feat: add message types to be sent over channels

src/lib.rs

@@ -1,3 +1,8 @@
 #![doc = include_str!("../README.md")]
 
 pub mod error;
+pub mod types;
+
+// Re-exports
+pub use error::Error;
+pub use types::ValueSource;

src/types.rs

@@ -0,0 +1,25 @@
+/// Request messages sent from consumer to producer
+pub enum Request {
+    GetValue,
+    Close,
+}
+
+/// Response messages sent from producer to consumer
+pub enum Response<T> {
+    Value(T),
+    NoSource,
+    Closed,
+}
+
+/// Represents the source of values: either static or dynamic
+pub enum ValueSource<T> {
+    Static(T),
+    Dynamic(Box<dyn Fn() -> T + Send + Sync + 'static>),
+    None,
+}
+
+/// Internal channel state shared between producer and consumer
+pub struct ChannelState<T> {
+    pub source: ValueSource<T>,
+    pub closed: bool,
+}