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use crate::router::RouterContext;
use crate::target::{Mapper, Target};
use yew::prelude::*;

#[derive(Clone, Debug, PartialEq)]
pub struct ScopeContext<C>
where
    C: Target,
{
    pub(crate) upwards: Callback<C>,
}

impl<C> ScopeContext<C>
where
    C: Target,
{
    pub(crate) fn push(&self, target: C) {
        self.upwards.emit(target);
    }
}

#[derive(Clone, Debug, PartialEq, Properties)]
pub struct ScopeProps<P, C>
where
    P: Target,
    C: Target,
{
    pub mapper: Callback<(), Mapper<P, C>>,

    #[prop_or_default]
    pub children: Children,
}

/// A component, translating down to the next level.
#[function_component(Scope)]
pub fn scope<P, C>(props: &ScopeProps<P, C>) -> Html
where
    P: Target + 'static,
    C: Target + 'static,
{
    let router = use_context::<RouterContext<P>>()
        .expect("Must be nested under a Router or Nested component of the parent type");

    let parent = use_context::<ScopeContext<P>>()
        .expect("Must be nested under a Router or Nested component of the parent type");

    let Mapper { downwards, upwards } = props.mapper.emit(());

    let scope = use_memo(
        |(parent, upwards)| {
            let parent = parent.upwards.clone();
            let upwards = upwards.clone();
            ScopeContext {
                upwards: Callback::from(move |child: C| {
                    parent.emit(upwards.emit(child));
                }),
            }
        },
        (parent.clone(), upwards),
    );

    let active = router.active();

    let context = use_memo(
        |(scope, target)| RouterContext {
            scope: scope.clone(),
            active_target: target.clone(),
        },
        (
            scope.clone(),
            active.clone().and_then(|p| downwards.emit(p)),
        ),
    );

    html!(
        <ContextProvider<RouterContext<C>> context={(*context).clone()}>
            <ContextProvider<ScopeContext<C>> context={(*scope).clone()}>
                { for props.children.iter() }
            </ContextProvider<ScopeContext<C>>>
        </ContextProvider<RouterContext<C>>>
    )
}