feat(atward): Support reading configuration from cookies

Adds support for reading configuration (currently only the `cs`
parameter) from cookies and from URL query parameters. The latter take
precedence if set explicitly.

This is useful for users which can not edit their search query
parameters.

To make this easier to use the atward landing page has been updated
with a simple form where settings can be toggled. This requires
Javascript, but the script is small, embedded and MIT licensed (as is
the rest of this project). Users without Javascript will be shown a
notice about this.

It is of course possible to set the cookies manually, too.

Change-Id: Ie9a9dbeab4d9a97a349d7988e21f1b46037e1f72
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3110
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

web/atward/src/main.rs

@@ -5,7 +5,8 @@
 //! browsers and attempts to send users to useful locations based on
 //! their search query (falling back to another search engine).
 use regex::Regex;
-use rouille::Response;
+use rouille::input::cookies;
+use rouille::{Request, Response};
 
 /// A query handler supported by atward. It consists of a pattern on
 /// which to match and trigger the query, and a function to execute
@@ -23,6 +24,7 @@ struct Handler {
 }
 
 /// An Atward query supplied by a user.
+#[derive(Debug, PartialEq)]
 struct Query {
     /// Query string itself.
     query: String,
@@ -31,19 +33,38 @@ struct Query {
     cs: bool,
 }
 
+/// Helper function for setting a parameter based on a query
+/// parameter.
+fn query_setting(req: &Request, config: &mut bool, param: &str) {
+    match req.get_param(param) {
+        Some(s) if s == "true" => *config = true,
+        Some(s) if s == "false" => *config = false,
+        _ => {}
+    }
+}
+
 impl Query {
-    fn from_request(req: &rouille::Request) -> Option<Query> {
-        let query = match req.get_param("q") {
-            Some(q) => q,
+    fn from_request(req: &Request) -> Option<Query> {
+        // First extract the actual search query ...
+        let mut query = match req.get_param("q") {
+            Some(query) => Query { query, cs: false },
             None => return None,
         };
 
-        let cs = match req.get_param("cs") {
-            Some(s) if s == "true" => true,
-            _ => false,
-        };
+        // ... then apply settings to it. Settings in query parameters
+        // take precedence over cookies.
+        for cookie in cookies(req) {
+            match cookie {
+                ("cs", "true") => {
+                    query.cs = true;
+                }
+                _ => {}
+            }
+        }
 
-        Some(Query { query, cs })
+        query_setting(req, &mut query.cs, "cs");
+
+        Some(query)
     }
 }
 
@@ -228,4 +249,70 @@ mod tests {
             None
         );
     }
+
+    #[test]
+    fn request_to_query() {
+        assert_eq!(
+            Query::from_request(&Request::fake_http("GET", "/?q=b%2F42", vec![], vec![]))
+                .expect("request should parse to a query"),
+            Query {
+                query: "b/42".to_string(),
+                cs: false,
+            },
+        );
+
+        assert_eq!(
+            Query::from_request(&Request::fake_http("GET", "/", vec![], vec![])),
+            None
+        );
+    }
+
+    #[test]
+    fn settings_from_cookie() {
+        assert_eq!(
+            Query::from_request(&Request::fake_http(
+                "GET",
+                "/?q=b%2F42",
+                vec![("Cookie".to_string(), "cs=true;".to_string())],
+                vec![]
+            ))
+            .expect("request should parse to a query"),
+            Query {
+                query: "b/42".to_string(),
+                cs: true,
+            },
+        );
+    }
+
+    #[test]
+    fn settings_from_query_parameter() {
+        assert_eq!(
+            Query::from_request(&Request::fake_http(
+                "GET",
+                "/?q=b%2F42&cs=true",
+                vec![],
+                vec![]
+            ))
+            .expect("request should parse to a query"),
+            Query {
+                query: "b/42".to_string(),
+                cs: true,
+            },
+        );
+
+        // Query parameter should override cookie
+        assert_eq!(
+            Query::from_request(&Request::fake_http(
+                "GET",
+                "/?q=b%2F42&cs=false",
+                vec![("Cookie".to_string(), "cs=true;".to_string())],
+                vec![]
+            ))
+            .expect("request should parse to a query"),
+            Query {
+                query: "b/42".to_string(),
+                cs: false,
+            },
+        );
+    }
 }