Implement stamina evaluator (untested yet)

osu.Game.Rulesets.Taiko/Difficulty/Evaluators/StaminaEvaluator.cs

@@ -0,0 +1,64 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Game.Rulesets.Difficulty.Preprocessing;
+using osu.Game.Rulesets.Difficulty.Skills;
+using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.Taiko.Difficulty.Preprocessing;
+using osu.Game.Rulesets.Taiko.Objects;
+
+namespace osu.Game.Rulesets.Taiko.Difficulty.Evaluators
+{
+    public class StaminaEvaluator
+    {
+        /// <summary>
+        /// Applies a speed bonus dependent on the time since the last hit performed using this key.
+        /// </summary>
+        /// <param name="notePairDuration">The duration between the current and previous note hit using the same key.</param>
+        private static double speedBonus(double notePairDuration)
+        {
+            return 175 / (notePairDuration + 100);
+        }
+
+        /// <summary>
+        /// Evaluates the minimum mechanical stamina required to play the current object. This is calculated using the
+        /// maximum  possible interval between two hits using the same key, by alternating 2 keys for each colour.
+        /// </summary>
+        public static double EvaluateDifficultyOf(DifficultyHitObject current)
+        {
+            if (!(current.BaseObject is Hit))
+            {
+                return 0.0;
+            }
+
+            // Find the previous hit object hit by the current key, which is two notes of the same colour prior.
+            // TODO: This could result in potential performance issue where it has to check the colour of a large amount
+            //       of objects due to previous objects being mono of the other colour. A potential fix for this would be
+            //       to store two separate lists of previous objects, one for each colour.
+            TaikoDifficultyHitObject taikoCurrent = (TaikoDifficultyHitObject)current;
+            TaikoDifficultyHitObject previous = taikoCurrent;
+            int monoNoteInterval = 2; // The amount of same-colour notes to go back
+            double currentKeyInterval = 0; // Interval of the current key being pressed
+            do
+            {
+                previous = (TaikoDifficultyHitObject)previous.Previous(1);
+                if (previous.BaseObject is Hit && previous.HitType == taikoCurrent.HitType)
+                {
+                    --monoNoteInterval;
+                }
+                currentKeyInterval += previous.DeltaTime;
+
+            } while (previous != null && monoNoteInterval > 0);
+
+            // This note is the first press of the current key
+            if (monoNoteInterval > 0)
+            {
+                return 0;
+            }
+
+            double objectStrain = 0.5;
+            objectStrain += speedBonus(currentKeyInterval);
+            return objectStrain;
+        }
+    }
+}

osu.Game.Rulesets.Taiko/Difficulty/Skills/SingleKeyStamina.cs

@@ -1,42 +0,0 @@
-// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
-// See the LICENCE file in the repository root for full licence text.
-
-using osu.Game.Rulesets.Difficulty.Preprocessing;
-using osu.Game.Rulesets.Difficulty.Skills;
-
-namespace osu.Game.Rulesets.Taiko.Difficulty.Skills
-{
-    /// <summary>
-    /// Stamina of a single key, calculated based on repetition speed.
-    /// </summary>
-    public class SingleKeyStamina
-    {
-        private double? previousHitTime;
-
-        /// <summary>
-        /// Similar to <see cref="StrainDecaySkill.StrainValueOf"/>
-        /// </summary>
-        public double StrainValueOf(DifficultyHitObject current)
-        {
-            if (previousHitTime == null)
-            {
-                previousHitTime = current.StartTime;
-                return 0;
-            }
-
-            double objectStrain = 0.5;
-            objectStrain += speedBonus(current.StartTime - previousHitTime.Value);
-            previousHitTime = current.StartTime;
-            return objectStrain;
-        }
-
-        /// <summary>
-        /// Applies a speed bonus dependent on the time since the last hit performed using this key.
-        /// </summary>
-        /// <param name="notePairDuration">The duration between the current and previous note hit using the same key.</param>
-        private double speedBonus(double notePairDuration)
-        {
-            return 175 / (notePairDuration + 100);
-        }
-    }
-}

osu.Game.Rulesets.Taiko/Difficulty/Skills/Stamina.cs

@@ -4,6 +4,7 @@
 using osu.Game.Rulesets.Difficulty.Preprocessing;
 using osu.Game.Rulesets.Difficulty.Skills;
 using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.Taiko.Difficulty.Evaluators;
 using osu.Game.Rulesets.Taiko.Difficulty.Preprocessing;
 using osu.Game.Rulesets.Taiko.Objects;
 
@@ -20,28 +21,6 @@ namespace osu.Game.Rulesets.Taiko.Difficulty.Skills
         protected override double SkillMultiplier => 1;
         protected override double StrainDecayBase => 0.4;
 
-        private readonly SingleKeyStamina[] centreKeyStamina =
-        {
-            new SingleKeyStamina(),
-            new SingleKeyStamina()
-        };
-
-        private readonly SingleKeyStamina[] rimKeyStamina =
-        {
-            new SingleKeyStamina(),
-            new SingleKeyStamina()
-        };
-
-        /// <summary>
-        /// Current index into <see cref="centreKeyStamina" /> for a centre hit.
-        /// </summary>
-        private int centreKeyIndex;
-
-        /// <summary>
-        /// Current index into <see cref="rimKeyStamina" /> for a rim hit.
-        /// </summary>
-        private int rimKeyIndex;
-
         /// <summary>
         /// Creates a <see cref="Stamina"/> skill.
         /// </summary>
@@ -51,32 +30,9 @@ namespace osu.Game.Rulesets.Taiko.Difficulty.Skills
         {
         }
 
-        /// <summary>
-        /// Get the next <see cref="SingleKeyStamina"/> to use for the given <see cref="TaikoDifficultyHitObject"/>.
-        /// </summary>
-        /// <param name="current">The current <see cref="TaikoDifficultyHitObject"/>.</param>
-        private SingleKeyStamina getNextSingleKeyStamina(TaikoDifficultyHitObject current)
-        {
-            // Alternate key for the same color.
-            if (current.HitType == HitType.Centre)
-            {
-                centreKeyIndex = (centreKeyIndex + 1) % 2;
-                return centreKeyStamina[centreKeyIndex];
-            }
-
-            rimKeyIndex = (rimKeyIndex + 1) % 2;
-            return rimKeyStamina[rimKeyIndex];
-        }
-
         protected override double StrainValueOf(DifficultyHitObject current)
         {
-            if (!(current.BaseObject is Hit))
+            return StaminaEvaluator.EvaluateDifficultyOf(current);
-            {
-                return 0.0;
-            }
-
-            TaikoDifficultyHitObject hitObject = (TaikoDifficultyHitObject)current;
-            return getNextSingleKeyStamina(hitObject).StrainValueOf(hitObject);
         }
     }
 }