/// This example is useful for testing how your terminal emulator handles different modifiers.
/// It will render a grid of combinations of foreground and background colors with all
/// modifiers applied to them.
use std::{
    error::Error,
    io::{self, Stdout},
    iter::once,
    result,
    time::Duration,
};

use crossterm::{
    event::{self, Event, KeyCode},
    execute,
    terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
};
use itertools::Itertools;
use ratatui::{prelude::*, widgets::*};

type Result<T> = result::Result<T, Box<dyn Error>>;

fn main() -> Result<()> {
    let mut terminal = setup_terminal()?;
    let res = run_app(&mut terminal);
    restore_terminal(terminal)?;
    if let Err(err) = res {
        eprintln!("{err:?}");
    }
    Ok(())
}

fn run_app<B: Backend>(terminal: &mut Terminal<B>) -> io::Result<()> {
    loop {
        terminal.draw(ui)?;

        if event::poll(Duration::from_millis(250))? {
            if let Event::Key(key) = event::read()? {
                if let KeyCode::Char('q') = key.code {
                    return Ok(());
                }
            }
        }
    }
}

fn ui(frame: &mut Frame) {
    let vertical = Layout::vertical([Constraint::Length(1), Constraint::Min(0)]);
    let [text_area, main_area] = frame.size().split(&vertical);
    frame.render_widget(
        Paragraph::new("Note: not all terminals support all modifiers")
            .style(Style::default().fg(Color::Red).add_modifier(Modifier::BOLD)),
        text_area,
    );
    let layout = Layout::vertical([Constraint::Length(1); 50])
        .split(main_area)
        .iter()
        .flat_map(|area| {
            Layout::horizontal([Constraint::Percentage(20); 5])
                .split(*area)
                .to_vec()
        })
        .collect_vec();

    let colors = [
        Color::Black,
        Color::DarkGray,
        Color::Gray,
        Color::White,
        Color::Red,
    ];
    let all_modifiers = once(Modifier::empty())
        .chain(Modifier::all().iter())
        .collect_vec();
    let mut index = 0;
    for bg in colors.iter() {
        for fg in colors.iter() {
            for modifier in &all_modifiers {
                let modifier_name = format!("{modifier:11?}");
                let padding = (" ").repeat(12 - modifier_name.len());
                let paragraph = Paragraph::new(Line::from(vec![
                    modifier_name.fg(*fg).bg(*bg).add_modifier(*modifier),
                    padding.fg(*fg).bg(*bg).add_modifier(*modifier),
                    // This is a hack to work around a bug in VHS which is used for rendering the
                    // examples to gifs. The bug is that the background color of a paragraph seems
                    // to bleed into the next character.
                    ".".black().on_black(),
                ]));
                frame.render_widget(paragraph, layout[index]);
                index += 1;
            }
        }
    }
}

fn setup_terminal() -> Result<Terminal<CrosstermBackend<Stdout>>> {
    enable_raw_mode()?;
    let mut stdout = io::stdout();
    execute!(stdout, EnterAlternateScreen)?;
    let backend = CrosstermBackend::new(stdout);
    let mut terminal = Terminal::new(backend)?;
    terminal.hide_cursor()?;
    Ok(terminal)
}

fn restore_terminal(mut terminal: Terminal<CrosstermBackend<Stdout>>) -> Result<()> {
    disable_raw_mode()?;
    execute!(terminal.backend_mut(), LeaveAlternateScreen)?;
    terminal.show_cursor()?;
    Ok(())
}