//! Aligns things to the container. Comes with caveats.
//! ```
//! use ::tengri::{output::*, tui::*};
//! let area: [u16;4] = [10, 10, 20, 20];
//! fn test (area: [u16;4], item: &impl Content<TuiOut>, expected: [u16;4]) {
//!     assert_eq!(Content::layout(item, area), expected);
//!     assert_eq!(Render::layout(item, area),  expected);
//! };
//!
//! let four = ||Fixed::xy(4, 4, "");
//! test(area, &Align::nw(four()), [10, 10, 4, 4]);
//! test(area, &Align::n(four()),  [18, 10, 4, 4]);
//! test(area, &Align::ne(four()), [26, 10, 4, 4]);
//! test(area, &Align::e(four()),  [26, 18, 4, 4]);
//! test(area, &Align::se(four()), [26, 26, 4, 4]);
//! test(area, &Align::s(four()),  [18, 26, 4, 4]);
//! test(area, &Align::sw(four()), [10, 26, 4, 4]);
//! test(area, &Align::w(four()),  [10, 18, 4, 4]);
//!
//! let two_by_four = ||Fixed::xy(4, 2, "");
//! test(area, &Align::nw(two_by_four()), [10, 10, 4, 2]);
//! test(area, &Align::n(two_by_four()),  [18, 10, 4, 2]);
//! test(area, &Align::ne(two_by_four()), [26, 10, 4, 2]);
//! test(area, &Align::e(two_by_four()),  [26, 19, 4, 2]);
//! test(area, &Align::se(two_by_four()), [26, 28, 4, 2]);
//! test(area, &Align::s(two_by_four()),  [18, 28, 4, 2]);
//! test(area, &Align::sw(two_by_four()), [10, 28, 4, 2]);
//! test(area, &Align::w(two_by_four()),  [10, 19, 4, 2]);
//! ```

use crate::*;

#[derive(Debug, Copy, Clone, Default)]
pub enum Alignment { #[default] Center, X, Y, NW, N, NE, E, SE, S, SW, W }

pub struct Align<A>(Alignment, A);

#[cfg(feature = "dsl")]
impl<'n, State: Give<A>, A: 'n> Take<'n, State> for Align<A> {
    fn take <'source> (state: &State, words: &mut TokenIter<'source>) -> Perhaps<Self> {
        if let Some(Token { value: Value::Key(key), .. }) = words.peek() {
            match key {
                "align/c"|"align/x"|"align/y"|
                "align/n"|"align/s"|"align/e"|"align/w"|
                "align/nw"|"align/sw"|"align/ne"|"align/se" => {
                    let _ = words.next().unwrap();
                    let content = state.give_or_fail(&mut words.clone(), ||"expected content")?;
                    return Ok(Some(match key {
                        "align/c"  => Self::c(content),
                        "align/x"  => Self::x(content),
                        "align/y"  => Self::y(content),
                        "align/n"  => Self::n(content),
                        "align/s"  => Self::s(content),
                        "align/e"  => Self::e(content),
                        "align/w"  => Self::w(content),
                        "align/nw" => Self::nw(content),
                        "align/ne" => Self::ne(content),
                        "align/sw" => Self::sw(content),
                        "align/se" => Self::se(content),
                        _ => unreachable!()
                    }))
                },
                _ => {}
            }
        }
        Ok(None)
    }
}

impl<A> Align<A> {
    #[inline] pub const fn c  (a: A) -> Self { Self(Alignment::Center, a) }
    #[inline] pub const fn x  (a: A) -> Self { Self(Alignment::X,      a) }
    #[inline] pub const fn y  (a: A) -> Self { Self(Alignment::Y,      a) }
    #[inline] pub const fn n  (a: A) -> Self { Self(Alignment::N,      a) }
    #[inline] pub const fn s  (a: A) -> Self { Self(Alignment::S,      a) }
    #[inline] pub const fn e  (a: A) -> Self { Self(Alignment::E,      a) }
    #[inline] pub const fn w  (a: A) -> Self { Self(Alignment::W,      a) }
    #[inline] pub const fn nw (a: A) -> Self { Self(Alignment::NW,     a) }
    #[inline] pub const fn sw (a: A) -> Self { Self(Alignment::SW,     a) }
    #[inline] pub const fn ne (a: A) -> Self { Self(Alignment::NE,     a) }
    #[inline] pub const fn se (a: A) -> Self { Self(Alignment::SE,     a) }
}

impl<E: Output, A: Content<E>> Content<E> for Align<A> {
    fn content (&self) -> impl Render<E> + '_ {
        &self.1
    }
    fn layout (&self, on: E::Area) -> E::Area {
        use Alignment::*;
        let it = Render::layout(&self.content(), on).xywh();
        let cx = on.x()+(on.w().minus(it.w())/2.into());
        let cy = on.y()+(on.h().minus(it.h())/2.into());
        let fx = (on.x()+on.w()).minus(it.w());
        let fy = (on.y()+on.h()).minus(it.h());
        let [x, y] = match self.0 {
            Center => [cx, cy],
            X =>  [cx, it.y()],
            Y =>  [it.x(), cy],
            NW => [on.x(), on.y()],
            N  => [cx,     on.y()],
            NE => [fx,     on.y()],
            W  => [on.x(), cy],
            E  => [fx,     cy],
            SW => [on.x(), fy],
            S  => [cx,     fy],
            SE => [fx,     fy],
        }.into();
        [x, y, it.w(), it.h()].into()
    }
    fn render (&self, to: &mut E) {
        to.place(Content::layout(self, to.area()), &self.content())
    }
}