From 1851bd3c54de7d2d0240adbabfc8a947d6a5907b Mon Sep 17 00:00:00 2001
From: PopSlime <popslime@qq.com>
Date: Sun, 5 Mar 2023 20:40:02 +0800
Subject: [PATCH] Fix inaccurate beat snapping for osu charts. Fix osu charts
 with too low BPM not able to be imported.

---
 Assets/Cryville/Common/Math/FractionUtils.cs        |  6 +++---
 Assets/Cryville/Crtr/Extensions/TimingModel.cs      | 13 +++++++++++--
 .../Crtr/Extensions/osu/osuChartConverter.cs        |  3 ++-
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/Assets/Cryville/Common/Math/FractionUtils.cs b/Assets/Cryville/Common/Math/FractionUtils.cs
index b5b8e20..4c1d868 100644
--- a/Assets/Cryville/Common/Math/FractionUtils.cs
+++ b/Assets/Cryville/Common/Math/FractionUtils.cs
@@ -12,12 +12,12 @@ namespace Cryville.Common.Math {
 		/// <param name="error">The error.</param>
 		/// <param name="n">The numerator.</param>
 		/// <param name="d">The denominator.</param>
-		/// <exception cref="ArgumentOutOfRangeException"><paramref name="value" /> is less than 0 or <paramref name="error" /> is not greater than 0 or not less than 1.</exception>
+		/// <exception cref="ArgumentOutOfRangeException"><paramref name="value" /> is less than 0 or <paramref name="error" /> is not greater than 0 or greater than 1.</exception>
 		public static void ToFraction(double value, double error, out int n, out int d) {
 			if (value < 0.0)
 				throw new ArgumentOutOfRangeException("value", "Must be >= 0.");
-			if (error <= 0.0 || error >= 1.0)
-				throw new ArgumentOutOfRangeException("accuracy", "Must be > 0 and < 1.");
+			if (error <= 0.0 || error > 1.0)
+				throw new ArgumentOutOfRangeException("error", "Must be > 0 and <= 1.");
 
 			int num = (int)System.Math.Floor(value);
 			value -= num;
diff --git a/Assets/Cryville/Crtr/Extensions/TimingModel.cs b/Assets/Cryville/Crtr/Extensions/TimingModel.cs
index 8081109..bb6b8f5 100644
--- a/Assets/Cryville/Crtr/Extensions/TimingModel.cs
+++ b/Assets/Cryville/Crtr/Extensions/TimingModel.cs
@@ -42,15 +42,24 @@ namespace Cryville.Crtr.Extensions {
 		}
 	}
 	public class TimeTimingModel : TimingModel {
-		public TimeTimingModel(double offset = 0) : base(offset) { }
+		public readonly double InputTimeAccuracy;
+		public TimeTimingModel(double accuracy = 2e-3, double offset = 0) : base(offset) {
+			if (accuracy <= 0) throw new ArgumentOutOfRangeException("accuracy");
+			InputTimeAccuracy = accuracy;
+		}
 		public void ForwardTo(double t) {
 			if (t == Time) return;
 			if (BPM == 0) throw new InvalidOperationException("BPM not determined");
 			BeatTime += (t - Time) * BPM / 60;
 			int n, d;
-			FractionUtils.ToFraction(BeatTime, 1f / 48 / BPM * 60, out n, out d);
+			FractionUtils.ToFraction(BeatTime, Math.Min(1, InputTimeAccuracy * BPM / 60), out n, out d);
 			FractionalBeatTime = new BeatTime(n, d);
 			Time = t;
 		}
+		public void ForceSnap() {
+			var alignedBeat = (int)Math.Round(BeatTime);
+			BeatTime = alignedBeat;
+			FractionalBeatTime = new BeatTime(alignedBeat, 1);
+		}
 	}
 }
diff --git a/Assets/Cryville/Crtr/Extensions/osu/osuChartConverter.cs b/Assets/Cryville/Crtr/Extensions/osu/osuChartConverter.cs
index c77c860..0f3b929 100644
--- a/Assets/Cryville/Crtr/Extensions/osu/osuChartConverter.cs
+++ b/Assets/Cryville/Crtr/Extensions/osu/osuChartConverter.cs
@@ -108,10 +108,11 @@ namespace Cryville.Crtr.Extensions.osu {
 				else if (ev is osuEvent.TimingChange) {
 					var tev = (osuEvent.TimingChange)ev;
 					if (tm == null) {
-						tm = new TimeTimingModel(tev.StartTime / 1e3);
+						tm = new TimeTimingModel(tev.StartTime / 1e3) { InputTimeAccuracy = 2e-3 };
 						bgmEv.offset = (float)(tev.StartTime / 1e3 + OFFSET);
 					}
 					tm.BeatLength = tev.BeatLength / 1e3;
+					tm.ForceSnap();
 					chart.sigs.Add(new Chart.Signature {
 						time = tm.FractionalBeatTime,
 						tempo = (float)tm.BPM,