use std::any::Any;
use std::collections::HashMap;

#[derive(Default)]
pub struct EventBus<'a> {
    pub events: HashMap<&'a str, (&'a str, Box<dyn Fn(&mut dyn Any)>)>
}

unsafe impl<'a> Sync for EventBus<'a> {}

unsafe impl<'a> Send for EventBus<'a> {}

impl<'a> EventBus<'a> {
    pub fn subscribe<H, T>(&mut self, subscription_id: &'a str, kind: &'a str, handle: H)
        where
            H: Fn(&mut T) + 'static,
            T: Any,
    {
        let handle = Box::new(move |erased_data: &mut dyn Any| {
            let actual_data = erased_data
                .downcast_mut()
                .expect("Woops, I broke my invariant");
            handle(actual_data);
        });

        self.events.insert(subscription_id, (kind, handle));
    }

    pub fn unsubscribe(&mut self, subscription_id: &str) -> Option<(&str, Box<dyn Fn(&mut dyn Any)>)> {
        self.events.remove(subscription_id)
    }

    pub fn unsubscribe_every(&mut self, kind: &str) {
        self.events.retain(|k, _| { k == &kind });
    }

    pub fn publish(&self, kind: &str, data: &mut dyn Any) {
        for (lookup_event, lookup_handler) in self.events.values() {
            if lookup_event == &kind {
                lookup_handler(data);
            }
        }
    }

    pub fn publish_single(&self, subscription_id: &str, data: &mut dyn Any) -> bool {
        let res = self.events.get(subscription_id);

        if res.is_none() {
            return false;
        }

        let event_tuple = res.unwrap();

        event_tuple.1(data);

        return true;
    }
}

#[cfg(test)]
mod test {
    use super::*;

    struct TestEventData<'a> {
        cancelled: bool,
        message: &'a str,
    }

    #[test]
    fn test_subscribe() {
        let mut bus = EventBus::default();

        bus.subscribe("test_sub", "test", |d: &mut TestEventData| {
            if !d.cancelled {
                println!("Message from the spaceport: {}", d.message);
            }
        });

        bus.publish("test", &mut TestEventData { cancelled: false, message: "no enemy ships detected!" });
    }
}