use crate::*;
use std::marker::PhantomData;
use ::tek_layout::{*, tek_engine::{Usually, Content, Render, Engine, Thunk}};
use Item::*;

//pub struct EdnContent<'a, E, T: AsRef<str>>(PhantomData<E>, &'a [Item<T>]);

//impl<'a, E, T: AsRef<str>> From<&'a [Item<T>]> for EdnContent<'a, E, T> {
    //fn from (items: &'a [Item<T>]) -> Self {
        //Self(Default::default(), items)
    //}
//}

pub struct EdnView<'a, E: Engine + 'a, T: EdnLayout<'a, E> + 'a>(
    PhantomData<&'a ()>,
    Box<dyn Fn(T)->Box<dyn Render<E> + Send + Sync> + Send + Sync>
);

impl<'a, E: Engine + 'a, T: EdnLayout<'a, E> + 'a> EdnView<'a, E, T> {
    fn from (source: &'a str) -> Usually<Self> {
        let items: Vec<Item<&'a str>>  = Item::read_all(source)?;
        let layout = T::parse(items.iter().map(|x|x.to_str()).collect::<Vec<_>>().as_slice());
        Ok(Self(Default::default(), Box::new(move|_|{
            let _ = layout;
            Box::new(())
        })))
    }
}

macro_rules! edn_ns {
    (|$state:ident, $items:ident| { $($match:pat => $handle:expr),* $(,)? }) => {
        match $items {
            $($match => |$state|Box::new($handle),)*
            _ => |$state|Box::new(())
        }
    }
}

pub trait EdnLayout<'a, E: Engine> where Self: 'a {
    fn get_bool    (&self, _: &Item<&str>) -> bool { false }
    fn get_unit    (&self, _: &Item<&str>) -> E::Unit { 0.into() }
    fn get_usize   (&self, _: &Item<&str>) -> usize { 0 }
    fn get_content (&self, _: &Item<&str>) -> Box<dyn Render<E>> { Box::new(()) }
    fn parse (items: &'a [Item<&'a str>]) -> impl Fn(&'a Self)->Box<dyn Render<E> + 'a> + 'a {
        edn_ns!(|state, items|{
            [Key("when"),   c, a,    ..] => When(state.get_bool(c), state.get_content(a)),
            [Key("either"), c, a, b, ..] => Either(state.get_bool(c), state.get_content(a), state.get_content(b)),
            [Key("fill"),   a,       ..] => Fill::xy(state.get_content(a)),
            [Key("fill/x"), a,       ..] => Fill::x(state.get_content(a)),
            [Key("fill/y"), a,       ..] => Fill::y(state.get_content(a)),
            [Key("fixed"),  x, y, a, ..] => Fixed::xy(state.get_unit(x), state.get_unit(y), state.get_content(a)),
            [Key("fixed/x"), x, a,   ..] => Fixed::x(state.get_unit(x), state.get_content(a)),
            [Key("fixed/y"), y, a,   ..] => Fixed::y(state.get_unit(y), state.get_content(a)),
            [Key("shrink"), x, y, a, ..] => Shrink::xy(state.get_unit(x), state.get_unit(y), state.get_content(a)),
            [Key("shrink/x"), x, a,  ..] => Shrink::x(state.get_unit(x), state.get_content(a)),
            [Key("shrink/y"), y, a,  ..] => Shrink::y(state.get_unit(y), state.get_content(a)),
            [Key("expand"), x, y, a, ..] => Expand::xy(state.get_unit(x), state.get_unit(y), state.get_content(a)),
            [Key("expand/x"), x, a,  ..] => Expand::x(state.get_unit(x), state.get_content(a)),
            [Key("expand/y"), y, a,  ..] => Expand::y(state.get_unit(y), state.get_content(a)),
            [Key("push"), x, y, a,   ..] => Push::xy(state.get_unit(x), state.get_unit(y), state.get_content(a)),
            [Key("push/x"), x, a,    ..] => Push::x(state.get_unit(x), state.get_content(a)),
            [Key("push/y"), y, a,    ..] => Push::y(state.get_unit(y), state.get_content(a)),
            [Key("pull"), x, y, a,   ..] => Pull::xy(state.get_unit(x), state.get_unit(y), state.get_content(a)),
            [Key("pull/x"), x, a,    ..] => Pull::x(state.get_unit(x), state.get_content(a)),
            [Key("pull/y"), y, a,    ..] => Pull::y(state.get_unit(y), state.get_content(a)),
        })
    }
}