#[macro_export] macro_rules! tui_app {
    ($Struct:ident { $($fields:tt)* }) => {
        #[dizzle::namespace(bool)]
        #[dizzle::namespace(u16)]
        #[dizzle::namespace(Option<u16>)]
        #[dizzle::namespace(Color)]
        #[derive(Debug, Default)]
        pub struct $Struct { $($fields)* }
        tui_main!($Struct { ..Default::default() });
    }
}

/// Implement standard [main] entrypoint for TUI apps.
#[macro_export] macro_rules! tui_main {
    ($state:expr) => {
        pub fn main () -> Usually<()> {
            Tui::setup_panic();
            Tui::run_main(Arc::new(RwLock::new($state)))
        }
    }
}

/// Enable TUI output for state struct.
#[macro_export] macro_rules! tui_view {
    ($self:ident: $State:ty $body:block) => {
        impl View<Tui> for $State {
            fn view (&$self) -> impl Draw<Tui> $body
        }
    }
}

#[macro_export] macro_rules! tui_interpret {
    ($self:ident: $State:ident, $to:pat, $pat:ident -> $Result:ty { $($body:tt)+ }) => {
        impl Interpret<Tui, $Result> for $State {
            fn interpret_word <'a> (&'a $self, $to: &mut Tui, $pat: &'a impl Symbol) -> Usually<$Result> {
                $($body)+
            }
            fn interpret_expr <'a> (&'a self, to: &mut Tui, src: &'a impl Expression) -> Usually<$Result> {
                Ok(Some(if let Some(area) = eval_view(self, to, src)? {
                    area
                } else if let Some(area) = eval_view_tui(self, to, src)? {
                    area
                } else {
                    return Err(format!("App::interpret_expr: unexpected: {src:?}").into())
                }))
            }
        }
    };
}

/// Enable TUI keyboard input for main state struct.
#[macro_export] macro_rules! tui_keys {
    ($self:ident:$State:ty,$input:ident $($body:tt)+) => {
        impl Apply<TuiEvent, Usually<()>> for $State {
            fn apply (&mut $self, $input: &TuiEvent) -> Usually<()> $($body)+
        }
    };
}

use crate::{*, lang::*};
mod border; pub use self::border::*;
mod event;  pub use self::event::*;
mod keys;   pub use self::keys::*;
mod buffer; pub use self::buffer::*;
mod repeat; pub use self::repeat::*;
mod scroll; pub use self::scroll::*;
mod colors; pub use self::colors::*;
mod phat; pub use self::phat::*;
mod button; pub use self::button::*;

//use unicode_width::{UnicodeWidthStr, UnicodeWidthChar};
//use rand::distributions::uniform::UniformSampler;
pub(crate) use ::{
    std::{
        io::{stdout, Write},
        time::Duration,
        ops::{Deref, DerefMut},
    },
    ratatui::{
        prelude::{Style, Position, Backend, Color},
        style::{Modifier, Color::*},
        backend::{CrosstermBackend, ClearType},
        layout::{Size, Rect},
        buffer::{Buffer, Cell},
        crossterm::{
            ExecutableCommand,
            terminal::{EnterAlternateScreen, LeaveAlternateScreen, enable_raw_mode, disable_raw_mode},
            //event::{poll, read, Event, KeyEvent, KeyCode, KeyModifiers, KeyEventKind, KeyEventState},
        }
    },
    crossterm::event::{
        read, Event, KeyEvent, KeyModifiers, KeyCode, KeyEventKind, KeyEventState
    },
};

impl Deref         for Tui { type Target = Buffer; fn deref (&self) -> &Buffer { &self.0 } }
impl DerefMut      for Tui { fn deref_mut (&mut self) -> &mut Buffer { &mut self.0 } }
impl AsMut<Buffer> for Tui { fn as_mut (&mut self) -> &mut Buffer { &mut self.0 } }
impl Wide<u16>     for Tui { fn w (&self) -> u16 { self.1.2 } }
impl Tall<u16>     for Tui { fn h (&self) -> u16 { self.1.3 } }
impl HasOrigin     for Tui { fn origin (&self) -> Azimuth { Azimuth::NW } }
impl Xy<u16>       for Tui { fn x (&self) -> u16 { self.1.0 } fn y (&self) -> u16 { self.1.1 } }
/// Terminal output.
pub struct Tui(
    /// Ratatui buffer; area is screen size
    pub Buffer,
    /// Current draw area
    pub XYWH<u16>
);
impl Tui {
    pub fn setup_panic () {
        use ::std::panic::{set_hook, PanicHookInfo};
        use ::better_panic::{Settings, Verbosity};
        let panic = Settings::auto()
            .verbosity(Verbosity::Full)
            .create_panic_handler();
        set_hook(Box::new(move |info: &PanicHookInfo|{
            let _ = Tui::teardown(&mut stdout());
            panic(info);
        }));
    }
    pub fn run_main <T> (state: Arc<RwLock<T>>) -> Usually<()> where
        T: View<Tui> + Apply<TuiEvent, Usually<()>> + Send + Sync + 'static
    {
        Exit::run(|exit|{
            let scan  = Duration::from_millis(100);
            let frame = Duration::from_millis(10);
            let (_input, output) = Tui::io(exit.as_ref(), &state, scan, frame, std::io::stdout())?;
            let _ = output.join();
            Tui::teardown(&mut stdout())
        })
    }
    /// Spawn the TUI input and output threadsl.
    pub fn io <
        T: View<Tui> + Apply<TuiEvent, Usually<()>> + Send + Sync + 'static,
        W: Write + Send + Sync + 'static,
    > (
        exited: &Arc<AtomicBool>,
        state:  &Arc<RwLock<T>>,
        poll:   Duration,
        sleep:  Duration,
        output: W,
    ) -> Result<(Task, Task), Box<dyn std::error::Error>> {
        Ok((
            Tui::input(exited, state, poll)?,
            Tui::output(exited, state, sleep, output)?,
        ))
    }
    /// Spawn the TUI input thread which reads keys from the terminal.
    pub fn input <T: Apply<TuiEvent, Usually<()>> + Send + Sync + 'static> (
        exited: &Arc<AtomicBool>, state: &Arc<RwLock<T>>, poll: Duration
    ) -> Result<Task, std::io::Error> {
        let exited = exited.clone();
        let state = state.clone();
        Task::new_poll(exited.clone(), poll, move |_| {
            let event = read().unwrap();
            if Exit::is(&event) {
                exited.store(true, Relaxed);
            } else if let Err(e) = state.write().unwrap().apply(&TuiEvent(event)) {
                panic!("{e}")
            }
        })
    }
    pub fn teardown <W: Write> (backend: &mut W) -> Usually<()> {
        use ::ratatui::backend::Backend;
        stdout().execute(LeaveAlternateScreen)?;
        CrosstermBackend::new(backend).show_cursor()?;
        disable_raw_mode().map_err(Into::into)
    }
    pub fn new (width: u16, height: u16) -> Self {
        Self(Buffer::empty(Rect { x: 0, y: 0, width, height }), XYWH(0, 0, width, height))
    }
    pub fn resize <W: Write> (&mut self, back: &mut CrosstermBackend<W>, width: u16, height: u16) {
        let size = Rect { x: 0, y: 0, width, height };
        if self.0.area != size {
            back.clear_region(ClearType::All).unwrap();
            self.0.resize(size);
            self.0.reset();
        }
    }
    pub fn redraw <'b, W: Write> (
        &'b mut self,
        back: &mut CrosstermBackend<W>,
        mut next: &'b mut Self
    ) {
        let updates = self.0.diff(&next.0);
        back.draw(updates.into_iter()).expect("failed to render");
        Backend::flush(back).expect("failed to flush output new");
        std::mem::swap(self, &mut next);
        next.0.reset();
    }
    pub fn update (&mut self, callback: &impl Fn(&mut Cell, u16, u16)) -> XYWH<u16> {
        for row in 0..self.h() {
            let y = self.y() + row;
            for col in 0..self.w() {
                let x = self.x() + col;
                if x < self.0.area.width && y < self.0.area.height {
                    if let Some(cell) = self.0.cell_mut(Position { x, y }) {
                        callback(cell, col, row);
                    }
                }
            }
        }
        self.xywh()
    }
    pub fn blit (&mut self, text: &impl AsRef<str>, x: u16, y: u16, style: Option<Style>) {
        let text = text.as_ref();
        let style = style.unwrap_or(Style::default());
        if x < self.0.area.width && y < self.0.area.height {
            self.0.set_string(x, y, text, style);
        }
    }
    pub fn tint_all (&mut self, fg: Color, bg: Color, modifier: Modifier) {
        for cell in self.0.content.iter_mut() {
            cell.fg = fg;
            cell.bg = bg;
            cell.modifier = modifier;
        }
    }
    /// Spawn the TUI output thread which writes colored characters to the terminal.
    ///
    /// ```
    /// let state = std::sync::Arc::new(std::sync::RwLock::new(()));
    /// let _ = tengri::Exit::run(|exit|{
    ///     tengri::Tui::output(
    ///         exit.as_ref(),
    ///         &state,
    ///         std::time::Duration::from_millis(10),
    ///         std::io::stdout()
    ///     )
    /// });
    /// ```
    pub fn output <
        W: Write + Send + Sync + 'static, T: View<Tui> + Send + Sync + 'static
    > (
        exited: &Arc<AtomicBool>,
        state:  &Arc<RwLock<T>>,
        sleep:  Duration,
        output: W,
    ) -> Usually<Task> {
        let state = state.clone();
        stdout().execute(EnterAlternateScreen)?;
        CrosstermBackend::new(stdout()).hide_cursor()?;
        enable_raw_mode()?;
        let mut backend = CrosstermBackend::new(output);
        let Size { width, height } = backend.size().expect("get size failed");
        let mut prev = Tui::new(width, height);
        let mut next = Tui::new(width, height);
        Ok(Task::new_sleep(exited.clone(), sleep, move |perf| {
            let Size { width, height } = backend.size().expect("get size failed");
            if let Ok(state) = state.try_read() {
                prev.resize(&mut backend, width, height);
                state.view().draw(&mut next).expect("draw failed"); // TODO draw error
                prev.redraw(&mut backend, &mut next);
            }
            let timer = format!("{:>3.3}ms", perf.used.load(Relaxed));
            prev.set_string(0, 0, &timer, Style::default());
        })?)
    }
    /// Draw TUI content or its error message.
    ///
    /// ```
    /// for variant in [
    ///     Ok(Some("hello")),
    ///     Ok(None),
    ///     Err("fail".into()),
    /// ] {
    ///     let _ = tengri::Tui::catcher(variant);
    /// }
    /// ```
    pub fn catcher <T: Draw<Tui>> (result: Usually<T>) -> impl Draw<Tui> {
        thunk(move|to: &mut Tui|match result {
            Ok(content) => content.draw(to),
            Err(e) => {
                let err_fg = Color::Rgb(255,224,244);
                let err_bg = Color::Rgb(96, 24, 24);
                let title  = east(bold(true, "upsi daisy. "), "rendering failed.");
                let error  = east("\"why?\" ", bold(true, format!("{e}")));
                fg(err_fg, bg(err_bg, south(title, error))).draw(to)
            }
        })
    }
}
impl Screen for Tui {
    type Unit = u16;
    /// Render drawable in subarea specified by `area`
    fn show (&mut self, content: impl Draw<Self>) -> Perhaps<XYWH<u16>> {
        let previous_area = self.1;
        Ok(if let Some(area) = content.layout(self.1)? {
            self.1 = area;
            if let Some(result_area) = content.draw(self)? {
                self.1 = previous_area;
                Some(result_area)
            } else {
                None
            }
        } else {
            None
        })
    }

    /// Get current clipping area
    fn area (&self) -> XYWH<Self::Unit> {
        self.1
    }

    fn clip <T> (
        &mut self,
        area: impl Into<Option<XYWH<u16>>>,
        draw: impl FnOnce(&mut Self)->T
    ) -> T {
        let prev = self.1;
        if let Some(area) = area.into() {
            self.1 = area.into();
        }
        let result = draw(self);
        self.1 = prev;
        result
    }
}

pub const fn fill_char (c: char) -> impl Draw<Tui> {
    thunk(move|to: &mut Tui|Ok(Some(to.update(&|cell,_,_|{
        cell.set_char(c);
    }))))
}

/// Draw contents with modifier applied.
pub const fn modify (on: bool, modifier: Modifier, draw: impl Draw<Tui>) -> impl Draw<Tui> {
    thunk(move|to: &mut Tui|{
        fill_mod(on, modifier).draw(to)?;
        draw.draw(to)
    })
}

pub const fn fill_mod (on: bool, modifier: Modifier) -> impl Draw<Tui> {
    thunk(move|to: &mut Tui|Ok(Some({
        if on {
            to.update(&|cell,_,_|cell.modifier.insert(modifier))
        } else {
            to.update(&|cell,_,_|cell.modifier.remove(modifier))
        }
    })))
}

/// Draw contents with bold modifier applied.
pub const fn bold (on: bool, draw: impl Draw<Tui>) -> impl Draw<Tui> {
    modify(on, Modifier::BOLD, draw)
}