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use crate::{Any, Arc, BoxAny, Closure};

extern "C" {
    fn pen_ffi_list_create() -> Arc<List>;
    fn pen_ffi_list_lazy(xs: Arc<Closure>) -> Arc<List>;
    fn pen_ffi_list_prepend(x: BoxAny, xs: Arc<List>) -> Arc<List>;
}

#[pen_ffi_macro::any(crate = "crate")]
#[repr(C)]
#[derive(Clone)]
pub struct List {
    node: Arc<Closure>,
}

impl List {
    pub fn new() -> Arc<Self> {
        unsafe { pen_ffi_list_create() }
    }

    pub fn prepend(this: Arc<Self>, x: impl Into<Any>) -> Arc<Self> {
        unsafe { pen_ffi_list_prepend(x.into().into(), this) }
    }

    pub fn lazy(xs: Arc<Closure>) -> Arc<Self> {
        unsafe { pen_ffi_list_lazy(xs) }
    }
}

impl Default for Arc<List> {
    fn default() -> Self {
        List::new()
    }
}

impl<T: Into<Any>, I: IntoIterator<Item = T>> From<I> for Arc<List>
where
    <I as IntoIterator>::IntoIter: DoubleEndedIterator,
{
    fn from(xs: I) -> Self {
        let mut list = List::new();

        for x in xs.into_iter().rev() {
            list = List::prepend(list, x);
        }

        list
    }
}