fix(ghosts): correct replay rendering and sampling

Author: wopian

Ghosting/Ghosts/GhostBase.cs

@@ -3,8 +3,139 @@
 
 namespace TNRD.Zeepkist.GTR.Ghosting.Ghosts;
 
+internal readonly struct GhostFrameSample
+{
+    internal GhostFrameSample(int currentIndex, int nextIndex, float interpolation)
+    {
+        CurrentIndex = currentIndex;
+        NextIndex = nextIndex;
+        Interpolation = interpolation;
+    }
+
+    internal int CurrentIndex { get; }
+    internal int NextIndex { get; }
+    internal float Interpolation { get; }
+}
+
 internal static class GhostFrameSearch
 {
+    internal static bool TryGetFrameSample(
+        int frameCount,
+        float time,
+        Func<int, float> getTimeAtIndex,
+        out GhostFrameSample sample)
+    {
+        sample = default;
+        if (frameCount <= 0)
+            return false;
+
+        if (frameCount == 1 || time < getTimeAtIndex(0))
+        {
+            sample = new GhostFrameSample(0, 0, 0f);
+            return true;
+        }
+
+        int currentIndex = FindLastFrameIndexAtOrBeforeTime(frameCount, time, getTimeAtIndex);
+        if (currentIndex < 0)
+        {
+            sample = new GhostFrameSample(0, 0, 0f);
+            return true;
+        }
+
+        if (currentIndex >= frameCount - 1)
+        {
+            int lastIndex = frameCount - 1;
+            sample = new GhostFrameSample(lastIndex, lastIndex, 0f);
+            return true;
+        }
+
+        int nextIndex = currentIndex + 1;
+        float currentTime = getTimeAtIndex(currentIndex);
+        float nextTime = getTimeAtIndex(nextIndex);
+        float interpolation = nextTime > currentTime
+            ? (time - currentTime) / (nextTime - currentTime)
+            : 0f;
+        if (interpolation < 0f)
+            interpolation = 0f;
+        else if (interpolation > 1f)
+            interpolation = 1f;
+
+        sample = new GhostFrameSample(currentIndex, nextIndex, interpolation);
+        return true;
+    }
+
+    internal static bool TryGetFrameSample(
+        int frameCount,
+        float time,
+        int currentIndexHint,
+        Func<int, float> getTimeAtIndex,
+        out GhostFrameSample sample)
+    {
+        sample = default;
+        if (frameCount <= 0)
+            return false;
+
+        if (currentIndexHint < 0 || currentIndexHint >= frameCount)
+            return TryGetFrameSample(frameCount, time, getTimeAtIndex, out sample);
+
+        float currentTime = getTimeAtIndex(currentIndexHint);
+        if (time < currentTime)
+        {
+            if (currentIndexHint == 0)
+            {
+                sample = new GhostFrameSample(0, 0, 0f);
+                return true;
+            }
+
+            return TryGetFrameSample(frameCount, time, getTimeAtIndex, out sample);
+        }
+
+        int currentIndex = currentIndexHint;
+        while (currentIndex < frameCount - 1)
+        {
+            int nextIndex = currentIndex + 1;
+            float nextTime = getTimeAtIndex(nextIndex);
+            if (nextTime > time)
+            {
+                float interpolation = nextTime > currentTime
+                    ? (time - currentTime) / (nextTime - currentTime)
+                    : 0f;
+                if (interpolation < 0f)
+                    interpolation = 0f;
+                else if (interpolation > 1f)
+                    interpolation = 1f;
+
+                sample = new GhostFrameSample(currentIndex, nextIndex, interpolation);
+                return true;
+            }
+
+            currentIndex++;
+            currentTime = nextTime;
+        }
+
+        sample = new GhostFrameSample(currentIndex, currentIndex, 0f);
+        return true;
+    }
+
+    private static int FindLastFrameIndexAtOrBeforeTime(
+        int frameCount,
+        float time,
+        Func<int, float> getTimeAtIndex)
+    {
+        int low = 0;
+        int high = frameCount;
+        while (low < high)
+        {
+            int mid = (low + high) >> 1;
+            if (getTimeAtIndex(mid) <= time)
+                low = mid + 1;
+            else
+                high = mid;
+        }
+
+        return low - 1;
+    }
+
     internal static int FindFirstFrameIndexAtOrAfterTime(
         int frameCount,
         float time,
@@ -41,7 +172,7 @@ internal static bool TryGetAdjacentFrameTime(
         out float adjacentTime)
     {
         adjacentTime = 0f;
-        if (frameCount <= 0 || direction is not (1 or -1))
+        if (frameCount <= 1 || direction is not (1 or -1))
             return false;
 
         if (direction > 0)

Ghosting/Ghosts/GhostFrameSearch.cs

@@ -7,11 +7,15 @@ public interface IGhost
 {
     Color Color { get; }
     float Duration { get; }
-    void Initialize(GhostData ghost);
+    void Initialize(
+        GhostData ghost,
+        BulkGhostModeState bulkModeState,
+        GhostTimingService timingService);
     void ApplyCosmetics(string steamName);
-    void Start();
-    void Stop();
+    void Start(float time);
+    void Stop(float time);
     void Seek(float time);
-    void Update();
-    void FixedUpdate();
+    void Pause(float time);
+    void Resume(float time);
+    void Sample(float time);
 }

Ghosting/Ghosts/IGhost.cs

@@ -11,8 +11,7 @@ public partial class V1Ghost : GhostBase
 {
     private readonly List<Frame> _frames;
 
-    public V1Ghost(GhostTimingService timingService, BulkGhostModeState bulkModeState, List<Frame> frames)
-        : base(timingService, bulkModeState)
+    public V1Ghost(List<Frame> frames)
     {
         _frames = frames;
     }

Ghosting/Ghosts/V1Ghost.cs

@@ -15,13 +15,11 @@ public partial class V2Ghost : GhostBase
     private readonly List<Frame> _frames;
 
     public V2Ghost(
-        GhostTimingService timingService,
-        BulkGhostModeState bulkModeState,
         ulong steamId,
         int soapboxId,
         int hatId,
         int colorId,
-        List<Frame> frames) : base(timingService, bulkModeState)
+        List<Frame> frames)
     {
         _steamId = steamId;
         _soapboxId = soapboxId;

Ghosting/Ghosts/V2Ghost.cs

@@ -15,13 +15,11 @@ public partial class V3Ghost : GhostBase, IGhostInputProvider
     private readonly List<Frame> _frames;
 
     public V3Ghost(
-        GhostTimingService timingService,
-        BulkGhostModeState bulkModeState,
         ulong steamId,
         int soapboxId,
         int hatId,
         int colorId,
-        List<Frame> frames) : base(timingService, bulkModeState)
+        List<Frame> frames)
     {
         _steamId = steamId;
         _soapboxId = soapboxId;

Ghosting/Ghosts/V3Ghost.cs

@@ -15,13 +15,11 @@ public partial class V4Ghost : GhostBase, IGhostInputProvider
     private readonly List<Frame> _frames;
 
     public V4Ghost(
-        GhostTimingService timingService,
-        BulkGhostModeState bulkModeState,
         ulong steamId,
         int soapboxId,
         int hatId,
         int colorId,
-        List<Frame> frames) : base(timingService, bulkModeState)
+        List<Frame> frames)
     {
         _steamId = steamId;
         _soapboxId = soapboxId;