tek/jack/src/jack_connect.rs

use crate::*;

/// This is a boxed realtime callback.
pub type BoxedAudioHandler     = Box<dyn FnMut(&Client, &ProcessScope) -> Control + Send>;

/// This is the notification handler wrapper for a boxed realtime callback.
pub type DynamicAudioHandler   = ClosureProcessHandler<(), BoxedAudioHandler>;

/// This is a boxed [JackEvent] callback.
pub type BoxedJackEventHandler = Box<dyn Fn(JackEvent) + Send + Sync>;

/// This is the notification handler wrapper for a boxed [JackEvent] callback.
pub type DynamicNotifications  = Notifications<BoxedJackEventHandler>;

/// This is a running JACK [AsyncClient] with maximum type erasure.
/// It has one [Box] containing a function that handles [JackEvent]s,
/// and another [Box] containing a function that handles realtime IO,
/// and that's all it knows about them.
pub type DynamicAsyncClient    = AsyncClient<DynamicNotifications, DynamicAudioHandler>;

/// This is a connection which may be `Inactive`, `Activating`, or `Active`.
/// In the `Active` and `Inactive` states, its `client` method returns a
/// [Client] which you can use to talk to the JACK API.
#[derive(Debug)]
pub enum JackConnection {
    /// Before activation.
    Inactive(Client),
    /// During activation.
    Activating,
    /// After activation. Must not be dropped for JACK thread to persist.
    Active(DynamicAsyncClient),
}

impl From<JackConnection> for Client {
    fn from (jack: JackConnection) -> Self {
        match jack {
            JackConnection::Inactive(client) => client,
            JackConnection::Activating       => panic!("jack client still activating"),
            JackConnection::Active(_)        => panic!("jack client already activated"),
        }
    }
}

impl JackConnection {
    pub fn new (name: &str) -> Usually<Self> {
        let (client, _) = Client::new(name, ClientOptions::NO_START_SERVER)?;
        Ok(Self::Inactive(client))
    }
    /// Return the internal [Client] handle that lets you call the JACK API.
    pub fn client (&self) -> &Client {
        match self {
            Self::Inactive(ref client) => client,
            Self::Activating           => panic!("jack client has not finished activation"),
            Self::Active(ref client)   => client.as_client(),
        }
    }
    /// Activate a connection with an application.
    ///
    /// Consume a `JackConnection::Inactive`,
    /// binding a process callback and
    /// returning a `JackConnection::Active`.
    ///
    /// Needs work. Strange ownership situation between the callback
    /// and the host object.
    fn activate (
        self,
        mut cb: impl FnMut(&Arc<RwLock<Self>>, &Client, &ProcessScope) -> Control + Send + 'static,
    ) -> Usually<Arc<RwLock<Self>>>
    where
        Self: Send + Sync + 'static
    {
        let client = Client::from(self);
        let state  = Arc::new(RwLock::new(Self::Activating));
        let event  = Box::new(move|_|{/*TODO*/}) as Box<dyn Fn(JackEvent) + Send + Sync>;
        let events = Notifications(event);
        let frame  = Box::new({let state = state.clone(); move|c: &_, s: &_|cb(&state, c, s)});
        let frames = ClosureProcessHandler::new(frame as BoxedAudioHandler);
        *state.write().unwrap() = Self::Active(client.activate_async(events, frames)?);
        Ok(state)
    }
    /// Activate a connection with an application.
    ///
    /// * Wrap a [JackConnection::Inactive] into [Arc<RwLock<_>>].
    /// * Pass it to the `init` callback
    ///   * This allows user code to connect to JACK
    ///   * While user code retains clone of the
    ///     [Arc<RwLock<JackConnection>>] that is
    ///     passed to `init`, the audio engine is running.
    pub fn activate_with <T: Audio + 'static> (
        self,
        init: impl FnOnce(&Arc<RwLock<JackConnection>>)->Usually<T>
    )
        -> Usually<Arc<RwLock<T>>>
    {
        // Wrap self for multiple ownership.
        let connection = Arc::new(RwLock::new(self));
        // Run init callback. Return value is target. Target must retain clone of `connection`.
        let target = Arc::new(RwLock::new(init(&connection)?));
        // Swap the `client` from the `JackConnection::Inactive`
        // for a `JackConnection::Activating`.
        let mut client = Self::Activating;
        std::mem::swap(&mut*connection.write().unwrap(), &mut client);
        // Replace the `JackConnection::Activating` with a
        // `JackConnection::Active` wrapping the [AsyncClient]
        // returned by the activation.
        *connection.write().unwrap() = Self::Active(Client::from(client).activate_async(
            // This is the misc notifications handler. It's a struct that wraps a [Box]
            // which performs type erasure on a callback that takes [JackEvent], which is
            // one of the available misc notifications.
            Notifications(Box::new(move|_|{/*TODO*/}) as BoxedJackEventHandler),
            // This is the main processing handler. It's a struct that wraps a [Box]
            // which performs type erasure on a callback that takes [Client] and [ProcessScope]
            // and passes them down to the `target`'s `process` callback, which in turn
            // implements audio and MIDI input and output on a realtime basis.
            ClosureProcessHandler::new(Box::new({
                let target = target.clone();
                move|c: &_, s: &_|if let Ok(mut target) = target.write() {
                    target.process(c, s)
                } else {
                    Control::Quit
                }
            }) as BoxedAudioHandler),
        )?);
        Ok(target)
    }
    pub fn port_by_name (&self, name: &str) -> Option<Port<Unowned>> {
        self.client().port_by_name(name)
    }
    pub fn register_port <PS: PortSpec> (&self, name: &str, spec: PS) -> Usually<Port<PS>> {
        Ok(self.client().register_port(name, spec)?)
    }
}