Set up message passing between app window and an app thread

fitnesstrax/app/src/main.rs

@@ -37,37 +37,14 @@ const APP_ID_PROD: &str = "com.luminescent-dreams.fitnesstrax";
 
 const RESOURCE_BASE_PATH: &str = "/com/luminescent-dreams/fitnesstrax/";
 
-/// Invocations are how parts of the application, primarily the UI, will send requests to the core.
 #[derive(Debug)]
 enum AppInvocation {
-    /// Tell the core to try to open a database.
     OpenDatabase(PathBuf),
-
-    /// Request a set of records from the core.
-    // Note: this will require a time range, but doesn't yet.
-    RequestRecords,
 }
 
-/// Responses are messages that the core sends to the UI. Though they are called responses, the
-/// could actually be pre-emptively sent, such as notifications. The UI will need to be able to
-/// process those any time they arrive.
-///
-/// A typical use would be for the UI to send an [AppInvocation::RequestRecords] request and
-/// receive [AppResponse::Records].
 #[derive(Debug)]
 enum AppResponse {
-    /// No database is available. The UI should typically display a placeholder, such as the
-    /// welcome view.
-    NoDatabase,
-
-    /// The database is open and here is a set of records. Typically, the set of records will be
-    /// all of the records within a time frame, but this can actually be any set of records.
-    Records,
-
-    /// The database has been changed. This message is useful for telling the UI that a significant
-    /// change has happened. Further, the UI needs to save PathBuf to settings, because the
-    /// gio::Settings system can't be run in the fully async background.
-    DatabaseChanged(PathBuf),
+    DatabaseChanged,
 }
 
 // Note that I have not yet figured out the communication channel or how the central dispatcher
@@ -76,38 +53,32 @@ enum AppResponse {
 /// The real, headless application. This is where all of the logic will reside.
 #[derive(Clone)]
 struct App {
+    settings: gio::Settings,
     database: Arc<RwLock<Option<Series<TraxRecord>>>>,
 }
 
 impl App {
-    pub fn new(db_path: Option<PathBuf>) -> Self {
-        let database = db_path.map(|path| Series::open(path).unwrap());
+    pub fn new(settings: gio::Settings) -> Self {
         let s = Self {
-            database: Arc::new(RwLock::new(database)),
+            settings,
+            database: Arc::new(RwLock::new(None)),
         };
 
-        s
+        if !s.settings.string("series-path").is_empty() {
+            let path = PathBuf::from(s.settings.string("series-path"));
+            let db = Series::open(path).unwrap();
+            *s.database.write().unwrap() = Some(db);
         }
 
-    pub async fn process_invocation(&self, invocation: AppInvocation) -> AppResponse {
-        match invocation {
-            AppInvocation::OpenDatabase(db_path) => {
-                self.open_db(&db_path);
-                AppResponse::DatabaseChanged(db_path)
-            }
-            AppInvocation::RequestRecords => {
-                if self.database.read().unwrap().is_none() {
-                    AppResponse::NoDatabase
-                } else {
-                    AppResponse::Records
-                }
-            }
-        }
+        s
     }
 
     pub fn open_db(&self, path: &Path) {
         let db = Series::open(path).unwrap();
         *self.database.write().unwrap() = Some(db);
+        self.settings
+            .set_string("series-path", path.to_str().unwrap())
+            .unwrap();
     }
 }
 
@@ -253,29 +224,6 @@ impl HistoricalView {
     }
 }
 
-#[derive(Clone, Debug, PartialEq)]
-enum ViewName {
-    Placeholder,
-    Welcome,
-    Historical,
-}
-
-enum View {
-    Placeholder(gtk::Widget),
-    Welcome(gtk::Widget),
-    Historical(gtk::Widget),
-}
-
-impl View {
-    fn widget<'a>(&'a self) -> &'a gtk::Widget {
-        match self {
-            View::Placeholder(widget) => widget,
-            View::Welcome(widget) => widget,
-            View::Historical(widget) => widget,
-        }
-    }
-}
-
 /// The application window, or the main window, is the main user interface for the app. Almost
 /// everything occurs here.
 #[derive(Clone)]
@@ -283,8 +231,7 @@ struct AppWindow {
     app_tx: Sender<AppInvocation>,
     window: adw::ApplicationWindow,
     layout: gtk::Box,
-    current_view: Rc<RefCell<View>>,
-    settings: gio::Settings,
+    current_view: Rc<RefCell<gtk::Widget>>,
 }
 
 impl AppWindow {
@@ -294,7 +241,7 @@ impl AppWindow {
     /// otherwise we don't use this.
     ///
     /// app is a core [App] object which encapsulates all of the basic logic.
-    fn new(app_id: &str, adw_app: &adw::Application, app_tx: Sender<AppInvocation>) -> AppWindow {
+    fn new(adw_app: &adw::Application, app_tx: Sender<AppInvocation>) -> AppWindow {
         let window = adw::ApplicationWindow::builder()
             .application(adw_app)
             .width_request(800)
@@ -325,10 +272,10 @@ impl AppWindow {
             .orientation(gtk::Orientation::Vertical)
             .build();
 
-        let initial_view = View::Placeholder(PlaceholderView::new().upcast());
+        let initial_view = PlaceholderView::new();
 
         layout.append(&header);
-        layout.append(initial_view.widget());
+        layout.append(&initial_view);
 
         window.set_content(Some(&layout));
         window.present();
@@ -337,32 +284,41 @@ impl AppWindow {
             app_tx,
             window,
             layout,
-            current_view: Rc::new(RefCell::new(initial_view)),
-            settings: gio::Settings::new(app_id),
+            current_view: Rc::new(RefCell::new(initial_view.upcast())),
         };
 
-        s
-    }
-
-    pub fn change_view(&self, view: ViewName) {
-        self.swap_main(self.construct_view(view));
-    }
-
-    pub fn process_response(&self, response: AppResponse) {
-        match response {
-            AppResponse::DatabaseChanged(db_path) => {
-                self.settings
-                    .set_string("series-path", db_path.to_str().unwrap())
+        let initial_view = if true {
+            WelcomeView::new({
+                let s = s.clone();
+                Box::new(move |path: PathBuf| {
+                    // The user has selected a path. Perhaps the path is new, perhaps it already
+                    // exists.
+                    //
+                    // If the file exists already, attempt to read it. Fail if that doesn't work.
+                    // A should show to the user something that indicates that the file exists but is
+                    // not already a database.
+                    //
+                    // If the file does not exist, create a new one. Again, show the user an error if
+                    // some kind of error occurs.
+                    // app.open_db(&path);
+                    // s.change_view(HistoricalView::new().upcast());
+                    let s = s.clone();
+                    glib::spawn_future_local(async move {
+                        s.app_tx
+                            .send(AppInvocation::OpenDatabase(path))
+                            .await
                             .unwrap();
-                self.change_view(ViewName::Historical);
-            }
-            AppResponse::NoDatabase => {
-                self.change_view(ViewName::Welcome);
-            }
-            AppResponse::Records => {
-                self.change_view(ViewName::Historical);
-            }
-        }
+                    });
+                })
+            })
+            .upcast()
+        } else {
+            HistoricalView::new().upcast()
+        };
+
+        s.change_view(initial_view);
+
+        s
     }
 
     // Switch views.
@@ -370,29 +326,11 @@ impl AppWindow {
     // This function only replaces the old view with the one which matches the current view state.
     // It is responsible for ensuring that the new view goes into the layout in the correct
     // position.
-    fn swap_main(&self, view: View) {
-        let mut current_widget = self.current_view.borrow_mut();
-        self.layout.remove(&*current_widget.widget());
-        *current_widget = view;
-        self.layout.append(&*current_widget.widget());
-    }
-
-    fn construct_view(&self, view: ViewName) -> View {
-        match view {
-            ViewName::Placeholder => View::Placeholder(PlaceholderView::new().upcast()),
-            ViewName::Welcome => View::Welcome(
-                WelcomeView::new({
-                    let s = self.clone();
-                    Box::new(move |path: PathBuf| {
-                        s.app_tx
-                            .send_blocking(AppInvocation::OpenDatabase(path))
-                            .unwrap();
-                    })
-                })
-                .upcast(),
-            ),
-            ViewName::Historical => View::Historical(HistoricalView::new().upcast()),
-        }
+    fn change_view(&self, view: gtk::Widget) {
+        let mut current_view = self.current_view.borrow_mut();
+        self.layout.remove(&*current_view);
+        *current_view = view;
+        self.layout.append(&*current_view);
     }
 }
 
@@ -411,14 +349,10 @@ fn main() {
     };
 
     let settings = gio::Settings::new(app_id);
-    let app = App::new({
-        let path = settings.string("series-path");
-        if path.is_empty() {
-            None
-        } else {
-            Some(PathBuf::from(path))
-        }
-    });
+
+    println!("database path: {}", settings.string("series-path"));
+
+    let app = App::new(settings);
 
     let adw_app = adw::Application::builder()
         .application_id(app_id)
@@ -431,47 +365,20 @@ fn main() {
         .unwrap();
 
     adw_app.connect_activate(move |adw_app| {
-        // These channels are used to send messages to the UI. Anything that needs to send a
-        // message to the UI will send it via `ui_tx`. We will have one single process that owns
-        // `ui_rx`. That process will read messages coming in and send them to AppWindow for proper
-        // processing.
-        //
-        // The core app will usually only send messages in response to a request, but this channel
-        // can also be used to tell the UI that something happened in the background, such as
-        // detecting a watch, detecting new tracks to import, and so forth.
-        let (ui_tx, ui_rx) = async_channel::unbounded::<AppResponse>();
-
-        // These channels are used for communicating with the app. Already I can see that a lot of
-        // different event handlers will need copies of app_tx in order to send requests into the
-        // UI.
+        let (gtk_tx, gtk_rx) = async_channel::unbounded::<AppResponse>();
         let (app_tx, app_rx) = async_channel::unbounded::<AppInvocation>();
 
-        let window = AppWindow::new(app_id, adw_app, app_tx.clone());
+        AppWindow::new(adw_app, app_tx.clone());
 
-        // Spawn a future where the UI will receive messages for the app window. Previously, this
-        // would have been done by creating a glib::MainContext::channel(), but that has been
-        // deprecated since gtk 4.10 in favor of using `async_channel`.
         glib::spawn_future_local(async move {
-            // The app requests data to start with. This kicks everything off. The response from
-            // the app will cause the window to be updated shortly.
-            let _ = app_tx.send(AppInvocation::RequestRecords).await;
-
-            while let Ok(response) = ui_rx.recv().await {
+            while let Ok(response) = gtk_rx.recv().await {
                 println!("response received: {:?}", response);
-                window.process_response(response);
             }
         });
 
-        // The tokio runtime starts up here and will handle all of the asynchronous operations that
-        // the application needs to do. Messages arrive on `app_rx` and responses will be sent via
-        // `ui_tx`.
-        runtime.spawn({
-            let app = app.clone();
-            async move {
+        runtime.spawn(async move {
             while let Ok(invocation) = app_rx.recv().await {
-                    let response = app.process_invocation(invocation).await;
-                    let _ = ui_tx.send(response).await;
-                }
+                println!("Received an invocation: {:?}", invocation);
             }
         });
     });