Add Printer trait + PrinterHandle enum domain model with polymorphism example

src/printer/klipper.rs

@@ -0,0 +1,37 @@
+use tracing::info;
+
+use super::{Printer, PrinterBase, PrinterError};
+
+pub struct KlipperPrinter {
+    base: PrinterBase,
+}
+
+impl KlipperPrinter {
+    pub fn new(id: impl Into<String>, name: impl Into<String>, host: impl Into<String>) -> Self {
+        Self {
+            base: PrinterBase { id: id.into(), name: name.into(), host: host.into() },
+        }
+    }
+}
+
+impl Printer for KlipperPrinter {
+    fn base(&self) -> &PrinterBase {
+        &self.base
+    }
+
+    /// OVERRIDE: Moonraker's real-time feed is a WebSocket JSON-RPC channel
+    /// (see adapters::moonraker::run for that), but it also exposes a plain
+    /// REST endpoint. `connect()` here is a lightweight reachability probe
+    /// against that REST endpoint before the daemon opens the WS stream —
+    /// a third, again-completely-different notion of "connect".
+    async fn connect(&mut self) -> Result<(), PrinterError> {
+        info!(printer = %self.base.id, host = %self.base.host, "probing Moonraker over HTTP");
+
+        reqwest::get(format!("http://{}/printer/info", self.base.host))
+            .await
+            .and_then(|resp| resp.error_for_status())
+            .map_err(|err| PrinterError::Connection(self.base.id.clone(), err.to_string()))?;
+
+        Ok(())
+    }
+}