feat(api): implement 30-minute cache for PDF link requests

.gitignore

@@ -1,3 +1,4 @@
 /target
 pdf
 csv
+pdf.json

src/api/mod.rs

@@ -28,6 +28,16 @@ pub fn get_routes() -> Router {
 }
 
 async fn get_pdf_links() -> Result<Vec<String>, reqwest::Error> {
+    if let Ok(metadata) = fs::metadata("pdf.json") {
+        let last_modified = metadata.modified().unwrap();
+        let now = std::time::SystemTime::now();
+        let diff = now.duration_since(last_modified).unwrap().as_secs();
+        if diff < 30 * 60 {
+            let data = fs::read_to_string("pdf.json").unwrap();
+            return Ok(serde_json::from_str(&data).unwrap());
+        }
+    }
+
     let response = reqwest::get("https://cassandroferminervi.edu.it/orario-scolastico/")
         .await?
         .text()
@@ -41,6 +51,9 @@ async fn get_pdf_links() -> Result<Vec<String>, reqwest::Error> {
         result.push(element.attr("href").unwrap().to_owned());
     }
 
+    let data = serde_json::to_string(&result).unwrap();
+    fs::write("pdf.json", data).unwrap();
+
     Ok(result)
 }