midi-keys/src/midi/daemon.rs

use std::{collections::HashMap, time::Duration};

use crossbeam::{
    channel::{Receiver, Sender},
    select,
};
use midir::{MidiInput, MidiInputConnection, MidiInputPort};

use crate::parser::parse_message;

use super::Message;

#[derive(PartialEq, Eq, Debug)]
pub enum Category {
    All,
    Drums,
    WindSynth,
    Piano,
    Ignore,
}

/// Architecture for the MIDI connectivity:
///
/// State is what's held by the daemon, and is used in an event loop.
/// - queues are passed in which are what we use to route messages
/// - this state can only be accessed directly by the event loop, as it owns the state
/// - does a `select!` (crossbeam) on the timer tick and on other channels
///     - each tick of the timer (on a timer rx channel), call `state.refresh_ports()` and assign
///       ports if they're mapped automatically (drums / windsynth / ignore) for anything that
///       isn't yet mapped (users can override in UI)
///     - listens to a queue of routing updates ("set connectionid to drums / windsynth / ignore")
///       from the UI
///     - receive from the message_receive queue and route the messages
///
/// ideal would be to do the port refresh on a separate thread. but! it's relatively cheap (250
/// microseconds per refresh) so it's not a big deal

type ConnectionId = String;
type Timestamp = u64;
type CTM = (ConnectionId, Timestamp, Message);

type MidiSend = crossbeam::channel::Sender<CTM>;
type MidiRecv = crossbeam::channel::Receiver<CTM>;

pub fn run_daemon(routes: Vec<(Category, MidiSend)>) {
    let mut state = State::new();

    let mut conn_mapping: HashMap<ConnectionId, Category> = HashMap::new();

    let messages_q = state.message_queue();
    let conn_mapping_q = state.connection_mapping_queue();
    let ticker = crossbeam::channel::tick(Duration::from_millis(250));

    loop {
        select! {
            recv(ticker) -> m => match m {
                Ok(_ts) => {
                    state.refresh_ports();
                }
                Err(e) => {
                    println!("borken {e:?}");
                }
            },
            recv(conn_mapping_q) -> m => match m {
                Ok((conn_id, category)) => {
                    conn_mapping.insert(conn_id, category);
                },
                Err(e) => {
                    println!("borken3 {e:?}");
                }
            },
            recv(messages_q) -> m => match m {
                Ok(ctm) => {
                    let (cid, _ts, _msg) = &ctm;
                    let msg_cat = conn_mapping.get(cid).unwrap_or(&Category::Ignore);
                    for (route_cat, q) in routes.iter() {
                        if route_cat == msg_cat || *route_cat == Category::All {
                            let _ = q.send(ctm.clone());
                        }
                    }
                }
                Err(e) => {
                    println!("borken2 {e:?}");
                }
            },
        }
    }
}

pub struct State {
    midi: MidiInput,
    ports: Vec<MidiInputPort>,
    connections: HashMap<String, MidiInputConnection<(ConnectionId, Sender<CTM>)>>,

    message_receive: Receiver<CTM>,
    message_send: Sender<CTM>,

    conn_map_receive: Receiver<(ConnectionId, Category)>,
    conn_map_send: Sender<(ConnectionId, Category)>,
}

impl State {
    pub fn new() -> State {
        let (msg_tx, msg_rx) = crossbeam::channel::unbounded();
        let (conn_tx, conn_rx) = crossbeam::channel::unbounded();

        State {
            midi: MidiInput::new("midi-keys daemon").expect("could not connect to system MIDI"),
            ports: vec![],
            connections: HashMap::new(),
            message_receive: msg_rx,
            message_send: msg_tx,
            conn_map_receive: conn_rx,
            conn_map_send: conn_tx,
        }
    }

    pub fn message_queue(&self) -> Receiver<CTM> {
        self.message_receive.clone()
    }

    pub fn connection_mapping_queue(&self) -> Receiver<(ConnectionId, Category)> {
        self.conn_map_receive.clone()
    }

    pub fn refresh_ports(&mut self) {
        let ports = self.midi.ports();
        for port in ports.iter() {
            self.refresh_port(port);
        }
        self.ports = ports;
    }

    pub fn refresh_port(&mut self, port: &MidiInputPort) {
        let connected = self.connections.contains_key(&port.id());

        let name = match self.midi.port_name(port) {
            Ok(s) => s,
            Err(_) => {
                // this case happens if we're using a MidiInputPort which has been disconnected,
                // so we will remove the device from our connections list. we can try this even
                // if it's not already in the map, as this is idempotent.
                self.connections.remove(&port.id());
                return;
            }
        };

        if connected {
            return;
        }

        let midi = MidiInput::new("midi-keys").expect("could not connect to system MIDI");
        let send_queue = self.message_send.clone();

        if let Ok(conn) = midi.connect(
            &port,
            &name,
            |timestamp, bytes, (conn_id, send_queue)| {
                handle_message(timestamp, bytes, &conn_id, &send_queue);
            },
            (port.id(), send_queue),
        ) {
            let category = guess_catgory(&name);
            println!("guessing category:");
            println!(" name> {name}");
            println!(" id>   {}", port.id());
            println!(" cat>   {category:?}");

            let _ = self.conn_map_send.send((port.id(), category)); // TODO error handler
            self.connections.insert(port.id(), conn);
        }
    }
}

fn guess_catgory(name: &str) -> Category {
    if name.contains("TravelSax2") || name.contains("AE-20") {
        Category::WindSynth
    } else if name.contains("MultiPad") {
        Category::Drums
    } else {
        Category::Ignore
    }
}

fn handle_message(ts: Timestamp, bytes: &[u8], conn_id: &ConnectionId, tx: &Sender<CTM>) {
    if let Ok((_rem, msg)) = parse_message(bytes) {
        let _ = tx.send((conn_id.clone(), ts, msg));
    }
}
// TODO: chain of handlers? -> handle event as keypress, send to UI