use crate::*;
use std::ops::Deref;

/// Custom layout and rendering.
pub trait Render<E: Output>: Send + Sync {
    fn layout (&self, area: E::Area) -> E::Area;
    fn render (&self, output: &mut E);
    fn boxed <'a> (self) -> RenderBox<'a, E> where Self: Sized + 'a {
        Box::new(self) as RenderBox<'a, E>
    }
}

pub type RenderDyn<'a, Output> = dyn Render<Output> + 'a;
impl<'a, E: Output> Content<E> for &RenderDyn<'a, E> where Self: Sized {
    fn content (&self) -> impl Render<E> { self.deref() }
    fn layout (&self, area: E::Area) -> E::Area { Render::layout(self.deref(), area) }
    fn render (&self, output: &mut E) { Render::render(self.deref(), output) }
}

pub type RenderBox<'a, E: Output> = Box<RenderDyn<'a, E>>;
impl<'a, E: Output> Content<E> for RenderBox<'a, E> {
    fn content (&self) -> impl Render<E> { self.deref() }
    //fn boxed <'b> (self) -> RenderBox<'b, E> where Self: Sized + 'b { self }
}

impl<E: Output, C: Content<E>> Render<E> for C {
    fn layout (&self, area: E::Area) -> E::Area { Content::layout(self, area) }
    fn render (&self, output: &mut E) { Content::render(self, output) }
}

#[macro_export] macro_rules! render {
    (($self:ident:$Struct:ty) => $content:expr) => {
        impl <E: Output> Content<E> for $Struct {
            fn content (&$self) -> impl Render<E> { Some($content) }
        }
    };
    (|$self:ident:$Struct:ident $(<
        $($L:lifetime),* $($T:ident $(:$Trait:path)?),*
    >)?, $to:ident | $render:expr) => {
        impl <$($($L),*)? E: Output, $($T$(:$Trait)?),*> Content<E>
        for $Struct $(<$($L),* $($T),*>>)? {
            fn render (&$self, $to: &mut E) { $render }
        }
    };
    ($Output:ty:
        ($self:ident:$Struct:ident $(<$(
            $($L:lifetime)? $($T:ident)? $(:$Trait:path)?
        ),+>)?) => $content:expr
    ) => {
        impl $(<$($($L)? $($T)? $(:$Trait)?),+>)? Content<$Output>
        for $Struct $(<$($($L)? $($T)?),+>)? {
            fn content (&$self) -> impl Render<$Output> { $content }
        }
    };

    ($Output:ty:
        |$self:ident : $Struct:ident $(<$(
            $($L:lifetime)? $($T:ident)? $(:$Trait:path)?
        ),+>)?, $to:ident| $render:expr
    ) => {
        impl $(<$($($L)? $($T)? $(:$Trait)?),+>)? Content<$Output>
        for $Struct $(<$($($L)? $($T)?),+>)? {
            fn render (&$self, $to: &mut $Output) { $render }
        }
    };
}