Allow client to be shared across threads (#26)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "stytch"
-version = "3.0.0"
+version = "3.0.1"
 edition = "2021"
 license = "MIT"
 description = "Stytch Rust client"

src/client.rs

@@ -1,5 +1,6 @@
 use base64::{engine::general_purpose, Engine as _};
 use serde::{de::DeserializeOwned, Deserialize, Serialize};
+use std::sync::{Arc, Mutex};
 
 const LIVE_URL: &str = "https://api.stytch.com/";
 const TEST_URL: &str = "https://test.stytch.com/";
@@ -13,7 +14,7 @@ pub struct Client {
     // This would be very natural as a OnceCell, but get_or_try_init is unstable
     // and would require marking this library as only usable with nightly rust.
     // When that feature is stabilized, we should switch to using OnceCell.
-    jwks: std::cell::RefCell<Option<Jwks>>,
+    jwks: Arc<Mutex<Option<Jwks>>>,
 }
 
 impl std::fmt::Debug for Client {
@@ -82,22 +83,34 @@ impl Client {
             project_id: project_id.to_string(),
             base_url,
             jwks_url,
-            jwks: std::cell::RefCell::new(None),
+            jwks: Arc::new(Mutex::new(None)),
         })
     }
 
     async fn fetch_jwks(&self) -> crate::Result<Jwks> {
-        if self.jwks.borrow().is_none() {
-            self.jwks.replace(
-                self.send(crate::Request {
-                    method: http::Method::GET,
-                    path: self.jwks_url.clone(),
-                    body: (),
-                })
-                .await?,
-            );
+        // First see if we already have the jwks cached
+        {
+            let guard = self.jwks.lock().map_err(|_| crate::Error::FetchJwks)?;
+            if let Some(jwks) = &*guard {
+                return Ok(jwks.clone());
+            }
         }
-        Ok(self.jwks.borrow().clone().unwrap())
+
+        let fetched_jwks: Jwks = self
+            .send(crate::Request {
+                method: http::Method::GET,
+                path: self.jwks_url.clone(),
+                body: (),
+            })
+            .await
+            .map_err(|_| crate::Error::FetchJwks)?;
+
+        {
+            let mut guard = self.jwks.lock().map_err(|_| crate::Error::FetchJwks)?;
+            *guard = Some(fetched_jwks.clone());
+        }
+
+        Ok(fetched_jwks)
     }
 
     pub async fn fetch_jwk(&self, kid: &str) -> crate::Result<Jwk> {

src/lib.rs

@@ -12,6 +12,9 @@ pub enum Error {
     #[error(transparent)]
     InvalidUrl(#[from] url::ParseError),
 
+    #[error("Failed to fetch JWKS")]
+    FetchJwks,
+
     #[error("{0:?}")]
     JwkNotFound(String),