Initial node implementation (#4)

Reviewed-on: #4
Co-authored-by: Zack <zack@bfpower.io>
Co-committed-by: Zack <zack@bfpower.io>

src/error.rs

@@ -0,0 +1,41 @@
+use crate::transducer::InvalidValue;
+
+/// An error that it is likely impossible to recover from. This error should only be created in
+/// situations where attempts to recover have already been attempted and have failed. Error handling
+/// should consist of attempting to alert another system for maintenance and attempting to shut down
+/// any systems that depend on the correct functionality of the component having errors.
+///
+/// In many systems there can be a single function for handling any critical error as a critical
+/// error always means everything needs to be stopped.
+#[derive(Copy, Clone, Eq, PartialEq, Debug)]
+pub enum CriticalError {
+    /// Critical communication failed and retries are either impossible or also failed.
+    Communication,
+    InvalidValue(InvalidValue),
+}
+
+impl CriticalError {
+    pub fn emergency_procedure(self, procedure: impl FnOnce(CriticalError) -> !) -> ! {
+        procedure(self);
+    }
+}
+
+/// [Result] where error type is [CriticalError].
+pub trait CriticalErrResult: Copy {
+    type Value: Copy;
+
+    /// Execute emergency procedure in the event of a critical, the emergency procedure cannot
+    /// return. It should usually terminate the program, potentially rebooting the device in some sort of recovery mode.
+    fn err_emproc(self, procedure: impl FnOnce(CriticalError) -> !) -> Self::Value;
+}
+
+impl<T: Copy> CriticalErrResult for Result<T, CriticalError> {
+    type Value = T;
+
+    fn err_emproc(self, procedure: impl FnOnce(CriticalError) -> !) -> Self::Value {
+        match self {
+            Ok(val) => val,
+            Err(error) => error.emergency_procedure(procedure),
+        }
+    }
+}