Cache post data using sled

Each post fetch was taking 800ms TAT, so I'm using sled to fetch and
cache post data. This reduced TAT down to 2ms.

However, this could cause storage issues. I must design some sort of
resource manager to clean up cache.

src/data.rs

@@ -15,19 +15,56 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 use actix_web::web;
+use graphql_client::{reqwest::post_graphql, GraphQLQuery};
 use reqwest::Client;
+use sled::{Db, Tree};
 
 #[derive(Clone)]
 pub struct Data {
     pub client: Client,
+    cache: Db,
+    pub posts: Tree,
 }
 
+#[derive(GraphQLQuery)]
+#[graphql(
+    schema_path = "schemas/schema.graphql",
+    query_path = "schemas/query.graphql",
+    response_derives = "Debug, Serialize, Deserialize, Clone"
+)]
+pub struct GetPost;
+
+pub type PostResp = get_post::GetPostPost;
+
 pub type AppData = web::Data<Data>;
 
 impl Data {
     pub fn new() -> AppData {
+        let cache = sled::open("posts_cache").unwrap();
+        let posts = cache.open_tree("posts").unwrap();
         AppData::new(Self {
             client: Client::new(),
+            cache,
+            posts,
         })
     }
+
+    pub async fn get_post(&self, id: &str) -> PostResp {
+        match self.posts.get(id) {
+            Ok(Some(v)) => bincode::deserialize(&v[..]).unwrap(),
+            _ => {
+                let vars = get_post::Variables { id: id.to_owned() };
+                const URL: &str = "https://medium.com/_/graphql";
+
+                let res = post_graphql::<GetPost, _>(&self.client, URL, vars)
+                    .await
+                    .unwrap();
+                let res = res.data.expect("missing response data").post.unwrap();
+                self.posts
+                    .insert(id, bincode::serialize(&res).unwrap())
+                    .unwrap();
+                res
+            }
+        }
+    }
 }