use crate::*;
use std::marker::PhantomData;
use EdnItem::*;

#[macro_export] macro_rules! edn_view {
    ($Output:ty: |$self:ident: $App:ty| $content:expr; {
        $( $type:ty { $($sym:literal => $value:expr),* } );*
    }) => {
        impl Content<$Output> for $App {
            fn content(&$self) -> impl Render<$Output> { $content }
        }
        $(
            impl<'a> EdnProvide<'a, $type> for $App {
                fn get <S: AsRef<str>> (&'a $self, edn: &'a EdnItem<S>) -> Option<$type> {
                    Some(match edn.to_ref() { $(EdnItem::Sym($sym) => $value,)* _ => return None })
                }
            }
        )*
    }
}

/// Implements `EdnProvide` for content components and expressions
#[macro_export] macro_rules! edn_provide_content {
    (|$self:ident:$State:ty|{ $($pat:pat => $expr:expr),* $(,)? }) => {
        impl<'a, E: Output> EdnProvide<'a, Box<dyn Render<E> + 'a>> for $State {
            fn get <S: AsRef<str>> (&'a $self, edn: &'a EdnItem<S>) -> Option<Box<dyn Render<E> + 'a>> {
                Some(match edn.to_ref() {
                    $(EdnItem::Sym($pat) => $expr),*,
                    _ => return None
                })
            }
        }
    };
    ($Output:ty: |$self:ident:$State:ty|{ $($pat:pat => $expr:expr),* $(,)? }) => {
        impl<'a> EdnProvide<'a, Box<dyn Render<$Output> + 'a>> for $State {
            fn get <S: AsRef<str>> (&'a $self, edn: &'a EdnItem<S>) -> Option<Box<dyn Render<$Output> + 'a>> {
                Some(match edn.to_ref() {
                    $(EdnItem::Sym($pat) => $expr),*,
                    _ => return None
                })
            }
        }
    }
}
/// Renders from EDN source and context.
#[derive(Default)] pub enum EdnView<'a, E: Output, T: EdnViewData<'a, E> + std::fmt::Debug> {
    #[default] Inert,
    Ok(T, EdnItem<&'a str>),
    //render: Box<dyn Fn(&'a T)->Box<dyn Render<E> + Send + Sync + 'a> + Send + Sync + 'a>
    Err(String),
    _Unused(PhantomData<&'a E>),
}
impl<'a, E: Output, T: EdnViewData<'a, E> + std::fmt::Debug> std::fmt::Debug for EdnView<'a, E, T> {
    fn fmt (&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
        match self {
            Self::Inert | Self::_Unused(_) =>
                write!(f, "EdnView::Inert"),
            Self::Ok(state, view) =>
                write!(f, "EdnView::Ok(state={state:?} view={view:?}"),
            Self::Err(error) =>
                write!(f, "EdnView::Err({error})"),
            _ => unreachable!()
        }
    }
}
impl<'a, E: Output, T> EdnViewData<'a, E> for T where T:
    EdnProvide<'a, bool> +
    EdnProvide<'a, usize> +
    EdnProvide<'a, E::Unit> +
    EdnProvide<'a, Box<dyn Render<E> + 'a>>
{}
impl<'a, E: Output, T: EdnViewData<'a, E> + std::fmt::Debug> EdnView<'a, E, T> {
    pub fn from_source (state: T, source: &'a str) -> Self {
        match EdnItem::read_one(&source) {
            Ok((layout, _)) => Self::Ok(state, layout),
            Err(error) => Self::Err(format!("{error} in {source}"))
        }
    }
    pub fn from_items (state: T, items: Vec<EdnItem<&'a str>>) -> Self {
        Self::Ok(state, EdnItem::Exp(items))
    }
}
impl<E: Output, T: for<'a>EdnViewData<'a, E> + Send + Sync + std::fmt::Debug> Content<E> for EdnView<'_, E, T> {
    fn content (&self) -> impl Render<E> {
        match self {
            Self::Ok(state, layout) => state.get_content(layout),
            Self::Err(_error) => {
                panic!("{self:?}");
                //TODO:&format!("EdnView error: {error:?}")) // FIXME: String is not Render
            },
            _ => todo!()
        }
    }
}
/// Provides values to the template
pub trait EdnViewData<'a, E: Output>:
    EdnProvide<'a, bool> +
    EdnProvide<'a, usize> +
    EdnProvide<'a, E::Unit> +
    EdnProvide<'a, Box<dyn Render<E> + 'a>>
{
    fn get_bool (&'a self, item: &'a EdnItem<&str>) -> Option<bool> {
        Some(match &item {
            Sym(":false") | Sym(":f") | Num(0) => false,
            Sym(":true")  | Sym(":t") | Num(_) => true,
            _ => return EdnProvide::get(self, item)
        })
    }
    fn get_usize (&'a self, item: &'a EdnItem<&str>) -> Option<usize> {
        Some(match &item { Num(n) => *n, _ => return EdnProvide::get(self, item) })
    }
    fn get_unit (&'a self, item: &'a EdnItem<&str>) -> Option<E::Unit> {
        Some(match &item { Num(n) => (*n as u16).into(), _ => return EdnProvide::get(self, item) })
    }
    fn get_content (&'a self, item: &'a EdnItem<&'a str>) -> Option<Box<dyn Render<E> + 'a>> where E: 'a {
        Some(match item {
            Nil    => Box::new(()),
            Exp(e) => if let [head, tail @ ..] = e.as_slice() {
                if let Some(builtin) = When::<_, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Either::<_, RenderBox<'a, E>, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Align::<_, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Bsp::<_, RenderBox<'a, E>, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Fill::<_, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Fixed::<_, _, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Min::<_, _, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Max::<_, _, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Shrink::<_, _, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Expand::<_, _, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Push::<_, _, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Pull::<_, _, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Margin::<_, _, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else if let Some(builtin) = Padding::<_, _, RenderBox<'a, E>>::try_from_edn(self, head, tail) {
                    builtin.boxed()
                } else {
                    EdnProvide::get_or_fail(self, &item)
                }
            } else {
                EdnProvide::get_or_fail(self, &item)
            },
            _ => EdnProvide::get_or_fail(self, &item)
        })
        //panic!("no content")
    }
}
// A function that returns a `RenderBox.
pub type EdnCallback<'a, O, State> =
    dyn Fn(&'a State)-> RenderBox<'a, O> + Send + Sync + 'a;
// A box containing a function that returns a `RenderBox.
pub type EdnRenderCallback<'a, O, State> =
    Box<EdnCallback<'a, O, State>>;