From 72c8ae8705bae27510e112b311237f3df4ff749a Mon Sep 17 00:00:00 2001
From: smoogipoo <smoogipoo@smgi.me>
Date: Fri, 12 Oct 2018 16:47:18 +0900
Subject: [PATCH] Port the old stacking algorithm

---
 .../Beatmaps/OsuBeatmapProcessor.cs           | 55 ++++++++++++++++---
 1 file changed, 48 insertions(+), 7 deletions(-)

diff --git a/osu.Game.Rulesets.Osu/Beatmaps/OsuBeatmapProcessor.cs b/osu.Game.Rulesets.Osu/Beatmaps/OsuBeatmapProcessor.cs
index cfb1b0f050..db80948c94 100644
--- a/osu.Game.Rulesets.Osu/Beatmaps/OsuBeatmapProcessor.cs
+++ b/osu.Game.Rulesets.Osu/Beatmaps/OsuBeatmapProcessor.cs
@@ -10,6 +10,8 @@ namespace osu.Game.Rulesets.Osu.Beatmaps
 {
     public class OsuBeatmapProcessor : BeatmapProcessor
     {
+        private const int stack_distance = 3;
+
         public OsuBeatmapProcessor(IBeatmap beatmap)
             : base(beatmap)
         {
@@ -18,17 +20,21 @@ namespace osu.Game.Rulesets.Osu.Beatmaps
         public override void PostProcess()
         {
             base.PostProcess();
-            applyStacking((Beatmap<OsuHitObject>)Beatmap);
+
+            var osuBeatmap = (Beatmap<OsuHitObject>)Beatmap;
+
+            // Reset stacking
+            foreach (var h in osuBeatmap.HitObjects)
+                h.StackHeight = 0;
+
+            if (Beatmap.BeatmapInfo.BeatmapVersion >= 6)
+                applyStacking(osuBeatmap);
+            else
+                applyStackingOld(osuBeatmap);
         }
 
         private void applyStacking(Beatmap<OsuHitObject> beatmap)
         {
-            const int stack_distance = 3;
-
-            // Reset stacking
-            for (int i = 0; i <= beatmap.HitObjects.Count - 1; i++)
-                beatmap.HitObjects[i].StackHeight = 0;
-
             // Extend the end index to include objects they are stacked on
             int extendedEndIndex = beatmap.HitObjects.Count - 1;
             for (int i = beatmap.HitObjects.Count - 1; i >= 0; i--)
@@ -167,5 +173,40 @@ namespace osu.Game.Rulesets.Osu.Beatmaps
                 }
             }
         }
+
+        private void applyStackingOld(Beatmap<OsuHitObject> beatmap)
+        {
+            for (int i = 0; i < beatmap.HitObjects.Count; i++)
+            {
+                OsuHitObject currHitObject = beatmap.HitObjects[i];
+
+                if (currHitObject.StackHeight != 0 && !(currHitObject is Slider))
+                    continue;
+
+                double startTime = (currHitObject as IHasEndTime)?.EndTime ?? currHitObject.StartTime;
+                int sliderStack = 0;
+
+                for (int j = i + 1; j < beatmap.HitObjects.Count; j++)
+                {
+                    double stackThreshold = beatmap.HitObjects[i].TimePreempt * beatmap.BeatmapInfo.StackLeniency;
+
+                    if (beatmap.HitObjects[j].StartTime - stackThreshold > startTime)
+                        break;
+
+                    if (Vector2Extensions.Distance(beatmap.HitObjects[j].Position, currHitObject.Position) < stack_distance)
+                    {
+                        currHitObject.StackHeight++;
+                        startTime = (beatmap.HitObjects[j] as IHasEndTime)?.EndTime ?? beatmap.HitObjects[i].StartTime;
+                    }
+                    else if (Vector2Extensions.Distance(beatmap.HitObjects[j].Position, currHitObject.EndPosition) < stack_distance)
+                    {
+                        //Case for sliders - bump notes down and right, rather than up and left.
+                        sliderStack++;
+                        beatmap.HitObjects[j].StackHeight -= sliderStack;
+                        startTime = (beatmap.HitObjects[j] as IHasEndTime)?.EndTime ?? beatmap.HitObjects[i].StartTime;
+                    }
+                }
+            }
+        }
     }
 }