membership.rs

        .collect::<Vec<_>>();

    for room_id in all_rooms {
        let room_id = match room_id {
            Ok(room_id) => room_id,
            Err(_) => continue,
        };

        let _ = leave_room(user_id, &room_id).await;
    }

    Ok(())
}

pub async fn leave_room(user_id: &UserId, room_id: &RoomId) -> Result<()> {
    // Ask a remote server if we don't have this room
    if !services().rooms.metadata.exists(room_id)?
        && room_id.server_name() != services().globals.server_name()
    {
        if let Err(e) = remote_leave_room(user_id, room_id).await {
            warn!("Failed to leave room {} remotely: {}", user_id, e);
            // Don't tell the client about this error
        }

        let last_state = services()
            .rooms
            .state_cache
            .invite_state(user_id, room_id)?
            .map_or_else(
                || services().rooms.state_cache.left_state(user_id, room_id),
                |s| Ok(Some(s)),
            )?;

        // We always drop the invite, we can't rely on other servers
        services().rooms.state_cache.update_membership(
            room_id,
            user_id,
            MembershipState::Leave,
            user_id,
            last_state,
            true,
        )?;
    } else {
        let mutex_state = Arc::clone(
            services()
                .globals
                .roomid_mutex_state
                .write()
                .unwrap()
                .entry(room_id.to_owned())
                .or_default(),
        );
        let state_lock = mutex_state.lock().await;

        let mut event: RoomMemberEventContent = serde_json::from_str(
            services()
                .rooms
                .state_accessor
                .room_state_get(room_id, &StateEventType::RoomMember, user_id.as_str())?
                .ok_or(Error::BadRequest(
                    ErrorKind::BadState,
                    "Cannot leave a room you are not a member of.",
                ))?
                .content
                .get(),
        )
        .map_err(|_| Error::bad_database("Invalid member event in database."))?;

        event.membership = MembershipState::Leave;

        services().rooms.timeline.build_and_append_pdu(
            PduBuilder {
                event_type: RoomEventType::RoomMember,
                content: to_raw_value(&event).expect("event is valid, we just created it"),
                unsigned: None,
                state_key: Some(user_id.to_string()),
                redacts: None,
            },
            user_id,
            room_id,
            &state_lock,
        )?;
    }

    Ok(())
}

async fn remote_leave_room(user_id: &UserId, room_id: &RoomId) -> Result<()> {
    let mut make_leave_response_and_server = Err(Error::BadServerResponse(
        "No server available to assist in leaving.",
    ));

    let invite_state = services()
        .rooms
        .state_cache
        .invite_state(user_id, room_id)?
        .ok_or(Error::BadRequest(
            ErrorKind::BadState,
            "User is not invited.",
        ))?;

    let servers: HashSet<_> = invite_state
        .iter()
        .filter_map(|event| serde_json::from_str(event.json().get()).ok())
        .filter_map(|event: serde_json::Value| event.get("sender").cloned())
        .filter_map(|sender| sender.as_str().map(|s| s.to_owned()))
        .filter_map(|sender| UserId::parse(sender).ok())
        .map(|user| user.server_name().to_owned())
        .collect();

    for remote_server in servers {
        let make_leave_response = services()
            .sending
            .send_federation_request(
                &remote_server,
                federation::membership::prepare_leave_event::v1::Request { room_id, user_id },
            )
            .await;

        make_leave_response_and_server = make_leave_response.map(|r| (r, remote_server));

        if make_leave_response_and_server.is_ok() {
            break;
        }
    }

    let (make_leave_response, remote_server) = make_leave_response_and_server?;

    let room_version_id = match make_leave_response.room_version {
        Some(version)
            if services()
                .globals
                .supported_room_versions()
                .contains(&version) =>
        {
            version
        }
        _ => return Err(Error::BadServerResponse("Room version is not supported")),
    };

    let mut leave_event_stub = serde_json::from_str::<CanonicalJsonObject>(
        make_leave_response.event.get(),
    )
    .map_err(|_| Error::BadServerResponse("Invalid make_leave event json received from server."))?;

    // TODO: Is origin needed?
    leave_event_stub.insert(
        "origin".to_owned(),
        CanonicalJsonValue::String(services().globals.server_name().as_str().to_owned()),
    );
    leave_event_stub.insert(
        "origin_server_ts".to_owned(),
        CanonicalJsonValue::Integer(
            utils::millis_since_unix_epoch()
                .try_into()
                .expect("Timestamp is valid js_int value"),
        ),
    );
    // We don't leave the event id in the pdu because that's only allowed in v1 or v2 rooms
    leave_event_stub.remove("event_id");

    // In order to create a compatible ref hash (EventID) the `hashes` field needs to be present
    ruma::signatures::hash_and_sign_event(
        services().globals.server_name().as_str(),
        services().globals.keypair(),
        &mut leave_event_stub,
        &room_version_id,
    )
    .expect("event is valid, we just created it");

    // Generate event id
    let event_id = EventId::parse(format!(
        "${}",
        ruma::signatures::reference_hash(&leave_event_stub, &room_version_id)
            .expect("ruma can calculate reference hashes")
    ))
    .expect("ruma's reference hashes are valid event ids");

    // Add event_id back
    leave_event_stub.insert(
        "event_id".to_owned(),
        CanonicalJsonValue::String(event_id.as_str().to_owned()),
    );

    // It has enough fields to be called a proper event now
    let leave_event = leave_event_stub;

    services()
        .sending
        .send_federation_request(
            &remote_server,
            federation::membership::create_leave_event::v2::Request {
                room_id,
                event_id: &event_id,
                pdu: &PduEvent::convert_to_outgoing_federation_event(leave_event.clone()),
            },
        )
        .await?;

    Ok(())
}