using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;
using Microsoft.AspNetCore.Mvc.ModelBinding;

namespace Diary.Shared
{
	public class ValidationFilter : IAsyncActionFilter
	{
		public const string OverviewTitle = "The request is invalid.";
		public const string OverviewMessage = "The request sent data that is not correct for the request.";

		public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
		{
			if (context.ModelState.IsValid)
			{
				await next();
			}
			else
			{
				ValidationExceptionDetails errorObj = new()
				{
					Title = OverviewTitle,
					Message = OverviewMessage,
					ModelState = GetErrors(context.ModelState)
				};
				context.Result = new BadRequestObjectResult(errorObj);
			}
		}

		private static List<ValidationProblemDescriptor> GetErrors(ModelStateDictionary modelState)
		{
			List<ValidationProblemDescriptor> errors = new();

			return modelState.Where(ms => ms.Value?.Errors.Count > 0)
					.Select(x => new ValidationProblemDescriptor
					{
						Property = x.Key,
						Errors = x.Value?.Errors.Select(e => e.ErrorMessage).ToArray()
					})
					.ToList();
		}
	}
}