refactor: improve helper function sanity

pure(er) functions are so much easier to work with
(see the bug fix in the pior commit)

there's a bit of duplicate code introduced but it's worth it

src/main.rs

@@ -79,9 +79,13 @@ impl State {
                     }
                 }
 
-                Key::Character("o") => {
+                Key::Character("o") => match self.pick_and_load_image() {
-                    return self.pick_and_load_image();
+                    Ok(task) => {
+                        self.error = None;
+                        return task;
                     }
+                    Err(e) => self.error = Some(e),
+                },
 
                 Key::Character("r") => {
                     match self.image.as_ref() {
@@ -115,9 +119,13 @@ impl State {
             },
 
             Message::Event(iced::Event::Window(window_event)) => match window_event {
-                window::Event::FileDropped(file) => {
+                window::Event::FileDropped(file) => match self.load_image(file) {
-                    return self.load_image(file);
+                    Ok(task) => {
+                        self.error = None;
+                        return task;
                     }
+                    Err(e) => self.error = Some(e),
+                },
 
                 // ignore unused window events
                 _ => {}
@@ -130,28 +138,14 @@ impl State {
         Task::none()
     }
 
-    #[must_use]
+    fn load_image(&mut self, path: impl AsRef<Path>) -> Result<Task<Message>, String> {
-    fn load_image(&mut self, path: impl AsRef<Path>) -> Task<Message> {
+        utils::load_image(path).and_then(|image| {
-        let task;
-        (self.error, task) = match utils::load_image(path) {
-            Ok(image) => {
             self.image = Some(image);
-                (None, self.allocate_image())
+            Ok(self.allocate_image())
-            }
+        })
-            Err(e) => (Some(e), Task::none()),
-        };
-
-        task
-    }
-    #[must_use]
-    fn pick_and_load_image(&mut self) -> Task<Message> {
-        match utils::pick_image() {
-            Ok(path) => self.load_image(path),
-            Err(e) => {
-                self.error = Some(e);
-                Task::none()
-            }
     }
+    fn pick_and_load_image(&mut self) -> Result<Task<Message>, String> {
+        utils::pick_image().and_then(|path| self.load_image(path))
     }
 
     fn save_image(&mut self) {