use std::collections::BTreeMap;

use axum::extract::State;
use futures::StreamExt;
use ruma::{
	api::{
		client::{error::ErrorKind, to_device::send_event_to_device},
		federation::{self, transactions::edu::DirectDeviceContent},
	},
	to_device::DeviceIdOrAllDevices,
};
use tuwunel_core::{Error, Result};
use tuwunel_service::sending::EduBuf;

use crate::Ruma;

/// # `PUT /_matrix/client/r0/sendToDevice/{eventType}/{txnId}`
///
/// Send a to-device event to a set of client devices.
pub(crate) async fn send_event_to_device_route(
	State(services): State<crate::State>,
	body: Ruma<send_event_to_device::v3::Request>,
) -> Result<send_event_to_device::v3::Response> {
	let sender_user = body.sender_user();
	let sender_device = body.sender_device.as_deref();

	// Check if this is a new transaction id
	if services
		.transaction_ids
		.existing_txnid(sender_user, sender_device, &body.txn_id)
		.await
		.is_ok()
	{
		return Ok(send_event_to_device::v3::Response {});
	}

	for (target_user_id, map) in &body.messages {
		for (target_device_id_maybe, event) in map {
			if !services.globals.user_is_local(target_user_id) {
				let mut map = BTreeMap::new();
				map.insert(target_device_id_maybe.clone(), event.clone());
				let mut messages = BTreeMap::new();
				messages.insert(target_user_id.clone(), map);

				let mut buf = EduBuf::new();
				serde_json::to_writer(
					&mut buf,
					&federation::transactions::edu::Edu::DirectToDevice(DirectDeviceContent {
						sender: sender_user.to_owned(),
						ev_type: body.event_type.clone(),
						message_id: services.globals.next_count().to_string().into(),
						messages,
					}),
				)
				.expect("DirectToDevice EDU can be serialized");

				services
					.sending
					.send_edu_server(target_user_id.server_name(), buf)?;

				continue;
			}

			let event_type = &body.event_type.to_string();

			let event = event
				.deserialize_as()
				.map_err(|_| Error::BadRequest(ErrorKind::InvalidParam, "Event is invalid"))?;

			match target_device_id_maybe {
				| DeviceIdOrAllDevices::DeviceId(target_device_id) => {
					services
						.users
						.add_to_device_event(
							sender_user,
							target_user_id,
							target_device_id,
							event_type,
							event,
						)
						.await;
				},

				| DeviceIdOrAllDevices::AllDevices => {
					let (event_type, event) = (&event_type, &event);
					services
						.users
						.all_device_ids(target_user_id)
						.for_each(|target_device_id| {
							services.users.add_to_device_event(
								sender_user,
								target_user_id,
								target_device_id,
								event_type,
								event.clone(),
							)
						})
						.await;
				},
			}
		}
	}

	// Save transaction id with empty data
	services
		.transaction_ids
		.add_txnid(sender_user, sender_device, &body.txn_id, &[]);

	Ok(send_event_to_device::v3::Response {})
}
