feat: add initial synchronous channel implementation

src/channel.rs

@@ -0,0 +1,181 @@
+use std::sync::mpsc;
+use std::sync::{Arc, Mutex};
+
+use crate::error::Error;
+use crate::types::{ChannelState, Request, Response, ValueSource};
+
+/// The consumer side of the channel that requests values
+pub struct Sucker<T> {
+    request_tx: mpsc::Sender<Request>,
+    response_rx: mpsc::Receiver<Response<T>>,
+    closed: Mutex<bool>,
+}
+
+/// The producer side of the channel that provides values
+pub struct Sourcer<T> {
+    request_rx: mpsc::Receiver<Request>,
+    response_tx: mpsc::Sender<Response<T>>,
+    state: Arc<Mutex<ChannelState<T>>>,
+}
+
+/// Helper type for creating Sucker and Sourcer instances
+pub struct SuckPair<T> {
+    _phantom: std::marker::PhantomData<T>,
+}
+
+impl<T> SuckPair<T> {
+    /// Create a new suck pair
+    pub fn pair() -> (Sucker<T>, Sourcer<T>)
+    where
+        T: Clone + Send + 'static,
+    {
+        let (request_tx, request_rx) = mpsc::channel();
+        let (response_tx, response_rx) = mpsc::channel();
+
+        let state = Arc::new(Mutex::new(ChannelState {
+            source: ValueSource::None,
+            closed: false,
+        }));
+
+        let sucker = Sucker {
+            request_tx,
+            response_rx,
+            closed: Mutex::new(false),
+        };
+
+        let sourcer = Sourcer {
+            request_rx,
+            response_tx,
+            state: Arc::clone(&state),
+        };
+
+        (sucker, sourcer)
+    }
+}
+
+impl<T> Sourcer<T>
+where
+    T: Clone + Send + 'static,
+{
+    /// Set a fixed value
+    pub fn set_static(&self, value: T) -> Result<(), Error> {
+        let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+        if state.closed {
+            return Err(Error::ChannelClosed);
+        }
+        state.source = ValueSource::Static(value);
+        Ok(())
+    }
+
+    /// Set a closure
+    pub fn set<F>(&self, closure: F) -> Result<(), Error>
+    where
+        F: Fn() -> T + Send + Sync + 'static,
+    {
+        let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+        if state.closed {
+            return Err(Error::ChannelClosed);
+        }
+        state.source = ValueSource::Dynamic(Box::new(closure));
+        Ok(())
+    }
+
+    /// Close the channel
+    pub fn close(&self) -> Result<(), Error> {
+        let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+        state.closed = true;
+        state.source = ValueSource::None;
+        Ok(())
+    }
+
+    /// Handles requests - blocking
+    pub fn run(self) -> Result<(), Error> {
+        loop {
+            match self.request_rx.recv() {
+                Ok(Request::GetValue) => {
+                    let response = self.handle_get_value()?;
+                    if self.response_tx.send(response).is_err() {
+                        // Consumer disconnected
+                        break;
+                    }
+                }
+                Ok(Request::Close) => {
+                    // Close channel
+                    let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+                    state.closed = true;
+                    state.source = ValueSource::None;
+                    break;
+                }
+                Err(_) => {
+                    // Consumer disconnected
+                    break;
+                }
+            }
+        }
+        Ok(())
+    }
+
+    fn handle_get_value(&self) -> Result<Response<T>, Error> {
+        let state = self.state.lock().map_err(|_| Error::InternalError)?;
+        if state.closed {
+            return Ok(Response::Closed);
+        }
+
+        match &state.source {
+            ValueSource::Static(value) => Ok(Response::Value(value.clone())),
+            ValueSource::Dynamic(closure) => {
+                let value = self.execute_closure_safely(closure);
+                match value {
+                    Ok(v) => Ok(Response::Value(v)),
+                    Err(_) => Ok(Response::NoSource), // Closure execution failed
+                }
+            }
+            ValueSource::None => Ok(Response::NoSource),
+        }
+    }
+
+    fn execute_closure_safely(
+        &self,
+        closure: &dyn Fn() -> T,
+    ) -> Result<T, Box<dyn std::any::Any + Send>> {
+        std::panic::catch_unwind(std::panic::AssertUnwindSafe(closure))
+    }
+}
+
+impl<T> Sucker<T> {
+    /// Get the current value from the producer
+    pub fn get(&self) -> Result<T, Error> {
+        // Check if locally marked as closed
+        if *self.closed.lock().unwrap() {
+            return Err(Error::ChannelClosed);
+        }
+
+        self.request_tx
+            .send(Request::GetValue)
+            .map_err(|_| Error::ProducerDisconnected)?;
+
+        match self.response_rx.recv() {
+            Ok(Response::Value(value)) => Ok(value),
+            Ok(Response::NoSource) => Err(Error::NoSource),
+            Ok(Response::Closed) => Err(Error::ChannelClosed),
+            Err(_) => Err(Error::ProducerDisconnected),
+        }
+    }
+
+    /// Check if the channel is closed
+    pub fn is_closed(&self) -> bool {
+        // Send a test request
+        self.request_tx.send(Request::GetValue).is_err()
+    }
+
+    /// Close the channel from the consumer side
+    pub fn close(&self) -> Result<(), Error> {
+        // Mark locally as closed
+        *self.closed.lock().unwrap() = true;
+
+        // Send close request
+        self.request_tx
+            .send(Request::Close)
+            .map_err(|_| Error::ProducerDisconnected)
+    }
+}