult(bool succeeded)
        {
            this.Succeeded = succeeded;
            this.errors = new Dictionary<string, string>();
        }

        private ModelResult(T value)
        {
            this.Succeeded = true;
            this.Value = value;
        }

        public T Value { get; }

        public bool Succeeded { get; }

        public IReadOnlyDictionary<string, string> ModelErrors 
            => this.errors;

        public void AddModelError(string key, string value)
        {
            if (key != null)
            {
                this.errors[key] = value;
            }
        }

        public static implicit operator ModelResult<T>(T value)
            => new ModelResult<T>(value);

        public static implicit operator ModelResult<T>(KeyValuePair<string, string> error)
        {
            var validationResults = new ModelResult<T>(false);

            validationResults.AddModelError(error.Key, error.Value);

            return validationResults;
        }

        public static implicit operator ModelResult<T>(ModelStateDictionary modelState)
        {
            var validationResults = new ModelResult<T>(false);

            if (modelState != null)
            {
                foreach (var entry in modelState)
                {
                    var errorKey = entry.Key;
                    var errorValue = entry.Value;

                    if (errorValue.ValidationState == ModelValidationState.Invalid && errorValue.Errors.Any())
                    {
                        validationResults.AddModelError(errorKey, errorValue.Errors.First().ErrorMessage);
                    }
                }
            }

            return validationResults;
        }

        public static implicit operator ActionResult(ModelResult<T> modelState)
        {
            if (modelState is null)
            {
                return new NotFoundResult();
            }
            else if (modelState.Succeeded)
            {
                return new OkObjectResult(modelState.Value);
            }

            return new BadRequestObjectResult(modelState.errors);
        }
    }
}