usbd_midi/message/
mod.rs

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//! Enum representing the MIDI message.

pub mod channel;
pub mod control_function;
pub mod data;
pub mod notes;
pub mod raw;

use crate::message::channel::Channel;
use crate::message::control_function::ControlFunction;
use crate::message::data::u7::U7;
use crate::message::data::FromClamped;
use crate::message::notes::Note;
use crate::message::raw::{Payload, Raw};
use crate::packet::cable_number::CableNumber;
use crate::packet::code_index_number::CodeIndexNumber;
use crate::packet::{UsbMidiEventPacket, UsbMidiEventPacketError};

type Velocity = U7;

/// Represents midi messages.
///
/// Note: not current exhaustive and SysEx messages end up
/// being a confusing case. So are currently note implemented
/// they are sort-of unbounded
#[derive(Debug, Eq, PartialEq, Clone)]
pub enum Message {
    /// Note On message.
    NoteOff(Channel, Note, Velocity),
    /// Note Off message.
    NoteOn(Channel, Note, Velocity),
    /// Polyphonic aftertouch (poly-pressure) message.
    PolyphonicAftertouch(Channel, Note, U7),
    /// Program change message.
    ProgramChange(Channel, U7),
    /// Channel aftertouch message.
    ChannelAftertouch(Channel, U7),
    /// Pitchwheel message.
    PitchWheelChange(Channel, U7, U7),
    /// Control Change (CC) message.
    ControlChange(Channel, ControlFunction, U7),
}

const NOTE_OFF_MASK: u8 = 0b1000_0000;
const NOTE_ON_MASK: u8 = 0b1001_0000;
const POLYPHONIC_MASK: u8 = 0b1010_0000;
const PROGRAM_MASK: u8 = 0b1100_0000;
const CHANNEL_AFTERTOUCH_MASK: u8 = 0b1101_0000;
const PITCH_BEND_MASK: u8 = 0b1110_0000;
const CONTROL_CHANGE_MASK: u8 = 0b1011_0000;

impl From<Message> for Raw {
    fn from(value: Message) -> Raw {
        match value {
            Message::NoteOn(chan, note, vel) => {
                let payload = Payload::DoubleByte(note.into(), vel);
                let status = NOTE_ON_MASK | u8::from(chan);
                Raw { status, payload }
            }
            Message::NoteOff(chan, note, vel) => {
                let payload = Payload::DoubleByte(note.into(), vel);
                let status = NOTE_OFF_MASK | u8::from(chan);
                Raw { status, payload }
            }
            Message::PolyphonicAftertouch(chan, note, pressure) => {
                let payload = Payload::DoubleByte(note.into(), pressure);
                let status = POLYPHONIC_MASK | u8::from(chan);
                Raw { status, payload }
            }
            Message::ProgramChange(chan, program) => {
                let payload = Payload::SingleByte(program);
                let status = PROGRAM_MASK | u8::from(chan);
                Raw { status, payload }
            }
            Message::ChannelAftertouch(chan, pressure) => {
                let payload = Payload::SingleByte(pressure);
                let status = CHANNEL_AFTERTOUCH_MASK | u8::from(chan);
                Raw { status, payload }
            }
            Message::PitchWheelChange(chan, lsb, msb) => {
                let payload = Payload::DoubleByte(lsb, msb);
                let status = PITCH_BEND_MASK | u8::from(chan);
                Raw { status, payload }
            }
            Message::ControlChange(chan, control_function, value) => {
                let payload = Payload::DoubleByte(control_function.0, value);
                let status = CONTROL_CHANGE_MASK | u8::from(chan);
                Raw { status, payload }
            }
        }
    }
}

impl TryFrom<&[u8]> for Message {
    type Error = UsbMidiEventPacketError;

    fn try_from(data: &[u8]) -> Result<Self, Self::Error> {
        let status_byte = match data.first() {
            Some(byte) => byte,
            None => return Err(UsbMidiEventPacketError::MissingDataPacket),
        };

        let event_type = status_byte & 0b1111_0000;
        let channel_bytes = (status_byte) & 0b0000_1111;

        let channel = Channel::try_from(channel_bytes).ok().unwrap();

        match event_type {
            NOTE_ON_MASK => Ok(Message::NoteOn(
                channel,
                get_note(data)?,
                get_u7_at(data, 2)?,
            )),
            NOTE_OFF_MASK => Ok(Message::NoteOff(
                channel,
                get_note(data)?,
                get_u7_at(data, 2)?,
            )),
            POLYPHONIC_MASK => Ok(Message::PolyphonicAftertouch(
                channel,
                get_note(data)?,
                get_u7_at(data, 2)?,
            )),
            PROGRAM_MASK => Ok(Message::ProgramChange(channel, get_u7_at(data, 1)?)),
            CHANNEL_AFTERTOUCH_MASK => Ok(Message::ChannelAftertouch(channel, get_u7_at(data, 1)?)),
            PITCH_BEND_MASK => Ok(Message::PitchWheelChange(
                channel,
                get_u7_at(data, 1)?,
                get_u7_at(data, 2)?,
            )),
            CONTROL_CHANGE_MASK => Ok(Message::ControlChange(
                channel,
                ControlFunction(get_u7_at(data, 1)?),
                get_u7_at(data, 2)?,
            )),
            _ => Err(UsbMidiEventPacketError::InvalidEventType(event_type)),
        }
    }
}

impl TryFrom<&UsbMidiEventPacket> for Message {
    type Error = UsbMidiEventPacketError;

    fn try_from(value: &UsbMidiEventPacket) -> Result<Self, Self::Error> {
        Self::try_from(&value.as_raw_bytes()[1..])
    }
}

impl Message {
    /// Create a packet from the message.
    pub fn into_packet(self, cable: CableNumber) -> UsbMidiEventPacket {
        let cin = self.code_index_number() as u8;

        let mut raw = [0; 4];
        raw[0] = (cable as u8) << 4 | cin;
        let r = Raw::from(self);
        raw[1] = r.status;

        match r.payload {
            Payload::Empty => {
                raw[2] = 0;
                raw[3] = 0;
            }
            Payload::SingleByte(byte) => {
                raw[2] = byte.0;
                raw[3] = 0;
            }
            Payload::DoubleByte(byte1, byte2) => {
                raw[2] = byte1.0;
                raw[3] = byte2.0;
            }
        };

        UsbMidiEventPacket::try_from(raw.as_slice()).unwrap()
    }

    /// Returns the code index number for a message.
    pub fn code_index_number(&self) -> CodeIndexNumber {
        match self {
            Self::NoteOn(_, _, _) => CodeIndexNumber::NoteOn,
            Self::NoteOff(_, _, _) => CodeIndexNumber::NoteOff,
            Self::ChannelAftertouch(_, _) => CodeIndexNumber::ChannelPressure,
            Self::PitchWheelChange(_, _, _) => CodeIndexNumber::PitchBendChange,
            Self::PolyphonicAftertouch(_, _, _) => CodeIndexNumber::PolyKeyPress,
            Self::ProgramChange(_, _) => CodeIndexNumber::ProgramChange,
            Self::ControlChange(_, _, _) => CodeIndexNumber::ControlChange,
        }
    }
}

fn get_note(data: &[u8]) -> Result<Note, UsbMidiEventPacketError> {
    let note_byte = get_byte_at_position(data, 1)?;
    match Note::try_from(note_byte) {
        Ok(note) => Ok(note),
        Err(_) => Err(UsbMidiEventPacketError::InvalidNote(note_byte)),
    }
}

fn get_u7_at(data: &[u8], index: usize) -> Result<U7, UsbMidiEventPacketError> {
    let data_byte = get_byte_at_position(data, index)?;
    Ok(U7::from_clamped(data_byte))
}

fn get_byte_at_position(data: &[u8], index: usize) -> Result<u8, UsbMidiEventPacketError> {
    match data.get(index) {
        Some(byte) => Ok(*byte),
        None => Err(UsbMidiEventPacketError::MissingDataPacket),
    }
}

#[cfg(test)]
mod tests {
    use crate::message::channel::Channel::{Channel1, Channel2};
    use crate::message::control_function::ControlFunction;
    use crate::message::data::u7::U7;
    use crate::message::notes::Note;
    use crate::message::Message;
    use crate::packet::cable_number::CableNumber::{Cable0, Cable1};
    use crate::packet::UsbMidiEventPacket;

    macro_rules! decode_message_test {
        ($($id:ident:$value:expr,)*) => {
            $(
                #[test]
                fn $id() {
                    let (usb_midi_data_packet, expected) = $value;
                    let message = UsbMidiEventPacket::try_from(&usb_midi_data_packet[..]).unwrap();
                    assert_eq!(expected, message);
                }
            )*
        }
    }

    decode_message_test! {
        note_on: ([9, 144, 36, 127], Message::NoteOn(Channel1, Note::C2, U7(127)).into_packet(Cable0)),
        note_off: ([8, 128, 36, 0], Message::NoteOff(Channel1, Note::C2, U7(0)).into_packet(Cable0)),
        polyphonic_aftertouch: ([10, 160, 36, 64], Message::PolyphonicAftertouch(Channel1, Note::C2, U7(64)).into_packet(Cable0)),
        program_change: ([28, 192, 127, 0], Message::ProgramChange(Channel1, U7(127)).into_packet(Cable1)),
        channel_aftertouch: ([13, 208, 127, 0], Message::ChannelAftertouch(Channel1, U7(127)).into_packet(Cable0)),
        pitch_wheel: ([14, 224, 64, 32], Message::PitchWheelChange(Channel1, U7(64), U7(32)).into_packet(Cable0)),
        control_change: ([11, 177, 1, 32], Message::ControlChange(Channel2, ControlFunction::MOD_WHEEL_1, U7(32)).into_packet(Cable0)),
    }
}