From 61bfaf01863de6caa0760e6852d47ee8af2e3a98 Mon Sep 17 00:00:00 2001
From: Shing Him Ng <shinghim@protonmail.com>
Date: Fri, 3 Jan 2025 09:03:31 -0600
Subject: [PATCH] Introduce DbPoolError to store Redis and timeout errors

---
 payjoin-directory/src/db.rs    | 18 ++++++++++++++----
 payjoin-directory/src/error.rs | 25 +++++++++++++++++++++++++
 payjoin-directory/src/lib.rs   | 20 ++++++++++++--------
 3 files changed, 51 insertions(+), 12 deletions(-)
 create mode 100644 payjoin-directory/src/error.rs

diff --git a/payjoin-directory/src/db.rs b/payjoin-directory/src/db.rs
index 6165abf9..33780067 100644
--- a/payjoin-directory/src/db.rs
+++ b/payjoin-directory/src/db.rs
@@ -4,6 +4,8 @@ use futures::StreamExt;
 use redis::{AsyncCommands, Client, ErrorKind, RedisError, RedisResult};
 use tracing::debug;
 
+use crate::error::DbPoolError;
+
 const DEFAULT_COLUMN: &str = "";
 const PJ_V1_COLUMN: &str = "pjv1";
 
@@ -19,11 +21,12 @@ impl DbPool {
         Ok(Self { client, timeout })
     }
 
+    /// Peek using [`DEFAULT_COLUMN`] as the channel type.
     pub async fn push_default(&self, subdirectory_id: &str, data: Vec<u8>) -> RedisResult<()> {
         self.push(subdirectory_id, DEFAULT_COLUMN, data).await
     }
 
-    pub async fn peek_default(&self, subdirectory_id: &str) -> Option<RedisResult<Vec<u8>>> {
+    pub async fn peek_default(&self, subdirectory_id: &str) -> Result<Vec<u8>, DbPoolError> {
         self.peek_with_timeout(subdirectory_id, DEFAULT_COLUMN).await
     }
 
@@ -31,7 +34,8 @@ impl DbPool {
         self.push(subdirectory_id, PJ_V1_COLUMN, data).await
     }
 
-    pub async fn peek_v1(&self, subdirectory_id: &str) -> Option<RedisResult<Vec<u8>>> {
+    /// Peek using [`PJ_V1_COLUMN`] as the channel type.
+    pub async fn peek_v1(&self, subdirectory_id: &str) -> Result<Vec<u8>, DbPoolError> {
         self.peek_with_timeout(subdirectory_id, PJ_V1_COLUMN).await
     }
 
@@ -52,8 +56,14 @@ impl DbPool {
         &self,
         subdirectory_id: &str,
         channel_type: &str,
-    ) -> Option<RedisResult<Vec<u8>>> {
-        tokio::time::timeout(self.timeout, self.peek(subdirectory_id, channel_type)).await.ok()
+    ) -> Result<Vec<u8>, DbPoolError> {
+        match tokio::time::timeout(self.timeout, self.peek(subdirectory_id, channel_type)).await {
+            Ok(redis_result) => match redis_result {
+                Ok(result) => Ok(result),
+                Err(redis_err) => Err(DbPoolError::Redis(redis_err)),
+            },
+            Err(elapsed) => Err(DbPoolError::Timeout(elapsed)),
+        }
     }
 
     async fn peek(&self, subdirectory_id: &str, channel_type: &str) -> RedisResult<Vec<u8>> {
diff --git a/payjoin-directory/src/error.rs b/payjoin-directory/src/error.rs
new file mode 100644
index 00000000..426da28b
--- /dev/null
+++ b/payjoin-directory/src/error.rs
@@ -0,0 +1,25 @@
+#[derive(Debug)]
+pub enum DbPoolError {
+    Redis(redis::RedisError),
+    Timeout(tokio::time::error::Elapsed),
+}
+
+impl std::fmt::Display for DbPoolError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        use DbPoolError::*;
+
+        match &self {
+            Redis(error) => write!(f, "Redis error: {}", error),
+            Timeout(timeout) => write!(f, "Timeout: {}", timeout),
+        }
+    }
+}
+
+impl std::error::Error for DbPoolError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        match self {
+            DbPoolError::Redis(e) => Some(e),
+            DbPoolError::Timeout(e) => Some(e),
+        }
+    }
+}
diff --git a/payjoin-directory/src/lib.rs b/payjoin-directory/src/lib.rs
index 9a1c651c..aa6512a2 100644
--- a/payjoin-directory/src/lib.rs
+++ b/payjoin-directory/src/lib.rs
@@ -34,7 +34,10 @@ const V1_UNAVAILABLE_RES_JSON: &str = r#"{{"errorCode": "unavailable", "message"
 const ID_LENGTH: usize = 13;
 
 mod db;
+mod error;
+
 use crate::db::DbPool;
+use crate::error::DbPoolError;
 
 #[cfg(feature = "_danger-local-https")]
 type BoxError = Box<dyn std::error::Error + Send + Sync>;
@@ -341,11 +344,11 @@ async fn post_fallback_v1(
         .await
         .map_err(|e| HandlerError::BadRequest(e.into()))?;
     match pool.peek_v1(id).await {
-        Some(result) => match result {
-            Ok(buffered_req) => Ok(Response::new(full(buffered_req))),
-            Err(e) => Err(HandlerError::BadRequest(e.into())),
+        Ok(buffered_req) => Ok(Response::new(full(buffered_req))),
+        Err(e) => match e {
+            DbPoolError::Redis(_) => Err(HandlerError::BadRequest(e.into())),
+            DbPoolError::Timeout(_) => Ok(none_response),
         },
-        None => Ok(none_response),
     }
 }
 
@@ -409,11 +412,12 @@ async fn get_subdir(
     trace!("get_subdir");
     let id = check_id_length(id)?;
     match pool.peek_default(id).await {
-        Some(result) => match result {
-            Ok(buffered_req) => Ok(Response::new(full(buffered_req))),
-            Err(e) => Err(HandlerError::BadRequest(e.into())),
+        Ok(buffered_req) => Ok(Response::new(full(buffered_req))),
+        Err(e) => match e {
+            DbPoolError::Redis(_) => Err(HandlerError::BadRequest(e.into())),
+            DbPoolError::Timeout(_) =>
+                Ok(Response::builder().status(StatusCode::ACCEPTED).body(empty())?),
         },
-        None => Ok(Response::builder().status(StatusCode::ACCEPTED).body(empty())?),
     }
 }