use std::collections::BTreeMap;

use gc_arena::{lock::GcRefLock, Collect, Gc, Rootable};
use piccolo::{Context, IntoValue, Singleton, UserData, Value};

#[derive(Collect)]
#[collect(no_drop)]
struct InternMapSingleton<'gc, A>(GcRefLock<'gc, BTreeMap<A, Gc<'gc, A>>>);

impl<'gc, A> Singleton<'gc> for InternMapSingleton<'gc, A>
where
    A: Collect,
{
    fn create(ctx: Context<'gc>) -> Self {
        InternMapSingleton(Gc::new(&ctx, Default::default()))
    }
}

pub fn intern_id<'gc, A>(ctx: Context<'gc>, input: A) -> Value<'gc>
where
    A: Collect + Ord + Clone + 'static,
{
    let intern_map: &'gc InternMapSingleton<'gc, A> =
        ctx.singleton::<Rootable!['gcb => InternMapSingleton<'gcb, A>]>();
    let gc_id = intern_map
        .0
        .borrow_mut(&ctx)
        .entry(input.clone())
        .or_insert_with(|| Gc::new(&ctx, input.clone()))
        .clone();
    UserData::<'gc>::new::<Rootable!['gcb => Gc<'gcb, A>]>(&ctx, gc_id).into_value(ctx)
}

pub fn unintern_id<'gc, A>(ctx: Context<'gc>, input: &A)
where
    A: Collect + Ord + Clone + 'static,
{
    let intern_map: &InternMapSingleton<'gc, A> =
        ctx.singleton::<Rootable!['gcb => InternMapSingleton<'gcb, A>]>();
    intern_map.0.borrow_mut(&ctx).remove(input);
}