use crate::{*, lang::*};
use ratatui::{prelude::{Style, Position, Backend, Color}};

/// TUI works in u16 coordinates.
impl Coord for u16 { fn plus (self, other: Self) -> Self { self.saturating_add(other) } }
impl_draw!(|self: u64, _to: Tui|{ todo!() });
impl_draw!(|self: f64, _to: Tui|{ todo!() });

impl Screen for Tui {
    type Unit = u16;
    /// Render drawable in subarea specified by `area`
    fn show <'t, T: Draw<Self>> (&mut self, content: T) -> 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
        })
    }
}

/// 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
        }
    }
}

/// Spawn the TUI output thread which writes colored characters to the terminal.
///
/// ```
/// let state = Arc::new(RwLock::new(()));
/// Exit::run(|exit|tui_output(exit, state, sleep, stdout()))
/// ```
pub fn tui_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());
    })?)
}

use self::colors::*; mod colors {
    use ratatui::prelude::Color;
    pub const fn tui_color_bg () -> Color { Color::Rgb(28, 35, 25) }
    pub const fn tui_bg0 () -> Color { Color::Rgb(20, 20, 20) }
    pub const fn tui_bo1 () -> Color { Color::Rgb(100, 110, 40) }
    pub const fn tui_bo2 () -> Color { Color::Rgb(70, 80, 50) }
    pub const fn tui_border_bg () -> Color { Color::Rgb(40, 50, 30) }
    pub const fn tui_border_fg (f: bool) -> Color { if f { tui_bo1() } else { tui_bo2() } }
    pub const fn tui_brown () -> Color { Color::Rgb(128,255,0) }
    pub const fn tui_electric () -> Color { Color::Rgb(0,255,128) }
    pub const fn tui_g (g: u8) -> Color { Color::Rgb(g, g, g) }
    pub const fn tui_green () -> Color { Color::Rgb(0,255,0) }
    pub const fn tui_mode_bg () -> Color { Color::Rgb(150, 160, 90) }
    pub const fn tui_mode_fg () -> Color { Color::Rgb(255, 255, 255) }
    pub const fn tui_null () -> Color { Color::Reset }
    pub const fn tui_orange () -> Color { Color::Rgb(255,128,0) }
    pub const fn tui_red () -> Color { Color::Rgb(255,0,  0) }
    pub const fn tui_separator_fg (_: bool) -> Color { Color::Rgb(0, 0, 0) }
    pub const fn tui_status_bar_bg () -> Color { Color::Rgb(28, 35, 25) }
    pub const fn tui_ti1 () -> Color { Color::Rgb(150, 160, 90) }
    pub const fn tui_ti2 () -> Color { Color::Rgb(120, 130, 100) }
    pub const fn tui_title_fg (f: bool) -> Color { if f { tui_ti1() } else { tui_ti2() } }
    pub const fn tui_yellow () -> Color { Color::Rgb(255,255,0) }
}

/// Apply foreground color.
pub const fn fg (fg: Color, draw: impl Draw<Tui>) -> impl Draw<Tui> {
    thunk(move|to: &mut Tui|{
        to.update(&|cell,_,_|{ cell.set_fg(fg); });
        draw.draw(to)
    })
}

/// Apply background color.
pub const fn bg (bg: Color, draw: impl Draw<Tui>) -> impl Draw<Tui> {
    thunk(move|to: &mut Tui|{
        to.update(&|cell,_,_|{ cell.set_bg(bg); });
        draw.draw(to)
    })
}

pub const fn fg_bg (fg: Color, bg: Color, draw: impl Draw<Tui>) -> impl Draw<Tui> {
    thunk(move|to: &mut Tui|{
        to.update(&|cell,_,_|{ cell.set_fg(fg); cell.set_bg(bg); });
        draw.draw(to)
    })
}

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)
}

pub const fn fill_ul (color: Option<Color>) -> impl Draw<Tui> {
    thunk(move|to: &mut Tui|Ok(Some(if let Some(color) = color {
        to.update(&|cell,_,_|{
            cell.modifier.insert(Modifier::UNDERLINED);
            cell.underline_color = color;
        })
    } else {
        to.update(&|cell,_,_|{
            cell.modifier.remove(Modifier::UNDERLINED);
            cell.underline_color = Reset;
        })
    })))
}

mod phat {
    use super::*;
    pub const LO: &'static str = "▄";
    pub const HI: &'static str = "▀";
    /// A phat line
    pub fn lo (fg: Color, bg: Color) -> impl Draw<Tui> {
        h_exact(1, fg_bg(fg, bg, x_repeat(self::phat::LO)))
    }
    /// A phat line
    pub fn hi (fg: Color, bg: Color) -> impl Draw<Tui> {
        h_exact(1, fg_bg(fg, bg, x_repeat(self::phat::HI)))
    }
}

mod scroll {
    pub const ICON_DEC_V: &[char] = &['▲'];
    pub const ICON_INC_V: &[char] = &['▼'];
    pub const ICON_DEC_H: &[char] = &[' ', '🞀', ' '];
    pub const ICON_INC_H: &[char] = &[' ', '🞂', ' '];
}

pub const fn x_repeat (c: &str) -> impl Draw<Tui> {
    thunk(move|to: &mut Tui|{
        let XYWH(x, y, w, _h) = to.xywh();
        for x in x..x+w {
            if let Some(cell) = to.0.cell_mut(Position::from((x, y))) {
                cell.set_symbol(&c);
            }
        }
        Ok(Some(XYWH(x, y, w, 1)))
    })
}

pub const fn y_repeat (c: &str) -> impl Draw<Tui> {
    thunk(move|to: &mut Tui|{
        let XYWH(x, y, _w, h) = to.xywh();
        for y in y..y+h {
            if let Some(cell) = to.0.cell_mut(Position::from((x, y))) {
                cell.set_symbol(&c);
            }
        }
        Ok(Some(XYWH(x, y, 1, h)))
    })
}

pub const fn xy_repeat (c: &str) -> impl Draw<Tui> {
    thunk(move|to: &mut Tui|{
        let XYWH(x, y, w, h) = to.xywh();
        let a = c.len();
        for (_v, y) in (y..y+h).enumerate() {
            for (u, x) in (x..x+w).enumerate() {
                if let Some(cell) = to.0.cell_mut(Position::from((x, y))) {
                    let u = u % a;
                    cell.set_symbol(&c[u..u+1]);
                }
            }
        }
        Ok(Some(XYWH(x, y, w, h)))
    })
}

/// ```
/// let _ = tengri::button_2("", "", true);
/// let _ = tengri::button_2("", "", false);
/// ```
pub const fn button_2 <'a> (key: impl Draw<Tui>, label: impl Draw<Tui>, hide: bool) -> impl Draw<Tui> {
    let c1 = tui_orange();
    let c2 = tui_g(0);
    let c3 = tui_g(96);
    let c4 = tui_g(255);
    bold(true, fg_bg(c1, c2, east(fg(c2, east(key, fg(c3, "▐"))), when(!hide, fg_bg(c4, c3, label)))))
}

/// ```
/// let _ = tengri::button_3("", "", "", true);
/// let _ = tengri::button_3("", "", "", false);
/// ```
pub const fn button_3 <'a> (
    key: impl Draw<Tui>, label: impl Draw<Tui>, value: impl Draw<Tui>, editing: bool,
) -> impl Draw<Tui> {
    bold(true, east(
        fg_bg(tui_orange(), tui_g(0),
            east(fg(tui_g(0), "▐"), east(key, fg(if editing { tui_g(128) } else { tui_g(96) }, "▐")))),
        east(
            when(!editing, east(fg_bg(tui_g(255), tui_g(96), label), fg_bg(tui_g(128), tui_g(96), "▐"),)),
            east(fg_bg(tui_g(224), tui_g(128), value), fg_bg(tui_g(128), Reset, "▌"), ))))
}

/// Stackably padded.
///
/// ```
/// /// TODO
/// ```
pub fn phat (w: u16, h: u16, [fg, bg, hi, lo]: [Color;4], draw: impl Draw<Tui>) -> impl Draw<Tui> {
    let top = w_exact(1, self::phat::lo(bg, hi));
    let low = w_exact(1, self::phat::hi(bg, lo));
    let draw = fg_bg(fg, bg, draw);
    wh_min(Some(w), Some(h), south(top, north(low, draw)))
}

fn x_scroll () -> impl Draw<Tui> {
    thunk(|Tui(buf, XYWH(x1, y1, w, h)): &mut Tui|{
        let x2 = *x1 + *w;
        for (i, x) in (*x1..=x2).enumerate() {
            if let Some(cell) = buf.cell_mut(Position::from((x, *y1))) {
                if i < (self::scroll::ICON_DEC_H.len()) {
                    cell.set_fg(Rgb(255, 255, 255));
                    cell.set_bg(Rgb(0, 0, 0));
                    cell.set_char(self::scroll::ICON_DEC_H[i as usize]);
                } else if i > (*w as usize - self::scroll::ICON_INC_H.len()) {
                    cell.set_fg(Rgb(255, 255, 255));
                    cell.set_bg(Rgb(0, 0, 0));
                    cell.set_char(self::scroll::ICON_INC_H[*w as usize - i]);
                } else if false {
                    cell.set_fg(Rgb(255, 255, 255));
                    cell.set_bg(Reset);
                    cell.set_char('━');
                } else {
                    cell.set_fg(Rgb(0, 0, 0));
                    cell.set_bg(Reset);
                    cell.set_char('╌');
                }
            }
        }
        Ok(Some(XYWH(*x1, *y1, *w, 1)))
    })
}

fn y_scroll () -> impl Draw<Tui> {
    thunk(|Tui(buf, XYWH(x1, y1, w, h)): &mut Tui|{
        let y2 = *y1 + *h;
        for (i, y) in (*y1..=y2).enumerate() {
            if let Some(cell) = buf.cell_mut(Position::from((*x1, y))) {
                if (i as usize) < (self::scroll::ICON_DEC_V.len()) {
                    cell.set_fg(Rgb(255, 255, 255));
                    cell.set_bg(Rgb(0, 0, 0));
                    cell.set_char(self::scroll::ICON_DEC_V[i as usize]);
                } else if (i as usize) > (*h as usize - self::scroll::ICON_INC_V.len()) {
                    cell.set_fg(Rgb(255, 255, 255));
                    cell.set_bg(Rgb(0, 0, 0));
                    cell.set_char(self::scroll::ICON_INC_V[*h as usize - i]);
                } else if false {
                    cell.set_fg(Rgb(255, 255, 255));
                    cell.set_bg(Reset);
                    cell.set_char('‖'); // ━
                } else {
                    cell.set_fg(Rgb(0, 0, 0));
                    cell.set_bg(Reset);
                    cell.set_char('╎'); // ━
                }
            }
        }
        Ok(Some(XYWH(*x1, *y1, 1, *h)))
    })
}

pub fn tui_update (
    Tui(buf, ..): &mut Tui,
    area: XYWH<u16>,
    callback: &impl Fn(&mut Cell, u16, u16)
) {
}

/// Draw TUI content or its error message.
///
/// ```
/// let _ = tengri::term::catcher(Ok(Some("hello")));
/// let _ = tengri::term::catcher(Ok(None));
/// let _ = tengri::term::catcher(Err("draw fail".into()));
/// ```
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)
        }
    })
}