From 23da0027b8b4405a280d6653c78d8e143f2b032d Mon Sep 17 00:00:00 2001
From: Wojciech Kozlowski <wk@wojciechkozlowski.eu>
Date: Sun, 28 Jan 2024 13:54:47 +0100
Subject: [PATCH] Working alternative type-based ui state

---
 src/tui/handler.rs | 123 +++++++++++++++++++++++----------------------
 src/tui/mod.rs     |  24 ++++-----
 src/tui/ui.rs      | 107 ++++++++++++++++++++-------------------
 3 files changed, 127 insertions(+), 127 deletions(-)

diff --git a/src/tui/handler.rs b/src/tui/handler.rs
index 41429d7..93b2a52 100644
--- a/src/tui/handler.rs
+++ b/src/tui/handler.rs
@@ -5,21 +5,25 @@ use mockall::automock;
 
 use crate::tui::{
     event::{Event, EventError, EventReceiver},
-    ui::{IUiBrowse, IUiCore, IUiInfo, Ui},
+    ui::{IUi, IUiBrowse, IUiInfo, UiState},
 };
 
 #[cfg_attr(test, automock)]
-pub trait IEventHandler<BS: IUiBrowse<IS>, IS: IUiInfo<BS>> {
-    fn handle_next_event(&self, ui: Ui<BS, IS>) -> Result<Ui<BS, IS>, EventError>;
+pub trait IEventHandler<UI: IUi> {
+    fn handle_next_event(&self, ui: &mut UI) -> Result<(), EventError>;
 }
 
-trait IEventHandlerPrivate<BS: IUiBrowse<IS>, IS: IUiInfo<BS>> {
-    fn handle_key_event(ui: Ui<BS, IS>, key_event: KeyEvent) -> Result<Ui<BS, IS>, EventError>;
-    fn handle_browse_key_event(ui: BS, key_event: KeyEvent) -> Result<Ui<BS, IS>, EventError>;
-    fn handle_info_key_event(ui: IS, key_event: KeyEvent) -> Result<Ui<BS, IS>, EventError>;
-    fn handle_core_key_event<C: IUiCore>(ui: &mut C, key_event: KeyEvent)
-        -> Result<(), EventError>;
-    fn quit<C: IUiCore>(ui: &mut C) -> Result<(), EventError>;
+trait IEventHandlerPrivate<UI: IUi> {
+    fn handle_key_event(ui: &mut UI, key_event: KeyEvent) -> Result<(), EventError>;
+    fn handle_browse_key_event(
+        ui: &mut <UI as IUi>::BS,
+        key_event: KeyEvent,
+    ) -> Result<(), EventError>;
+    fn handle_info_key_event(
+        ui: &mut <UI as IUi>::IS,
+        key_event: KeyEvent,
+    ) -> Result<(), EventError>;
+    fn quit(ui: &mut UI) -> Result<(), EventError>;
 }
 
 pub struct EventHandler {
@@ -33,26 +37,46 @@ impl EventHandler {
     }
 }
 
-impl<BS: IUiBrowse<IS>, IS: IUiInfo<BS>> IEventHandler<BS, IS> for EventHandler {
-    fn handle_next_event(&self, mut ui: Ui<BS, IS>) -> Result<Ui<BS, IS>, EventError> {
+impl<UI: IUi> IEventHandler<UI> for EventHandler {
+    fn handle_next_event(&self, ui: &mut UI) -> Result<(), EventError> {
         match self.events.recv()? {
-            Event::Key(key_event) => ui = Self::handle_key_event(ui, key_event)?,
+            Event::Key(key_event) => Self::handle_key_event(ui, key_event)?,
             Event::Mouse(_) => {}
             Event::Resize(_, _) => {}
         };
-        Ok(ui)
+        Ok(())
     }
 }
 
-impl<BS: IUiBrowse<IS>, IS: IUiInfo<BS>> IEventHandlerPrivate<BS, IS> for EventHandler {
-    fn handle_key_event(ui: Ui<BS, IS>, key_event: KeyEvent) -> Result<Ui<BS, IS>, EventError> {
-        match ui {
-            Ui::Browse(browse) => Self::handle_browse_key_event(browse, key_event),
-            Ui::Info(info) => Self::handle_info_key_event(info, key_event),
-        }
+impl<UI: IUi> IEventHandlerPrivate<UI> for EventHandler {
+    fn handle_key_event(ui: &mut UI, key_event: KeyEvent) -> Result<(), EventError> {
+        match key_event.code {
+            // Exit application on `ESC` or `q`.
+            KeyCode::Esc | KeyCode::Char('q') => {
+                Self::quit(ui)?;
+            }
+            // Exit application on `Ctrl-C`.
+            KeyCode::Char('c') | KeyCode::Char('C') => {
+                if key_event.modifiers == KeyModifiers::CONTROL {
+                    Self::quit(ui)?;
+                }
+            }
+            _ => match ui.state() {
+                UiState::Browse(browse) => {
+                    <Self as IEventHandlerPrivate<UI>>::handle_browse_key_event(browse, key_event)?;
+                }
+                UiState::Info(info) => {
+                    <Self as IEventHandlerPrivate<UI>>::handle_info_key_event(info, key_event)?;
+                }
+            },
+        };
+        Ok(())
     }
 
-    fn handle_browse_key_event(mut ui: BS, key_event: KeyEvent) -> Result<Ui<BS, IS>, EventError> {
+    fn handle_browse_key_event(
+        ui: &mut <UI as IUi>::BS,
+        key_event: KeyEvent,
+    ) -> Result<(), EventError> {
         match key_event.code {
             // Category change.
             KeyCode::Left => ui.decrement_category(),
@@ -61,52 +85,29 @@ impl<BS: IUiBrowse<IS>, IS: IUiInfo<BS>> IEventHandlerPrivate<BS, IS> for EventH
             KeyCode::Up => ui.decrement_selection(),
             KeyCode::Down => ui.increment_selection(),
             // Toggle overlay.
-            KeyCode::Char('m') | KeyCode::Char('M') => {
-                return Ok(ui.display_info_overlay());
-            }
-            // Other keys.
-            _ => <Self as IEventHandlerPrivate<BS, IS>>::handle_core_key_event(&mut ui, key_event)?,
-        }
-
-        Ok(Ui::Browse(ui))
-    }
-
-    fn handle_info_key_event(mut ui: IS, key_event: KeyEvent) -> Result<Ui<BS, IS>, EventError> {
-        match key_event.code {
-            // Toggle overlay.
-            KeyCode::Char('m') | KeyCode::Char('M') => {
-                return Ok(ui.hide_info_overlay());
-            }
-            // Other keys.
-            _ => <Self as IEventHandlerPrivate<BS, IS>>::handle_core_key_event(&mut ui, key_event)?,
-        }
-
-        Ok(Ui::Info(ui))
-    }
-
-    fn handle_core_key_event<C: IUiCore>(
-        ui: &mut C,
-        key_event: KeyEvent,
-    ) -> Result<(), EventError> {
-        match key_event.code {
-            // Exit application on `ESC` or `q`.
-            KeyCode::Esc | KeyCode::Char('q') => {
-                <Self as IEventHandlerPrivate<BS, IS>>::quit(ui)?;
-            }
-            // Exit application on `Ctrl-C`.
-            KeyCode::Char('c') | KeyCode::Char('C') => {
-                if key_event.modifiers == KeyModifiers::CONTROL {
-                    <Self as IEventHandlerPrivate<BS, IS>>::quit(ui)?;
-                }
-            }
-            // Other keys.
+            KeyCode::Char('m') | KeyCode::Char('M') => ui.display_info_overlay(),
+            // Othey keys.
             _ => {}
         }
 
         Ok(())
     }
 
-    fn quit<C: IUiCore>(ui: &mut C) -> Result<(), EventError> {
+    fn handle_info_key_event(
+        ui: &mut <UI as IUi>::IS,
+        key_event: KeyEvent,
+    ) -> Result<(), EventError> {
+        match key_event.code {
+            // Toggle overlay.
+            KeyCode::Char('m') | KeyCode::Char('M') => ui.hide_info_overlay(),
+            // Othey keys.
+            _ => {}
+        }
+
+        Ok(())
+    }
+
+    fn quit(ui: &mut UI) -> Result<(), EventError> {
         ui.quit();
         ui.save()?;
         Ok(())
diff --git a/src/tui/mod.rs b/src/tui/mod.rs
index 3376814..11b1da8 100644
--- a/src/tui/mod.rs
+++ b/src/tui/mod.rs
@@ -15,7 +15,7 @@ use std::marker::PhantomData;
 use self::event::EventError;
 use self::handler::IEventHandler;
 use self::listener::IEventListener;
-use self::ui::{IUiBrowse, IUiInfo, Ui};
+use self::ui::IUi;
 
 #[derive(Debug, PartialEq, Eq)]
 pub enum Error {
@@ -43,12 +43,12 @@ impl From<EventError> for Error {
     }
 }
 
-pub struct Tui<B: Backend, BS: IUiBrowse<IS>, IS: IUiInfo<BS>> {
+pub struct Tui<B: Backend, UI: IUi> {
     terminal: Terminal<B>,
-    _phantom: PhantomData<Ui<BS, IS>>,
+    _phantom: PhantomData<UI>,
 }
 
-impl<B: Backend, BS: IUiBrowse<IS>, IS: IUiInfo<BS>> Tui<B, BS, IS> {
+impl<B: Backend, UI: IUi> Tui<B, UI> {
     fn init(&mut self) -> Result<(), Error> {
         self.terminal.hide_cursor()?;
         self.terminal.clear()?;
@@ -65,14 +65,10 @@ impl<B: Backend, BS: IUiBrowse<IS>, IS: IUiInfo<BS>> Tui<B, BS, IS> {
         self.exit();
     }
 
-    fn main_loop(
-        &mut self,
-        mut ui: Ui<BS, IS>,
-        handler: impl IEventHandler<BS, IS>,
-    ) -> Result<(), Error> {
+    fn main_loop(&mut self, mut ui: UI, handler: impl IEventHandler<UI>) -> Result<(), Error> {
         while ui.is_running() {
             self.terminal.draw(|frame| ui.render(frame))?;
-            ui = handler.handle_next_event(ui)?;
+            handler.handle_next_event(&mut ui)?;
         }
 
         Ok(())
@@ -80,8 +76,8 @@ impl<B: Backend, BS: IUiBrowse<IS>, IS: IUiInfo<BS>> Tui<B, BS, IS> {
 
     fn main(
         term: Terminal<B>,
-        ui: Ui<BS, IS>,
-        handler: impl IEventHandler<BS, IS>,
+        ui: UI,
+        handler: impl IEventHandler<UI>,
         listener: impl IEventListener,
     ) -> Result<(), Error> {
         let mut tui = Tui {
@@ -139,8 +135,8 @@ impl<B: Backend, BS: IUiBrowse<IS>, IS: IUiInfo<BS>> Tui<B, BS, IS> {
 
     pub fn run(
         term: Terminal<B>,
-        ui: Ui<BS, IS>,
-        handler: impl IEventHandler<BS, IS>,
+        ui: UI,
+        handler: impl IEventHandler<UI>,
         listener: impl IEventListener,
     ) -> Result<(), Error> {
         Self::enable()?;
diff --git a/src/tui/ui.rs b/src/tui/ui.rs
index 2cb8cf9..a40af98 100644
--- a/src/tui/ui.rs
+++ b/src/tui/ui.rs
@@ -35,48 +35,46 @@ impl From<musichoard::Error> for UiError {
     }
 }
 
-pub enum Ui<BS: IUiBrowse<IS>, IS: IUiInfo<BS>> {
+pub enum UiState<BS, IS> {
     Browse(BS),
     Info(IS),
 }
 
-impl<BS: IUiBrowse<IS>, IS: IUiInfo<BS>> Ui<BS, IS> {
-    pub fn is_running(&self) -> bool {
-        match self {
-            Ui::Browse(ref browse) => browse.is_running(),
-            Ui::Info(ref info) => info.is_running(),
-        }
+impl<BS, IS> UiState<BS, IS> {
+    fn is_browse(&self) -> bool {
+        matches!(self, UiState::Browse(_))
     }
 
-    pub fn render<B: Backend>(&mut self, frame: &mut Frame<'_, B>) {
-        match self {
-            Ui::Browse(ref mut browse) => browse.render_browse_frame(frame),
-            Ui::Info(ref mut info) => info.render_info_frame(frame),
-        }
+    fn is_info(&self) -> bool {
+        matches!(self, UiState::Info(_))
     }
 }
 
-pub trait IUiCore {
+pub trait IUi {
+    type BS: IUiBrowse;
+    type IS: IUiInfo;
+
     fn is_running(&self) -> bool;
     fn quit(&mut self);
+
     fn save(&mut self) -> Result<(), UiError>;
+
+    fn render<B: Backend>(&mut self, frame: &mut Frame<'_, B>);
+
+    fn state(&mut self) -> UiState<&mut Self::BS, &mut Self::IS>;
 }
 
-pub trait IUiBrowse<IS: IUiInfo<Self>>: IUiCore + Sized {
+pub trait IUiBrowse {
     fn increment_category(&mut self);
     fn decrement_category(&mut self);
     fn increment_selection(&mut self);
     fn decrement_selection(&mut self);
 
-    fn display_info_overlay(self) -> Ui<Self, IS>;
-
-    fn render_browse_frame<B: Backend>(&mut self, frame: &mut Frame<'_, B>);
+    fn display_info_overlay(&mut self);
 }
 
-pub trait IUiInfo<BS: IUiBrowse<Self>>: IUiCore + Sized {
-    fn hide_info_overlay(self) -> Ui<BS, Self>;
-
-    fn render_info_frame<B: Backend>(&mut self, frame: &mut Frame<'_, B>);
+pub trait IUiInfo {
+    fn hide_info_overlay(&mut self);
 }
 
 struct TrackSelection {
@@ -306,12 +304,6 @@ impl Selection {
     }
 }
 
-pub struct UiImpl<MH> {
-    music_hoard: MH,
-    selection: Selection,
-    running: bool,
-}
-
 struct ArtistArea {
     list: Rect,
 }
@@ -563,21 +555,23 @@ impl<'a, 'b> TrackState<'a, 'b> {
     }
 }
 
-impl<MH: IMusicHoard> Ui<UiImpl<MH>, UiImpl<MH>> {
-    pub fn new(mh: MH) -> Result<Self, Error> {
-        Ok(Ui::Browse(UiImpl::new(mh)?))
-    }
+pub struct Ui<MH> {
+    running: bool,
+    music_hoard: MH,
+    selection: Selection,
+    state: UiState<(), ()>,
 }
 
-impl<MH: IMusicHoard> UiImpl<MH> {
+impl<MH: IMusicHoard> Ui<MH> {
     pub fn new(mut music_hoard: MH) -> Result<Self, Error> {
         music_hoard.load_from_database()?;
         music_hoard.rescan_library()?;
         let selection = Selection::new(Some(music_hoard.get_collection()));
-        Ok(UiImpl {
+        Ok(Ui {
+            running: true,
             music_hoard,
             selection,
-            running: true,
+            state: UiState::Browse(()),
         })
     }
 
@@ -724,7 +718,10 @@ impl<MH: IMusicHoard> UiImpl<MH> {
     }
 }
 
-impl<MH: IMusicHoard> IUiCore for UiImpl<MH> {
+impl<MH: IMusicHoard> IUi for Ui<MH> {
+    type BS = Self;
+    type IS = Self;
+
     fn is_running(&self) -> bool {
         self.running
     }
@@ -734,12 +731,25 @@ impl<MH: IMusicHoard> IUiCore for UiImpl<MH> {
     }
 
     fn save(&mut self) -> Result<(), UiError> {
-        self.music_hoard.save_to_database()?;
-        Ok(())
+        Ok(self.music_hoard.save_to_database()?)
+    }
+
+    fn render<B: Backend>(&mut self, frame: &mut Frame<'_, B>) {
+        self.render_collection(frame);
+        if self.state.is_info() {
+            self.render_overlay(frame);
+        }
+    }
+
+    fn state(&mut self) -> UiState<&mut Self::BS, &mut Self::IS> {
+        match self.state {
+            UiState::Browse(_) => UiState::Browse(self),
+            UiState::Info(_) => UiState::Info(self),
+        }
     }
 }
 
-impl<MH: IMusicHoard> IUiBrowse<Self> for UiImpl<MH> {
+impl<MH: IMusicHoard> IUiBrowse for Ui<MH> {
     fn increment_category(&mut self) {
         self.selection.increment_category();
     }
@@ -758,23 +768,16 @@ impl<MH: IMusicHoard> IUiBrowse<Self> for UiImpl<MH> {
             .decrement_selection(self.music_hoard.get_collection());
     }
 
-    fn display_info_overlay(self) -> Ui<Self, Self> {
-        Ui::Info(self)
-    }
-
-    fn render_browse_frame<B: Backend>(&mut self, frame: &mut Frame<'_, B>) {
-        self.render_collection(frame);
+    fn display_info_overlay(&mut self) {
+        assert!(self.state.is_browse());
+        self.state = UiState::Info(());
     }
 }
 
-impl<MH: IMusicHoard> IUiInfo<Self> for UiImpl<MH> {
-    fn hide_info_overlay(self) -> Ui<Self, Self> {
-        Ui::Browse(self)
-    }
-
-    fn render_info_frame<B: Backend>(&mut self, frame: &mut Frame<'_, B>) {
-        self.render_collection(frame);
-        self.render_overlay(frame);
+impl<MH: IMusicHoard> IUiInfo for Ui<MH> {
+    fn hide_info_overlay(&mut self) {
+        assert!(self.state.is_info());
+        self.state = UiState::Browse(());
     }
 }