Ratatui scrollbar test/example

use std::{
    error::Error,
    io,
    time::{Duration, Instant},
};

use crossterm::{
    event::{self, DisableMouseCapture, EnableMouseCapture, Event, KeyCode, KeyEventKind},
    execute,
    terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
};
use ratatui::{prelude::*, symbols::scrollbar, widgets::*};

#[derive(Default)]
struct App {
    pub vertical_scroll_state: ScrollbarState,
    pub horizontal_scroll_state: ScrollbarState,
    pub vertical_scroll: usize,
    pub horizontal_scroll: usize,
}

fn main() -> Result<(), Box<dyn Error>> {
    // setup terminal
    enable_raw_mode()?;
    let mut stdout = io::stdout();
    execute!(stdout, EnterAlternateScreen, EnableMouseCapture)?;
    let backend = CrosstermBackend::new(stdout);
    let mut terminal = Terminal::new(backend)?;

    // create app and run it
    let tick_rate = Duration::from_millis(250);
    let app = App::default();
    let res = run_app(&mut terminal, app, tick_rate);

    // restore terminal
    disable_raw_mode()?;
    execute!(terminal.backend_mut(), LeaveAlternateScreen, DisableMouseCapture)?;
    terminal.show_cursor()?;

    if let Err(err) = res {
        println!("{err:?}");
    }

    Ok(())
}

fn run_app<B: Backend>(terminal: &mut Terminal<B>, mut app: App, tick_rate: Duration) -> io::Result<()> {
    let mut last_tick = Instant::now();
    loop {
        terminal.draw(|f| ui(f, &mut app))?;

        let timeout = tick_rate.saturating_sub(last_tick.elapsed());
        if crossterm::event::poll(timeout)? {
            if let Event::Key(key) = event::read()? {
                if key.kind == KeyEventKind::Release {
                    continue;
                }

                match key.code {
                    KeyCode::Char('q') => return Ok(()),
                    KeyCode::Char('j') | KeyCode::Down => {
                        app.vertical_scroll = app.vertical_scroll.saturating_add(1);
                        app.vertical_scroll_state = app.vertical_scroll_state.position(app.vertical_scroll);
                    }
                    KeyCode::Char('k') | KeyCode::Up => {
                        app.vertical_scroll = app.vertical_scroll.saturating_sub(1);
                        app.vertical_scroll_state = app.vertical_scroll_state.position(app.vertical_scroll);
                    }
                    KeyCode::Char('h') | KeyCode::Left => {
                        app.horizontal_scroll = app.horizontal_scroll.saturating_sub(1);
                        app.horizontal_scroll_state = app.horizontal_scroll_state.position(app.horizontal_scroll);
                    }
                    KeyCode::Char('l') | KeyCode::Right => {
                        app.horizontal_scroll = app.horizontal_scroll.saturating_add(1);
                        app.horizontal_scroll_state = app.horizontal_scroll_state.position(app.horizontal_scroll);
                    }
                    _ => {}
                }
            }
        }
        if last_tick.elapsed() >= tick_rate {
            last_tick = Instant::now();
        }
    }
}

fn ui(f: &mut Frame, app: &mut App) {
    let size = f.size();

    let chunks = Layout::vertical([
        Constraint::Min(1),
        Constraint::Percentage(25),
        Constraint::Percentage(25),
        Constraint::Percentage(25),
        Constraint::Percentage(25),
    ])
    .split(size);

    app.vertical_scroll_state = app.vertical_scroll_state.content_length(80);
    app.horizontal_scroll_state = app.horizontal_scroll_state.content_length(7500);

    let create_block = |title: &'static str| Block::bordered().gray().title(title.bold());

    let title = Block::default()
        .title(format!("The terminal's size is {size}").bold())
        .title_alignment(Alignment::Center);
    f.render_widget(title, chunks[0]);

    f.render_widget(create_block("Vertical scrollbar with arrows"), chunks[1]);
    f.render_stateful_widget(
        Scrollbar::default()
            .orientation(ScrollbarOrientation::VerticalRight)
            .begin_symbol(Some("↑"))
            .end_symbol(Some("↓")),
        chunks[1],
        &mut app.vertical_scroll_state,
    );

    f.render_widget(
        create_block("Vertical scrollbar without arrows, without track symbol and mirrored"),
        chunks[2],
    );
    f.render_stateful_widget(
        Scrollbar::default()
            .orientation(ScrollbarOrientation::VerticalLeft)
            .symbols(scrollbar::VERTICAL)
            .begin_symbol(None)
            .track_symbol(None)
            .end_symbol(None),
        chunks[2].inner(&Margin {
            vertical: 1,
            horizontal: 0,
        }),
        &mut app.vertical_scroll_state,
    );

    f.render_widget(
        create_block("Horizontal scrollbar with only begin arrow & custom thumb symbol"),
        chunks[3],
    );
    f.render_stateful_widget(
        Scrollbar::default()
            .orientation(ScrollbarOrientation::HorizontalBottom)
            .thumb_symbol("█")
            .end_symbol(None),
        chunks[3].inner(&Margin {
            vertical: 0,
            horizontal: 1,
        }),
        &mut app.horizontal_scroll_state,
    );

    f.render_widget(
        create_block("Horizontal scrollbar without arrows & custom thumb and track symbol"),
        chunks[4],
    );
    f.render_stateful_widget(
        Scrollbar::default()
            .orientation(ScrollbarOrientation::HorizontalBottom)
            .thumb_symbol("░")
            .track_symbol(Some("─")),
        chunks[4].inner(&Margin {
            vertical: 0,
            horizontal: 1,
        }),
        &mut app.horizontal_scroll_state,
    );
}