utils: Implement psql db pool state

- Implement a PSQL DB Pool which is managed as a Rocket State

Signed-off-by: supercmmetry <vishaals2000@gmail.com>

src/utils/db.rs

@@ -0,0 +1,55 @@
+use diesel::pg::PgConnection;
+use diesel::{r2d2, Connection};
+use diesel::r2d2::{PooledConnection, ConnectionManager};
+use rocket::{Outcome, Request, State};
+use rocket::http::Status;
+use rocket::request::{self, FromRequest};
+use std::env;
+use std::ops::Deref;
+use crate::utils::errors::{Error, ErrorCode};
+
+pub type Pool = r2d2::Pool<ConnectionManager<PgConnection>>;
+
+pub fn pool() -> Pool {
+    let manager = ConnectionManager::<PgConnection>::new(database_url());
+    Pool::new(manager).expect("db pool")
+}
+
+fn database_url() -> String {
+    env::var("DATABASE_URL").expect("DATABASE_URL must be set")
+}
+
+pub fn pg_connection() -> PgConnection {
+    PgConnection::establish(database_url().as_str()).unwrap()
+}
+
+pub struct DbConn(pub r2d2::PooledConnection<ConnectionManager<PgConnection>>);
+
+impl<'a, 'r> FromRequest<'a, 'r> for DbConn {
+    type Error = ();
+
+    fn from_request(request: &'a Request<'r>) -> request::Outcome<DbConn, Self::Error> {
+        let pool = request.guard::<State<Pool>>()?;
+        match pool.get() {
+            Ok(conn) => Outcome::Success(DbConn(conn)),
+            Err(_) => Outcome::Failure((Status::ServiceUnavailable, ())),
+        }
+    }
+}
+
+impl Deref for DbConn {
+    type Target = PgConnection;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+pub fn get_connection(pool: &Pool) -> Result<PooledConnection<ConnectionManager<PgConnection>>, Error> {
+    let result = pool.get();
+    if let Err(e) = result {
+        return Err(Error::custom(ErrorCode::DatabaseError, e.to_string()));
+    }
+
+    Ok(result.unwrap())
+}

src/utils/mod.rs

@@ -1 +1,2 @@
 pub mod errors;
+pub mod db;