nomicon/hardware/devices/euro-yesman-1u/src/seq.rs

const SEQ_LEN: usize = 4;

/// Represent a single layer on the sequencer
pub struct SeqLayer {
    /// List of steps that are either on or off
    steps: [bool; SEQ_LEN],
    /// The length of the sequence to loop
    length: u8,
}

impl Default for SeqLayer {
    fn default() -> Self {
        Self {
            steps: [true; SEQ_LEN],
            length: SEQ_LEN as u8,
        }
    }
}

impl SeqLayer {
    fn toggle(&mut self, idx: usize) {
        self.steps[idx] = !self.steps[idx];
    }
}

/// Indicate which layer is selected
pub enum LayerSelect {
    A,
    B,
    C,
    D,
}

impl Default for LayerSelect {
    fn default() -> Self {
        Self::A
    }
}

/// Main sequencer state structure
#[derive(Default)]
pub struct Sequencer {
    a: SeqLayer,
    b: SeqLayer,
    c: SeqLayer,
    d: SeqLayer,
    active_layer: LayerSelect,
    active_step: u8,
}

impl Sequencer {
    /// Step to the next step, wrapping around at SEQ_LEN
    pub fn step(&mut self) {
        self.active_step += 1;
        self.active_step %= SEQ_LEN as u8;
    }

    /// Get the current step for all four layers
    pub fn get(&self) -> (bool, bool, bool, bool) {
        let i = self.active_step as usize;
        (
            self.a.steps[i],
            self.b.steps[i],
            self.c.steps[i],
            self.d.steps[i],
        )
    }

    pub fn toggle(&mut self, idx: usize) {
        assert!(idx <= 16);
        match self.active_layer {
            LayerSelect::A => self.a.toggle(idx),
            LayerSelect::B => self.b.toggle(idx),
            LayerSelect::C => self.c.toggle(idx),
            LayerSelect::D => self.d.toggle(idx),
        }
    }

    pub fn layer(&self, sel: LayerSelect) -> &[bool; SEQ_LEN] {
        match sel {
            LayerSelect::A => &self.a.steps,
            LayerSelect::B => &self.b.steps,
            LayerSelect::C => &self.c.steps,
            LayerSelect::D => &self.d.steps,
        }
    }
}