move read_line to IterableRx, improve read_response

src/modem.rs

@@ -20,6 +20,7 @@ pub enum ModemError {
     CommandError(String),
     SetupError(String),
     SendDataError,
+    ReadError,
     TimeoutError,
 }
 
@@ -46,6 +47,26 @@ impl<UART: serial::Uart> IterableRx<UART> {
         println!("clearing serial rx");
         self.reset(Duration::from_millis(500)).for_each(drop);
     }
+
+    /// Reads a whole line (that ends with \\n) within the given `timeout` passed on input.
+    fn read_line(&mut self, timeout: Duration) -> Result<String> {
+        let mut line: String = self.reset(timeout)
+            .map(|b| char::from(b))
+            .take_while(|c| *c != '\n')
+            .collect();
+
+        // \r must come right before \n on read; take_while excludes the matched element.
+        if line.ends_with('\r') {
+            line.push('\n');
+            Ok(line)
+        }
+        else if self.timeout.as_millis() == 0 {
+            Err(ModemError::TimeoutError)
+        }
+        else {
+            Err(ModemError::ReadError)
+        }
+    }
 }
 
 impl<UART: serial::Uart> Iterator for IterableRx<UART> {
@@ -117,15 +138,6 @@ impl<UART: serial::Uart> Modem<UART> {
         Ok(())
     }
 
-    /// Reads a whole line (that ends with \\n) within the given `timeout` passed on input.
-    ///
-    fn read_line(&mut self, timeout: Duration) -> String {
-        self.rx.reset(timeout)
-            .map(|b| char::from(b))
-            .take_while(|c| *c != '\n')
-            .collect()
-    }
-
     /// Reads the serial RX until a \\n char is encoutered, or a timeout is reached. The timeout is
     /// provided on input via the `timeout` argument. The first argument `contains` is checked
     /// against a line in the response, if it's there the reading stops.
@@ -138,20 +150,15 @@ impl<UART: serial::Uart> Modem<UART> {
         let match_text: String = contains.unwrap_or("\n".to_string());
 
         loop {
-            let line = self.read_line(timeout.saturating_sub(start.elapsed()));
-            if line != "" {
-                println!("Read {} bytes from serial ({})", line.len(), line);
+            let timeout = timeout - start.elapsed();
+            let line = self.rx.read_line(timeout)?;
+            print!("Read {} bytes from serial: {}", line.len(), line);
             response.push_str(&line);
             if line.contains("ERROR") || line.contains(&match_text) {
                 println!("Found match {} for line {} ; exiting response reader now ...", match_text, line);
                 println!("-----------------------------------------------------------");
                 break Ok(response.to_string())
             }
-            } else {
-                println!("-----------------------------------------------------------");
-                println!("got empty line from read_line :(");
-                break Err(ModemError::TimeoutError)
-            }
         }
     }