use crate::*;
pub(crate) use ratatui::buffer::Cell;
pub(crate) use crossterm::{ExecutableCommand};
pub use crossterm::event::{Event, KeyEvent, KeyCode, KeyModifiers};
pub use ratatui::prelude::{Rect, Style, Color, Buffer};
pub use ratatui::style::{Stylize, Modifier};
use ratatui::backend::{Backend, CrosstermBackend};
use std::io::Stdout;
use crossterm::terminal::{
    EnterAlternateScreen, LeaveAlternateScreen,
    enable_raw_mode, disable_raw_mode
};

submod! { tui_border tui_buffer tui_colors tui_layout }

pub struct Tui {
    exited:  Arc<AtomicBool>,
    buffer:  usize,
    buffers: [Buffer;2],
    backend: CrosstermBackend<Stdout>,
    event:   RwLock<Option<TuiEvent>>,
    area:    [u16;4],
}

impl Engine for Tui {
    type Unit        = u16;
    type Area        = [Self::Unit;4];
    type HandleInput = Self;
    type Handled     = bool;
    type RenderInput = Self;
    type Rendered    = Self::Area;
    fn exited (&self) -> bool {
        self.exited.fetch_and(true, Ordering::Relaxed)
    }
    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::PanicInfo|{
            stdout().execute(LeaveAlternateScreen).unwrap();
            disable_raw_mode().unwrap();
            better_panic_handler(info);
        }));
        stdout().execute(EnterAlternateScreen)?;
        self.backend.hide_cursor()?;
        enable_raw_mode().map_err(Into::into)
    }
    fn teardown (&mut self) -> Usually<()> {
        stdout().execute(LeaveAlternateScreen)?;
        self.backend.show_cursor()?;
        disable_raw_mode().map_err(Into::into)
    }
    // FIXME
    fn area (&self) -> Self::Area {
        self.area
    }
    #[inline]
    fn with_area (&mut self, x: u16, y: u16, w: u16, h: u16) -> &mut Self {
        self.with_rect([x, y, w, h]);
        self
    }
}
impl Tui {
    /// Run the main loop.
    pub fn run <R: Component<Tui> + Sized + 'static> (
        state: Arc<RwLock<R>>
    ) -> Usually<Arc<RwLock<R>>> {
        let backend = CrosstermBackend::new(stdout());
        let area    = backend.size()?;
        let mut engine = Self {
            exited:  Arc::new(AtomicBool::new(false)),
            event:   RwLock::new(None),
            buffer:  0,
            buffers: [Buffer::empty(area), Buffer::empty(area)],
            backend,
            area: area.xywh(),
        };
        engine.setup()?;
        let engine = Arc::new(RwLock::new(engine));
        let _input_thread = {
            let engine = engine.clone();
            let state  = state.clone();
            let poll   = Duration::from_millis(100);
            spawn(move || loop {
                if ::crossterm::event::poll(poll).is_ok() {
                    let event = TuiEvent::Input(::crossterm::event::read().unwrap());
                    match event {
                        key!(Ctrl-KeyCode::Char('c')) => {
                            engine.write().unwrap().exited.store(true, Ordering::Relaxed);
                        },
                        _ => {
                            *engine.write().unwrap().event.write().unwrap() = Some(event);
                            if let Err(e) = state.write().unwrap().handle(&*engine.read().unwrap()) {
                                panic!("{e}")
                            }
                        }
                    }
                }
                if engine.read().unwrap().exited() {
                    break
                }
                //engine.read().unwrap().handle(&mut *state.write().unwrap()).expect("handle failed");
            })
        };
        let main_thread = {
            let engine = engine.clone();
            let state  = state.clone();
            let sleep  = Duration::from_millis(20);
            spawn(move || loop {
                if let (Ok(mut engine), Ok(state)) = (engine.write(), state.try_read()) {
                    if engine.exited() {
                        break
                    }
                    engine.area = engine.backend.size().expect("get size failed").xywh();
                    state.render(&mut engine).expect("render failed");
                    engine.flip();
                }
                std::thread::sleep(sleep);
            })
        };
        main_thread.join().expect("main thread failed");
        engine.write().unwrap().teardown()?;
        Ok(state)
    }
    pub fn event (&self) -> TuiEvent {
        self.event.read().unwrap().clone().unwrap()
    }
    pub fn buffer (&mut self) -> &mut Buffer {
        &mut self.buffers[self.buffer]
    }
    fn flip (&mut self) {
        let previous_buffer = &self.buffers[1 - self.buffer];
        let current_buffer  = &self.buffers[self.buffer];
        let updates = previous_buffer.diff(current_buffer);
        self.backend.draw(updates.into_iter()).expect("failed to render");
        self.buffers[1 - self.buffer].reset();
        self.buffer = 1 - self.buffer;
    }
    pub fn buffer_update (&mut self, area: [u16;4], callback: &impl Fn(&mut Cell, u16, u16)) {
        buffer_update(self.buffer(), area, callback)
    }
    pub fn fill_bg (&mut self, area: [u16;4], color: Color) {
        self.buffer_update(area, &|cell,_,_|{cell.set_bg(color);})
    }
    pub fn fill_fg (&mut self, area: [u16;4], color: Color) {
        self.buffer_update(area, &|cell,_,_|{cell.set_fg(color);})
    }
    pub fn fill_ul (&mut self, area: [u16;4], color: Color) {
        self.buffer_update(area, &|cell,_,_|{
            cell.modifier = ratatui::prelude::Modifier::UNDERLINED;
            cell.underline_color = color;
        })
    }
    pub fn fill_char (&mut self, area: [u16;4], c: char) {
        self.buffer_update(area, &|cell,_,_|{cell.set_char(c);})
    }
    pub fn make_dim (&mut self) {
        for cell in self.buffer().content.iter_mut() {
            cell.bg = ratatui::style::Color::Rgb(30,30,30);
            cell.fg = ratatui::style::Color::Rgb(100,100,100);
            cell.modifier = ratatui::style::Modifier::DIM;
        }
    }
    pub fn blit (
        &mut self, text: &impl AsRef<str>, x: u16, y: u16, style: Option<Style>
    ) -> Perhaps<[u16;4]> {
        let text = text.as_ref();
        let buf = self.buffer();
        if x < buf.area.width && y < buf.area.height {
            buf.set_string(x, y, text, style.unwrap_or(Style::default()));
        }
        Ok(Some([x, y, text.len() as u16, 1]))
    }
    #[inline]
    pub fn alter_area (
        &mut self, alter: impl Fn([u16;4])->[u16;4]
    ) -> &mut Self {
        let [x, y, w, h] = alter(self.area.xywh());
        self.with_area(x, y, w, h)
    }
    #[inline]
    pub fn with_rect (&mut self, area: [u16;4]) -> &mut Self {
        self.area = area;
        self
    }
}
#[derive(Debug, Clone)]
pub enum TuiEvent {
    /// Terminal input
    Input(::crossterm::event::Event),
    /// Update values but not the whole form.
    Update,
    /// Update the whole form.
    Redraw,
    /// Device gains focus
    Focus,
    /// Device loses focus
    Blur,
    // /// JACK notification
    // Jack(JackEvent)
}

/// Rendering unit struct to Ratatui returns zero-sized [Area] at render coordinates.
impl Render<Tui> for () {
    fn render (&self, to: &mut Tui) -> Perhaps<[u16;4]> {
        Ok(Some([to.area.x(), to.area.y(), 0, 0]))
    }
}

impl Area<u16> for Rect {
    fn x (&self) -> u16 { self.x }
    fn y (&self) -> u16 { self.y }
    fn w (&self) -> u16 { self.width }
    fn h (&self) -> u16 { self.height }
}

pub fn half_block (lower: bool, upper: bool) -> Option<char> {
    match (lower, upper) {
        (true, true)  => Some('█'),
        (true, false) => Some('▄'),
        (false, true) => Some('▀'),
        _ => None
    }
}