From b62344371e4ce07aa19da5e7faeef322e907653e Mon Sep 17 00:00:00 2001
From: Harald Eilertsen <haraldei@anduin.net>
Date: Sun, 1 Oct 2017 22:12:36 +0200
Subject: Get database connection on request

---
 src/lib.rs  | 33 +++++++++++++++++++++++++++++++++
 src/main.rs |  2 +-
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index 5152ae5..0c2d440 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,6 +5,7 @@ extern crate diesel_codegen;
 extern crate dotenv;
 extern crate r2d2_diesel;
 extern crate r2d2;
+extern crate rocket;
 
 use diesel::pg::PgConnection;
 use r2d2_diesel::ConnectionManager;
@@ -25,3 +26,35 @@ pub fn init_db_pool() -> Pool {
     let manager = ConnectionManager::<PgConnection>::new(dburl);
     r2d2::Pool::new(config, manager).expect("db pool")
 }
+
+use std::ops::Deref;
+use rocket::http::Status;
+use rocket::request::{self, FromRequest};
+use rocket::{Request, State, Outcome};
+
+// Connection request guard type: a wrapper around an r2d2 pooled connection.
+pub struct DbConn(pub r2d2::PooledConnection<ConnectionManager<PgConnection>>);
+
+/// Attempts to retrieve a single connection from the managed database pool. If
+/// no pool is currently managed, fails with an `InternalServerError` status. If
+/// no connections are available, fails with a `ServiceUnavailable` status.
+impl<'a, 'r> FromRequest<'a, 'r> for DbConn {
+    type Error = ();
+
+    fn from_request(request: &'a Request<'r>) -> request::Outcome<DbConn, ()> {
+        let pool = request.guard::<State<Pool>>()?;
+        match pool.get() {
+            Ok(conn) => Outcome::Success(DbConn(conn)),
+            Err(_) => Outcome::Failure((Status::ServiceUnavailable, ()))
+        }
+    }
+}
+
+// For the convenience of using an &DbConn as an &SqliteConnection.
+impl Deref for DbConn {
+    type Target = PgConnection;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index d9747c9..711c343 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,7 +5,7 @@ extern crate rocket;
 extern crate rocket_blog;
 
 #[get("/")]
-fn index() -> &'static str {
+fn index(conn: rocket_blog::DbConn) -> &'static str {
     "Hallo, for faen!"
 }
 
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