use std::sync::Arc;
use std::collections::HashSet;
use crate::Result;
use ruma::{EventId, RoomId};
use tokio::sync::MutexGuard;

pub trait Data: Send + Sync {
    /// Returns the last state hash key added to the db for the given room.
    fn get_room_shortstatehash(&self, room_id: &RoomId) -> Result<Option<u64>>;

    /// Update the current state of the room.
    fn set_room_state(&self, room_id: &RoomId, new_shortstatehash: u64,
        _mutex_lock: &MutexGuard<'_, ()>, // Take mutex guard to make sure users get the room state mutex
    ) -> Result<()>;

    /// Associates a state with an event.
    fn set_event_state(&self, shorteventid: u64, shortstatehash: u64) -> Result<()>;

    /// Returns all events we would send as the prev_events of the next event.
    fn get_forward_extremities(&self, room_id: &RoomId) -> Result<HashSet<Arc<EventId>>>;

    /// Replace the forward extremities of the room.
    fn set_forward_extremities<'a>(&self,
        room_id: &RoomId,
        event_ids: &mut dyn Iterator<Item = &'a EventId>,
        _mutex_lock: &MutexGuard<'_, ()>, // Take mutex guard to make sure users get the room state mutex
    ) -> Result<()>;
}