using System.Globalization;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Localization;

namespace gehGassi.Web.Helper
{
    /// <summary>
    /// Hilfsklasse die das Routing basierend auf Cultures implementiert und die gewählte Sprache setzt
    /// </summary>
    public class RouteValueRequestCultureProvider : RequestCultureProvider
    {
        /// <inheritdoc />
        public override Task<ProviderCultureResult> DetermineProviderCultureResult(HttpContext httpContext)
        {
            string cultureCode = null;

            if (httpContext.Request.Path.HasValue && httpContext.Request.Path.Value == "/")
                cultureCode = CultureInfo.CurrentCulture.TwoLetterISOLanguageName; //this.GetDefaultCultureCode();

            else if (httpContext.Request.Path.HasValue && httpContext.Request.Path.Value.Length >= 4 && httpContext.Request.Path.Value[0] == '/' && httpContext.Request.Path.Value[3] == '/')
            {
                cultureCode = httpContext.Request.Path.Value.Substring(1, 2);

                if (!this.CheckCultureCode(cultureCode))
                    cultureCode = this.GetDefaultCultureCode(); //throw new HttpException(HttpStatusCode.NotFound);
            }
            else if (httpContext.Request.Path.HasValue && httpContext.Request.Path.Value.Length == 3 && httpContext.Request.Path.Value[0] == '/')
            {
                cultureCode = httpContext.Request.Path.Value.Substring(1, 2);

                if (!this.CheckCultureCode(cultureCode))
                    cultureCode = this.GetDefaultCultureCode(); //throw new HttpException(HttpStatusCode.NotFound);
            }
            else cultureCode = this.GetDefaultCultureCode(); //throw new HttpException(HttpStatusCode.NotFound);

            ProviderCultureResult requestCulture = new ProviderCultureResult(cultureCode);

            return Task.FromResult(requestCulture);
        }

        /// <summary>
        /// Standard-Culture holen
        /// </summary>
        /// <returns>Standard-Culture</returns>
        private string GetDefaultCultureCode()
        {
            return this.Options.DefaultRequestCulture.Culture.TwoLetterISOLanguageName;
        }

        /// <summary>
        /// Prüft ob die gewählte Culture unterstützt wird
        /// </summary>
        /// <param name="cultureCode">Culture</param>
        /// <returns>true wenn unterstützt, false sonst</returns>
        private bool CheckCultureCode(string cultureCode)
        {
            return this.Options.SupportedCultures.Select(c => c.TwoLetterISOLanguageName).Contains(cultureCode);
        }
    }
}