add refresh flow

lib/komainu/src/flow/refresh.rs

@@ -0,0 +1,71 @@
+use super::TokenResponse;
+use crate::{
+    error::{Error, Result},
+    Client, ClientExtractor, OptionExt,
+    params::ParamStorage,
+};
+use bytes::Bytes;
+use headers::HeaderMapExt;
+use std::future::Future;
+
+pub trait Issuer {
+    fn issue_token(
+        &self,
+        client: &Client<'_>,
+        refresh_token: &str,
+    ) -> impl Future<Output = Result<TokenResponse<'_>>>;
+}
+
+#[instrument(skip_all)]
+pub async fn perform<CE, I>(
+    req: http::Request<Bytes>,
+    client_extractor: CE,
+    token_issuer: I,
+) -> Result<http::Response<Bytes>>
+where
+    CE: ClientExtractor,
+    I: Issuer,
+{
+    let body: ParamStorage<&str, &str> = crate::deserialize_body(&req)?;
+
+    let basic_auth = req
+        .headers()
+        .typed_get::<headers::Authorization<headers::authorization::Basic>>();
+
+    let (client_id, client_secret) = if let Some(ref auth) = basic_auth {
+        (auth.username(), auth.password())
+    } else {
+        debug!("attempting to read client credentials from body (naughty :3)");
+
+        // As a fallback, try to read from the body.
+        // Not recommended but some clients do this. Done to increase compatibility.
+        let client_id = body.get("client_id").or_missing_param()?;
+        let client_secret = body.get("client_secret").or_missing_param()?;
+
+        (*client_id, *client_secret)
+    };
+
+    let grant_type = body.get("grant_type").or_missing_param()?;
+    let refresh_token = body.get("refresh_token").or_missing_param()?;
+
+    if *grant_type != "refresh_token" {
+        debug!(?client_id, "grant_type is not refresh_token");
+        return Err(Error::Unauthorized);
+    }
+
+    let client = client_extractor
+        .extract(client_id, Some(client_secret))
+        .await?;
+
+    let token = token_issuer.issue_token(&client, refresh_token).await?;
+    let body = sonic_rs::to_vec(&token).unwrap();
+
+    debug!("token successfully issued. building response");
+
+    let response = http::Response::builder()
+        .status(http::StatusCode::OK)
+        .body(body.into())
+        .unwrap();
+
+    Ok(response)
+}