From 22761ee92ea41eb9014f85ca4a2e7a0d6d23fd5c Mon Sep 17 00:00:00 2001
From: Daniel Flanagan <daniel@lyte.dev>
Date: Tue, 14 Nov 2023 14:07:47 -0600
Subject: [PATCH] Setup a proper error type for the web application

---
 src/error.rs  | 46 +++++++++++++++++++++++++++++++---------------
 src/router.rs | 13 +++----------
 src/views.rs  | 34 +++++++++++++++++++---------------
 3 files changed, 53 insertions(+), 40 deletions(-)

diff --git a/src/error.rs b/src/error.rs
index fb3678e..01cae08 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -1,25 +1,41 @@
+use core::fmt;
+
 use axum::{
     http::StatusCode,
     response::{IntoResponse, Response},
 };
+use thiserror::Error;
 
-pub struct AppError(anyhow::Error);
+#[derive(Error, Debug)]
+pub enum AppError {
+    InvalidCsrf(#[from] axum_csrf::CsrfError),
+    Other(#[from] anyhow::Error),
+}
+
+impl AppError {
+    fn status_code(&self) -> StatusCode {
+        match self {
+            AppError::Other(_) => StatusCode::INTERNAL_SERVER_ERROR,
+            AppError::InvalidCsrf(_) => StatusCode::BAD_REQUEST,
+        }
+    }
+
+    fn message(&self) -> String {
+        match self {
+            AppError::Other(e) => format!("something went wrong: {}", e),
+            AppError::InvalidCsrf(e) => format!("unable to verify csrf: {}", e),
+        }
+    }
+}
+
+impl fmt::Display for AppError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.message())
+    }
+}
 
 impl IntoResponse for AppError {
     fn into_response(self) -> Response {
-        (
-            StatusCode::INTERNAL_SERVER_ERROR,
-            format!("Something went wrong: {}", self.0),
-        )
-            .into_response()
-    }
-}
-
-impl<E> From<E> for AppError
-where
-    E: Into<anyhow::Error>,
-{
-    fn from(err: E) -> Self {
-        Self(err.into())
+        (self.status_code(), self.message()).into_response()
     }
 }
diff --git a/src/router.rs b/src/router.rs
index acffcbb..fec7920 100644
--- a/src/router.rs
+++ b/src/router.rs
@@ -66,7 +66,7 @@ struct Register {
 }
 
 impl<'a> TryInto<NewUser<'a>> for &'a Register {
-    type Error = argon2::password_hash::Error;
+    type Error = anyhow::Error;
 
     fn try_into(self: &'a Register) -> Result<NewUser<'a>, Self::Error> {
         let salt = SaltString::generate(&mut OsRng);
@@ -86,18 +86,11 @@ impl<'a> TryInto<NewUser<'a>> for &'a Register {
 }
 
 async fn register(
-    csrf_token: CsrfToken,
+    c: CsrfToken,
     Form(register): Form<Register>,
 ) -> Result<impl IntoResponse, AppError> {
     // TODO: https://docs.rs/axum_csrf/latest/axum_csrf/#prevent-post-replay-attacks-with-csrf
-
-    let v = csrf_token.verify(&register.authenticity_token);
-    if v.is_err() {
-        return Ok((
-            StatusCode::BAD_REQUEST,
-            Html(html! { "invalid request" }.into_string()),
-        ));
-    }
+    c.verify(&register.authenticity_token)?;
 
     let new_user: NewUser = (&register).try_into()?;
 
diff --git a/src/views.rs b/src/views.rs
index b75d7ce..76a1978 100644
--- a/src/views.rs
+++ b/src/views.rs
@@ -12,6 +12,14 @@ use crate::{
     partials::{footer, header},
 };
 
+pub async fn csrf<F>(csrf: CsrfToken, cb: F) -> impl IntoResponse
+where
+    F: Fn(&str) -> Html<String>,
+{
+    let token = csrf.authenticity_token().unwrap();
+    (csrf, cb(&token))
+}
+
 #[instrument]
 pub async fn index() -> Html<String> {
     Html(
@@ -39,10 +47,8 @@ pub async fn index() -> Html<String> {
     )
 }
 
-pub async fn register(csrf: CsrfToken) -> impl IntoResponse {
-    let token = csrf.authenticity_token().unwrap();
-    (
-        csrf,
+pub async fn register(t: CsrfToken) -> impl IntoResponse {
+    csrf(t, |token| {
         Html(
             html! {
                 (header())
@@ -64,22 +70,20 @@ pub async fn register(csrf: CsrfToken) -> impl IntoResponse {
                 (footer())
             }
             .into_string(),
-        ),
-    )
-        .into_response()
+        )
+    })
+    .await
 }
 
-pub async fn login(csrf: CsrfToken) -> impl IntoResponse {
-    let token = csrf.authenticity_token().unwrap();
-    (
-        csrf,
+pub async fn login(t: CsrfToken) -> impl IntoResponse {
+    csrf(t, |token| {
         Html(
             html! {
                 (header())
                 main class="prose" {
                     h1 { "Login" }
                     form method="post" {
-                            input type="hidden" name="authenticity_token" value=(token) {}
+                        input type="hidden" name="authenticity_token" value=(token) {}
                         label {
                             input {}
                         }
@@ -91,9 +95,9 @@ pub async fn login(csrf: CsrfToken) -> impl IntoResponse {
                 (footer())
             }
             .into_string(),
-        ),
-    )
-        .into_response()
+        )
+    })
+    .await
 }
 
 #[allow(unreachable_code)]