pocket-chords/crates/domain/src/value_objects/note.rs

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Note {
    A,
    ASharpBFlat,
    B,
    C,
    CSharpDFlat,
    D,
    DSharpEFlat,
    E,
    F,
    FSharpGFlat,
    G,
    GSharpAFlat,
}

impl Note {
    pub fn semitone(&self) -> u8 {
        match self {
            Note::C => 0,
            Note::CSharpDFlat => 1,
            Note::D => 2,
            Note::DSharpEFlat => 3,
            Note::E => 4,
            Note::F => 5,
            Note::FSharpGFlat => 6,
            Note::G => 7,
            Note::GSharpAFlat => 8,
            Note::A => 9,
            Note::ASharpBFlat => 10,
            Note::B => 11,
        }
    }

    pub fn from_semitone(s: u8) -> Note {
        match s % 12 {
            0 => Note::C,
            1 => Note::CSharpDFlat,
            2 => Note::D,
            3 => Note::DSharpEFlat,
            4 => Note::E,
            5 => Note::F,
            6 => Note::FSharpGFlat,
            7 => Note::G,
            8 => Note::GSharpAFlat,
            9 => Note::A,
            10 => Note::ASharpBFlat,
            11 => Note::B,
            _ => unreachable!(),
        }
    }

    pub fn to_sharp_str(&self) -> &'static str {
        match self {
            Note::C => "C",
            Note::CSharpDFlat => "C#",
            Note::D => "D",
            Note::DSharpEFlat => "D#",
            Note::E => "E",
            Note::F => "F",
            Note::FSharpGFlat => "F#",
            Note::G => "G",
            Note::GSharpAFlat => "G#",
            Note::A => "A",
            Note::ASharpBFlat => "A#",
            Note::B => "B",
        }
    }

    pub fn to_flat_str(&self) -> &'static str {
        match self {
            Note::C => "C",
            Note::CSharpDFlat => "Db",
            Note::D => "D",
            Note::DSharpEFlat => "Eb",
            Note::E => "E",
            Note::F => "F",
            Note::FSharpGFlat => "Gb",
            Note::G => "G",
            Note::GSharpAFlat => "Ab",
            Note::A => "A",
            Note::ASharpBFlat => "Bb",
            Note::B => "B",
        }
    }

    pub fn parse_prefix(s: &str) -> Option<(Note, usize)> {
        let mut chars = s.chars();
        let root = match chars.next()? {
            'A' => Note::A,
            'B' => Note::B,
            'C' => Note::C,
            'D' => Note::D,
            'E' => Note::E,
            'F' => Note::F,
            'G' => Note::G,
            _ => return None,
        };
        match chars.next() {
            Some('#') => Some((Self::sharp_of(root), 2)),
            Some('b') if s.len() > 1 => {
                let flatted = Self::flat_of(root)?;
                Some((flatted, 2))
            }
            _ => Some((root, 1)),
        }
    }

    pub fn parse(s: &str) -> Option<Note> {
        let (note, consumed) = Self::parse_prefix(s)?;
        if consumed == s.len() {
            Some(note)
        } else {
            None
        }
    }

    fn sharp_of(root: Note) -> Note {
        Note::from_semitone((root.semitone() + 1) % 12)
    }

    fn flat_of(root: Note) -> Option<Note> {
        Some(Note::from_semitone((root.semitone() + 11) % 12))
    }
}

#[cfg(test)]
#[path = "../tests/note.rs"]
mod tests;