use std::{
    io::{self, BufWriter},
    sync::mpsc::channel,
};

use crossterm::{
    event::{self, Event, KeyCode, KeyEventKind},
    execute,
    terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
};
use portable_pty::{CommandBuilder, NativePtySystem, PtySize, PtySystem};
use ratatui::{
    backend::{Backend, CrosstermBackend},
    layout::Alignment,
    style::{Modifier, Style},
    text::Line,
    widgets::{Block, Borders, Paragraph},
    Frame, Terminal,
};
use tui_term::widget::PseudoTerminal;
use vt100::Screen;

fn main() -> std::io::Result<()> {
    let (mut terminal, size) = setup_terminal().unwrap();

    let pty_system = NativePtySystem::default();
    let cwd = std::env::current_dir().unwrap();
    let mut cmd = CommandBuilder::new("ls");
    cmd.cwd(cwd);

    let pair = pty_system
        .openpty(PtySize {
            rows: size.rows,
            cols: size.cols,
            pixel_width: 0,
            pixel_height: 0,
        })
        .unwrap();
    let mut child = pair.slave.spawn_command(cmd).unwrap();
    drop(pair.slave);

    let (tx, rx) = channel();
    let mut reader = pair.master.try_clone_reader().unwrap();
    let mut parser = vt100::Parser::new(size.rows - 1, size.cols - 1, 0);

    std::thread::spawn(move || {
        // Consume the output from the child
        let mut s = String::new();
        reader.read_to_string(&mut s).unwrap();
        tx.send(s).unwrap();
    });

    {
        // Drop writer on purpose
        let _writer = pair.master.take_writer().unwrap();
    }

    // Wait for the child to complete
    let _child_exit_status = child.wait().unwrap();

    drop(pair.master);

    let output = rx.recv().unwrap();
    parser.process(output.as_bytes());

    run(&mut terminal, parser.screen())?;

    // restore terminal
    cleanup_terminal(&mut terminal).unwrap();
    Ok(())
}

fn run<B: Backend>(terminal: &mut Terminal<B>, screen: &Screen) -> io::Result<()> {
    loop {
        terminal.draw(|f| ui(f, screen))?;

        if let Event::Key(key) = event::read()? {
            if key.kind == KeyEventKind::Press {
                if let KeyCode::Char('q') = key.code {
                    return Ok(());
                }
            }
        }
    }
}

fn ui(f: &mut Frame, screen: &Screen) {
    let chunks = ratatui::layout::Layout::default()
        .direction(ratatui::layout::Direction::Vertical)
        .margin(1)
        .constraints(
            [
                ratatui::layout::Constraint::Percentage(50),
                ratatui::layout::Constraint::Percentage(50),
                ratatui::layout::Constraint::Min(1),
            ]
            .as_ref(),
        )
        .split(f.area());
    let title = Line::from("[ Running: ls ]");
    let block = Block::default()
        .borders(Borders::ALL)
        .title(title)
        .style(Style::default().add_modifier(Modifier::BOLD));
    let pseudo_term = PseudoTerminal::new(screen).block(block.clone());
    f.render_widget(pseudo_term, chunks[0]);
    let pseudo_term = PseudoTerminal::new(screen).block(block);
    f.render_widget(pseudo_term, chunks[1]);
    let block = Block::default().borders(Borders::ALL);
    f.render_widget(block, f.area());
    let explanation = "Press q to exit";
    let explanation = Paragraph::new(explanation)
        .style(Style::default().add_modifier(Modifier::BOLD | Modifier::REVERSED))
        .alignment(Alignment::Center);
    f.render_widget(explanation, chunks[2]);
}

fn setup_terminal() -> io::Result<(Terminal<CrosstermBackend<BufWriter<io::Stdout>>>, Size)> {
    enable_raw_mode()?;
    let stdout = io::stdout();
    let backend = CrosstermBackend::new(BufWriter::new(stdout));
    let mut terminal = Terminal::new(backend)?;
    let initial_size = terminal.size()?;
    let size = Size {
        rows: initial_size.height,
        cols: initial_size.width,
    };
    execute!(terminal.backend_mut(), EnterAlternateScreen)?;
    Ok((terminal, size))
}

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

#[derive(Debug, Clone)]
struct Size {
    cols: u16,
    rows: u16,
}