From e0315538a36be9ef558392264052da366db576a2 Mon Sep 17 00:00:00 2001
From: Derek Christ <christ.derek@gmail.com>
Date: Sun, 19 Nov 2023 20:28:55 +0100
Subject: [PATCH] Add some error handling

---
 Cargo.lock     |  7 +++++++
 Cargo.toml     |  1 +
 src/index.html |  2 +-
 src/main.rs    | 55 ++++++++++++++++++++++++++++++++++++++------------
 4 files changed, 51 insertions(+), 14 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 973f903..da8ed39 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -47,6 +47,12 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "anyhow"
+version = "1.0.75"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4668cab20f66d8d020e1fbc0ebe47217433c1b6c8f2040faf858554e394ace6"
+
 [[package]]
 name = "async-trait"
 version = "0.1.74"
@@ -171,6 +177,7 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 name = "elwa-dc"
 version = "0.1.0"
 dependencies = [
+ "anyhow",
  "axum",
  "base64",
  "log",
diff --git a/Cargo.toml b/Cargo.toml
index e0c5214..0721848 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,6 +7,7 @@ edition = "2021"
 dummy = []
 
 [dependencies]
+anyhow = "1.0.75"
 axum = "0.6.20"
 base64 = "0.21.5"
 log = "0.4.20"
diff --git a/src/index.html b/src/index.html
index 518ecf1..37d3aee 100644
--- a/src/index.html
+++ b/src/index.html
@@ -29,7 +29,7 @@
     
     <h2>Zustand</h2>
     <p>Isolationsmessung: {11}</p>
-    <p>Gerätetemperatur: {12}</p>
+    <p>Gerätetemperatur: {12} °C</p>
     <p>Status: {13}</p>
     <p>DC Trenner: {14}</p>
     <p>DC Relais: {15}</p>
diff --git a/src/main.rs b/src/main.rs
index 582b75d..47b68b3 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,10 @@
-use axum::{response::Html, routing::get, Router};
+use anyhow::Context;
+use axum::{
+    http::StatusCode,
+    response::{Html, IntoResponse, Response},
+    routing::get,
+    Router,
+};
 use strum::{EnumIter, IntoEnumIterator};
 
 #[derive(EnumIter, Debug)]
@@ -68,6 +74,27 @@ struct Status<'a> {
     seriennummer: &'a str,
 }
 
+struct AppError(anyhow::Error);
+
+impl IntoResponse for AppError {
+    fn into_response(self) -> Response {
+        (
+            StatusCode::INTERNAL_SERVER_ERROR,
+            format!("Internal Server Error:\n{:?}", self.0),
+        )
+            .into_response()
+    }
+}
+
+impl<E> From<E> for AppError
+where
+    E: Into<anyhow::Error>,
+{
+    fn from(err: E) -> Self {
+        Self(err.into())
+    }
+}
+
 #[tokio::main]
 async fn main() {
     let app = Router::new().route("/", get(handler));
@@ -78,10 +105,10 @@ async fn main() {
         .unwrap();
 }
 
-async fn handler() -> Html<String> {
+async fn handler() -> Result<Html<String>, AppError> {
     log::info!("Fetch new data");
 
-    let data = read_device();
+    let data = read_device().context("Could not retrieve device data")?;
     let data_string = std::str::from_utf8(&data).unwrap();
 
     let mut status = Status::default();
@@ -127,7 +154,7 @@ async fn handler() -> Html<String> {
         }
     }
 
-    Html(format!(
+    Ok(Html(format!(
         include_str!("index.html"),
         status.wassertemp,
         status.wassertemp_min,
@@ -149,32 +176,34 @@ async fn handler() -> Html<String> {
         status.betriebstag,
         status.firmware,
         status.seriennummer,
-    ))
+    )))
 }
 
 #[cfg(not(feature = "dummy"))]
-fn read_device() -> Vec<u8> {
+fn read_device() -> anyhow::Result<Vec<u8>> {
     use std::io::{BufRead, BufReader};
     use std::time::Duration;
 
     let mut port = serialport::new("/dev/ttyUSB0", 9600)
-        .timeout(Duration::from_secs(5))
+        .timeout(Duration::from_millis(100))
         .open()
-        .expect("Failed to open port");
+        .context("Could not open serial device port")?;
 
-    write!(&mut port, "rs\r\n").expect("Write failed!");
+    write!(&mut port, "rs\r\n").context("Could not write to serial connection")?;
 
     let mut reader = BufReader::new(port);
 
     let mut data: Vec<u8> = Vec::new();
-    reader.read_until(b'\n', &mut data).expect("Found no data!");
+    reader
+        .read_until(b'\n', &mut data)
+        .context("Could not read from serial connection")?;
 
-    data
+    Ok(data)
 }
 
 #[cfg(feature = "dummy")]
-fn read_device() -> Vec<u8> {
+fn read_device() -> anyhow::Result<Vec<u8>> {
     use base64::{engine::general_purpose, Engine as _};
     const SAMPLE_OUTPUT: &str = "ZHIJVjEuMzEJMzUJMTIJMQkxCTEJMjM1CTE3NQkyNDUJNzU5CTY1MAkyNQk5MAkxODkuNQkxOTAuMDMJMS4xNDM1CTIxNy4yOQk3NzgJOTE3MjUJMAktNwk3LjkJNTI1CTM2OAkzNTgJMjQwCTEJMTIwMTAwMjMwMjEwMDAyMwk3NTkJNg0K";
-    general_purpose::STANDARD.decode(SAMPLE_OUTPUT).unwrap()
+    Ok(general_purpose::STANDARD.decode(SAMPLE_OUTPUT)?)
 }