From e84aa971548429c6c4cd7fac07b27c56f3514175 Mon Sep 17 00:00:00 2001
From: Wojciech Kozlowski <wk@wojciechkozlowski.eu>
Date: Sun, 28 Jan 2024 11:49:41 +0100
Subject: [PATCH] Add type-based statefulness for ui

---
 src/tui/handler.rs | 96 ++++++++++++++++++++++++++++++----------------
 src/tui/mod.rs     | 24 +++++++-----
 src/tui/ui.rs      | 76 ++++++++++++++++++++++++++++--------
 3 files changed, 136 insertions(+), 60 deletions(-)

diff --git a/src/tui/handler.rs b/src/tui/handler.rs
index 2c65098..235aaf3 100644
--- a/src/tui/handler.rs
+++ b/src/tui/handler.rs
@@ -5,17 +5,21 @@ use mockall::automock;
 
 use crate::tui::{
     event::{Event, EventError, EventReceiver},
-    ui::IUi,
+    ui::{IUiBrowse, IUiCore, IUiInfo, Ui},
 };
 
 #[cfg_attr(test, automock)]
-pub trait IEventHandler<UI> {
-    fn handle_next_event(&self, ui: &mut UI) -> Result<(), EventError>;
+pub trait IEventHandler<BS: IUiBrowse<IS>, IS: IUiInfo<BS>> {
+    fn handle_next_event(&self, ui: Ui<BS, IS>) -> Result<Ui<BS, IS>, EventError>;
 }
 
-trait IEventHandlerPrivate<UI> {
-    fn handle_key_event(ui: &mut UI, key_event: KeyEvent) -> Result<(), EventError>;
-    fn quit(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>;
 }
 
 pub struct EventHandler {
@@ -29,48 +33,74 @@ impl EventHandler {
     }
 }
 
-impl<UI: IUi> IEventHandler<UI> for EventHandler {
-    fn handle_next_event(&self, ui: &mut UI) -> Result<(), EventError> {
+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> {
         match self.events.recv()? {
-            Event::Key(key_event) => Self::handle_key_event(ui, key_event)?,
+            Event::Key(key_event) => {
+                ui = Self::handle_key_event(ui, key_event)?;
+            }
             Event::Mouse(_) => {}
             Event::Resize(_, _) => {}
         };
-        Ok(())
+        Ok(ui)
     }
 }
 
-impl<UI: IUi> IEventHandlerPrivate<UI> for EventHandler {
-    fn handle_key_event(ui: &mut UI, key_event: KeyEvent) -> Result<(), EventError> {
+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),
+        }
+    }
+
+    fn handle_browse_key_event(mut ui: BS, key_event: KeyEvent) -> Result<Ui<BS, IS>, EventError> {
+        match key_event.code {
+            // Category change.
+            KeyCode::Left => ui.decrement_category(),
+            KeyCode::Right => ui.increment_category(),
+            // Selection change.
+            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::quit(ui)?;
+                <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::quit(ui)?;
+                    <Self as IEventHandlerPrivate<BS, IS>>::quit(ui)?;
                 }
             }
-            // Category change.
-            KeyCode::Left => {
-                ui.decrement_category();
-            }
-            KeyCode::Right => {
-                ui.increment_category();
-            }
-            // Selection change.
-            KeyCode::Up => {
-                ui.decrement_selection();
-            }
-            KeyCode::Down => {
-                ui.increment_selection();
-            }
-            // Toggle overlay.
-            KeyCode::Char('m') | KeyCode::Char('M') => {
-                ui.toggle_overlay();
-            }
             // Other keys.
             _ => {}
         }
@@ -78,7 +108,7 @@ impl<UI: IUi> IEventHandlerPrivate<UI> for EventHandler {
         Ok(())
     }
 
-    fn quit(ui: &mut UI) -> Result<(), EventError> {
+    fn quit<C: IUiCore>(ui: &mut C) -> Result<(), EventError> {
         ui.quit();
         ui.save()?;
         Ok(())
diff --git a/src/tui/mod.rs b/src/tui/mod.rs
index c4584da..3376814 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::IUi;
+use self::ui::{IUiBrowse, IUiInfo, Ui};
 
 #[derive(Debug, PartialEq, Eq)]
 pub enum Error {
@@ -43,12 +43,12 @@ impl From<EventError> for Error {
     }
 }
 
-pub struct Tui<B: Backend, UI> {
+pub struct Tui<B: Backend, BS: IUiBrowse<IS>, IS: IUiInfo<BS>> {
     terminal: Terminal<B>,
-    _phantom: PhantomData<UI>,
+    _phantom: PhantomData<Ui<BS, IS>>,
 }
 
-impl<B: Backend, UI: IUi> Tui<B, UI> {
+impl<B: Backend, BS: IUiBrowse<IS>, IS: IUiInfo<BS>> Tui<B, BS, IS> {
     fn init(&mut self) -> Result<(), Error> {
         self.terminal.hide_cursor()?;
         self.terminal.clear()?;
@@ -65,10 +65,14 @@ impl<B: Backend, UI: IUi> Tui<B, UI> {
         self.exit();
     }
 
-    fn main_loop(&mut self, mut ui: UI, handler: impl IEventHandler<UI>) -> Result<(), Error> {
+    fn main_loop(
+        &mut self,
+        mut ui: Ui<BS, IS>,
+        handler: impl IEventHandler<BS, IS>,
+    ) -> Result<(), Error> {
         while ui.is_running() {
             self.terminal.draw(|frame| ui.render(frame))?;
-            handler.handle_next_event(&mut ui)?;
+            ui = handler.handle_next_event(ui)?;
         }
 
         Ok(())
@@ -76,8 +80,8 @@ impl<B: Backend, UI: IUi> Tui<B, UI> {
 
     fn main(
         term: Terminal<B>,
-        ui: UI,
-        handler: impl IEventHandler<UI>,
+        ui: Ui<BS, IS>,
+        handler: impl IEventHandler<BS, IS>,
         listener: impl IEventListener,
     ) -> Result<(), Error> {
         let mut tui = Tui {
@@ -135,8 +139,8 @@ impl<B: Backend, UI: IUi> Tui<B, UI> {
 
     pub fn run(
         term: Terminal<B>,
-        ui: UI,
-        handler: impl IEventHandler<UI>,
+        ui: Ui<BS, IS>,
+        handler: impl IEventHandler<BS, IS>,
         listener: impl IEventListener,
     ) -> Result<(), Error> {
         Self::enable()?;
diff --git a/src/tui/ui.rs b/src/tui/ui.rs
index 826a184..863d243 100644
--- a/src/tui/ui.rs
+++ b/src/tui/ui.rs
@@ -35,20 +35,54 @@ impl From<musichoard::Error> for UiError {
     }
 }
 
-pub trait IUi {
+pub enum Ui<BS: IUiBrowse<IS>, IS: IUiInfo<BS>> {
+    Browse(BS),
+    Info(IS),
+}
+
+impl<MH: IMusicHoard> Ui<UiImpl<MH>, UiImpl<MH>> {
+    pub fn new(mh: MH) -> Result<Self, Error> {
+        Ok(Ui::Browse(UiImpl::new(mh)?))
+    }
+}
+
+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(),
+        }
+    }
+
+    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),
+        }
+    }
+}
+
+pub trait IUiCore {
     fn is_running(&self) -> bool;
     fn quit(&mut self);
-
     fn save(&mut self) -> Result<(), UiError>;
+}
 
+pub trait IUiBrowse<IS: IUiInfo<Self>>: IUiCore + Sized {
     fn increment_category(&mut self);
     fn decrement_category(&mut self);
-
     fn increment_selection(&mut self);
     fn decrement_selection(&mut self);
 
-    fn toggle_overlay(&mut self);
-    fn render<B: Backend>(&mut self, frame: &mut Frame<'_, B>);
+    fn display_info_overlay(self) -> Ui<Self, IS>;
+
+    fn render_browse_frame<B: Backend>(&mut self, frame: &mut Frame<'_, B>);
+}
+
+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>);
 }
 
 struct TrackSelection {
@@ -278,10 +312,9 @@ impl Selection {
     }
 }
 
-pub struct Ui<MH> {
+pub struct UiImpl<MH> {
     music_hoard: MH,
     selection: Selection,
-    overlay: bool,
     running: bool,
 }
 
@@ -536,15 +569,14 @@ impl<'a, 'b> TrackState<'a, 'b> {
     }
 }
 
-impl<MH: IMusicHoard> Ui<MH> {
+impl<MH: IMusicHoard> UiImpl<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(Ui {
+        Ok(UiImpl {
             music_hoard,
             selection,
-            overlay: false,
             running: true,
         })
     }
@@ -692,7 +724,7 @@ impl<MH: IMusicHoard> Ui<MH> {
     }
 }
 
-impl<MH: IMusicHoard> IUi for Ui<MH> {
+impl<MH: IMusicHoard> IUiCore for UiImpl<MH> {
     fn is_running(&self) -> bool {
         self.running
     }
@@ -705,7 +737,9 @@ impl<MH: IMusicHoard> IUi for Ui<MH> {
         self.music_hoard.save_to_database()?;
         Ok(())
     }
+}
 
+impl<MH: IMusicHoard> IUiBrowse<Self> for UiImpl<MH> {
     fn increment_category(&mut self) {
         self.selection.increment_category();
     }
@@ -724,15 +758,23 @@ impl<MH: IMusicHoard> IUi for Ui<MH> {
             .decrement_selection(self.music_hoard.get_collection());
     }
 
-    fn toggle_overlay(&mut self) {
-        self.overlay = !self.overlay;
+    fn display_info_overlay(self) -> Ui<Self, Self> {
+        Ui::Info(self)
     }
 
-    fn render<B: Backend>(&mut self, frame: &mut Frame<'_, B>) {
+    fn render_browse_frame<B: Backend>(&mut self, frame: &mut Frame<'_, B>) {
         self.render_collection(frame);
-        if self.overlay {
-            self.render_overlay(frame);
-        }
+    }
+}
+
+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);
     }
 }