elf on a shelf challenge

src/main.rs

@@ -97,6 +97,25 @@ async fn contest(Json(reindeers): Json<Vec<ContestReindeer>>) -> impl IntoRespon
     }
 }
 
+#[derive(Debug, Serialize, Deserialize, Default, PartialEq, Eq)]
+struct ElfOnShelfResult {
+    elf: u32,
+    #[serde(alias = "elf on a shelf")]
+    elf_on_shelf: u32,
+    #[serde(alias = "shelf with no elf on it")]
+    shelf_with_no_elf: u32,
+}
+async fn elf_on_shelf(elf_text: String) -> impl IntoResponse {
+    let shelf = elf_text.matches("shelf").count() as u32;
+    let elf_on_shelf = elf_text.matches("elf on a shelf").count() as u32;
+    let elf = elf_text.matches("elf").count() as u32;
+    Json(ElfOnShelfResult {
+        elf,
+        elf_on_shelf,
+        shelf_with_no_elf: shelf - elf_on_shelf,
+    })
+}
+
 #[allow(dead_code)]
 fn app() -> Router {
     Router::new()
@@ -105,6 +124,7 @@ fn app() -> Router {
         .route("/1/*ids", get(packet_ids))
         .route("/4/strength", post(sum_strength))
         .route("/4/contest", post(contest))
+        .route("/6", post(elf_on_shelf))
 }
 
 #[shuttle_runtime::main]
@@ -267,4 +287,46 @@ mod tests {
             .await;
         assert_eq!(res.status(), StatusCode::BAD_REQUEST);
     }
+
+    #[tokio::test]
+    async fn elf() {
+        let app = app();
+
+        let client = TestClient::new(app);
+        let res = client
+            .post("/6")
+            .body(
+                "The mischievous elf peeked out from behind the toy workshop,
+      and another elf joined in the festive dance.
+      Look, there is also an elf on that shelf!",
+            )
+            .header("Content-Type", "text/plain")
+            .send()
+            .await;
+        assert_eq!(res.status(), StatusCode::OK);
+        let expected = ElfOnShelfResult {
+            elf: 4,
+            ..Default::default()
+        };
+        assert_eq!(res.json::<ElfOnShelfResult>().await.elf, expected.elf);
+    }
+    #[tokio::test]
+    async fn elf_on_shelf() {
+        let app = app();
+
+        let client = TestClient::new(app);
+        let res = client
+            .post("/6")
+            .body("there is an elf on a shelf on an elf. there is also another shelf in Belfast.")
+            .header("Content-Type", "text/plain")
+            .send()
+            .await;
+        assert_eq!(res.status(), StatusCode::OK);
+        let expected = ElfOnShelfResult {
+            elf: 5,
+            shelf_with_no_elf: 1,
+            elf_on_shelf: 1,
+        };
+        assert_eq!(res.json::<ElfOnShelfResult>().await, expected);
+    }
 }