use crossterm::{
    event::{self, Event, KeyCode},
    execute,
    terminal::{EnterAlternateScreen, LeaveAlternateScreen, disable_raw_mode, enable_raw_mode},
};
use ratatui::{
    Terminal,
    backend::CrosstermBackend,
    layout::{Constraint, Direction, Layout},
    style::{Color, Style},
    widgets::{Block, Borders, Paragraph},
};
use std::io;

/// Runs the TUI and returns the entered username and password.
/// This module owns all terminal state.
pub fn run() -> io::Result<(String, String)> {
    enable_raw_mode()?;
    let mut stdout = io::stdout();
    execute!(stdout, EnterAlternateScreen)?;

    let backend = CrosstermBackend::new(stdout);
    let mut terminal = Terminal::new(backend)?;

    let mut username = String::new();
    let mut password = String::new();
    let mut focus = 0;

    loop {
        terminal.draw(|f| {
            let chunks = Layout::default()
                .direction(Direction::Vertical)
                .constraints([Constraint::Length(3), Constraint::Length(3)])
                .split(f.area());

            let user = Paragraph::new(username.as_str())
                .block(Block::default().borders(Borders::ALL).title("User"))
                .style(if focus == 0 {
                    Style::new().fg(Color::from_u32(0x00235759))
                } else {
                    Style::default()
                });

            let pass = Paragraph::new(password.as_str())
                .block(Block::default().borders(Borders::ALL).title("Password"))
                .style(if focus == 1 {
                    Style::new().fg(Color::from_u32(0x00235759))
                } else {
                    Style::default()
                });

            f.render_widget(user, chunks[0]);
            f.render_widget(pass, chunks[1]);
        })?;

        if let Event::Key(key) = event::read()? {
            match key.code {
                KeyCode::Esc => break,
                KeyCode::Tab => focus = (focus + 1) % 2,
                KeyCode::Enter => break,
                KeyCode::Backspace => {
                    if focus == 0 {
                        username.pop();
                    } else {
                        password.pop();
                    }
                }
                KeyCode::Char(c) => {
                    if focus == 0 {
                        username.push(c);
                    } else {
                        password.push(c);
                    }
                }
                _ => {}
            }
        }
    }

    disable_raw_mode()?;
    execute!(terminal.backend_mut(), LeaveAlternateScreen)?;

    Ok((username, password))
}