improve episode sorting with embedded specials

MediaBrowser.Server.Implementations/Sorting/AiredEpisodeOrderComparer.cs

@@ -0,0 +1,134 @@
+using System;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Entities.TV;
+using MediaBrowser.Controller.Sorting;
+using MediaBrowser.Model.Querying;
+
+namespace MediaBrowser.Server.Implementations.Sorting
+{
+    class AiredEpisodeOrderComparer : IBaseItemComparer
+    {
+        /// <summary>
+        /// Compares the specified x.
+        /// </summary>
+        /// <param name="x">The x.</param>
+        /// <param name="y">The y.</param>
+        /// <returns>System.Int32.</returns>
+        public int Compare(BaseItem x, BaseItem y)
+        {
+            var val = DateTime.Compare(x.PremiereDate ?? DateTime.MinValue, y.PremiereDate ?? DateTime.MinValue);
+
+            if (val != 0)
+            {
+                return val;
+            }
+
+            var episode1 = x as Episode;
+            var episode2 = y as Episode;
+
+            if (episode1 == null)
+            {
+                if (episode2 == null)
+                {
+                    return 0;
+                }
+
+                return 1;
+            }
+
+            if (episode2 == null)
+            {
+                return -1;
+            }
+
+            return Compare(episode1, episode2);
+        }
+
+        private int Compare(Episode x, Episode y)
+        {
+            var isXSpecial = (x.ParentIndexNumber ?? -1) == 0;
+            var isYSpecial = (y.ParentIndexNumber ?? -1) == 0;
+
+            if (isXSpecial && isYSpecial)
+            {
+                return CompareSpecials(x, y);
+            }
+
+            if (!isXSpecial && !isYSpecial)
+            {
+                return CompareEpisodes(x, y);
+            }
+
+            if (!isXSpecial && isYSpecial)
+            {
+                return CompareEpisodeToSpecial(x, y);
+            }
+
+            return CompareEpisodeToSpecial(x, y) * -1;
+        }
+
+        private int CompareEpisodeToSpecial(Episode x, Episode y)
+        {
+            var xSeason = x.ParentIndexNumber ?? -1;
+            var ySeason = y.AirsAfterSeasonNumber ?? y.AirsBeforeSeasonNumber ?? -1;
+
+            if (xSeason != ySeason)
+            {
+                return xSeason.CompareTo(ySeason);
+            }
+
+            // Now we know they have the same season
+
+            // Compare episode number
+
+            // Add 1 to to non-specials to account for AirsBeforeEpisodeNumber
+            var xEpisode = (x.IndexNumber ?? 0) * 1000 + 1;
+            var yEpisode = (y.AirsBeforeEpisodeNumber ?? 0) * 1000;
+
+            return xEpisode.CompareTo(yEpisode);
+        }
+
+        private int CompareSpecials(Episode x, Episode y)
+        {
+            return GetSpecialCompareValue(x).CompareTo(GetSpecialCompareValue(y));
+        }
+
+        private int GetSpecialCompareValue(Episode item)
+        {
+            // First sort by season number
+            // Since there are three sort orders, pad with 9 digits (3 for each, figure 1000 episode buffer should be enough)
+            var val = (item.AirsBeforeSeasonNumber ?? item.AirsAfterSeasonNumber ?? 0) * 1000000000;
+
+            // Second sort order is if it airs after the season
+            if (item.AirsAfterSeasonNumber.HasValue)
+            {
+                val += 1000000;
+            }
+
+            // Third level is the episode number
+            val += (item.AirsBeforeEpisodeNumber ?? 0) * 1000;
+
+            // Finally, if that's still the same, last resort is the special number itself
+            val += item.IndexNumber ?? 0;
+
+            return val;
+        }
+
+        private int CompareEpisodes(Episode x, Episode y)
+        {
+            var xValue = ((x.ParentIndexNumber ?? -1) * 1000) + (x.IndexNumber ?? -1);
+            var yValue = ((y.ParentIndexNumber ?? -1) * 1000) + (y.IndexNumber ?? -1);
+
+            return xValue.CompareTo(yValue);
+        }
+
+        /// <summary>
+        /// Gets the name.
+        /// </summary>
+        /// <value>The name.</value>
+        public string Name
+        {
+            get { return ItemSortBy.AiredEpisodeOrder; }
+        }
+    }
+}