use rhai::{Dynamic, Engine, ImmutableString};
use crate::api::board::BoardRef;
use crate::script::Registerable;
use crate::utils::{LogSink, RegistryValue};

/// The board's script registry, pushed into scope as the constant `Registry`.
/// `get`/`set`/`get_or` methods let scripts read and write per-board key→value pairs
/// that persist across board transitions. Mutation goes through the inner
/// `Rc<RefCell<Board>>`, so the struct itself can be shared as a scope constant.
#[derive(Clone)]
pub struct Registry(pub BoardRef);

impl Registerable for Registry {
    fn register(engine: &mut Engine, _log_sink: LogSink) {
        engine.register_type_with_name::<Registry>("Registry");

        // Registry.get(key) -> Dynamic  — returns () if the key is absent.
        engine.register_fn("get", |r: &mut Registry, key: ImmutableString| -> Dynamic {
            r.0
                .borrow()
                .registry
                .get(key.as_str())
                .map(|v| v.clone().into())
                .unwrap_or(Dynamic::UNIT)
        });

        // Registry.set(key, value)  — stores a primitive value; () removes the key;
        // unsupported types (closures, custom objects) are silently ignored.
        engine.register_fn(
            "set",
            |r: &mut Registry, key: ImmutableString, value: Dynamic| {
                match RegistryValue::try_from(value.clone()) {
                    Ok(rv) => {
                        r.0.borrow_mut().registry.insert(key.to_string(), rv);
                    }
                    Err(()) if value.is_unit() => {
                        r.0.borrow_mut().registry.remove(key.as_str());
                    }
                    Err(()) => {} // unsupported type — silently ignore
                }
            },
        );

        // Registry.get_or(key, default) — returns the stored value when present and the
        // same Rhai type as `default`; falls back to `default` otherwise.
        engine.register_fn(
            "get_or",
            |r: &mut Registry, key: ImmutableString, default: Dynamic| -> Dynamic {
                if let Some(stored) = r.0.borrow().registry.get(key.as_str()).cloned() {
                    let candidate: Dynamic = stored.into();
                    // Only return the stored value if it matches the type of the default.
                    if candidate.type_id() == default.type_id() {
                        candidate
                    } else {
                        default
                    }
                } else {
                    default
                }
            },
        );
    }
}