continuwuity/src/api/server/make_leave.rs

use axum::extract::State;
use ruma::{
	api::federation::membership::prepare_leave_event,
	events::room::member::{MembershipState, RoomMemberEventContent},
};
use serde_json::value::to_raw_value;
use tuwunel_core::{Err, Result, matrix::pdu::PduBuilder};

use super::make_join::maybe_strip_event_id;
use crate::Ruma;

/// # `GET /_matrix/federation/v1/make_leave/{roomId}/{eventId}`
///
/// Creates a leave template.
pub(crate) async fn create_leave_event_template_route(
	State(services): State<crate::State>,
	body: Ruma<prepare_leave_event::v1::Request>,
) -> Result<prepare_leave_event::v1::Response> {
	if !services
		.rooms
		.metadata
		.exists(&body.room_id)
		.await
	{
		return Err!(Request(NotFound("Room is unknown to this server.")));
	}

	if body.user_id.server_name() != body.origin() {
		return Err!(Request(Forbidden(
			"Not allowed to leave on behalf of another server/user."
		)));
	}

	// ACL check origin
	services
		.rooms
		.event_handler
		.acl_check(body.origin(), &body.room_id)
		.await?;

	let room_version_id = services
		.rooms
		.state
		.get_room_version(&body.room_id)
		.await?;
	let state_lock = services
		.rooms
		.state
		.mutex
		.lock(&body.room_id)
		.await;

	let (_pdu, mut pdu_json) = services
		.rooms
		.timeline
		.create_hash_and_sign_event(
			PduBuilder::state(
				body.user_id.to_string(),
				&RoomMemberEventContent::new(MembershipState::Leave),
			),
			&body.user_id,
			&body.room_id,
			&state_lock,
		)
		.await?;

	drop(state_lock);

	// room v3 and above removed the "event_id" field from remote PDU format
	maybe_strip_event_id(&mut pdu_json, &room_version_id)?;

	Ok(prepare_leave_event::v1::Response {
		room_version: Some(room_version_id),
		event: to_raw_value(&pdu_json).expect("CanonicalJson can be serialized to JSON"),
	})
}