use full preferred language names in ui (#137)

ErsatzTV.Infrastructure/Data/Repositories/MediaItemRepository.cs

@@ -1,6 +1,8 @@
 using System.Collections.Generic;
+using System.Data;
 using System.Linq;
 using System.Threading.Tasks;
+using Dapper;
 using ErsatzTV.Core.Domain;
 using ErsatzTV.Core.Interfaces.Repositories;
 using LanguageExt;
@@ -11,10 +13,14 @@ namespace ErsatzTV.Infrastructure.Data.Repositories
 {
     public class MediaItemRepository : IMediaItemRepository
     {
+        private readonly IDbConnection _dbConnection;
         private readonly IDbContextFactory<TvContext> _dbContextFactory;
 
-        public MediaItemRepository(IDbContextFactory<TvContext> dbContextFactory) =>
+        public MediaItemRepository(IDbContextFactory<TvContext> dbContextFactory, IDbConnection dbConnection)
+        {
             _dbContextFactory = dbContextFactory;
+            _dbConnection = dbConnection;
+        }
 
         public async Task<Option<MediaItem>> Get(int id)
         {
@@ -38,5 +44,16 @@ namespace ErsatzTV.Infrastructure.Data.Repositories
             context.MediaItems.Update(mediaItem);
             return await context.SaveChangesAsync() > 0;
         }
+
+        public Task<List<string>> GetAllLanguageCodes() =>
+            _dbConnection.QueryAsync<string>(
+                    @"SELECT LanguageCode FROM
+                    (SELECT Language AS LanguageCode
+                    FROM MediaStream WHERE Language IS NOT NULL
+                    UNION ALL SELECT PreferredLanguageCode AS LanguageCode
+                    FROM Channel WHERE PreferredLanguageCode IS NOT NULL)
+                    GROUP BY LanguageCode
+                    ORDER BY COUNT(LanguageCode) DESC")
+                .Map(result => result.ToList());
     }
 }