feat: validate url as a Lemmy instance before making API requests (#30)

* feat: make Api creation fallible

* feat: check if instance url is a lemmy instance during initalization

* feat: make Api creation async

* feat: better error message for non-lemmy instance url

* style: use unwrap, we're not dealing with user input here

* style: format blocks in main.rs

src/lemmy/api.rs

@@ -17,15 +17,22 @@ pub struct Api {
 }
 
 impl Api {
-    pub fn new(instance: Url) -> Api {
+    pub async fn new(instance: Url) -> Result<Api, Error> {
         let mut client_builder = ClientBuilder::new();
         client_builder = client_builder.user_agent("LASIM - https://github.com/CMahaff/lasim");
         let new_client = client_builder.build().unwrap();
 
-        return Api {
+        // Check if instance is an actual Lemmy url by checking getSite
+        new_client
+            .get(instance.join("/api/v3/site").unwrap())
+            .send()
+            .await?
+            .error_for_status()?;
+
+        return Ok(Api {
             client: new_client,
             instance,
-        }
+        });
     }
 
     pub async fn login(&self, username: &str, password: &str, two_factor_token: Option<String>) -> Result<String, Error> {

src/main.rs

@@ -182,7 +182,15 @@ async fn process_download(processing_instruction: ProcessingInstruction, mut log
     }
     let instance_url = instance_url_result.unwrap();
 
-    let api = lemmy::api::Api::new(instance_url);
+    let api = match lemmy::api::Api::new(instance_url).await {
+        Ok(api) => api,
+        Err(e) => {
+            logger(format!(
+                "ERROR: Invalid Instance URL (or instance is down) - {e}"
+            ));
+            return;
+        }
+    };
 
     // Login
     logger(format!("Logging in as {}", username));
@@ -370,7 +378,15 @@ async fn process_upload(processing_instruction: ProcessingInstruction, mut logge
     }
     let instance_url = instance_url_result.unwrap();
 
-    let api = lemmy::api::Api::new(instance_url);
+    let api = match lemmy::api::Api::new(instance_url).await {
+        Ok(api) => api,
+        Err(e) => {
+            logger(format!(
+                "ERROR: Invalid Instance URL (or instance is down) - {e}"
+            ));
+            return;
+        }
+    };
 
     // Login
     logger(format!("Logging in as {}", username));