using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
using Microsoft.AspNetCore.Mvc.Routing;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.DependencyInjection;
using System.Collections.Generic;

namespace System.ComponentModel.DataAnnotations
{
    public class AjaxSelectAttribute : UIHintAttribute, IClientModelValidator
    {
        protected string RouteName { get; set; }
        protected RouteValueDictionary RouteData { get; } = new RouteValueDictionary();

        public AjaxSelectAttribute(string action, string controller, string areaName = null) : base("AjaxSelect")
        {
            if (action != null)
            {
                RouteData["action"] = action;
            }
            if (controller != null)
            {
                RouteData["controller"] = controller;
            }
            if (controller != null)
            {
                RouteData["area"] = areaName;
            }
        }

        public void AddValidation(ClientModelValidationContext context)
        {
            MergeAttribute(context.Attributes, "data-ajax-url", GetUrl(context));
        }

        private string GetUrl(ClientModelValidationContext context)
        {
            return context.ActionContext.HttpContext.RequestServices.GetRequiredService<IUrlHelperFactory>()
                .GetUrlHelper(context.ActionContext).RouteUrl(new UrlRouteContext
                {
                    RouteName = RouteName,
                    Values = RouteData
                });
        }

        private static void MergeAttribute(IDictionary<string, string> attributes, string key, string value)
        {
            if (!attributes.ContainsKey(key))
            {
                attributes.Add(key, value);
            }
        }
    }
}