Redirect on invalid UTF-8 in /p/

Previously, uploading a paste with invalid UTF-8 and then viewing it
with the pretty URL would cause a panic.
With this change, it simply redirects to the raw URL.

src/models/maybe_redirect.rs

@@ -0,0 +1,31 @@
+use rocket::{
+    request::Request,
+    response::{Redirect, Responder, Result},
+};
+use rocket_dyn_templates::Template;
+
+pub enum MaybeRedirect {
+    Redirect(Box<Redirect>),
+    Template(Box<Template>),
+}
+
+impl From<Redirect> for MaybeRedirect {
+    fn from(other: Redirect) -> Self {
+        Self::Redirect(Box::new(other))
+    }
+}
+
+impl From<Template> for MaybeRedirect {
+    fn from(other: Template) -> Self {
+        Self::Template(Box::new(other))
+    }
+}
+
+impl<'r, 'o: 'r> Responder<'r, 'o> for MaybeRedirect {
+    fn respond_to(self, req: &'r Request<'_>) -> Result<'o> {
+        match self {
+            Self::Template(t) => t.respond_to(req),
+            Self::Redirect(r) => r.respond_to(req),
+        }
+    }
+}

src/models/mod.rs

@@ -1,3 +1,4 @@
+pub mod maybe_redirect;
 pub mod paste_id;
 pub mod pretty;
 pub mod pretty_syntax;

src/models/pretty.rs

@@ -10,16 +10,16 @@ static SYNTAXES: &[u8] =
 static THEMES: &[u8] =
     include_bytes!("../../resources/themes/ayu_dark.tmTheme");
 
-pub fn get_pretty_body(path: &Path, ext: &str) -> String {
+pub fn get_pretty_body(path: &Path, ext: &str) -> std::io::Result<String> {
     let ss: SyntaxSet = syntect::dumps::from_binary(SYNTAXES);
 
     let mut theme_cursor = std::io::Cursor::new(THEMES);
     let theme = ThemeSet::load_from_reader(&mut theme_cursor).unwrap();
 
-    let content = fs::read_to_string(path).unwrap();
+    let content = fs::read_to_string(path)?;
     let syntax = ss
         .find_syntax_by_token(ext)
         .unwrap_or_else(|| ss.find_syntax_plain_text());
 
-    highlighted_html_for_string(&content, &ss, syntax, &theme)
+    Ok(highlighted_html_for_string(&content, &ss, syntax, &theme))
 }