implemented taiko pp update

src/beatmap/converts/mania/pattern_generator/distance_object.rs

@@ -55,6 +55,8 @@ impl<'h> DistanceObjectPatternGenerator<'h> {
             PatternType::LOW_PROBABILITY
         };
 
+        // ! BUG: Since `LegacyDifficultyControlPoint` are not considered while parsing,
+        // ! this value can be slightly off due to float arithmetics.
         let beat_len = timing_point.beat_len / difficulty_point.speed_multiplier;
 
         let span_count = (repeats + 1) as i32;

src/beatmap/converts/taiko.rs

@@ -38,7 +38,9 @@ impl Beatmap {
 
                         let edge_sound_count = edge_sounds.len().max(1);
 
-                        while j <= obj.start_time + params.duration + params.tick_spacing / 8.0 {
+                        while j
+                            <= obj.start_time + params.duration as f64 + params.tick_spacing / 8.0
+                        {
                             let h = HitObject {
                                 pos: Default::default(),
                                 start_time: j,
@@ -109,6 +111,8 @@ impl Beatmap {
         let timing_point = self.timing_point_at(*start_time);
         let difficulty_point = self.difficulty_point_at(*start_time).unwrap_or_default();
 
+        // ! BUG: Since `LegacyDifficultyControlPoint` are not considered while parsing,
+        // ! this value can be slightly off due to float arithmetics.
         let mut beat_len = timing_point.beat_len / difficulty_point.speed_multiplier;
 
         let slider_scoring_point_dist =
@@ -116,7 +120,7 @@ impl Beatmap {
 
         // * The velocity and duration of the taiko hit object - calculated as the velocity of a drum roll.
         let taiko_vel = slider_scoring_point_dist * self.tick_rate;
-        *duration = (dist / taiko_vel * beat_len).floor();
+        *duration = (dist / taiko_vel * beat_len) as u32;
 
         let osu_vel = taiko_vel * (1000.0_f32 as f64 / beat_len);
 
@@ -126,7 +130,7 @@ impl Beatmap {
         }
 
         // * If the drum roll is to be split into hit circles, assume the ticks are 1/8 spaced within the duration of one beat
-        *tick_spacing = (beat_len / self.tick_rate).min(*duration / spans);
+        *tick_spacing = (beat_len / self.tick_rate).min(*duration as f64 / spans);
 
         *tick_spacing > 0.0 && dist / osu_vel * 1000.0 < 2.0 * beat_len
     }
@@ -134,7 +138,7 @@ impl Beatmap {
 
 struct SliderParams<'c> {
     curve: &'c Curve,
-    duration: f64,
+    duration: u32,
     repeats: usize,
     start_time: f64,
     tick_spacing: f64,
@@ -146,7 +150,7 @@ impl<'c> SliderParams<'c> {
             curve,
             repeats,
             start_time,
-            duration: 0.0,
+            duration: 0,
             tick_spacing: 0.0,
         }
     }

src/lib.rs

@@ -453,7 +453,7 @@ impl PerformanceAttributes {
             Self::Catch(attributes) => DifficultyAttributes::Catch(attributes.difficulty.clone()),
             Self::Mania(attributes) => DifficultyAttributes::Mania(attributes.difficulty),
             Self::Osu(attributes) => DifficultyAttributes::Osu(attributes.difficulty.clone()),
-            Self::Taiko(attributes) => DifficultyAttributes::Taiko(attributes.difficulty),
+            Self::Taiko(attributes) => DifficultyAttributes::Taiko(attributes.difficulty.clone()),
         }
     }
 

src/limited_queue.rs

@@ -1,5 +1,4 @@
 use std::{
-    cmp::Ordering,
     iter::{Cycle, Skip, Take},
     ops::Index,
     slice::Iter,
@@ -71,11 +70,6 @@ impl<T, const N: usize> LimitedQueue<T, N> {
         }
     }
 
-    pub(crate) fn clear(&mut self) {
-        self.end = N - 1;
-        self.len = 0;
-    }
-
     pub(crate) fn full(&self) -> bool {
         self.len == N
     }
@@ -91,20 +85,6 @@ impl<T, const N: usize> LimitedQueue<T, N> {
 
 pub(crate) type LimitedQueueIter<'a, T> = Take<Skip<Cycle<Iter<'a, T>>>>;
 
-impl<T: PartialOrd, const N: usize> LimitedQueue<T, N> {
-    pub(crate) fn min(&self) -> Option<&T> {
-        self.queue
-            .iter()
-            .take(self.len)
-            .reduce(|min, next| match min.partial_cmp(next) {
-                Some(Ordering::Less) => min,
-                Some(Ordering::Equal) => min,
-                Some(Ordering::Greater) => next,
-                None => min,
-            })
-    }
-}
-
 impl<T, const N: usize> Index<usize> for LimitedQueue<T, N> {
     type Output = T;
 

src/taiko/colours/alternating_mono_pattern.rs

@@ -0,0 +1,72 @@
+use std::{
+    cell::RefCell,
+    fmt::{Debug, Formatter, Result as FmtResult},
+    rc::{Rc, Weak},
+};
+
+use crate::taiko::difficulty_object::TaikoDifficultyObject;
+
+use super::{mono_streak::MonoStreak, repeating_hit_patterns::RepeatingHitPatterns};
+
+pub(crate) struct AlternatingMonoPattern<'o> {
+    pub(crate) mono_streaks: Vec<Rc<RefCell<MonoStreak<'o>>>>,
+    pub(crate) parent: Option<Weak<RefCell<RepeatingHitPatterns<'o>>>>,
+    pub(crate) idx: usize,
+}
+
+impl Debug for AlternatingMonoPattern<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        write!(
+            f,
+            "(idx={}, mono_len={}, has_parent={})",
+            self.idx,
+            self.mono_streaks.len(),
+            self.parent.is_some()
+        )
+    }
+}
+
+impl<'o> AlternatingMonoPattern<'o> {
+    pub(crate) fn new() -> Rc<RefCell<Self>> {
+        let this = Self {
+            mono_streaks: Vec::new(),
+            parent: None,
+            idx: 0,
+        };
+
+        Rc::new(RefCell::new(this))
+    }
+
+    pub(crate) fn first_hit_object(&self) -> Option<Weak<RefCell<TaikoDifficultyObject<'o>>>> {
+        self.mono_streaks
+            .first()
+            .and_then(|streak| streak.borrow().first_hit_object())
+    }
+
+    pub(crate) fn is_repetition_of(&self, other: &Self) -> bool {
+        self.has_identical_mono_len(other)
+            && other.mono_streaks.len() == self.mono_streaks.len()
+            && other
+                .mono_streaks
+                .first()
+                .map(|streak| streak.borrow().hit_kind())
+                == self
+                    .mono_streaks
+                    .first()
+                    .map(|streak| streak.borrow().hit_kind())
+    }
+
+    pub(crate) fn has_identical_mono_len(&self, other: &Self) -> bool {
+        let other_len = other
+            .mono_streaks
+            .first()
+            .map(|streak| streak.borrow().run_len());
+
+        let self_len = self
+            .mono_streaks
+            .first()
+            .map(|streak| streak.borrow().run_len());
+
+        other_len == self_len
+    }
+}

src/taiko/colours/mod.rs

@@ -0,0 +1,27 @@
+use std::{
+    cell::RefCell,
+    rc::{Rc, Weak},
+};
+
+pub(crate) use self::{
+    alternating_mono_pattern::AlternatingMonoPattern, mono_streak::MonoStreak,
+    preprocessor::ColourDifficultyPreprocessor, repeating_hit_patterns::RepeatingHitPatterns,
+};
+
+mod alternating_mono_pattern;
+mod mono_streak;
+mod preprocessor;
+mod repeating_hit_patterns;
+
+#[derive(Clone, Debug, Default)]
+pub(crate) struct TaikoDifficultyColour<'o> {
+    pub(crate) mono_streak: Option<Weak<RefCell<MonoStreak<'o>>>>,
+    pub(crate) alternating_mono_pattern: Option<Weak<RefCell<AlternatingMonoPattern<'o>>>>,
+    pub(crate) repeating_hit_patterns: Option<Rc<RefCell<RepeatingHitPatterns<'o>>>>,
+}
+
+#[derive(Copy, Clone, Eq, PartialEq)]
+pub(crate) enum HitKind {
+    Centre,
+    Rim,
+}

src/taiko/colours/mono_streak.rs

@@ -0,0 +1,58 @@
+use std::{
+    cell::RefCell,
+    fmt::{Debug, Formatter, Result as FmtResult},
+    rc::{Rc, Weak},
+};
+
+use crate::taiko::difficulty_object::{MonoIndex, TaikoDifficultyObject};
+
+use super::{alternating_mono_pattern::AlternatingMonoPattern, HitKind};
+
+pub(crate) struct MonoStreak<'o> {
+    pub(crate) hit_objects: Vec<Weak<RefCell<TaikoDifficultyObject<'o>>>>,
+    pub(crate) parent: Option<Weak<RefCell<AlternatingMonoPattern<'o>>>>,
+    pub(crate) idx: usize,
+}
+
+impl Debug for MonoStreak<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        write!(
+            f,
+            "(idx={}, obj_len={}, has_parent={})",
+            self.idx,
+            self.hit_objects.len(),
+            self.parent.is_some()
+        )
+    }
+}
+
+impl<'o> MonoStreak<'o> {
+    pub(crate) fn new() -> Rc<RefCell<Self>> {
+        let this = Self {
+            hit_objects: Vec::new(),
+            parent: None,
+            idx: 0,
+        };
+
+        Rc::new(RefCell::new(this))
+    }
+
+    pub(crate) fn first_hit_object(&self) -> Option<Weak<RefCell<TaikoDifficultyObject<'o>>>> {
+        self.hit_objects.first().map(Weak::clone)
+    }
+
+    pub(crate) fn hit_kind(&self) -> Option<HitKind> {
+        self.hit_objects
+            .first()
+            .and_then(Weak::upgrade)
+            .and_then(|obj| match obj.borrow().mono_idx {
+                MonoIndex::Centre(_) => Some(HitKind::Centre),
+                MonoIndex::Rim(_) => Some(HitKind::Rim),
+                MonoIndex::None => None,
+            })
+    }
+
+    pub(crate) fn run_len(&self) -> usize {
+        self.hit_objects.len()
+    }
+}

src/taiko/colours/preprocessor.rs

@@ -0,0 +1,205 @@
+use std::{
+    cell::RefCell,
+    collections::VecDeque,
+    rc::{Rc, Weak},
+};
+
+use crate::taiko::difficulty_object::ObjectLists;
+
+use super::{
+    alternating_mono_pattern::AlternatingMonoPattern, mono_streak::MonoStreak,
+    repeating_hit_patterns::RepeatingHitPatterns,
+};
+
+pub(crate) struct ColourDifficultyPreprocessor {}
+
+impl<'o> ColourDifficultyPreprocessor {
+    pub(crate) fn process_and_assign(lists: &mut ObjectLists<'o>) {
+        // * Assign indexing and encoding data to all relevant objects. Only the first note of each encoding type is
+        // * assigned with the relevant encodings.
+        for repeating_hit_pattern in Self::encode(lists) {
+            if let Some(obj) = repeating_hit_pattern
+                .borrow()
+                .first_hit_object()
+                .as_ref()
+                .and_then(Weak::upgrade)
+            {
+                obj.borrow_mut().colour.repeating_hit_patterns =
+                    Some(Rc::clone(&repeating_hit_pattern));
+            }
+
+            // * The outermost loop is kept a ForEach loop since it doesn't need index information, and we want to
+            // * keep i and j for AlternatingMonoPattern's and MonoStreak's index respectively, to keep it in line with
+            // * documentation.
+            for i in 0..repeating_hit_pattern
+                .borrow()
+                .alternating_mono_patterns
+                .len()
+            {
+                let borrowed_repeating_hit_pattern = repeating_hit_pattern.borrow();
+                let mono_pattern = &borrowed_repeating_hit_pattern.alternating_mono_patterns[i];
+
+                {
+                    let mut borrowed = mono_pattern.borrow_mut();
+                    borrowed.parent = Some(Rc::downgrade(&repeating_hit_pattern));
+                    borrowed.idx = i;
+                }
+
+                if let Some(obj) = mono_pattern
+                    .borrow()
+                    .first_hit_object()
+                    .as_ref()
+                    .and_then(Weak::upgrade)
+                {
+                    obj.borrow_mut().colour.alternating_mono_pattern =
+                        Some(Rc::downgrade(mono_pattern));
+                }
+
+                for j in 0..mono_pattern.borrow().mono_streaks.len() {
+                    let borrowed_mono_pattern = mono_pattern.borrow();
+                    let mono_streak = &borrowed_mono_pattern.mono_streaks[j];
+
+                    {
+                        let mut borrowed = mono_streak.borrow_mut();
+                        borrowed.parent = Some(Rc::downgrade(mono_pattern));
+                        borrowed.idx = j;
+                    }
+
+                    if let Some(obj) = mono_streak
+                        .borrow()
+                        .first_hit_object()
+                        .as_ref()
+                        .and_then(Weak::upgrade)
+                    {
+                        obj.borrow_mut().colour.mono_streak = Some(Rc::downgrade(mono_streak));
+                    };
+                }
+            }
+        }
+    }
+
+    fn encode(data: &mut ObjectLists<'o>) -> Vec<Rc<RefCell<RepeatingHitPatterns<'o>>>> {
+        let mono_streaks = Self::encode_mono_streak(data);
+        let alternating_mono_patterns = Self::encode_alternating_mono_pattern(mono_streaks);
+
+        Self::encode_repeating_hit_pattern(alternating_mono_patterns)
+    }
+
+    fn encode_mono_streak(data: &mut ObjectLists<'o>) -> Vec<Rc<RefCell<MonoStreak<'o>>>> {
+        let mut mono_streaks = vec![MonoStreak::new()];
+        let mut curr_mono_streak = mono_streaks.last_mut();
+        let mut data_iter = data.all.iter();
+
+        if let (Some(curr), Some(taiko_obj)) = (&curr_mono_streak, data_iter.next()) {
+            curr.borrow_mut().hit_objects.push(Rc::downgrade(taiko_obj));
+        }
+
+        for taiko_obj in data_iter {
+            // * This ignores all non-note objects, which may or may not be the desired behaviour
+            let prev = data.prev_note(taiko_obj.borrow().idx, 0);
+
+            // * If this is the first object in the list or the colour changed, create a new mono streak
+            let condition = prev.filter(|prev| {
+                !(taiko_obj.borrow().base.is_hit()
+                    && prev.borrow().base.is_hit()
+                    && (taiko_obj.borrow().base.is_rim() != prev.borrow().base.is_rim()))
+            });
+
+            if condition.is_none() {
+                mono_streaks.push(MonoStreak::new());
+                curr_mono_streak = mono_streaks.last_mut();
+            }
+
+            // * Add the current object to the encoded payload.
+            if let Some(ref curr) = curr_mono_streak {
+                curr.borrow_mut().hit_objects.push(Rc::downgrade(taiko_obj));
+            }
+        }
+
+        mono_streaks
+    }
+
+    fn encode_alternating_mono_pattern(
+        data: Vec<Rc<RefCell<MonoStreak<'o>>>>,
+    ) -> VecDeque<Rc<RefCell<AlternatingMonoPattern<'o>>>> {
+        let mut mono_patterns = VecDeque::new();
+        mono_patterns.push_back(AlternatingMonoPattern::new());
+        let mut curr_mono_pattern = mono_patterns.back_mut();
+
+        if let (Some(curr), Some(mono)) = (&curr_mono_pattern, data.first()) {
+            curr.borrow_mut().mono_streaks.push(Rc::clone(mono));
+        }
+
+        for (prev, curr) in data.iter().zip(data.iter().skip(1)) {
+            // * Start a new AlternatingMonoPattern if the previous MonoStreak has a different mono length,
+            // * or if this is the first MonoStreak in the list.
+            if curr.borrow().run_len() != prev.borrow().run_len() {
+                mono_patterns.push_back(AlternatingMonoPattern::new());
+                curr_mono_pattern = mono_patterns.back_mut();
+            }
+
+            // * Add the current MonoStreak to the encoded payload.
+            if let Some(ref curr_mono_pattern) = curr_mono_pattern {
+                curr_mono_pattern
+                    .borrow_mut()
+                    .mono_streaks
+                    .push(Rc::clone(curr));
+            }
+        }
+
+        mono_patterns
+    }
+
+    fn encode_repeating_hit_pattern(
+        mut data: VecDeque<Rc<RefCell<AlternatingMonoPattern<'o>>>>,
+    ) -> Vec<Rc<RefCell<RepeatingHitPatterns<'o>>>> {
+        let mut hit_patterns = Vec::new();
+        let mut curr_hit_pattern: Option<Rc<std::cell::RefCell<_>>> = None;
+
+        while !data.is_empty() {
+            let old = curr_hit_pattern.as_ref().map(Rc::downgrade);
+            let curr_hit_pattern = curr_hit_pattern.insert(RepeatingHitPatterns::new(old));
+
+            let mut is_coupled = data.get(2).map_or(false, |other| {
+                data[0].borrow().is_repetition_of(&other.borrow())
+            });
+
+            if is_coupled {
+                // * If so, add the current AlternatingMonoPattern to the encoded payload and start repeatedly checking if the
+                // * subsequent AlternatingMonoPatterns should be grouped by increasing i and doing the appropriate isCoupled check.
+                while is_coupled {
+                    curr_hit_pattern
+                        .borrow_mut()
+                        .alternating_mono_patterns
+                        .push(data.pop_front().unwrap());
+
+                    is_coupled = data.get(2).map_or(false, |other| {
+                        data[0].borrow().is_repetition_of(&other.borrow())
+                    });
+                }
+
+                // * Skip over viewed data and add the rest to the payload
+                for front in data.drain(..2) {
+                    curr_hit_pattern
+                        .borrow_mut()
+                        .alternating_mono_patterns
+                        .push(front);
+                }
+            } else {
+                // * If not, add the current AlternatingMonoPattern to the encoded payload and continue.
+                curr_hit_pattern
+                    .borrow_mut()
+                    .alternating_mono_patterns
+                    .push(data.pop_front().unwrap());
+            }
+
+            hit_patterns.push(Rc::clone(&*curr_hit_pattern));
+        }
+
+        hit_patterns
+            .iter_mut()
+            .for_each(|pattern| pattern.borrow_mut().find_repetition_interval());
+
+        hit_patterns
+    }
+}

src/taiko/colours/repeating_hit_patterns.rs

@@ -0,0 +1,90 @@
+use std::{
+    cell::RefCell,
+    fmt::{Debug, Formatter, Result as FmtResult},
+    rc::{Rc, Weak},
+};
+
+use crate::taiko::difficulty_object::TaikoDifficultyObject;
+
+use super::alternating_mono_pattern::AlternatingMonoPattern;
+
+pub(crate) struct RepeatingHitPatterns<'o> {
+    pub(crate) alternating_mono_patterns: Vec<Rc<RefCell<AlternatingMonoPattern<'o>>>>,
+    pub(crate) prev: Option<Weak<RefCell<Self>>>,
+    pub(crate) repetition_interval: usize,
+}
+
+impl Debug for RepeatingHitPatterns<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        write!(
+            f,
+            "(interval={}, alt_len={}, has_prev={})",
+            self.repetition_interval,
+            self.alternating_mono_patterns.len(),
+            self.prev.is_some()
+        )
+    }
+}
+
+impl<'o> RepeatingHitPatterns<'o> {
+    const MAX_REPETITION_INTERVAL: usize = 16;
+
+    pub(crate) fn new(prev: Option<Weak<RefCell<Self>>>) -> Rc<RefCell<Self>> {
+        let this = Self {
+            alternating_mono_patterns: Vec::new(),
+            prev,
+            repetition_interval: 0,
+        };
+
+        Rc::new(RefCell::new(this))
+    }
+
+    pub(crate) fn first_hit_object(&self) -> Option<Weak<RefCell<TaikoDifficultyObject<'o>>>> {
+        self.alternating_mono_patterns
+            .first()
+            .and_then(|pattern| pattern.borrow().first_hit_object())
+    }
+
+    fn is_repetition_of(&self, other: &Self) -> bool {
+        if self.alternating_mono_patterns.len() != other.alternating_mono_patterns.len() {
+            return false;
+        }
+
+        self.alternating_mono_patterns
+            .iter()
+            .zip(other.alternating_mono_patterns.iter())
+            .take(2)
+            .all(|(self_pat, other_pat)| {
+                self_pat
+                    .borrow()
+                    .has_identical_mono_len(&other_pat.borrow())
+            })
+    }
+
+    pub(crate) fn find_repetition_interval(&mut self) {
+        let mut other = match self.prev.as_ref().and_then(Weak::upgrade) {
+            Some(prev) => prev,
+            None => return self.repetition_interval = Self::MAX_REPETITION_INTERVAL + 1,
+        };
+
+        let mut interval = 1;
+
+        while interval < Self::MAX_REPETITION_INTERVAL {
+            if self.is_repetition_of(&other.borrow()) {
+                return self.repetition_interval = interval.min(Self::MAX_REPETITION_INTERVAL);
+            }
+
+            let next = match other.borrow().prev.as_ref().and_then(Weak::upgrade) {
+                Some(prev) => prev,
+                None => break,
+            };
+
+            // gotta love NLL...
+            other = next;
+
+            interval += 1;
+        }
+
+        self.repetition_interval = Self::MAX_REPETITION_INTERVAL + 1;
+    }
+}

src/taiko/difficulty_object.rs

@@ -1,34 +1,192 @@
-use super::{closest_rhythm, taiko_object::TaikoObject, HitObjectRhythm};
+use std::{cell::RefCell, cmp::Ordering, rc::Rc};
 
-#[derive(Clone, Debug)]
-pub(crate) struct DifficultyObject<'o> {
-    pub(crate) idx: usize,
-    pub(crate) base: TaikoObject<'o>,
-    pub(crate) prev: TaikoObject<'o>,
-    pub(crate) delta: f64,
-    pub(crate) rhythm: &'static HitObjectRhythm,
-    pub(crate) start_time: f64,
+use crate::parse::HitObject;
+
+use super::{colours::TaikoDifficultyColour, rim::Rim, taiko_object::TaikoObject};
+
+#[derive(Clone, Debug, Default)]
+pub(crate) struct ObjectLists<'o> {
+    pub(crate) all: Vec<Rc<RefCell<TaikoDifficultyObject<'o>>>>,
+    pub(crate) centres: Vec<usize>,
+    pub(crate) rims: Vec<usize>,
+    pub(crate) notes: Vec<usize>,
 }
 
-impl<'o> DifficultyObject<'o> {
-    #[inline]
+impl<'o> ObjectLists<'o> {
+    pub(crate) fn prev_mono(
+        &self,
+        curr: usize,
+        backwards_idx: usize,
+    ) -> Option<&'_ Rc<RefCell<TaikoDifficultyObject<'o>>>> {
+        let curr = &self.all[curr];
+
+        let prev = match curr.borrow().mono_idx {
+            MonoIndex::Centre(idx) => idx
+                .checked_sub(backwards_idx + 1)
+                .and_then(|idx| self.centres.get(idx))?,
+            MonoIndex::Rim(idx) => idx
+                .checked_sub(backwards_idx + 1)
+                .and_then(|idx| self.rims.get(idx))?,
+            MonoIndex::None => return None,
+        };
+
+        self.all.get(*prev)
+    }
+
+    #[allow(unused)]
+    pub(crate) fn next_mono(
+        &self,
+        curr: usize,
+        forwards_idx: usize,
+    ) -> Option<&'_ Rc<RefCell<TaikoDifficultyObject<'o>>>> {
+        let curr = &self.all[curr];
+
+        let next = match curr.borrow().mono_idx {
+            MonoIndex::Centre(idx) => self.centres.get(idx + (forwards_idx + 1))?,
+            MonoIndex::Rim(idx) => self.rims.get(idx + (forwards_idx + 1))?,
+            MonoIndex::None => return None,
+        };
+
+        self.all.get(*next)
+    }
+
+    pub(crate) fn prev_note(
+        &self,
+        curr: usize,
+        backwards_idx: usize,
+    ) -> Option<&'_ Rc<RefCell<TaikoDifficultyObject<'o>>>> {
+        let curr = &self.all[curr];
+        let note_idx = curr.borrow().note_idx?;
+        let idx = note_idx.checked_sub(backwards_idx + 1)?;
+        let prev = self.notes.get(idx)?;
+
+        self.all.get(*prev)
+    }
+
+    #[allow(unused)]
+    pub(crate) fn next_note(
+        &self,
+        curr: usize,
+        forwards_idx: usize,
+    ) -> Option<&'_ Rc<RefCell<TaikoDifficultyObject<'o>>>> {
+        let curr = &self.all[curr];
+        let note_idx = curr.borrow().note_idx?;
+        let idx = note_idx + (forwards_idx + 1);
+        let prev = self.notes.get(idx)?;
+
+        self.all.get(*prev)
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+pub(crate) enum MonoIndex {
+    Centre(usize),
+    Rim(usize),
+    None,
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct TaikoDifficultyObject<'o> {
+    pub(crate) base: TaikoObject<'o>,
+    pub(crate) prev_time: f64,
+    pub(crate) colour: TaikoDifficultyColour<'o>,
+    pub(crate) rhythm: &'static HitObjectRhythm,
+    pub(crate) mono_idx: MonoIndex,
+    pub(crate) note_idx: Option<usize>,
+    pub(crate) idx: usize,
+    pub(crate) delta: f64,
+}
+
+impl<'o> TaikoDifficultyObject<'o> {
     pub(crate) fn new(
-        idx: usize,
         base: TaikoObject<'o>,
-        prev: TaikoObject<'o>,
-        prev_prev: TaikoObject<'o>,
+        last: TaikoObject<'o>,
+        last_last: TaikoObject<'o>,
         clock_rate: f64,
+        lists: &ObjectLists<'o>,
+        idx: usize,
     ) -> Self {
-        let delta = (base.h.start_time - prev.h.start_time) / clock_rate;
-        let rhythm = closest_rhythm(delta, prev.h, prev_prev.h, clock_rate);
+        // * Create the Colour object, its properties should be filled in by TaikoDifficultyPreprocessor
+        let colour = TaikoDifficultyColour::default();
+
+        let delta = (base.h.start_time - last.h.start_time) / clock_rate;
+        let rhythm = closest_rhythm(delta, last.h, last_last.h, clock_rate);
+
+        let mono_idx = if !base.is_hit() {
+            MonoIndex::None
+        } else if base.sound.is_rim() {
+            MonoIndex::Rim(lists.rims.len())
+        } else {
+            MonoIndex::Centre(lists.centres.len())
+        };
+
+        let note_idx = base.is_hit().then_some(lists.notes.len());
 
         Self {
-            idx,
             base,
-            prev,
-            delta,
+            prev_time: last.h.start_time / clock_rate,
+            colour,
             rhythm,
-            start_time: base.h.start_time / clock_rate,
+            mono_idx,
+            note_idx,
+            idx,
+            delta,
         }
     }
 }
+
+#[rustfmt::skip]
+pub(crate) static COMMON_RHYTHMS: [HitObjectRhythm; 9] = [
+    HitObjectRhythm { id: 0, ratio: 1.0, difficulty: 0.0 },
+    HitObjectRhythm { id: 1, ratio: 2.0 / 1.0, difficulty: 0.3 },
+    HitObjectRhythm { id: 2, ratio: 1.0 / 2.0, difficulty: 0.5 },
+    HitObjectRhythm { id: 3, ratio: 3.0 / 1.0, difficulty: 0.3 },
+    HitObjectRhythm { id: 4, ratio: 1.0 / 3.0, difficulty: 0.35 },
+    // * purposefully higher (requires hand switch in full alternating gameplay style)
+    HitObjectRhythm { id: 5, ratio: 3.0 / 2.0, difficulty: 0.6 },
+    HitObjectRhythm { id: 6, ratio: 2.0 / 3.0, difficulty: 0.4 },
+    HitObjectRhythm { id: 7, ratio: 5.0 / 4.0, difficulty: 0.5 },
+    HitObjectRhythm { id: 8, ratio: 4.0 / 5.0, difficulty: 0.7 },
+];
+
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct HitObjectRhythm {
+    id: u8,
+    pub(crate) ratio: f64,
+    pub(crate) difficulty: f64,
+}
+
+impl HitObjectRhythm {
+    pub(crate) fn static_ref() -> &'static Self {
+        &COMMON_RHYTHMS[0]
+    }
+}
+
+impl PartialEq for HitObjectRhythm {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        self.id == other.id
+    }
+}
+
+impl Eq for HitObjectRhythm {}
+
+fn closest_rhythm(
+    delta_time: f64,
+    last: &HitObject,
+    last_last: &HitObject,
+    clock_rate: f64,
+) -> &'static HitObjectRhythm {
+    let prev_len = (last.start_time - last_last.start_time) / clock_rate;
+    let ratio = delta_time / prev_len;
+
+    COMMON_RHYTHMS
+        .iter()
+        .min_by(|r1, r2| {
+            (r1.ratio - ratio)
+                .abs()
+                .partial_cmp(&(r2.ratio - ratio).abs())
+                .unwrap_or(Ordering::Equal)
+        })
+        .unwrap()
+}

src/taiko/gradual_difficulty.rs

@@ -1,22 +1,13 @@
-use std::{
-    cmp::Ordering,
-    iter::{self, Enumerate, Skip, Zip},
-};
+use std::{cell::RefCell, rc::Rc, vec::IntoIter};
 
-use crate::{
-    parse::{HitObject, HitObjectKind},
-    taiko::{
-        difficulty_object::DifficultyObject, norm, rescale, simple_color_penalty,
-        stamina_cheese::StaminaCheeseDetector, COLOR_SKILL_MULTIPLIER, RHYTHM_SKILL_MULTIPLIER,
-        SECTION_LEN, STAMINA_SKILL_MULTIPLIER,
-    },
-    Beatmap, Mods,
-};
+use crate::{beatmap::BeatmapHitWindows, taiko::rescale, Beatmap, Mods};
 
 use super::{
-    skill::Skills,
-    taiko_object::{IntoTaikoObjectIter, TaikoObjectIter},
-    TaikoDifficultyAttributes,
+    colours::ColourDifficultyPreprocessor,
+    difficulty_object::{MonoIndex, ObjectLists, TaikoDifficultyObject},
+    skills::{Peaks, PeaksDifficultyValues, Skill},
+    taiko_object::IntoTaikoObjectIter,
+    TaikoDifficultyAttributes, DIFFICULTY_MULTIPLIER,
 };
 
 /// Gradually calculate the difficulty attributes of an osu!taiko map.
@@ -52,205 +43,122 @@ use super::{
 #[derive(Clone, Debug)]
 pub struct TaikoGradualDifficultyAttributes<'map> {
     pub(crate) idx: usize,
-    difficulty_objects: GradualTaikoObjectIter<'map>,
-    cheese: Vec<bool>,
-    skills: Skills,
-    curr_section_end: f64,
-    strain_peak_buf: Vec<f64>,
+    attrs: TaikoDifficultyAttributes,
+    hit_objects: IntoIter<Rc<RefCell<TaikoDifficultyObject<'map>>>>,
+    lists: ObjectLists<'map>,
+    peaks: Peaks,
 }
 
 impl<'map> TaikoGradualDifficultyAttributes<'map> {
     /// Create a new difficulty attributes iterator for osu!taiko maps.
-    pub fn new(map: &'map Beatmap, mods: impl Mods) -> Self {
-        // True if the object at that index is stamina cheese
-        let cheese = map.find_cheese();
-
-        let skills = Skills::new();
+    pub fn new(map: &'map Beatmap, mods: u32) -> Self {
+        let peaks = Peaks::new();
         let clock_rate = mods.clock_rate();
-        let difficulty_objects = GradualTaikoObjectIter::new(map, clock_rate);
+
+        let BeatmapHitWindows { od: hit_window, .. } = map
+            .attributes()
+            .mods(mods)
+            .clock_rate(clock_rate)
+            .hit_windows();
+
+        let attrs = TaikoDifficultyAttributes {
+            stamina: 0.0,
+            rhythm: 0.0,
+            colour: 0.0,
+            peak: 0.0,
+            hit_window,
+            stars: 0.0,
+            max_combo: 0,
+        };
+
+        let mut diff_objects = map
+            .taiko_objects()
+            .enumerate()
+            .skip(2)
+            .zip(map.taiko_objects().skip(1))
+            .zip(map.taiko_objects())
+            .fold(
+                ObjectLists::default(),
+                |mut lists, (((idx, base), last), last_last)| {
+                    let diff_obj =
+                        TaikoDifficultyObject::new(base, last, last_last, clock_rate, &lists, idx);
+
+                    match &diff_obj.mono_idx {
+                        MonoIndex::Centre(_) => lists.centres.push(idx),
+                        MonoIndex::Rim(_) => lists.rims.push(idx),
+                        MonoIndex::None => {}
+                    }
+
+                    if diff_obj.note_idx.is_some() {
+                        lists.notes.push(idx);
+                    }
+
+                    lists.all.push(Rc::new(RefCell::new(diff_obj)));
+
+                    lists
+                },
+            );
+
+        ColourDifficultyPreprocessor::process_and_assign(&mut diff_objects);
 
         Self {
             idx: 0,
-            difficulty_objects,
-            cheese,
-            skills,
-            curr_section_end: 0.0,
-            strain_peak_buf: Vec::new(),
+            hit_objects: diff_objects.all.clone().into_iter(),
+            lists: diff_objects,
+            peaks,
+            attrs,
         }
     }
-
-    fn locally_combined_difficulty(&mut self, stamina_penalty: f64) -> f64 {
-        let iter = self
-            .skills
-            .color
-            .strain_peaks
-            .iter()
-            .zip(self.skills.rhythm.strain_peaks.iter())
-            .zip(self.skills.stamina_right.strain_peaks.iter())
-            .zip(self.skills.stamina_left.strain_peaks.iter())
-            .map(|(((&color, &rhythm), &stamina_right), &stamina_left)| {
-                norm(
-                    2.0,
-                    color * COLOR_SKILL_MULTIPLIER,
-                    rhythm * RHYTHM_SKILL_MULTIPLIER,
-                    (stamina_right + stamina_left) * STAMINA_SKILL_MULTIPLIER * stamina_penalty,
-                )
-            });
-
-        self.strain_peak_buf.clear();
-        self.strain_peak_buf.extend(iter);
-
-        let last = norm(
-            2.0,
-            self.skills.color.curr_section_peak * COLOR_SKILL_MULTIPLIER,
-            self.skills.rhythm.curr_section_peak * RHYTHM_SKILL_MULTIPLIER,
-            (self.skills.stamina_right.curr_section_peak
-                + self.skills.stamina_left.curr_section_peak)
-                * STAMINA_SKILL_MULTIPLIER
-                * stamina_penalty,
-        );
-
-        self.strain_peak_buf.push(last);
-
-        self.strain_peak_buf
-            .sort_unstable_by(|a, b| b.partial_cmp(a).unwrap_or(Ordering::Equal));
-
-        let mut difficulty = 0.0;
-        let mut weight = 1.0;
-
-        for strain in &self.strain_peak_buf {
-            difficulty += strain * weight;
-            weight *= 0.9;
-        }
-
-        difficulty
-    }
 }
 
 impl Iterator for TaikoGradualDifficultyAttributes<'_> {
     type Item = TaikoDifficultyAttributes;
 
     fn next(&mut self) -> Option<Self::Item> {
-        self.idx = self.idx.saturating_add(1);
+        let curr = self.hit_objects.next()?;
 
-        if self.idx == 1 {
-            if self.difficulty_objects.first_object.is_empty() {
-                return None;
-            }
-
-            self.difficulty_objects.max_combo +=
-                self.difficulty_objects.first_object.is_circle() as usize;
-
-            let attributes = TaikoDifficultyAttributes {
-                stars: 0.0,
-                max_combo: self.difficulty_objects.max_combo,
-            };
-
-            return Some(attributes);
-        } else if self.idx == 2 {
-            if self.difficulty_objects.second_object.is_empty() {
-                return None;
-            }
-
-            self.difficulty_objects.max_combo +=
-                self.difficulty_objects.second_object.is_circle() as usize;
-
-            let attributes = TaikoDifficultyAttributes {
-                stars: 0.0,
-                max_combo: self.difficulty_objects.max_combo,
-            };
-
-            return Some(attributes);
+        {
+            let curr = curr.borrow();
+            self.peaks.process(&curr, &self.lists);
+            self.attrs.max_combo += curr.base.h.is_circle() as usize;
         }
 
-        let h = self.difficulty_objects.next()?;
+        let PeaksDifficultyValues {
+            mut colour_rating,
+            mut rhythm_rating,
+            mut stamina_rating,
+            mut combined_rating,
+        } = self.peaks.clone().difficulty_values();
 
-        if self.idx == 3 {
-            self.curr_section_end = (h.start_time / SECTION_LEN).ceil() * SECTION_LEN;
-        } else {
-            while h.start_time > self.curr_section_end {
-                self.skills
-                    .save_peak_and_start_new_section(self.curr_section_end);
-                self.curr_section_end += SECTION_LEN;
+        colour_rating *= DIFFICULTY_MULTIPLIER;
+        rhythm_rating *= DIFFICULTY_MULTIPLIER;
+        stamina_rating *= DIFFICULTY_MULTIPLIER;
+        combined_rating *= DIFFICULTY_MULTIPLIER;
+
+        let mut star_rating = rescale(combined_rating * 1.4);
+
+        // TODO: adjust once converts are available for gradual processing
+        let is_convert = false;
+
+        // * TODO: This is temporary measure as we don't detect abuse of multiple-input
+        // * playstyles of converts within the current system.
+        if is_convert {
+            star_rating *= 0.925;
+
+            // * For maps with low colour variance and high stamina requirement,
+            // * multiple inputs are more likely to be abused.
+            if colour_rating < 2.0 && stamina_rating > 8.0 {
+                star_rating *= 0.8;
             }
         }
 
-        self.skills.process(&h, &self.cheese);
+        self.attrs.stamina = stamina_rating;
+        self.attrs.colour = colour_rating;
+        self.attrs.rhythm = rhythm_rating;
+        self.attrs.peak = combined_rating;
+        self.attrs.stars = star_rating;
 
-        let len = self.skills.strain_peaks_len();
-        let missing = len + 1 - self.strain_peak_buf.len();
-        self.strain_peak_buf.extend(iter::repeat(0.0).take(missing));
-
-        self.skills
-            .color
-            .copy_strain_peaks(&mut self.strain_peak_buf[..len]);
-
-        if let Some(last) = self.strain_peak_buf.last_mut() {
-            *last = self.skills.color.curr_section_peak;
-        }
-
-        let color_rating = self
-            .skills
-            .color
-            .difficulty_value(&mut self.strain_peak_buf)
-            * COLOR_SKILL_MULTIPLIER;
-
-        self.skills
-            .rhythm
-            .copy_strain_peaks(&mut self.strain_peak_buf[..len]);
-
-        if let Some(last) = self.strain_peak_buf.last_mut() {
-            *last = self.skills.rhythm.curr_section_peak;
-        }
-
-        let rhythm_rating = self
-            .skills
-            .rhythm
-            .difficulty_value(&mut self.strain_peak_buf)
-            * RHYTHM_SKILL_MULTIPLIER;
-
-        self.skills
-            .stamina_right
-            .copy_strain_peaks(&mut self.strain_peak_buf[..len]);
-
-        if let Some(last) = self.strain_peak_buf.last_mut() {
-            *last = self.skills.stamina_right.curr_section_peak;
-        }
-
-        let stamina_right = self
-            .skills
-            .stamina_right
-            .difficulty_value(&mut self.strain_peak_buf);
-
-        self.skills
-            .stamina_left
-            .copy_strain_peaks(&mut self.strain_peak_buf[..len]);
-
-        if let Some(last) = self.strain_peak_buf.last_mut() {
-            *last = self.skills.stamina_left.curr_section_peak;
-        }
-
-        let stamina_left = self
-            .skills
-            .stamina_left
-            .difficulty_value(&mut self.strain_peak_buf);
-
-        let mut stamina_rating = (stamina_right + stamina_left) * STAMINA_SKILL_MULTIPLIER;
-
-        let stamina_penalty = simple_color_penalty(stamina_rating, color_rating);
-        stamina_rating *= stamina_penalty;
-
-        let combined_rating = self.locally_combined_difficulty(stamina_penalty);
-        let separate_rating = norm(1.5, color_rating, rhythm_rating, stamina_rating);
-
-        let stars = rescale(1.4 * separate_rating + 0.5 * combined_rating);
-
-        let attributes = TaikoDifficultyAttributes {
-            stars,
-            max_combo: self.difficulty_objects.max_combo,
-        };
-
-        Some(attributes)
+        Some(self.attrs.clone())
     }
 
     #[inline]
@@ -262,112 +170,6 @@ impl Iterator for TaikoGradualDifficultyAttributes<'_> {
 }
 
 impl ExactSizeIterator for TaikoGradualDifficultyAttributes<'_> {
-    #[inline]
-    fn len(&self) -> usize {
-        let mut len = self.difficulty_objects.len();
-
-        if self.idx == 0 && !self.difficulty_objects.first_object.is_empty() {
-            len += 1 + !self.difficulty_objects.second_object.is_empty() as usize;
-        } else if self.idx == 1 && !self.difficulty_objects.second_object.is_empty() {
-            len += 1;
-        }
-
-        len
-    }
-}
-
-type InnerIter<'map> = Zip<
-    Zip<Skip<Enumerate<TaikoObjectIter<'map>>>, Skip<TaikoObjectIter<'map>>>,
-    TaikoObjectIter<'map>,
->;
-
-#[derive(Copy, Clone, Debug, Eq, PartialEq)]
-#[repr(u8)]
-enum SimpleObject {
-    Circle,
-    Empty,
-    NonCircle,
-}
-
-impl From<&HitObject> for SimpleObject {
-    fn from(h: &HitObject) -> Self {
-        match h.kind {
-            HitObjectKind::Circle => Self::Circle,
-            _ => Self::NonCircle,
-        }
-    }
-}
-
-impl SimpleObject {
-    fn is_empty(self) -> bool {
-        self == Self::Empty
-    }
-
-    fn is_circle(self) -> bool {
-        self == Self::Circle
-    }
-}
-
-#[derive(Clone, Debug)]
-struct GradualTaikoObjectIter<'map> {
-    hit_objects: InnerIter<'map>,
-    max_combo: usize,
-    clock_rate: f64,
-    first_object: SimpleObject,
-    second_object: SimpleObject,
-}
-
-impl<'map> GradualTaikoObjectIter<'map> {
-    fn new(map: &'map Beatmap, clock_rate: f64) -> Self {
-        let first_object = map
-            .hit_objects
-            .get(0)
-            .map_or(SimpleObject::Empty, From::from);
-        let second_object = map
-            .hit_objects
-            .get(1)
-            .map_or(SimpleObject::Empty, From::from);
-
-        let hit_objects = map
-            .taiko_objects()
-            .enumerate()
-            .skip(2)
-            .zip(map.taiko_objects().skip(1))
-            .zip(map.taiko_objects());
-
-        Self {
-            hit_objects,
-            max_combo: 0,
-            clock_rate,
-            first_object,
-            second_object,
-        }
-    }
-}
-
-impl<'map> Iterator for GradualTaikoObjectIter<'map> {
-    type Item = DifficultyObject<'map>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        let (((idx, base), prev), prev_prev) = self.hit_objects.next()?;
-        self.max_combo += base.h.is_circle() as usize;
-
-        Some(DifficultyObject::new(
-            idx,
-            base,
-            prev,
-            prev_prev,
-            self.clock_rate,
-        ))
-    }
-
-    #[inline]
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        self.hit_objects.size_hint()
-    }
-}
-
-impl ExactSizeIterator for GradualTaikoObjectIter<'_> {
     #[inline]
     fn len(&self) -> usize {
         self.hit_objects.len()

src/taiko/hitobject_rhythm.rs

@@ -1,94 +0,0 @@
-use crate::parse::HitObject;
-
-use std::cmp::Ordering;
-
-static COMMON_RHYTHMS: [HitObjectRhythm; 9] = [
-    HitObjectRhythm {
-        id: 0,
-        ratio: 1.0,
-        difficulty: 0.0,
-    },
-    HitObjectRhythm {
-        id: 1,
-        ratio: 2.0 / 1.0,
-        difficulty: 0.3,
-    },
-    HitObjectRhythm {
-        id: 2,
-        ratio: 1.0 / 2.0,
-        difficulty: 0.5,
-    },
-    HitObjectRhythm {
-        id: 3,
-        ratio: 3.0 / 1.0,
-        difficulty: 0.3,
-    },
-    HitObjectRhythm {
-        id: 4,
-        ratio: 1.0 / 3.0,
-        difficulty: 0.35,
-    },
-    HitObjectRhythm {
-        id: 5,
-        ratio: 3.0 / 2.0,
-        difficulty: 0.6,
-    },
-    HitObjectRhythm {
-        id: 6,
-        ratio: 2.0 / 3.0,
-        difficulty: 0.4,
-    },
-    HitObjectRhythm {
-        id: 7,
-        ratio: 5.0 / 4.0,
-        difficulty: 0.5,
-    },
-    HitObjectRhythm {
-        id: 8,
-        ratio: 4.0 / 5.0,
-        difficulty: 0.7,
-    },
-];
-
-#[derive(Copy, Clone, Debug)]
-pub(crate) struct HitObjectRhythm {
-    id: u8,
-    ratio: f64,
-    pub(crate) difficulty: f64,
-}
-
-impl HitObjectRhythm {
-    pub(crate) fn static_ref() -> &'static Self {
-        &COMMON_RHYTHMS[0]
-    }
-}
-
-impl PartialEq for HitObjectRhythm {
-    #[inline]
-    fn eq(&self, other: &Self) -> bool {
-        self.id == other.id
-    }
-}
-
-impl Eq for HitObjectRhythm {}
-
-#[inline]
-pub(crate) fn closest_rhythm(
-    delta_time: f64,
-    last: &HitObject,
-    last_last: &HitObject,
-    clock_rate: f64,
-) -> &'static HitObjectRhythm {
-    let prev_len = (last.start_time - last_last.start_time) / clock_rate;
-    let ratio = delta_time / prev_len;
-
-    COMMON_RHYTHMS
-        .iter()
-        .min_by(|r1, r2| {
-            (r1.ratio - ratio)
-                .abs()
-                .partial_cmp(&(r2.ratio - ratio).abs())
-                .unwrap_or(Ordering::Equal)
-        })
-        .unwrap()
-}

src/taiko/mod.rs

@@ -1,36 +1,31 @@
+mod colours;
 mod difficulty_object;
 mod gradual_difficulty;
 mod gradual_performance;
-mod hitobject_rhythm;
 mod pp;
 mod rim;
-mod skill;
-mod skill_kind;
+mod skills;
 mod stamina_cheese;
 mod taiko_object;
 
-use difficulty_object::DifficultyObject;
 pub use gradual_difficulty::*;
 pub use gradual_performance::*;
-use hitobject_rhythm::{closest_rhythm, HitObjectRhythm};
 pub use pp::*;
 use rim::Rim;
-use skill_kind::SkillKind;
-use stamina_cheese::StaminaCheeseDetector;
 use taiko_object::IntoTaikoObjectIter;
 
-use crate::taiko::skill::Skills;
+use crate::beatmap::BeatmapHitWindows;
 use crate::{Beatmap, GameMode, Mods, OsuStars};
 
-use std::borrow::Cow;
-use std::cmp::Ordering;
-use std::f64::consts::PI;
+use std::{borrow::Cow, cell::RefCell, rc::Rc};
 
-const SECTION_LEN: f64 = 400.0;
+use self::colours::ColourDifficultyPreprocessor;
+use self::difficulty_object::{MonoIndex, ObjectLists, TaikoDifficultyObject};
+use self::skills::{Peaks, PeaksDifficultyValues, PeaksRaw, Skill};
 
-const COLOR_SKILL_MULTIPLIER: f64 = 0.01;
-const RHYTHM_SKILL_MULTIPLIER: f64 = 0.014;
-const STAMINA_SKILL_MULTIPLIER: f64 = 0.02;
+const SECTION_LEN: usize = 400;
+
+const DIFFICULTY_MULTIPLIER: f64 = 1.35;
 
 /// Difficulty calculator on osu!taiko maps.
 ///
@@ -56,6 +51,7 @@ pub struct TaikoStars<'map> {
     mods: u32,
     passed_objects: Option<usize>,
     clock_rate: Option<f64>,
+    is_convert: bool,
 }
 
 impl<'map> TaikoStars<'map> {
@@ -67,6 +63,7 @@ impl<'map> TaikoStars<'map> {
             mods: 0,
             passed_objects: None,
             clock_rate: None,
+            is_convert: false,
         }
     }
 
@@ -102,35 +99,65 @@ impl<'map> TaikoStars<'map> {
         self
     }
 
+    /// Specify whether the map is a convert i.e. an osu!standard map.
+    #[inline]
+    pub fn is_convert(mut self, is_convert: bool) -> Self {
+        self.is_convert = is_convert;
+
+        self
+    }
+
     /// Calculate all difficulty related values, including stars.
     #[inline]
     pub fn calculate(self) -> TaikoDifficultyAttributes {
-        let (skills, max_combo) = calculate_skills(self);
-        let mut buf = vec![0.0; skills.strain_peaks_len()];
+        let clock_rate = self.clock_rate.unwrap_or_else(|| self.mods.clock_rate());
 
-        skills.color.copy_strain_peaks(&mut buf);
-        let color_rating = skills.color.difficulty_value(&mut buf) * COLOR_SKILL_MULTIPLIER;
+        let BeatmapHitWindows { od: hit_window, .. } = self
+            .map
+            .attributes()
+            .mods(self.mods)
+            .clock_rate(clock_rate)
+            .hit_windows();
 
-        skills.rhythm.copy_strain_peaks(&mut buf);
-        let rhythm_rating = skills.rhythm.difficulty_value(&mut buf) * RHYTHM_SKILL_MULTIPLIER;
+        let is_convert = self.is_convert || matches!(self.map, Cow::Owned(_));
 
-        skills.stamina_right.copy_strain_peaks(&mut buf);
-        let stamina_right = skills.stamina_right.difficulty_value(&mut buf);
+        let (peaks, max_combo) = calculate_skills(self);
 
-        skills.stamina_left.copy_strain_peaks(&mut buf);
-        let stamina_left = skills.stamina_left.difficulty_value(&mut buf);
+        let PeaksDifficultyValues {
+            mut colour_rating,
+            mut rhythm_rating,
+            mut stamina_rating,
+            mut combined_rating,
+        } = peaks.difficulty_values();
 
-        let mut stamina_rating = (stamina_right + stamina_left) * STAMINA_SKILL_MULTIPLIER;
+        colour_rating *= DIFFICULTY_MULTIPLIER;
+        rhythm_rating *= DIFFICULTY_MULTIPLIER;
+        stamina_rating *= DIFFICULTY_MULTIPLIER;
+        combined_rating *= DIFFICULTY_MULTIPLIER;
 
-        let stamina_penalty = simple_color_penalty(stamina_rating, color_rating);
-        stamina_rating *= stamina_penalty;
+        let mut star_rating = rescale(combined_rating * 1.4);
 
-        let combined_rating = locally_combined_difficulty(&mut buf, &skills, stamina_penalty);
-        let separate_rating = norm(1.5, color_rating, rhythm_rating, stamina_rating);
+        // * TODO: This is temporary measure as we don't detect abuse of multiple-input
+        // * playstyles of converts within the current system.
+        if is_convert {
+            star_rating *= 0.925;
 
-        let stars = rescale(1.4 * separate_rating + 0.5 * combined_rating);
+            // * For maps with low colour variance and high stamina requirement,
+            // * multiple inputs are more likely to be abused.
+            if colour_rating < 2.0 && stamina_rating > 8.0 {
+                star_rating *= 0.8;
+            }
+        }
 
-        TaikoDifficultyAttributes { stars, max_combo }
+        TaikoDifficultyAttributes {
+            stamina: stamina_rating,
+            rhythm: rhythm_rating,
+            colour: colour_rating,
+            peak: combined_rating,
+            hit_window,
+            stars: star_rating,
+            max_combo,
+        }
     }
 
     /// Calculate the skill strains.
@@ -139,14 +166,19 @@ impl<'map> TaikoStars<'map> {
     #[inline]
     pub fn strains(self) -> TaikoStrains {
         let clock_rate = self.clock_rate.unwrap_or_else(|| self.mods.clock_rate());
-        let (skills, _) = calculate_skills(self);
+        let (peaks, _) = calculate_skills(self);
+
+        let PeaksRaw {
+            colour,
+            rhythm,
+            stamina,
+        } = peaks.into_raw();
 
         TaikoStrains {
-            section_len: SECTION_LEN * clock_rate,
-            color: skills.color.strain_peaks,
-            rhythm: skills.rhythm.strain_peaks,
-            stamina_right: skills.stamina_right.strain_peaks,
-            stamina_left: skills.stamina_left.strain_peaks,
+            section_len: SECTION_LEN as f64 * clock_rate,
+            color: colour,
+            rhythm,
+            stamina,
         }
     }
 }
@@ -161,10 +193,8 @@ pub struct TaikoStrains {
     pub color: Vec<f64>,
     /// Strain peaks of the rhythm skill.
     pub rhythm: Vec<f64>,
-    /// Strain peaks of the left-stamina skill.
-    pub stamina_right: Vec<f64>,
-    /// Strain peaks of the right-stamina skill.
-    pub stamina_left: Vec<f64>,
+    /// Strain peaks of the stamina skill.
+    pub stamina: Vec<f64>,
 }
 
 impl TaikoStrains {
@@ -176,67 +206,68 @@ impl TaikoStrains {
     }
 }
 
-fn calculate_skills(params: TaikoStars<'_>) -> (Skills, usize) {
+fn calculate_skills(params: TaikoStars<'_>) -> (Peaks, usize) {
     let TaikoStars {
         map,
         mods,
         passed_objects,
         clock_rate,
+        ..
     } = params;
 
     let take = passed_objects.unwrap_or(map.hit_objects.len());
     let clock_rate = clock_rate.unwrap_or_else(|| mods.clock_rate());
 
-    // True if the object at that index is stamina cheese
-    let cheese = map.find_cheese();
-    let mut skills = Skills::new();
+    let mut peaks = Peaks::new();
     let mut max_combo = 0;
 
     match map.hit_objects.get(0) {
         Some(h) => max_combo += h.is_circle() as usize,
-        None => return (skills, max_combo),
+        None => return (peaks, max_combo),
     }
 
     match map.hit_objects.get(1) {
         Some(h) => max_combo += h.is_circle() as usize,
-        None => return (skills, max_combo),
+        None => return (peaks, max_combo),
     }
 
-    let mut hit_objects = map
+    let mut diff_objects = map
         .taiko_objects()
         .take(take)
-        .enumerate()
         .skip(2)
         .zip(map.taiko_objects().skip(1))
         .zip(map.taiko_objects())
-        .inspect(|(((_, base), _), _)| max_combo += base.h.is_circle() as usize)
-        .map(|(((idx, base), prev), prev_prev)| {
-            DifficultyObject::new(idx, base, prev, prev_prev, clock_rate)
-        });
+        .enumerate()
+        .inspect(|(_, ((base, _), _))| max_combo += base.h.is_circle() as usize)
+        .fold(
+            ObjectLists::default(),
+            |mut lists, (idx, ((base, last), last_last))| {
+                let diff_obj =
+                    TaikoDifficultyObject::new(base, last, last_last, clock_rate, &lists, idx);
 
-    // Handle first element distinctly
-    let h = match hit_objects.next() {
-        Some(h) => h,
-        None => return (skills, max_combo),
-    };
+                match &diff_obj.mono_idx {
+                    MonoIndex::Centre(_) => lists.centres.push(idx),
+                    MonoIndex::Rim(_) => lists.rims.push(idx),
+                    MonoIndex::None => {}
+                }
 
-    // No strain for first object
-    let mut curr_section_end = (h.start_time / SECTION_LEN).ceil() * SECTION_LEN;
-    skills.process(&h, &cheese);
+                if diff_obj.note_idx.is_some() {
+                    lists.notes.push(idx);
+                }
 
-    // Handle all other objects
-    for h in hit_objects {
-        while h.start_time > curr_section_end {
-            skills.save_peak_and_start_new_section(curr_section_end);
-            curr_section_end += SECTION_LEN;
-        }
+                lists.all.push(Rc::new(RefCell::new(diff_obj)));
 
-        skills.process(&h, &cheese);
+                lists
+            },
+        );
+
+    ColourDifficultyPreprocessor::process_and_assign(&mut diff_objects);
+
+    for hit_object in diff_objects.all.iter() {
+        peaks.process(&hit_object.borrow(), &diff_objects);
     }
 
-    skills.save_current_peak();
-
-    (skills, max_combo)
+    (peaks, max_combo)
 }
 
 #[inline]
@@ -248,56 +279,19 @@ fn rescale(stars: f64) -> f64 {
     }
 }
 
-#[inline]
-fn simple_color_penalty(stamina: f64, color: f64) -> f64 {
-    if color <= 0.0 {
-        0.79 - 0.25
-    } else {
-        0.79 - (stamina / color - 12.0).atan() / PI / 2.0
-    }
-}
-
-fn locally_combined_difficulty(peaks: &mut Vec<f64>, skills: &Skills, stamina_penalty: f64) -> f64 {
-    peaks.clear();
-
-    let iter = skills
-        .color
-        .strain_peaks
-        .iter()
-        .zip(skills.rhythm.strain_peaks.iter())
-        .zip(skills.stamina_right.strain_peaks.iter())
-        .zip(skills.stamina_left.strain_peaks.iter())
-        .map(|(((&color, &rhythm), &stamina_right), &stamina_left)| {
-            norm(
-                2.0,
-                color * COLOR_SKILL_MULTIPLIER,
-                rhythm * RHYTHM_SKILL_MULTIPLIER,
-                (stamina_right + stamina_left) * STAMINA_SKILL_MULTIPLIER * stamina_penalty,
-            )
-        });
-
-    peaks.extend(iter);
-    peaks.sort_unstable_by(|a, b| b.partial_cmp(a).unwrap_or(Ordering::Equal));
-
-    let mut difficulty = 0.0;
-    let mut weight = 1.0;
-
-    for strain in peaks {
-        difficulty += *strain * weight;
-        weight *= 0.9;
-    }
-
-    difficulty
-}
-
-#[inline]
-fn norm(p: f64, a: f64, b: f64, c: f64) -> f64 {
-    (a.powf(p) + b.powf(p) + c.powf(p)).powf(p.recip())
-}
-
 /// The result of a difficulty calculation on an osu!taiko map.
-#[derive(Copy, Clone, Debug, Default, PartialEq)]
+#[derive(Clone, Debug, Default, PartialEq)]
 pub struct TaikoDifficultyAttributes {
+    /// The difficulty corresponding to the stamina skill.
+    pub stamina: f64,
+    /// The difficulty corresponding to the rhythm skill.
+    pub rhythm: f64,
+    /// The difficulty corresponding to the colour skill.
+    pub colour: f64,
+    /// The difficulty corresponding to the hardest parts of the map.
+    pub peak: f64,
+    /// The perceived hit window for an n300 inclusive of rate-adjusting mods (DT/HT/etc)
+    pub hit_window: f64,
     /// The final star rating.
     pub stars: f64,
     /// The maximum combo.
@@ -322,7 +316,9 @@ pub struct TaikoPerformanceAttributes {
     /// The accuracy portion of the final pp.
     pub pp_acc: f64,
     /// The strain portion of the final pp.
-    pub pp_strain: f64,
+    pub pp_difficulty: f64,
+    /// Scaled miss count based on total hits.
+    pub effective_miss_count: f64,
 }
 
 impl TaikoPerformanceAttributes {
@@ -367,6 +363,7 @@ impl<'map> From<OsuStars<'map>> for TaikoStars<'map> {
             mods,
             passed_objects,
             clock_rate,
+            is_convert: true,
         }
     }
 }

src/taiko/pp.rs

@@ -38,7 +38,7 @@ use crate::{
 #[derive(Clone, Debug)]
 #[allow(clippy::upper_case_acronyms)]
 pub struct TaikoPP<'map> {
-    map: Cow<'map, Beatmap>,
+    pub(crate) map: Cow<'map, Beatmap>,
     attributes: Option<TaikoDifficultyAttributes>,
     mods: u32,
     combo: Option<usize>,
@@ -176,7 +176,9 @@ impl<'map> TaikoPP<'map> {
     /// Calculate all performance related values, including pp and stars.
     pub fn calculate(mut self) -> TaikoPerformanceAttributes {
         let attributes = self.attributes.take().unwrap_or_else(|| {
-            let mut calculator = TaikoStars::new(self.map.as_ref()).mods(self.mods);
+            let mut calculator = TaikoStars::new(self.map.as_ref())
+                .mods(self.mods)
+                .is_convert(matches!(self.map, Cow::Owned(_)));
 
             if let Some(passed_objects) = self.passed_objects {
                 calculator = calculator.passed_objects(passed_objects);
@@ -189,36 +191,65 @@ impl<'map> TaikoPP<'map> {
             calculator.calculate()
         });
 
-        if self.n300.or(self.n100).is_some() {
-            let total = self.map.n_circles as usize;
-            let misses = self.n_misses;
+        self.assert_hitresults(attributes).calculate()
+    }
 
-            let mut n300 = self.n300.unwrap_or(0).min(total - misses);
-            let mut n100 = self.n100.unwrap_or(0).min(total - n300 - misses);
+    fn assert_hitresults(&'map self, attributes: TaikoDifficultyAttributes) -> TaikoPPInner<'map> {
+        let total_result_count = attributes.max_combo();
+        let misses = self.n_misses;
 
-            let given = n300 + n100 + misses;
-            let missing = total - given;
+        let (n300, n100) = match (self.n300, self.n100) {
+            (Some(n300), Some(n100)) => {
+                let n300 = n300.min(total_result_count - misses);
+                let n100 = n100.min(total_result_count - n300 - misses);
 
-            match (self.n300, self.n100) {
-                (Some(_), Some(_)) => n300 += missing,
-                (Some(_), None) => n100 += missing,
-                (None, Some(_)) => n300 += missing,
-                (None, None) => unreachable!(),
-            };
+                let given = n300 + n100 + misses;
+                let missing = total_result_count - given;
 
-            self.acc = (2 * n300 + n100) as f64 / (2 * (n300 + n100 + misses)) as f64;
-        }
+                (n300 + missing, n100)
+            }
+            (Some(n300), None) => {
+                let n300 = n300.min(total_result_count - misses);
 
-        let inner = TaikoPPInner {
-            map: self.map.as_ref(),
-            attributes,
-            mods: self.mods,
-            acc: self.acc,
-            n_misses: self.n_misses,
-            clock_rate: self.clock_rate.unwrap_or_else(|| self.mods.clock_rate()),
+                let n100 = total_result_count
+                    .saturating_sub(n300)
+                    .saturating_sub(misses);
+
+                (n300, n100)
+            }
+            (None, Some(n100)) => {
+                let n100 = n100.min(total_result_count - misses);
+
+                let n300 = total_result_count
+                    .saturating_sub(n100)
+                    .saturating_sub(misses);
+
+                (n300, n100)
+            }
+            (None, None) => {
+                let target_total = (self.acc * (total_result_count * 2) as f64) as usize;
+
+                let n300 = target_total - total_result_count.saturating_sub(misses);
+                let n100 = total_result_count
+                    .saturating_sub(n300)
+                    .saturating_sub(misses);
+
+                (n300, n100)
+            }
         };
 
-        inner.calculate()
+        let acc = (2 * n300 + n100) as f64 / (2 * (n300 + n100 + misses)) as f64;
+
+        TaikoPPInner {
+            map: self.map.as_ref(),
+            attributes,
+            acc,
+            n300,
+            n100,
+            mods: self.mods,
+            n_misses: misses,
+            clock_rate: self.clock_rate.unwrap_or_else(|| self.mods.clock_rate()),
+        }
     }
 }
 
@@ -229,57 +260,73 @@ struct TaikoPPInner<'map> {
     acc: f64,
     n_misses: usize,
     clock_rate: f64,
+    n300: usize,
+    n100: usize,
 }
 
 impl<'map> TaikoPPInner<'map> {
     fn calculate(self) -> TaikoPerformanceAttributes {
-        let mut multiplier = 1.1;
+        // * The effectiveMissCount is calculated by gaining a ratio for totalSuccessfulHits
+        // * and increasing the miss penalty for shorter object counts lower than 1000.
+        let total_successful_hits = self.total_successful_hits();
 
-        if self.mods.nf() {
-            multiplier *= 0.9;
-        }
+        let effective_miss_count = if total_successful_hits > 0 {
+            (1000.0 / (total_successful_hits as f64)).max(1.0) * self.n_misses as f64
+        } else {
+            0.0
+        };
+
+        let mut multiplier = 1.13;
 
         if self.mods.hd() {
-            multiplier *= 1.1;
+            multiplier *= 1.075;
         }
 
-        let strain_value = self.compute_strain_value();
+        if self.mods.ez() {
+            multiplier *= 0.975;
+        }
+
+        let diff_value = self.compute_difficulty_value(effective_miss_count);
         let acc_value = self.compute_accuracy_value();
 
-        let pp = (strain_value.powf(1.1) + acc_value.powf(1.1)).powf(1.0 / 1.1) * multiplier;
+        let pp = (diff_value.powf(1.1) + acc_value.powf(1.1)).powf(1.0 / 1.1) * multiplier;
 
         TaikoPerformanceAttributes {
             difficulty: self.attributes,
             pp,
             pp_acc: acc_value,
-            pp_strain: strain_value,
+            pp_difficulty: diff_value,
+            effective_miss_count,
         }
     }
 
-    fn compute_strain_value(&self) -> f64 {
-        let attributes = &self.attributes;
-        let exp_base = 5.0 * (attributes.stars / 0.0075).max(1.0) - 4.0;
-        let mut strain = exp_base * exp_base / 100_000.0;
+    fn compute_difficulty_value(&self, effective_miss_count: f64) -> f64 {
+        let attrs = &self.attributes;
+        let exp_base = 5.0 * (attrs.stars / 0.115).max(1.0) - 4.0;
+        let mut diff_value = exp_base.powf(2.25) / 1150.0;
 
-        // Longer maps are worth more
-        let len_bonus = 1.0 + 0.1 * (attributes.max_combo as f64 / 1500.0).min(1.0);
-        strain *= len_bonus;
+        let len_bonus = 1.0 + 0.1 * (attrs.max_combo as f64 / 1500.0).min(1.0);
+        diff_value *= len_bonus;
 
-        // Penalize misses exponentially
-        strain *= 0.985_f64.powi(self.n_misses as i32);
+        diff_value *= 0.986_f64.powf(effective_miss_count);
+
+        if self.mods.ez() {
+            diff_value *= 0.985;
+        }
 
-        // HD bonus
         if self.mods.hd() {
-            strain *= 1.025;
+            diff_value *= 1.025;
+        }
+
+        if self.mods.hr() {
+            diff_value *= 1.05;
         }
 
-        // FL bonus
         if self.mods.fl() {
-            strain *= 1.05 * len_bonus;
+            diff_value *= 1.05 * len_bonus;
         }
 
-        // Scale with accuracy
-        strain * self.acc
+        diff_value * self.acc * self.acc
     }
 
     #[inline]
@@ -291,12 +338,32 @@ impl<'map> TaikoPPInner<'map> {
             .clock_rate(self.clock_rate)
             .hit_windows();
 
-        let max_combo = self.attributes.max_combo;
+        if hit_window <= 0.0 {
+            return 0.0;
+        }
 
-        (150.0 / hit_window).powf(1.1)
-            * self.acc.powi(15)
-            * 22.0
-            * (max_combo as f64 / 1500.0).powf(0.3).min(1.15)
+        let mut acc_value = (60.0 / hit_window).powf(1.1)
+            * self.acc.powi(8)
+            * self.attributes.stars.powf(0.4)
+            * 27.0;
+
+        let len_bonus = (self.total_hits() as f64 / 1500.0).powf(0.3).min(1.15);
+        acc_value *= len_bonus;
+
+        // * Slight HDFL Bonus for accuracy. A clamp is used to prevent against negative values
+        if self.mods.hd() && self.mods.fl() {
+            acc_value *= (1.075 * len_bonus).max(1.05);
+        }
+
+        acc_value
+    }
+
+    fn total_hits(&self) -> usize {
+        self.n300 + self.n100 + self.n_misses
+    }
+
+    fn total_successful_hits(&self) -> usize {
+        self.n300 + self.n100
     }
 }
 

src/taiko/skill.rs

@@ -1,153 +0,0 @@
-use super::{DifficultyObject, SkillKind};
-
-use std::cmp::Ordering;
-
-const DECAY_WEIGHT: f64 = 0.9;
-
-const COLOR_SKILL_MULTIPLIER: f64 = 1.0;
-const COLOR_STRAIN_DECAY_BASE: f64 = 0.4;
-
-const RHYTHM_SKILL_MULTIPLIER: f64 = 10.0;
-const RHYTHM_STRAIN_DECAY_BASE: f64 = 0.0;
-
-const STAMINA_SKILL_MULTIPLIER: f64 = 1.0;
-const STAMINA_STRAIN_DECAY_BASE: f64 = 0.4;
-
-#[derive(Clone, Debug)]
-pub(crate) struct Skills {
-    pub(crate) color: Skill,
-    pub(crate) rhythm: Skill,
-    pub(crate) stamina_right: Skill,
-    pub(crate) stamina_left: Skill,
-}
-
-impl Skills {
-    pub(crate) fn new() -> Self {
-        Self {
-            color: Skill::new(SkillKind::color()),
-            rhythm: Skill::new(SkillKind::rhythm()),
-            stamina_right: Skill::new(SkillKind::stamina(true)),
-            stamina_left: Skill::new(SkillKind::stamina(false)),
-        }
-    }
-
-    pub(crate) fn save_peak_and_start_new_section(&mut self, time: f64) {
-        self.color.save_current_peak();
-        self.color.start_new_section_from(time);
-        self.rhythm.save_current_peak();
-        self.rhythm.start_new_section_from(time);
-        self.stamina_right.save_current_peak();
-        self.stamina_right.start_new_section_from(time);
-        self.stamina_left.save_current_peak();
-        self.stamina_left.start_new_section_from(time);
-    }
-
-    pub(crate) fn save_current_peak(&mut self) {
-        self.color.save_current_peak();
-        self.rhythm.save_current_peak();
-        self.stamina_right.save_current_peak();
-        self.stamina_left.save_current_peak();
-    }
-
-    pub(crate) fn process(&mut self, curr: &DifficultyObject<'_>, cheese: &[bool]) {
-        self.color.process(curr, cheese);
-        self.rhythm.process(curr, cheese);
-        self.stamina_right.process(curr, cheese);
-        self.stamina_left.process(curr, cheese);
-    }
-
-    pub(crate) fn strain_peaks_len(&self) -> usize {
-        self.color.strain_peaks.len()
-    }
-}
-
-#[derive(Clone, Debug)]
-pub(crate) struct Skill {
-    pub(crate) current_strain: f64,
-    pub(crate) curr_section_peak: f64,
-
-    kind: SkillKind,
-    pub(crate) strain_peaks: Vec<f64>,
-
-    prev_time: Option<f64>,
-}
-
-impl Skill {
-    #[inline]
-    pub(crate) fn new(kind: SkillKind) -> Self {
-        Self {
-            current_strain: 1.0,
-            curr_section_peak: 1.0,
-
-            kind,
-            strain_peaks: Vec::with_capacity(128),
-
-            prev_time: None,
-        }
-    }
-
-    #[inline]
-    pub(crate) fn save_current_peak(&mut self) {
-        self.strain_peaks.push(self.curr_section_peak);
-    }
-
-    #[inline]
-    pub(crate) fn start_new_section_from(&mut self, time: f64) {
-        self.curr_section_peak = self.peak_strain(time - self.prev_time.unwrap());
-    }
-
-    #[inline]
-    pub(crate) fn process(&mut self, curr: &DifficultyObject<'_>, cheese: &[bool]) {
-        self.current_strain *= self.strain_decay(curr.delta);
-        self.current_strain += self.kind.strain_value_of(curr, cheese) * self.skill_multiplier();
-        self.curr_section_peak = self.curr_section_peak.max(self.current_strain);
-        self.prev_time.replace(curr.start_time);
-    }
-
-    pub(crate) fn copy_strain_peaks(&self, buf: &mut [f64]) {
-        buf.copy_from_slice(&self.strain_peaks);
-    }
-
-    #[inline]
-    pub(crate) fn difficulty_value(&self, peaks: &mut [f64]) -> f64 {
-        let mut difficulty = 0.0;
-        let mut weight = 1.0;
-
-        peaks.sort_unstable_by(|a, b| b.partial_cmp(a).unwrap_or(Ordering::Equal));
-
-        for &strain in peaks.iter() {
-            difficulty += strain * weight;
-            weight *= DECAY_WEIGHT;
-        }
-
-        difficulty
-    }
-
-    #[inline]
-    fn skill_multiplier(&self) -> f64 {
-        match self.kind {
-            SkillKind::Color { .. } => COLOR_SKILL_MULTIPLIER,
-            SkillKind::Rhythm { .. } => RHYTHM_SKILL_MULTIPLIER,
-            SkillKind::Stamina { .. } => STAMINA_SKILL_MULTIPLIER,
-        }
-    }
-
-    #[inline]
-    fn strain_decay_base(&self) -> f64 {
-        match self.kind {
-            SkillKind::Color { .. } => COLOR_STRAIN_DECAY_BASE,
-            SkillKind::Rhythm { .. } => RHYTHM_STRAIN_DECAY_BASE,
-            SkillKind::Stamina { .. } => STAMINA_STRAIN_DECAY_BASE,
-        }
-    }
-
-    #[inline]
-    fn peak_strain(&self, delta_time: f64) -> f64 {
-        self.current_strain * self.strain_decay(delta_time)
-    }
-
-    #[inline]
-    fn strain_decay(&self, ms: f64) -> f64 {
-        self.strain_decay_base().powf(ms / 1000.0)
-    }
-}

src/taiko/skill_kind.rs

@@ -1,311 +0,0 @@
-use crate::limited_queue::LimitedQueue;
-
-use super::{DifficultyObject, HitObjectRhythm, Rim};
-
-const RHYTHM_STRAIN_DECAY: f64 = 0.96;
-const MOST_RECENT_PATTERNS_TO_COMPARE: usize = 2;
-
-const MONO_HISTORY_MAX_LEN: usize = 5;
-const RHYTHM_HISTORY_MAX_LEN: usize = 8;
-const STAMINA_HISTORY_MAX_LEN: usize = 2;
-
-#[derive(Copy, Clone, Debug)]
-pub(crate) struct RhythmHistoryElement {
-    idx: usize,
-    rhythm: &'static HitObjectRhythm,
-}
-
-impl RhythmHistoryElement {
-    fn new(difficulty_object: &DifficultyObject<'_>) -> Self {
-        Self {
-            idx: difficulty_object.idx,
-            rhythm: difficulty_object.rhythm,
-        }
-    }
-}
-
-impl Default for RhythmHistoryElement {
-    fn default() -> Self {
-        Self {
-            idx: 0,
-            rhythm: HitObjectRhythm::static_ref(),
-        }
-    }
-}
-
-#[derive(Clone, Debug)]
-pub(crate) enum SkillKind {
-    Color {
-        mono_history: LimitedQueue<usize, MONO_HISTORY_MAX_LEN>,
-        prev_is_rim: Option<bool>,
-        current_mono_len: usize,
-    },
-    Rhythm {
-        rhythm_history: LimitedQueue<RhythmHistoryElement, RHYTHM_HISTORY_MAX_LEN>,
-        notes_since_rhythm_change: usize,
-        current_strain: f64,
-    },
-    Stamina {
-        note_pair_duration_history: LimitedQueue<f64, STAMINA_HISTORY_MAX_LEN>,
-        hand: u8,
-        off_hand_object_duration: f64,
-    },
-}
-
-impl SkillKind {
-    #[inline]
-    pub(crate) fn color() -> Self {
-        Self::Color {
-            mono_history: LimitedQueue::new(),
-            prev_is_rim: None,
-            current_mono_len: 0,
-        }
-    }
-
-    #[inline]
-    pub(crate) fn rhythm() -> Self {
-        Self::Rhythm {
-            rhythm_history: LimitedQueue::new(),
-            notes_since_rhythm_change: 0,
-            current_strain: 0.0,
-        }
-    }
-
-    #[inline]
-    pub(crate) fn stamina(right_hand: bool) -> Self {
-        Self::Stamina {
-            note_pair_duration_history: LimitedQueue::new(),
-            hand: right_hand as u8,
-            off_hand_object_duration: f64::MAX,
-        }
-    }
-
-    pub(crate) fn strain_value_of(
-        &mut self,
-        current: &DifficultyObject<'_>,
-        cheese: &[bool],
-    ) -> f64 {
-        match self {
-            Self::Color {
-                mono_history,
-                prev_is_rim,
-                current_mono_len,
-            } => {
-                let prev_is_circle = current.prev.h.is_circle();
-                let base_is_circle = current.base.h.is_circle();
-                let curr_is_rim = current.base.sound.is_rim();
-
-                if !(current.delta < 1000.0 && prev_is_circle && base_is_circle) {
-                    mono_history.clear();
-                    *current_mono_len = base_is_circle as usize;
-
-                    *prev_is_rim = if base_is_circle {
-                        Some(curr_is_rim)
-                    } else {
-                        None
-                    };
-
-                    return 0.0;
-                }
-
-                let mut strain = 0.0;
-
-                if prev_is_rim
-                    .filter(|&is_rim| is_rim != curr_is_rim)
-                    .is_some()
-                {
-                    strain = if mono_history.len() < 2
-                        || (*mono_history.last().unwrap() + *current_mono_len) % 2 == 0
-                    {
-                        0.0
-                    } else {
-                        1.0
-                    };
-
-                    let mut reps_penalty = 1.0;
-
-                    mono_history.push(*current_mono_len);
-
-                    let iter = (0..mono_history
-                        .len()
-                        .saturating_sub(MOST_RECENT_PATTERNS_TO_COMPARE))
-                        .rev();
-
-                    for start in iter {
-                        let different_pattern = (0..MOST_RECENT_PATTERNS_TO_COMPARE).any(|i| {
-                            let to_compare =
-                                mono_history.len() + i - MOST_RECENT_PATTERNS_TO_COMPARE;
-
-                            mono_history[start + i] != mono_history[to_compare]
-                        });
-
-                        if different_pattern {
-                            continue;
-                        }
-
-                        let mut notes_since = 0;
-
-                        for i in start..mono_history.len() {
-                            notes_since += mono_history[i];
-                        }
-
-                        reps_penalty *= repetition_penalty(notes_since);
-
-                        break;
-                    }
-
-                    strain *= reps_penalty;
-
-                    *current_mono_len = 1;
-                } else {
-                    *current_mono_len += 1;
-                }
-
-                *prev_is_rim = Some(curr_is_rim);
-
-                strain
-            }
-            Self::Rhythm {
-                rhythm_history,
-                notes_since_rhythm_change,
-                current_strain,
-            } => {
-                let base_is_circle = current.base.h.is_circle();
-
-                if !base_is_circle {
-                    *current_strain = 0.0;
-                    *notes_since_rhythm_change = 0;
-
-                    return 0.0;
-                }
-
-                *current_strain *= RHYTHM_STRAIN_DECAY;
-                *notes_since_rhythm_change += 1;
-
-                if current.rhythm.difficulty.abs() <= f64::EPSILON {
-                    return 0.0;
-                }
-
-                let mut strain = current.rhythm.difficulty;
-
-                rhythm_history.push(RhythmHistoryElement::new(current));
-
-                let mut reps_penalty = 1.0;
-
-                for most_recent_patterns_to_compare in 2..=RHYTHM_HISTORY_MAX_LEN / 2 {
-                    let iter = (0..rhythm_history
-                        .len()
-                        .saturating_sub(most_recent_patterns_to_compare))
-                        .rev();
-
-                    for start in iter {
-                        let different_pattern = (0..most_recent_patterns_to_compare).any(|i| {
-                            let to_compare =
-                                rhythm_history.len() + i - most_recent_patterns_to_compare;
-
-                            rhythm_history[start + i].rhythm != rhythm_history[to_compare].rhythm
-                        });
-
-                        if different_pattern {
-                            continue;
-                        }
-
-                        reps_penalty *= repetition_penalty(current.idx - rhythm_history[start].idx);
-
-                        break;
-                    }
-                }
-
-                let speed_penalty = if current.delta < 80.0 {
-                    1.0
-                } else if current.delta < 210.0 {
-                    (1.4 - 0.005 * current.delta).max(0.0)
-                } else {
-                    *current_strain = 0.0;
-                    *notes_since_rhythm_change = 0;
-
-                    0.0
-                };
-
-                strain *= reps_penalty;
-                strain *= pattern_len_penalty(*notes_since_rhythm_change);
-                strain *= speed_penalty;
-
-                *notes_since_rhythm_change = 0;
-                *current_strain += strain;
-
-                *current_strain
-            }
-            Self::Stamina {
-                hand,
-                note_pair_duration_history,
-                off_hand_object_duration,
-            } => {
-                let base_is_circle = current.base.h.is_circle();
-
-                if !base_is_circle {
-                    return 0.0;
-                }
-
-                if current.idx % 2 == *hand as usize {
-                    if current.idx == 1 {
-                        return 1.0;
-                    }
-
-                    let mut strain = 1.0;
-                    note_pair_duration_history.push(current.delta + *off_hand_object_duration);
-                    let shortest_recent_note = *note_pair_duration_history.min().unwrap();
-                    strain += speed_bonus(shortest_recent_note);
-
-                    if cheese[current.idx] {
-                        let p = cheese_penalty(current.delta + *off_hand_object_duration);
-                        strain *= p;
-                    }
-
-                    return strain;
-                }
-
-                *off_hand_object_duration = current.delta;
-
-                0.0
-            }
-        }
-    }
-}
-
-#[inline]
-fn pattern_len_penalty(pattern_len: usize) -> f64 {
-    let pattern_len = pattern_len as f64;
-    let short_pattern_penalty = (0.15 * pattern_len).min(1.0);
-    let long_pattern_penalty = (2.5 - 0.15 * pattern_len).max(0.0).min(1.0);
-
-    short_pattern_penalty.min(long_pattern_penalty)
-}
-
-#[inline]
-fn cheese_penalty(note_pair_duration: f64) -> f64 {
-    if note_pair_duration > 125.0 {
-        1.0
-    } else if note_pair_duration < 100.0 {
-        0.6
-    } else {
-        0.6 + (note_pair_duration - 100.0) * 0.016
-    }
-}
-
-#[inline]
-fn speed_bonus(note_pair_duration: f64) -> f64 {
-    if note_pair_duration > 200.0 {
-        return 0.0;
-    }
-
-    let mut bonus = 200.0 - note_pair_duration;
-    bonus *= bonus;
-
-    bonus / 100_000.0
-}
-
-#[inline]
-fn repetition_penalty(notes_since: usize) -> f64 {
-    (0.032 * notes_since as f64).min(1.0)
-}

src/taiko/skills/colour.rs

@@ -0,0 +1,154 @@
+use std::{
+    cell::RefCell,
+    rc::{Rc, Weak},
+};
+
+use crate::taiko::{
+    colours::{AlternatingMonoPattern, MonoStreak, RepeatingHitPatterns},
+    difficulty_object::{ObjectLists, TaikoDifficultyObject},
+};
+
+use super::{Skill, StrainDecaySkill, StrainSkill};
+
+#[derive(Clone, Debug)]
+pub(crate) struct Colour {
+    curr_strain: f64,
+    curr_section_peak: f64,
+    curr_section_end: f64,
+    pub(crate) strain_peaks: Vec<f64>,
+}
+
+impl Colour {
+    pub(crate) fn new() -> Self {
+        Self {
+            curr_strain: 0.0,
+            curr_section_peak: 0.0,
+            curr_section_end: 0.0,
+            strain_peaks: Vec::new(),
+        }
+    }
+}
+
+impl Skill for Colour {
+    fn process(&mut self, curr: &TaikoDifficultyObject<'_>, hit_objects: &ObjectLists<'_>) {
+        <Self as StrainSkill>::process(self, curr, hit_objects)
+    }
+
+    fn difficulty_value(self) -> f64 {
+        <Self as StrainSkill>::difficulty_value(self)
+    }
+}
+
+impl StrainSkill for Colour {
+    fn strain_peaks_mut(&mut self) -> &mut Vec<f64> {
+        &mut self.strain_peaks
+    }
+
+    fn curr_section_peak(&mut self) -> &mut f64 {
+        &mut self.curr_section_peak
+    }
+
+    fn curr_section_end(&mut self) -> &mut f64 {
+        &mut self.curr_section_end
+    }
+
+    fn strain_value_at(
+        &mut self,
+        curr: &TaikoDifficultyObject<'_>,
+        hit_objects: &ObjectLists<'_>,
+    ) -> f64 {
+        <Self as StrainDecaySkill>::strain_value_at(self, curr, hit_objects)
+    }
+
+    fn calculate_initial_strain(&self, time: f64, curr: &TaikoDifficultyObject<'_>) -> f64 {
+        <Self as StrainDecaySkill>::calculate_initial_strain(self, time, curr)
+    }
+}
+
+impl StrainDecaySkill for Colour {
+    const SKILL_MULTIPLIER: f64 = 0.12;
+    const STRAIN_DECAY_BASE: f64 = 0.8;
+
+    fn curr_strain(&self) -> f64 {
+        self.curr_strain
+    }
+
+    fn curr_strain_mut(&mut self) -> &mut f64 {
+        &mut self.curr_strain
+    }
+
+    fn strain_value_of(&mut self, curr: &TaikoDifficultyObject<'_>, _: &ObjectLists<'_>) -> f64 {
+        ColourEvaluator::evaluate_diff_of(curr)
+    }
+}
+
+struct ColourEvaluator;
+
+impl ColourEvaluator {
+    fn sigmoid(val: f64, center: f64, width: f64, middle: f64, height: f64) -> f64 {
+        let sigmoid = (std::f64::consts::E * -(val - center) / width).tanh();
+
+        sigmoid * (height / 2.0) + middle
+    }
+
+    fn evaluate_diff_of_mono_streak(mono_streak: Rc<RefCell<MonoStreak<'_>>>) -> f64 {
+        let mono_streak = mono_streak.borrow();
+
+        let parent_eval = mono_streak
+            .parent
+            .as_ref()
+            .and_then(Weak::upgrade)
+            .map_or(1.0, Self::evaluate_diff_of_alternating_mono_pattern);
+
+        Self::sigmoid(mono_streak.idx as f64, 2.0, 2.0, 0.5, 1.0) * parent_eval * 0.5
+    }
+
+    fn evaluate_diff_of_alternating_mono_pattern(
+        alternating_mono_pattern: Rc<RefCell<AlternatingMonoPattern<'_>>>,
+    ) -> f64 {
+        let alternating_mono_pattern = alternating_mono_pattern.borrow();
+
+        let parent_eval = alternating_mono_pattern
+            .parent
+            .as_ref()
+            .and_then(Weak::upgrade)
+            .map_or(1.0, Self::evaluate_diff_of_repeating_hit_patterns);
+
+        Self::sigmoid(alternating_mono_pattern.idx as f64, 2.0, 2.0, 0.5, 1.0) * parent_eval
+    }
+
+    fn evaluate_diff_of_repeating_hit_patterns(
+        repeating_hit_patterns: Rc<RefCell<RepeatingHitPatterns<'_>>>,
+    ) -> f64 {
+        let repetition_interval = repeating_hit_patterns.borrow().repetition_interval as f64;
+
+        2.0 * (1.0 - Self::sigmoid(repetition_interval, 2.0, 2.0, 0.5, 1.0))
+    }
+
+    fn evaluate_diff_of(hit_object: &TaikoDifficultyObject<'_>) -> f64 {
+        let colour = &hit_object.colour;
+        let mut difficulty = 0.0;
+
+        // * Difficulty for MonoStreak
+        if let Some(mono_streak) = colour.mono_streak.as_ref().and_then(Weak::upgrade) {
+            difficulty += Self::evaluate_diff_of_mono_streak(mono_streak);
+        }
+
+        // * Difficulty for AlternatingMonoPattern
+        if let Some(alternating_mono_pattern) = colour
+            .alternating_mono_pattern
+            .as_ref()
+            .and_then(Weak::upgrade)
+        {
+            difficulty += Self::evaluate_diff_of_alternating_mono_pattern(alternating_mono_pattern);
+        }
+
+        // * Difficulty for RepeatingHitPattern
+        if let Some(repeating_hit_patterns) = colour.repeating_hit_patterns.as_ref().map(Rc::clone)
+        {
+            difficulty += Self::evaluate_diff_of_repeating_hit_patterns(repeating_hit_patterns);
+        }
+
+        difficulty
+    }
+}

src/taiko/skills/mod.rs

@@ -0,0 +1,131 @@
+mod colour;
+mod peaks;
+mod rhythm;
+mod stamina;
+
+use std::{cmp::Ordering, mem};
+
+pub(crate) use self::peaks::{Peaks, PeaksDifficultyValues, PeaksRaw};
+
+use super::{
+    difficulty_object::{ObjectLists, TaikoDifficultyObject},
+    SECTION_LEN,
+};
+
+pub(crate) trait Skill: Sized {
+    fn process(&mut self, curr: &TaikoDifficultyObject<'_>, hit_objects: &ObjectLists<'_>);
+    fn difficulty_value(self) -> f64;
+}
+
+pub(crate) trait StrainSkill: Skill {
+    const DECAY_WEIGHT: f64 = 0.9;
+
+    fn strain_peaks_mut(&mut self) -> &mut Vec<f64>;
+    fn curr_section_peak(&mut self) -> &mut f64;
+    fn curr_section_end(&mut self) -> &mut f64;
+
+    fn strain_value_at(
+        &mut self,
+        curr: &TaikoDifficultyObject<'_>,
+        hit_objects: &ObjectLists<'_>,
+    ) -> f64;
+
+    fn calculate_initial_strain(&self, time: f64, curr: &TaikoDifficultyObject<'_>) -> f64;
+
+    fn process(&mut self, curr: &TaikoDifficultyObject<'_>, hit_objects: &ObjectLists<'_>) {
+        // * The first object doesn't generate a strain, so we begin with an incremented section end
+        if curr.idx == 0 {
+            let section_len = SECTION_LEN as f64;
+            *self.curr_section_end() = (curr.base.h.start_time / section_len).ceil() * section_len;
+        }
+
+        while curr.base.h.start_time > *self.curr_section_end() {
+            self.save_curr_peak();
+
+            {
+                let section_end = *self.curr_section_end();
+                self.start_new_section_from(section_end, curr);
+            }
+
+            *self.curr_section_end() += SECTION_LEN as f64;
+        }
+
+        *self.curr_section_peak() = self
+            .strain_value_at(curr, hit_objects)
+            .max(*self.curr_section_peak());
+    }
+
+    fn save_curr_peak(&mut self) {
+        let peak = *self.curr_section_peak();
+        self.strain_peaks_mut().push(peak);
+    }
+
+    fn start_new_section_from(&mut self, time: f64, curr: &TaikoDifficultyObject<'_>) {
+        // * The maximum strain of the new section is not zero by default
+        // * This means we need to capture the strain level at the beginning of the new section,
+        // * and use that as the initial peak level.
+        *self.curr_section_peak() = self.calculate_initial_strain(time, curr);
+    }
+
+    fn difficulty_value(self) -> f64 {
+        let mut difficulty = 0.0;
+        let mut weight = 1.0;
+
+        // * Sections with 0 strain are excluded to avoid worst-case time complexity of the following sort (e.g. /b/2351871).
+        // * These sections will not contribute to the difficulty.
+        let mut peaks = self.get_curr_strain_peaks();
+
+        peaks.retain(|&peak| peak > 0.0);
+        peaks.sort_unstable_by(|a, b| b.partial_cmp(a).unwrap_or(Ordering::Equal));
+
+        // * Difficulty is the weighted sum of the highest strains from every section.
+        // * We're sorting from highest to lowest strain.
+        for strain in peaks {
+            difficulty += strain * weight;
+            weight *= Self::DECAY_WEIGHT;
+        }
+
+        difficulty
+    }
+
+    fn get_curr_strain_peaks(mut self) -> Vec<f64> {
+        let curr_peak = *self.curr_section_peak();
+        let mut strain_peaks = mem::take(self.strain_peaks_mut());
+        strain_peaks.push(curr_peak);
+
+        strain_peaks
+    }
+}
+
+pub(crate) trait StrainDecaySkill: StrainSkill {
+    const SKILL_MULTIPLIER: f64;
+    const STRAIN_DECAY_BASE: f64;
+
+    fn curr_strain(&self) -> f64;
+    fn curr_strain_mut(&mut self) -> &mut f64;
+
+    fn strain_value_of(
+        &mut self,
+        curr: &TaikoDifficultyObject<'_>,
+        hit_objects: &ObjectLists<'_>,
+    ) -> f64;
+
+    fn calculate_initial_strain(&self, time: f64, curr: &TaikoDifficultyObject<'_>) -> f64 {
+        self.curr_strain() * self.strain_decay(time - curr.prev_time)
+    }
+
+    fn strain_value_at(
+        &mut self,
+        curr: &TaikoDifficultyObject<'_>,
+        hit_objects: &ObjectLists<'_>,
+    ) -> f64 {
+        *self.curr_strain_mut() *= self.strain_decay(curr.delta);
+        *self.curr_strain_mut() += self.strain_value_of(curr, hit_objects) * Self::SKILL_MULTIPLIER;
+
+        self.curr_strain()
+    }
+
+    fn strain_decay(&self, ms: f64) -> f64 {
+        Self::STRAIN_DECAY_BASE.powf(ms / 1000.0)
+    }
+}

src/taiko/skills/peaks.rs

@@ -0,0 +1,122 @@
+use std::cmp::Ordering;
+
+use crate::taiko::difficulty_object::{ObjectLists, TaikoDifficultyObject};
+
+use super::{colour::Colour, rhythm::Rhythm, stamina::Stamina, Skill, StrainSkill};
+
+#[derive(Clone, Debug)]
+pub(crate) struct Peaks {
+    colour: Colour,
+    rhythm: Rhythm,
+    stamina: Stamina,
+}
+
+impl Peaks {
+    const RHYTHM_SKILL_MULTIPLIER: f64 = 0.2 * Self::FINAL_MULTIPLIER;
+    const COLOUR_SKILL_MULTIPLIER: f64 = 0.375 * Self::FINAL_MULTIPLIER;
+    const STAMINA_SKILL_MULTIPLIER: f64 = 0.375 * Self::FINAL_MULTIPLIER;
+
+    const FINAL_MULTIPLIER: f64 = 0.0625;
+
+    pub(crate) fn new() -> Self {
+        Self {
+            colour: Colour::new(),
+            rhythm: Rhythm::new(),
+            stamina: Stamina::new(),
+        }
+    }
+
+    pub(crate) fn difficulty_values(self) -> PeaksDifficultyValues {
+        let colour_rating =
+            StrainSkill::difficulty_value(self.colour) * Self::COLOUR_SKILL_MULTIPLIER;
+        // let rhythm_rating =
+        //     StrainSkill::difficulty_value(self.rhythm.clone()) * Self::RHYTHM_SKILL_MULTIPLIER;
+        // let stamina_rating =
+        //     StrainSkill::difficulty_value(self.stamina.clone()) * Self::STAMINA_SKILL_MULTIPLIER;
+
+        PeaksDifficultyValues {
+            colour_rating,
+            rhythm_rating: 0.0,
+            stamina_rating: 0.0,
+            // combined_rating: self.difficulty_value(),
+            combined_rating: 0.0,
+        }
+    }
+
+    pub(crate) fn into_raw(self) -> PeaksRaw {
+        PeaksRaw {
+            colour: self.colour.strain_peaks,
+            rhythm: self.rhythm.strain_peaks,
+            stamina: self.stamina.strain_peaks,
+        }
+    }
+
+    fn norm(p: f64, values: impl IntoIterator<Item = f64>) -> f64 {
+        values
+            .into_iter()
+            .fold(0.0, |sum, x| sum + x.powf(p))
+            .powf(p.recip())
+    }
+}
+
+impl Skill for Peaks {
+    fn process(&mut self, curr: &TaikoDifficultyObject<'_>, hit_objects: &ObjectLists<'_>) {
+        StrainSkill::process(&mut self.colour, curr, hit_objects);
+        StrainSkill::process(&mut self.rhythm, curr, hit_objects);
+        StrainSkill::process(&mut self.stamina, curr, hit_objects);
+    }
+
+    fn difficulty_value(self) -> f64 {
+        let mut peaks = Vec::new();
+
+        let colour_peaks = self.colour.get_curr_strain_peaks();
+        let rhythm_peaks = self.rhythm.get_curr_strain_peaks();
+        let stamina_peaks = self.stamina.get_curr_strain_peaks();
+
+        let zip = colour_peaks
+            .into_iter()
+            .zip(rhythm_peaks)
+            .zip(stamina_peaks);
+
+        for ((mut colour_peak, mut rhythm_peak), mut stamina_peak) in zip {
+            colour_peak *= Self::COLOUR_SKILL_MULTIPLIER;
+            rhythm_peak *= Self::RHYTHM_SKILL_MULTIPLIER;
+            stamina_peak *= Self::STAMINA_SKILL_MULTIPLIER;
+
+            let mut peak = Self::norm(1.5, [colour_peak, stamina_peak]);
+            peak = Self::norm(2.0, [peak, rhythm_peak]);
+
+            // * Sections with 0 strain are excluded to avoid worst-case
+            // * time complexity of the following sort (e.g. /b/2351871).
+            // * These sections will not contribute to the difficulty.
+            if peak > 0.0 {
+                peaks.push(peak);
+            }
+        }
+
+        let mut difficulty = 0.0;
+        let mut weight = 1.0;
+
+        peaks.sort_unstable_by(|a, b| b.partial_cmp(a).unwrap_or(Ordering::Equal));
+
+        for strain in peaks {
+            difficulty += strain * weight;
+            weight *= 0.9;
+        }
+
+        difficulty
+    }
+}
+
+pub(crate) struct PeaksDifficultyValues {
+    pub(crate) colour_rating: f64,
+    pub(crate) rhythm_rating: f64,
+    pub(crate) stamina_rating: f64,
+    pub(crate) combined_rating: f64,
+}
+
+pub(crate) struct PeaksRaw {
+    pub(crate) colour: Vec<f64>,
+    pub(crate) rhythm: Vec<f64>,
+    pub(crate) stamina: Vec<f64>,
+}

src/taiko/skills/rhythm.rs

@@ -0,0 +1,205 @@
+use crate::{
+    limited_queue::LimitedQueue,
+    taiko::difficulty_object::{HitObjectRhythm, ObjectLists, TaikoDifficultyObject},
+};
+
+use super::{Skill, StrainDecaySkill, StrainSkill};
+
+const HISTORY_MAX_LEN: usize = 8;
+
+#[derive(Clone, Debug)]
+pub(crate) struct Rhythm {
+    // Equal to osu's CurrentStrain from abstract class StrainDecaySkill
+    curr_decay_strain: f64,
+    // Equal to osu's currentStrain from class Rhythm
+    curr_strain: f64,
+    notes_since_rhythm_change: usize,
+    history: LimitedQueue<HistoryElement, HISTORY_MAX_LEN>,
+    curr_section_peak: f64,
+    curr_section_end: f64,
+    pub(crate) strain_peaks: Vec<f64>,
+}
+
+impl Rhythm {
+    const STRAIN_DECAY: f64 = 0.96;
+
+    pub(crate) fn new() -> Self {
+        Self {
+            curr_decay_strain: 0.0,
+            curr_strain: 0.0,
+            notes_since_rhythm_change: 0,
+            history: LimitedQueue::new(),
+            curr_section_peak: 0.0,
+            curr_section_end: 0.0,
+            strain_peaks: Vec::new(),
+        }
+    }
+
+    fn reset_rhythm_and_strain(&mut self) {
+        self.curr_strain = 0.0;
+        self.notes_since_rhythm_change = 0;
+    }
+
+    fn repetition_penalties(&mut self, hit_object: &TaikoDifficultyObject<'_>) -> f64 {
+        let mut penalty = 1.0;
+
+        self.history.push(HistoryElement::new(hit_object));
+
+        for most_recent_patterns_to_compare in 2..=(HISTORY_MAX_LEN / 2).min(self.history.len()) {
+            for start in (0..self.history.len() - most_recent_patterns_to_compare).rev() {
+                if !self.same_pattern(start, most_recent_patterns_to_compare) {
+                    continue;
+                }
+
+                let notes_since = hit_object.idx - self.history[start].idx;
+                penalty *= Self::repetition_penalty(notes_since);
+
+                break;
+            }
+        }
+
+        penalty
+    }
+
+    fn same_pattern(&self, start: usize, most_recent_patterns_to_compare: usize) -> bool {
+        let start = self.history.iter().skip(start);
+
+        let most_recent_patterns_to_compare = self
+            .history
+            .iter()
+            .skip(self.history.len() - most_recent_patterns_to_compare);
+
+        start
+            .zip(most_recent_patterns_to_compare)
+            .all(|(a, b)| a.rhythm == b.rhythm)
+    }
+
+    fn repetition_penalty(notes_since: usize) -> f64 {
+        (0.032 * notes_since as f64).min(1.0)
+    }
+
+    fn pattern_len_penalty(pattern_len: usize) -> f64 {
+        let pattern_len = pattern_len as f64;
+        let short_pattern_penalty = (0.15 * pattern_len).min(1.0);
+        let long_pattern_penalty = (2.5 - 0.15 * pattern_len).clamp(0.0, 1.0);
+
+        short_pattern_penalty.min(long_pattern_penalty)
+    }
+
+    fn speed_penalty(&mut self, delta: f64) -> f64 {
+        if delta < 80.0 {
+            return 1.0;
+        } else if delta < 210.0 {
+            return (1.4 - 0.005 * delta).max(0.0);
+        }
+
+        self.reset_rhythm_and_strain();
+
+        0.0
+    }
+}
+
+impl Skill for Rhythm {
+    fn process(&mut self, curr: &TaikoDifficultyObject<'_>, hit_objects: &ObjectLists<'_>) {
+        <Self as StrainSkill>::process(self, curr, hit_objects)
+    }
+
+    fn difficulty_value(self) -> f64 {
+        <Self as StrainSkill>::difficulty_value(self)
+    }
+}
+
+impl StrainSkill for Rhythm {
+    fn strain_peaks_mut(&mut self) -> &mut Vec<f64> {
+        &mut self.strain_peaks
+    }
+
+    fn curr_section_peak(&mut self) -> &mut f64 {
+        &mut self.curr_section_peak
+    }
+
+    fn curr_section_end(&mut self) -> &mut f64 {
+        &mut self.curr_section_end
+    }
+
+    fn strain_value_at(
+        &mut self,
+        curr: &TaikoDifficultyObject<'_>,
+        hit_objects: &ObjectLists<'_>,
+    ) -> f64 {
+        <Self as StrainDecaySkill>::strain_value_at(self, curr, hit_objects)
+    }
+
+    fn calculate_initial_strain(&self, time: f64, curr: &TaikoDifficultyObject<'_>) -> f64 {
+        <Self as StrainDecaySkill>::calculate_initial_strain(self, time, curr)
+    }
+}
+
+impl StrainDecaySkill for Rhythm {
+    const SKILL_MULTIPLIER: f64 = 10.0;
+    const STRAIN_DECAY_BASE: f64 = 0.0;
+
+    fn curr_strain(&self) -> f64 {
+        self.curr_decay_strain
+    }
+
+    fn curr_strain_mut(&mut self) -> &mut f64 {
+        &mut self.curr_decay_strain
+    }
+
+    fn strain_value_of(&mut self, curr: &TaikoDifficultyObject<'_>, _: &ObjectLists<'_>) -> f64 {
+        let base_is_circle = curr.base.h.is_circle();
+
+        // * drum rolls and swells are exempt.
+        if !base_is_circle {
+            self.reset_rhythm_and_strain();
+
+            return 0.0;
+        }
+
+        self.curr_strain *= Self::STRAIN_DECAY;
+        self.notes_since_rhythm_change += 1;
+
+        // * rhythm difficulty zero (due to rhythm not changing) => no rhythm strain.
+        if curr.rhythm.difficulty.abs() <= f64::EPSILON {
+            return 0.0;
+        }
+
+        let mut obj_strain = curr.rhythm.difficulty;
+
+        obj_strain *= self.repetition_penalties(curr);
+        obj_strain *= Self::pattern_len_penalty(self.notes_since_rhythm_change);
+        obj_strain *= self.speed_penalty(curr.delta);
+
+        // * careful - needs to be done here since calls above read this value
+        self.notes_since_rhythm_change = 0;
+
+        self.curr_strain += obj_strain;
+
+        self.curr_strain
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct HistoryElement {
+    idx: usize,
+    rhythm: &'static HitObjectRhythm,
+}
+
+impl HistoryElement {
+    fn new(difficulty_object: &TaikoDifficultyObject<'_>) -> Self {
+        Self {
+            idx: difficulty_object.idx,
+            rhythm: difficulty_object.rhythm,
+        }
+    }
+}
+
+impl Default for HistoryElement {
+    fn default() -> Self {
+        Self {
+            idx: 0,
+            rhythm: HitObjectRhythm::static_ref(),
+        }
+    }
+}

src/taiko/skills/stamina.rs

@@ -0,0 +1,113 @@
+use crate::taiko::difficulty_object::{ObjectLists, TaikoDifficultyObject};
+
+use super::{Skill, StrainDecaySkill, StrainSkill};
+
+#[derive(Clone, Debug)]
+pub(crate) struct Stamina {
+    curr_strain: f64,
+    curr_section_peak: f64,
+    curr_section_end: f64,
+    pub(crate) strain_peaks: Vec<f64>,
+}
+
+impl Stamina {
+    pub(crate) fn new() -> Self {
+        Self {
+            curr_strain: 0.0,
+            curr_section_peak: 0.0,
+            curr_section_end: 0.0,
+            strain_peaks: Vec::new(),
+        }
+    }
+}
+
+impl Skill for Stamina {
+    fn process(&mut self, curr: &TaikoDifficultyObject<'_>, hit_objects: &ObjectLists<'_>) {
+        <Self as StrainSkill>::process(self, curr, hit_objects)
+    }
+
+    fn difficulty_value(self) -> f64 {
+        <Self as StrainSkill>::difficulty_value(self)
+    }
+}
+
+impl StrainSkill for Stamina {
+    fn strain_peaks_mut(&mut self) -> &mut Vec<f64> {
+        &mut self.strain_peaks
+    }
+
+    fn curr_section_peak(&mut self) -> &mut f64 {
+        &mut self.curr_section_peak
+    }
+
+    fn curr_section_end(&mut self) -> &mut f64 {
+        &mut self.curr_section_end
+    }
+
+    fn strain_value_at(
+        &mut self,
+        curr: &TaikoDifficultyObject<'_>,
+        hit_objects: &ObjectLists<'_>,
+    ) -> f64 {
+        <Self as StrainDecaySkill>::strain_value_at(self, curr, hit_objects)
+    }
+
+    fn calculate_initial_strain(&self, time: f64, curr: &TaikoDifficultyObject<'_>) -> f64 {
+        <Self as StrainDecaySkill>::calculate_initial_strain(self, time, curr)
+    }
+}
+
+impl StrainDecaySkill for Stamina {
+    const SKILL_MULTIPLIER: f64 = 1.1;
+    const STRAIN_DECAY_BASE: f64 = 0.4;
+
+    fn curr_strain(&self) -> f64 {
+        self.curr_strain
+    }
+
+    fn curr_strain_mut(&mut self) -> &mut f64 {
+        &mut self.curr_strain
+    }
+
+    fn strain_value_of(
+        &mut self,
+        curr: &TaikoDifficultyObject<'_>,
+        hit_objects: &ObjectLists<'_>,
+    ) -> f64 {
+        StaminaEvaluator::evaluate_diff_of(curr, hit_objects)
+    }
+}
+
+struct StaminaEvaluator;
+
+impl StaminaEvaluator {
+    fn speed_bonus(mut interval: f64) -> f64 {
+        // * Cap to 600bpm 1/4, 25ms note interval, 50ms key interval
+        // * Interval will be capped at a very small value to avoid infinite/negative speed bonuses.
+        // * TODO - This is a temporary measure as we need to implement methods of detecting playstyle-abuse of SpeedBonus.
+        interval = interval.max(50.0);
+
+        30.0 / interval
+    }
+
+    fn evaluate_diff_of(
+        hit_object: &TaikoDifficultyObject<'_>,
+        hit_objects: &ObjectLists<'_>,
+    ) -> f64 {
+        if !hit_object.base.is_hit() {
+            return 0.0;
+        }
+
+        // * Find the previous hit object hit by the current key, which is two notes of the same colour prior.
+        let curr = hit_object;
+        let key_prev = hit_objects.prev_mono(curr.idx, 1);
+
+        if let Some(key_prev) = key_prev {
+            // * Add a base strain to all objects
+            0.5 + Self::speed_bonus(curr.base.h.start_time - key_prev.borrow().base.h.start_time)
+        } else {
+            // * There is no previous hit object hit by the current key
+            0.0
+        }
+    }
+}

src/taiko/taiko_object.rs

@@ -2,12 +2,24 @@ use std::slice::Iter;
 
 use crate::{parse::HitObject, Beatmap};
 
+use super::rim::Rim;
+
 #[derive(Copy, Clone, Debug)]
 pub(crate) struct TaikoObject<'h> {
     pub(crate) h: &'h HitObject,
     pub(crate) sound: u8,
 }
 
+impl TaikoObject<'_> {
+    pub(crate) fn is_rim(&self) -> bool {
+        self.sound.is_rim()
+    }
+
+    pub(crate) fn is_hit(&self) -> bool {
+        self.h.is_circle()
+    }
+}
+
 pub(crate) trait IntoTaikoObjectIter {
     fn taiko_objects(&self) -> TaikoObjectIter<'_>;
 }