fix(receiver): add filepath for download on android.

caesar-core/src/receiver/client.rs

@@ -22,6 +22,9 @@ use tracing::error;
 const DESTINATION: u8 = 0;
 const NONCE_SIZE: usize = 12;
 
+#[cfg(target_os = "android")]
+const FILE_PATH_PREFIX: &str = "/storage/emulated/0/Download";
+
 struct File {
     name: String,
     size: u64,
@@ -73,11 +76,29 @@ fn on_list(context: &mut Context, list: ListPacket) -> Status {
 
     for entry in list.entries {
         let path = sanitize_filename::sanitize(entry.name.clone());
+        #[cfg(target_os = "android")]
+        let file_path = format!("{}/{}", FILE_PATH_PREFIX, path);
 
+        #[cfg(target_os = "android")]
+        if Path::new(&file_path).exists() {
+            return Status::Err(format!("The file '{}' already exists.", path));
+        }
+        #[cfg(target_os = "android")]
+        let handle = match fs::File::create(&file_path) {
+            Ok(handle) => handle,
+            Err(error) => {
+                return Status::Err(format!(
+                    "Error: Failed to create file '{}': {}",
+                    file_path, error
+                ));
+            }
+        };
+        #[cfg(not(target_os = "android"))]
         if Path::new(&path).exists() {
             return Status::Err(format!("The file '{}' already exists.", path));
         }
         
+        #[cfg(not(target_os = "android"))]
         let handle = match fs::File::create(&path) {
             Ok(handle) => handle,
             Err(error) => {