use crate::*;

pub struct Tui {
    pub exited:  Arc<AtomicBool>,
    pub backend: CrosstermBackend<Stdout>,
    pub buffer:  Buffer,
    pub area:    [u16;4],
}

impl Tui {
    /// Construct a new TUI engine and wrap it for shared ownership.
    pub fn new () -> Usually<Arc<RwLock<Self>>> {
        let backend = CrosstermBackend::new(stdout());
        let Size { width, height } = backend.size()?;
        Ok(Arc::new(RwLock::new(Self {
            exited:  Arc::new(AtomicBool::new(false)),
            buffer:  Buffer::empty(Rect { x: 0, y: 0, width, height }),
            area:    [0, 0, width, height],
            backend,
        })))
    }
    /// True if done
    pub fn exited (&self) -> bool {
        self.exited.fetch_and(true, Relaxed)
    }
    /// Prepare before run
    pub fn setup (&mut self) -> Usually<()> {
        let better_panic_handler = Settings::auto().verbosity(Verbosity::Full).create_panic_handler();
        std::panic::set_hook(Box::new(move |info: &std::panic::PanicHookInfo|{
            stdout().execute(LeaveAlternateScreen).unwrap();
            CrosstermBackend::new(stdout()).show_cursor().unwrap();
            disable_raw_mode().unwrap();
            better_panic_handler(info);
        }));
        stdout().execute(EnterAlternateScreen)?;
        self.backend.hide_cursor()?;
        enable_raw_mode().map_err(Into::into)
    }
    /// Update the display buffer.
    pub fn flip (&mut self, mut buffer: Buffer, size: ratatui::prelude::Rect) -> Buffer {
        if self.buffer.area != size {
            self.backend.clear_region(ClearType::All).unwrap();
            self.buffer.resize(size);
            self.buffer.reset();
        }
        let updates = self.buffer.diff(&buffer);
        self.backend.draw(updates.into_iter()).expect("failed to render");
        self.backend.flush().expect("failed to flush output buffer");
        std::mem::swap(&mut self.buffer, &mut buffer);
        buffer.reset();
        buffer
    }
    /// Clean up after run
    pub fn teardown (&mut self) -> Usually<()> {
        stdout().execute(LeaveAlternateScreen)?;
        self.backend.show_cursor()?;
        disable_raw_mode().map_err(Into::into)
    }
}