From e0a668a58170e75fc2944e6aa855181296afd849 Mon Sep 17 00:00:00 2001
From: Joscha <joscha@plugh.de>
Date: Sun, 10 Mar 2024 15:26:50 +0100
Subject: [PATCH] Improve server error handling

---
 showbits-thermal-printer/src/server.rs        | 41 ++++++++-----------
 .../src/server/somehow.rs                     | 39 ++++++++++++++++++
 showbits-thermal-printer/src/server/static.rs | 12 +++---
 .../src/server/statuscode.rs                  | 15 +++++++
 showbits-thermal-printer/static/image.html    |  3 +-
 showbits-thermal-printer/static/index.html    |  2 +-
 6 files changed, 79 insertions(+), 33 deletions(-)
 create mode 100644 showbits-thermal-printer/src/server/somehow.rs
 create mode 100644 showbits-thermal-printer/src/server/statuscode.rs

diff --git a/showbits-thermal-printer/src/server.rs b/showbits-thermal-printer/src/server.rs
index aaa7fa5..4bb2ce6 100644
--- a/showbits-thermal-printer/src/server.rs
+++ b/showbits-thermal-printer/src/server.rs
@@ -1,8 +1,11 @@
+mod somehow;
 mod r#static;
+mod statuscode;
 
 use axum::{
     extract::{DefaultBodyLimit, Multipart, State},
     http::StatusCode,
+    response::{IntoResponse, Redirect, Response},
     routing::{get, post},
     Form, Router,
 };
@@ -11,6 +14,8 @@ use tokio::{net::TcpListener, sync::mpsc};
 
 use crate::drawer::Command;
 
+use self::{r#static::get_static_file, statuscode::status_code};
+
 #[derive(Clone)]
 struct Server {
     tx: mpsc::Sender<Command>,
@@ -22,9 +27,9 @@ pub async fn run(tx: mpsc::Sender<Command>, addr: String) -> anyhow::Result<()>
         .route("/test", post(post_test))
         .route("/rip", post(post_rip))
         .route("/text", post(post_text))
-        .route("/image", post(post_image))
+        .route("/image", post(post_image).fallback(get_static_file))
         .route("/chat_message", post(post_chat_message))
-        .fallback(get(r#static::get_static_file))
+        .fallback(get(get_static_file))
         .layer(DefaultBodyLimit::max(32 * 1024 * 1024)) // 32 MiB
         .with_state(Server { tx });
 
@@ -54,35 +59,25 @@ async fn post_text(server: State<Server>, request: Form<PostTextForm>) {
     let _ = server.tx.send(Command::Text(request.0.text)).await;
 }
 
-async fn post_image(server: State<Server>, mut multipart: Multipart) -> Result<(), StatusCode> {
+async fn post_image(server: State<Server>, mut multipart: Multipart) -> somehow::Result<Response> {
     let mut image = None;
 
-    while let Some(field) = multipart
-        .next_field()
-        .await
-        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?
-    {
-        let name = field.name().ok_or(StatusCode::INTERNAL_SERVER_ERROR)?;
-        if name == "image" {
-            let data = field
-                .bytes()
-                .await
-                .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
-
-            let decoded = image::load_from_memory(&data)
-                .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?
-                .into_rgba8();
-
-            image = Some(decoded);
+    while let Some(field) = multipart.next_field().await? {
+        if let Some(name) = field.name() {
+            if name == "image" {
+                let data = field.bytes().await?;
+                let decoded = image::load_from_memory(&data)?.into_rgba8();
+                image = Some(decoded);
+            }
         }
     }
 
     if let Some(image) = image {
         let _ = server.tx.send(Command::Image(image)).await;
-        Ok(())
-    } else {
-        Err(StatusCode::INTERNAL_SERVER_ERROR)
+        return Ok(Redirect::to("image").into_response());
     }
+
+    Ok(status_code(StatusCode::UNPROCESSABLE_ENTITY))
 }
 
 #[derive(Deserialize)]
diff --git a/showbits-thermal-printer/src/server/somehow.rs b/showbits-thermal-printer/src/server/somehow.rs
new file mode 100644
index 0000000..de3908c
--- /dev/null
+++ b/showbits-thermal-printer/src/server/somehow.rs
@@ -0,0 +1,39 @@
+use std::{error, fmt, result};
+
+use axum::{
+    http::StatusCode,
+    response::{IntoResponse, Response},
+};
+
+use super::statuscode::status_code_with_info;
+
+pub struct Error(pub anyhow::Error);
+
+impl<E> From<E> for Error
+where
+    E: error::Error + Send + Sync + 'static,
+{
+    fn from(value: E) -> Self {
+        Self(anyhow::Error::from(value))
+    }
+}
+
+impl fmt::Debug for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl IntoResponse for Error {
+    fn into_response(self) -> Response {
+        status_code_with_info(StatusCode::INTERNAL_SERVER_ERROR, &self.0)
+    }
+}
+
+pub type Result<T> = result::Result<T, Error>;
diff --git a/showbits-thermal-printer/src/server/static.rs b/showbits-thermal-printer/src/server/static.rs
index dc987ea..6e7efac 100644
--- a/showbits-thermal-printer/src/server/static.rs
+++ b/showbits-thermal-printer/src/server/static.rs
@@ -4,16 +4,14 @@ use axum::{
 };
 use rust_embed::RustEmbed;
 
+use super::statuscode::status_code;
+
 #[derive(RustEmbed)]
 #[folder = "static"]
 struct StaticFiles;
 
 struct StaticFile(String);
 
-fn not_found() -> Response {
-    (StatusCode::NOT_FOUND, "404 Not Found").into_response()
-}
-
 fn look_up_path(path: &str) -> Option<Response> {
     let path = path.trim_start_matches('/');
     let file = StaticFiles::get(path)?;
@@ -32,13 +30,13 @@ impl IntoResponse for StaticFile {
         if path.ends_with(".html") {
             // A file `/foo/bar.html` should not be accessible directly, only
             // indirectly at `/foo/bar`.
-            return not_found();
+            return status_code(StatusCode::NOT_FOUND);
         }
 
         if path.ends_with("/index") {
             // A file `/foo/index.html` should not be accessible directly, only
             // indirectly at `/foo/`.
-            return not_found();
+            return status_code(StatusCode::NOT_FOUND);
         }
 
         if path.ends_with('/') {
@@ -55,7 +53,7 @@ impl IntoResponse for StaticFile {
             return response;
         }
 
-        not_found()
+        status_code(StatusCode::NOT_FOUND)
     }
 }
 
diff --git a/showbits-thermal-printer/src/server/statuscode.rs b/showbits-thermal-printer/src/server/statuscode.rs
new file mode 100644
index 0000000..c63e8e5
--- /dev/null
+++ b/showbits-thermal-printer/src/server/statuscode.rs
@@ -0,0 +1,15 @@
+use core::fmt;
+
+use axum::{
+    http::StatusCode,
+    response::{IntoResponse, Response},
+};
+
+pub fn status_code(code: StatusCode) -> Response {
+    (code, code.to_string()).into_response()
+}
+
+pub fn status_code_with_info<I: fmt::Display>(code: StatusCode, info: &I) -> Response {
+    let message = format!("{code}\n\n{info}");
+    (code, message).into_response()
+}
diff --git a/showbits-thermal-printer/static/image.html b/showbits-thermal-printer/static/image.html
index 6054f4e..1a6f399 100644
--- a/showbits-thermal-printer/static/image.html
+++ b/showbits-thermal-printer/static/image.html
@@ -7,11 +7,10 @@
   </head>
   <body>
     <h1>Upload an image</h1>
-    <form action="image" method="post" enctype="multipart/form-data">
+    <form method="post" enctype="multipart/form-data">
       <ol>
         <li><input type="file" name="image" /></li>
         <li><button>Print!</button></li>
-        <li>Come back to this page</li>
       </ol>
     </form>
   </body>
diff --git a/showbits-thermal-printer/static/index.html b/showbits-thermal-printer/static/index.html
index f3be9de..05d51f7 100644
--- a/showbits-thermal-printer/static/index.html
+++ b/showbits-thermal-printer/static/index.html
@@ -8,7 +8,7 @@
   <body>
     <h1>Thermal Printer Control</h1>
     <ul>
-      <a href="image.html">Upload an image</a>
+      <a href="image">Upload an image</a>
     </ul>
   </body>
 </html>