Use Error type for reply parsing

red/src/main.rs

@@ -7,7 +7,10 @@ const DEFAULT_TTY: &str = "/dev/ttyUSB0";
 #[tokio::main]
 async fn main() -> tokio_serial::Result<()> {
     let printer = Printer::connect(DEFAULT_TTY).await.unwrap();
-    printer.printer_in.send(Box::new(red::printer::M114Command::new())).await;
+    printer
+        .printer_in
+        .send(Box::new(red::printer::M114Command::new()))
+        .await;
     tokio::time::sleep(std::time::Duration::from_secs(15)).await;
     Ok(())
 }

red/src/printer/gcode.rs

@@ -3,9 +3,28 @@ use std::fmt::Debug;
 use lazy_static::lazy_static;
 use regex::Regex;
 
+type Result<T> = std::result::Result<T, GcodeReplyError>;
+
+#[derive(Debug, Clone)]
+pub struct GcodeReplyError {
+    sent_command: String,
+    parsed_input: String,
+    problem: String,
+}
+
+impl std::fmt::Display for GcodeReplyError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "Failed to parse response `{}` to command {}: {}",
+            self.parsed_input, self.sent_command, self.problem
+        )
+    }
+}
+
 pub trait GcodeCommand: Debug + Send {
     fn command(&self) -> &str;
-    fn parse_reply(&self, reply: &str) -> GcodeReply;
+    fn parse_reply(&self, reply: &str) -> Result<GcodeReply>;
 }
 
 #[derive(Debug)]
@@ -13,12 +32,7 @@ pub struct M114Command;
 
 #[derive(Debug)]
 pub enum GcodeReply {
-    M114Reply {
-        x: Option<f64>,
-        y: Option<f64>,
-        z: Option<f64>,
-        e: Option<f64>,
-    },
+    M114Reply { x: f64, y: f64, z: f64, e: f64 },
 }
 
 impl M114Command {
@@ -31,7 +45,7 @@ impl GcodeCommand for M114Command {
     fn command(&self) -> &'static str {
         "M114"
     }
-    fn parse_reply(&self, reply: &str) -> GcodeReply {
+    fn parse_reply(&self, reply: &str) -> Result<GcodeReply> {
         lazy_static! {
             static ref RE_SET: Vec<Regex> = vec![
                 Regex::new(r"X:(\d+(?:\.\d+))").unwrap(),
@@ -41,20 +55,25 @@ impl GcodeCommand for M114Command {
             ];
         }
 
-        let fields: Vec<Option<f64>> = RE_SET
+        let fields: Vec<Result<f64>> = RE_SET
             .iter()
             .map(|re| {
                 re.captures(reply)
                     .and_then(|cpt| cpt.get(1).map(|mtch| mtch.as_str().to_string()))
                     .and_then(|s| s.parse().ok())
+                    .ok_or(GcodeReplyError {
+                        parsed_input: reply.to_string(),
+                        problem: format!("Failed to match to regex {}", re.as_str()),
+                        sent_command: self.command().to_string(),
+                    })
             })
             .collect();
 
-        GcodeReply::M114Reply {
-            x: fields[0],
-            y: fields[1],
-            z: fields[2],
-            e: fields[3],
-        }
+        Ok(GcodeReply::M114Reply {
+            x: fields[0].clone()?,
+            y: fields[1].clone()?,
+            z: fields[2].clone()?,
+            e: fields[3].clone()?,
+        })
     }
 }

red/src/printer/mod.rs

@@ -5,8 +5,8 @@ use futures::sink::SinkExt;
 use futures::stream::StreamExt;
 use std::{fmt::Write, io, rc::Rc, str};
 use tokio;
+use tokio::sync::mpsc::{channel, Sender};
 use tokio_serial::SerialPortBuilderExt;
-use tokio::sync::mpsc::{Sender, channel};
 use tokio_util::codec::{Decoder, Encoder};
 
 pub use gcode::{GcodeCommand, GcodeReply, M114Command};