api: Add a CORS fairing

Signed-off-by: ATechnoHazard <amolele@gmail.com>

src/api/fairings/cors.rs

@@ -0,0 +1,29 @@
+use rocket::{Request, Response};
+use rocket::fairing::{Fairing, Info, Kind};
+use rocket::http::{Header, ContentType, Method};
+use std::io::Cursor;
+
+pub struct CORS();
+
+impl Fairing for CORS {
+    fn info(&self) -> Info {
+        Info {
+            name: "Add CORS headers to requests",
+            kind: Kind::Response
+        }
+    }
+
+    fn on_response(&self, request: &Request, response: &mut Response) {
+        if request.method() == Method::Options || response.content_type() == Some(ContentType::JSON) {
+            response.set_header(Header::new("Access-Control-Allow-Origin", "*"));
+            response.set_header(Header::new("Access-Control-Allow-Methods", "POST, GET, OPTIONS"));
+            response.set_header(Header::new("Access-Control-Allow-Headers", "Content-Type"));
+            response.set_header(Header::new("Access-Control-Allow-Credentials", "true"));
+        }
+
+        if request.method() == Method::Options {
+            response.set_header(ContentType::Plain);
+            response.set_sized_body(Cursor::new(""));
+        }
+    }
+}

src/api/fairings/mod.rs

@@ -0,0 +1 @@
+pub mod cors;

src/api/mod.rs

@@ -1,5 +1,6 @@
 pub mod catchers;
 pub mod routes;
+pub mod fairings;
 
 mod guards;
 mod misc;

src/api/routes/mod.rs

@@ -1,4 +1,5 @@
 use rocket::Rocket;
+use crate::api::fairings::cors::CORS;
 
 pub mod health;
 pub mod paste;
@@ -8,5 +9,5 @@ pub fn fuel(rocket: Rocket) -> Rocket {
     let mut rocket = rocket;
     rocket = health::fuel(rocket);
     rocket = paste::fuel(rocket);
-    rocket
+    rocket.attach(CORS())
 }