Fetch schedule message endpoint (#21)

Reviewed-on: phoenix/textsender_api#21

src/repo/message/scheduling.rs

@@ -84,6 +84,36 @@ pub async fn get_with_user_id(
     }
 }
 
+pub async fn fetch(
+    pool: &sqlx::PgPool,
+) -> Result<textsender_models::message::scheduling::ScheduledMessage, sqlx::Error> {
+    match sqlx::query(
+        r#"
+        UPDATE "scheduled_messages"
+		SET status = $1
+		WHERE id = (
+			SELECT id FROM "scheduled_messages"
+			WHERE status = $2
+			ORDER BY id
+			FOR UPDATE SKIP LOCKED
+			LIMIT 1
+		)
+		RETURNING id, scheduled, created, status, user_id
+        "#,
+    )
+    .bind(textsender_models::message::scheduling::PROCESSING)
+    .bind(textsender_models::message::scheduling::READY)
+    .fetch_one(pool)
+    .await
+    {
+        Ok(row) => match parse_row(&row).await {
+            Ok(scheduled_message) => Ok(scheduled_message),
+            Err(err) => Err(err),
+        },
+        Err(err) => Err(err),
+    }
+}
+
 pub async fn update_status(
     pool: &sqlx::PgPool,
     id: &uuid::Uuid,