Add Printer trait + PrinterHandle enum domain model with polymorphism example

src/printer/bambu.rs

@@ -0,0 +1,54 @@
+use std::path::Path;
+
+use tracing::info;
+
+use super::{Printer, PrinterBase, PrinterError};
+
+/// Bambu-specific fields — this is the "extends GenericBambuPrinter" part of
+/// your original design, expressed as extra struct fields instead of a
+/// second inheritance layer.
+pub struct BambuPrinter {
+    base: PrinterBase,
+    pub access_code: String,
+}
+
+impl BambuPrinter {
+    pub fn new(id: impl Into<String>, name: impl Into<String>, host: impl Into<String>, access_code: impl Into<String>) -> Self {
+        Self {
+            base: PrinterBase { id: id.into(), name: name.into(), host: host.into() },
+            access_code: access_code.into(),
+        }
+    }
+
+    /// A method that ONLY exists on `BambuPrinter` — not part of the
+    /// `Printer` trait at all. This is what "adding a printer-specific
+    /// method" looks like: just define it in this struct's own `impl`
+    /// block. `PrusaPrinter` and `KlipperPrinter` have no equivalent, and
+    /// calling this requires a `PrinterHandle::Bambu(..)` match first (see
+    /// the example), which is the price for not doing runtime downcasting.
+    ///
+    /// Real implementation lives in `adapters::bambu::dispatch_file` (FTPS
+    /// on port 990); this is the domain-model-facing wrapper around it.
+    pub async fn dispatch_gcode_ftp(&mut self, local_path: &Path, remote_name: &str) -> Result<(), PrinterError> {
+        info!(printer = %self.base.id, remote_name = %remote_name, path = ?local_path, "dispatching gcode over FTPS");
+        // See adapters::bambu::dispatch_file for the full FTPS upload.
+        Ok(())
+    }
+}
+
+impl Printer for BambuPrinter {
+    fn base(&self) -> &PrinterBase {
+        &self.base
+    }
+
+    /// OVERRIDE: Bambu speaks MQTTS on port 8883, authenticated with the
+    /// printer's LAN access code. Completely different transport from the
+    /// other two vendors below.
+    async fn connect(&mut self) -> Result<(), PrinterError> {
+        info!(printer = %self.base.id, host = %self.base.host, "connecting to Bambu printer over MQTTS:8883");
+        // Real implementation: open the MQTTS session and wait for the
+        // first `report` message — see adapters::bambu::run_telemetry,
+        // which this would delegate to once wired into the daemon.
+        Ok(())
+    }
+}