first commit

src/app/components/navigation/navigation_model.rs

@@ -0,0 +1,31 @@
+use crate::app::state::ScreenName;
+use crate::app::{ActionDispatcher, AppModel, BrowserAction};
+use std::ops::Deref;
+use std::rc::Rc;
+
+pub struct NavigationModel {
+    app_model: Rc<AppModel>,
+    dispatcher: Box<dyn ActionDispatcher>,
+}
+
+impl NavigationModel {
+    pub fn new(app_model: Rc<AppModel>, dispatcher: Box<dyn ActionDispatcher>) -> Self {
+        Self {
+            app_model,
+            dispatcher,
+        }
+    }
+
+    pub fn visible_child_name(&self) -> impl Deref<Target = ScreenName> + '_ {
+        self.app_model.map_state(|s| s.browser.current_screen())
+    }
+
+    pub fn set_nav_hidden(&self, hidden: bool) {
+        self.dispatcher
+            .dispatch(BrowserAction::SetNavigationHidden(hidden).into());
+    }
+
+    pub fn children_count(&self) -> usize {
+        self.app_model.get_state().browser.count()
+    }
+}