Add Caddy HTTP error files

Caddyfile

@@ -2,8 +2,26 @@ emacssurvey.tecosaur.net
 
 @dynamic {
 	not path /css/*
+	not path /favicon.ico
+	not path /robots.txt
 }
 reverse_proxy @dynamic localhost:8000
 
-root /css/* /opt/emacs-survey/public/css/
+root * /opt/emacs-survey/public
-file_server /css/style.css
+file_server
+
+handle_errors {
+	@404 expression `{err.status_code} == 404`
+	handle @404 {
+		rewrite * /caddy-error.html
+		templates
+		file_server
+	}
+
+	handle {
+		rewrite * /{err.status_code}
+		reverse_proxy https://http.cat {
+			header_up Host {upstream_hostport}
+		}
+	}
+}

setup.org

@@ -72,22 +72,51 @@ SETUPDIR=$(dirname "$(readlink --canonicalize-existing "$0")")
 #+end_src
 
 ** Caddy Config
+:PROPERTIES:
+:header-args:prog: :tangle Caddyfile
+:END:
 
 We just need to redirect to Genie for now, which makes for a rather simple
 config. The only complication is serving the static files through Caddy not
 Genie, for performance reasons (Genie recommends against serving static files
 with it).
 
-#+begin_src prog :tangle Caddyfile
+#+begin_src prog
 emacssurvey.tecosaur.net
 
 @dynamic {
 	not path /css/*
+	not path /favicon.ico
+	not path /robots.txt
 }
 reverse_proxy @dynamic localhost:8000
+#+end_src
 
-root /css/* /opt/emacs-survey/public/css/
+We'll just pass all other requests to the public folder of the Emacs Survey.
-file_server /css/style.css
+#+begin_src prog
+root * /opt/emacs-survey/public
+file_server
+#+end_src
+
+The only thing left is error pages, for which we'll use a combination of error
+pages and http.cat 🐱.
+
+#+begin_src prog
+handle_errors {
+	@404 expression `{err.status_code} == 404`
+	handle @404 {
+		rewrite * /caddy-error.html
+		templates
+		file_server
+	}
+
+	handle {
+		rewrite * /{err.status_code}
+		reverse_proxy https://http.cat {
+			header_up Host {upstream_hostport}
+		}
+	}
+}
 #+end_src
 
 Just this one file is all it takes to get Caddy set up to our liking 🙂.