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src/nome.rs

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+use std::time::Instant;
+use crate::grid::{Grid, NoteType};
+
+pub const LOOP_LENGTH: u32 = 16;
+
+pub struct Nome {
+    /// Tempo in beats per minute
+    pub tempo: u32,
+
+    // A count _in beats_ of where we are in the loop
+    timer: f32,
+
+    /// Whether or not we're playing; false == paused
+    pub playing: bool,
+
+    // The instant of the last time we called tick()
+    last_tick: Option<Instant>,
+
+    /// The grids that we currently have going
+    pub grids: Vec<Grid>,
+
+    // Running count of windows created (for ids)
+    window_counter: usize
+}
+
+impl Default for Nome {
+    fn default() -> Self {
+        Self {
+            tempo: 90,
+            timer: 0.0,
+            playing: true,
+            last_tick: None,
+            grids: vec![],
+            window_counter: 0
+        }
+    }
+}
+
+impl Nome {
+    /// Call this every frame to update the timer / last tick based on the current instant
+    /// and the tempo
+    pub fn tick(&mut self) -> bool {
+        let now = Instant::now();
+        let old_beat = self.beat();
+        if let Some(last) = self.last_tick && self.playing {
+            let dt = (now - last).as_secs_f32();
+            let bps = (self.tempo as f32) / 60.0;
+            // Timer is an amount of time _in beats_ and some of those beats might have been for a
+            // different tempo.
+            // We know now a time delta in seconds and a conversion factor to turn that to beats, so:
+            self.timer += dt * bps;
+            // 16 beats in the loop, so timer should never be over 16:
+            while self.timer > LOOP_LENGTH as f32 { self.timer -= LOOP_LENGTH as f32 }
+        }
+
+        // Playing or not, update last_tick so that the next frame adds the correct duration to timer
+        self.last_tick = Some(now);
+
+        // Did we enter a new beat?
+        self.beat() != old_beat
+    }
+
+    /// Which beat (0..loop_length) we're on
+    pub fn beat(&self) -> u32 {
+        self.timer.floor() as u32
+    }
+
+    /// What fraction we are (0.0..1.0) through the loop
+    /// (multiply by window width to find the x coord to draw the cursor line)
+    pub fn ratio(&self) -> f32 {
+        self.timer / LOOP_LENGTH as f32
+    }
+
+    pub fn add_window(&mut self, note_type: NoteType) {
+        self.window_counter += 1;
+        self.grids.push(Grid::for_note_type(note_type, self.window_counter));
+    }
+
+    pub fn notes_for_beat(&self) -> Vec<(String, u32)> {
+        let mut notes = vec![];
+        let beat = self.beat();
+
+        for grid in self.grids.iter() {
+            for note in grid.notes(beat).into_iter() {
+                notes.push((grid.id.clone(), note))
+            }
+        }
+        notes
+    }
+}