Only upgrade main.unity3d request to HTTPS if it's available

Author: yungcomputerchair

src-tauri/src/lib.rs

@@ -561,9 +561,14 @@ async fn prep_launch(
             state.proxy = Some(handle);
         }
 
-        // Upgrade the main URL to HTTPS, since ffrunner supports it
+        // Upgrade the main URL to HTTPS, if it's available, since ffrunner supports it
         if main_url.starts_with("http://") {
-            main_url = main_url.replacen("http://", "https://", 1);
+            let main_url_upgraded = main_url.replacen("http://", "https://", 1);
+            if util::does_web_file_exist(&main_url_upgraded).await {
+                main_url = main_url_upgraded;
+            } else if !util::does_web_file_exist(&main_url).await {
+                return Err(format!("Main file not found: {}", main_url).into());
+            }
         }
 
         debug!("Asset URL: {}", asset_url);

src-tauri/src/util.rs

@@ -554,3 +554,14 @@ pub(crate) fn log_command(command: &Command) {
     let command_str = get_launch_cmd_dbg_str(command, true);
     debug!("Launching game: {}", command_str);
 }
+
+pub(crate) async fn does_web_file_exist(url: &str) -> bool {
+    let client = get_http_client();
+    match client.head(url).send().await {
+        Ok(response) => response.status().is_success(),
+        Err(e) => {
+            debug!("Failed to check if web file exists: {}", e);
+            false
+        }
+    }
+}