Improved PlayAlong logic (#175)

* Fixes bug of jumping/ignoring non-pressed notes, adding accuracy to score/midi

* More improvements

* Basic stats counting

* Count miss and hit after the song is done, rather than live

---------

Co-authored-by: captainerd <frapenation@gmail.com>

neothesia/src/scene/playing_scene/midi_player.rs

@@ -5,7 +5,7 @@ use crate::{
     song::{PlayerConfig, Song},
 };
 use std::{
-    collections::{HashSet, VecDeque},
+    collections::{HashMap, HashSet},
     time::{Duration, Instant},
 };
 
@@ -194,21 +194,64 @@ pub enum MidiEventSource {
     User,
 }
 
+type NoteId = u8;
+
+#[derive(Debug, Default)]
+struct PlayerStats {
+    /// User notes that expired, or were simply wrong
+    wrong_notes: usize,
+    /// List of deltas of notes played early
+    played_early: Vec<Duration>,
+    /// List of deltas of notes played late
+    played_late: Vec<Duration>,
+}
+
+impl PlayerStats {
+    #[allow(unused)]
+    fn timing_acurracy(&self) -> f64 {
+        let all = self.played_early.len() + self.played_late.len();
+        let early_count = self.count_too_early();
+        let late_count = self.count_too_late();
+        (early_count + late_count) as f64 / all as f64
+    }
+
+    fn count_too_early(&self) -> usize {
+        // 500 is the same as expire time, so this does not make much sense, but we can chooses
+        // better threshold later down the line
+        Self::count_with_threshold(&self.played_early, Duration::from_millis(500))
+    }
+
+    fn count_too_late(&self) -> usize {
+        // 160 to forgive touching the bottom
+        Self::count_with_threshold(&self.played_late, Duration::from_millis(160))
+    }
+
+    fn count_with_threshold(events: &[Duration], threshold: Duration) -> usize {
+        events
+            .iter()
+            .filter(|delta| **delta > threshold)
+            .fold(0, |n, _| n + 1)
+    }
+}
+
 #[derive(Debug)]
-struct UserPress {
+struct NotePress {
     timestamp: Instant,
-    note_id: u8,
 }
 
 #[derive(Debug)]
 pub struct PlayAlong {
     user_keyboard_range: piano_math::KeyboardRange,
 
-    required_notes: HashSet<u8>,
+    /// Notes required to proggres further in the song
+    required_notes: HashMap<NoteId, NotePress>,
+    /// List of user key press events that happened in last 500ms,
+    /// used for play along leeway logic
+    user_pressed_recently: HashMap<NoteId, NotePress>,
+    /// File notes that had NoteOn event, but no NoteOff yet
+    in_proggres_file_notes: HashSet<NoteId>,
 
-    // List of user key press events that happened in last 500ms,
-    // used for play along leeway logic
-    user_pressed_recently: VecDeque<UserPress>,
+    stats: PlayerStats,
 }
 
 impl PlayAlong {
@@ -217,50 +260,71 @@ impl PlayAlong {
             user_keyboard_range,
             required_notes: Default::default(),
             user_pressed_recently: Default::default(),
+            in_proggres_file_notes: Default::default(),
+            stats: PlayerStats::default(),
         }
     }
 
     fn update(&mut self) {
         // Instead of calling .elapsed() per item let's fetch `now` once, and subtract it ourselves
         let now = Instant::now();
+        let threshold = Duration::from_millis(500);
 
-        while let Some(item) = self.user_pressed_recently.front_mut() {
-            let elapsed = now - item.timestamp;
+        // Track the count of items before retain
+        let count_before = self.user_pressed_recently.len();
 
-            // If older than 500ms
-            if elapsed.as_millis() > 500 {
-                self.user_pressed_recently.pop_front();
-            } else {
-                // All subsequent items will by younger than front item, so we can break
-                break;
-            }
-        }
+        // Retain only the items that are within the threshold
+        self.user_pressed_recently
+            .retain(|_, item| now.duration_since(item.timestamp) <= threshold);
+
+        self.stats.wrong_notes += count_before - self.user_pressed_recently.len();
     }
 
     fn user_press_key(&mut self, note_id: u8, active: bool) {
         let timestamp = Instant::now();
 
         if active {
-            self.user_pressed_recently
-                .push_back(UserPress { timestamp, note_id });
-            self.required_notes.remove(&note_id);
+            // Check if note has already been played by a file
+            if let Some(required_press) = self.required_notes.remove(&note_id) {
+                self.stats
+                    .played_late
+                    .push(timestamp.duration_since(required_press.timestamp));
+            } else {
+                // This note was not played by file yet, place it in recents
+                let got_replaced = self
+                    .user_pressed_recently
+                    .insert(note_id, NotePress { timestamp })
+                    .is_some();
+
+                if got_replaced {
+                    self.stats.wrong_notes += 1
+                }
+            }
         }
     }
 
     fn file_press_key(&mut self, note_id: u8, active: bool) {
+        let timestamp = Instant::now();
         if active {
-            if let Some((id, _)) = self
-                .user_pressed_recently
-                .iter()
-                .enumerate()
-                .find(|(_, item)| item.note_id == note_id)
-            {
-                self.user_pressed_recently.remove(id);
+            // Check if note got pressed earlier 500ms (user_pressed_recently)
+            if let Some(press) = self.user_pressed_recently.remove(&note_id) {
+                self.stats
+                    .played_early
+                    .push(timestamp.duration_since(press.timestamp));
             } else {
-                self.required_notes.insert(note_id);
+                // Player never pressed that note, let it reach required_notes
+
+                // Ignore overlapping notes
+                if self.in_proggres_file_notes.contains(&note_id) {
+                    return;
+                }
+
+                self.required_notes.insert(note_id, NotePress { timestamp });
             }
+
+            self.in_proggres_file_notes.insert(note_id);
         } else {
-            self.required_notes.remove(&note_id);
+            self.in_proggres_file_notes.remove(&note_id);
         }
     }
 
@@ -284,7 +348,9 @@ impl PlayAlong {
     }
 
     pub fn clear(&mut self) {
-        self.required_notes.clear()
+        self.required_notes.clear();
+        self.user_pressed_recently.clear();
+        self.in_proggres_file_notes.clear();
     }
 
     pub fn are_required_keys_pressed(&self) -> bool {