mod remote;

use std::sync::Arc;

use conduwuit::{
	Err, Event, Result, err,
	utils::{ReadyExt, stream::TryIgnore},
};
use database::{Deserialized, Ignore, Interfix, Map};
use futures::{Stream, StreamExt, TryFutureExt};
use ruma::{
	OwnedRoomAliasId, OwnedRoomId, OwnedServerName, OwnedUserId, RoomAliasId, RoomId, RoomOrAliasId, UserId, events::{
		StateEventType,
		room::power_levels::{RoomPowerLevels, RoomPowerLevelsEventContent},
	}
};

use crate::{Dep, admin, appservice, appservice::RegistrationInfo, globals, rooms, sending};

pub struct Service {
	db: Data,
	services: Services,
}

struct Data {
	alias_userid: Arc<Map>,
	alias_roomid: Arc<Map>,
	aliasid_alias: Arc<Map>,
}

struct Services {
	admin: Dep<admin::Service>,
	appservice: Dep<appservice::Service>,
	globals: Dep<globals::Service>,
	sending: Dep<sending::Service>,
	state_accessor: Dep<rooms::state_accessor::Service>,
	state_cache: Dep<rooms::state_cache::Service>,
}

impl crate::Service for Service {
	fn build(args: crate::Args<'_>) -> Result<Arc<Self>> {
		Ok(Arc::new(Self {
			db: Data {
				alias_userid: args.db["alias_userid"].clone(),
				alias_roomid: args.db["alias_roomid"].clone(),
				aliasid_alias: args.db["aliasid_alias"].clone(),
			},
			services: Services {
				admin: args.depend::<admin::Service>("admin"),
				appservice: args.depend::<appservice::Service>("appservice"),
				globals: args.depend::<globals::Service>("globals"),
				sending: args.depend::<sending::Service>("sending"),
				state_accessor: args
					.depend::<rooms::state_accessor::Service>("rooms::state_accessor"),
				state_cache: args.depend::<rooms::state_cache::Service>("rooms::state_cache"),
			},
		}))
	}

	fn name(&self) -> &str { crate::service::make_name(std::module_path!()) }
}

impl Service {
	#[tracing::instrument(skip(self))]
	pub fn set_alias(
		&self,
		alias: &RoomAliasId,
		room_id: &RoomId,
		user_id: &UserId,
	) -> Result<()> {
		if alias == self.services.globals.admin_alias
			&& user_id != self.services.globals.server_user
		{
			return Err!(Request(Forbidden("Only the server user can set this alias")));
		}

		// Comes first as we don't want a stuck alias
		self.db
			.alias_userid
			.insert(alias.alias().as_bytes(), user_id.as_bytes());

		self.db
			.alias_roomid
			.insert(alias.alias().as_bytes(), room_id.as_bytes());

		let mut aliasid = room_id.as_bytes().to_vec();
		aliasid.push(0xFF);
		aliasid.extend_from_slice(&self.services.globals.next_count()?.to_be_bytes());
		self.db.aliasid_alias.insert(&aliasid, alias.as_bytes());

		Ok(())
	}

	#[tracing::instrument(skip(self))]
	pub async fn remove_alias(&self, alias: &RoomAliasId, user_id: &UserId) -> Result<()> {
		if alias == self.services.globals.admin_alias
			&& user_id != self.services.globals.server_user
		{
			return Err!(Request(Forbidden("Only the server user can remove this alias")));
		}

		if !self.user_can_remove_alias(alias, user_id).await? {
			return Err!(Request(Forbidden("User is not permitted to remove this alias.")));
		}

		let alias_full = alias.as_bytes().to_vec();
		let alias = alias.alias();
		let Ok(room_id) = self.db.alias_roomid.get(&alias).await else {
			return Err!(Request(NotFound("Alias does not exist or is invalid.")));
		};

		self.remove_aliasid_alias_entries(&room_id, &alias_full)
			.await;

		self.db.alias_roomid.remove(alias.as_bytes());
		self.db.alias_userid.remove(alias.as_bytes());

		Ok(())
	}

	/// Resolves the given room ID or alias, returning the resolved room ID.
	/// Unlike resolve_with_servers (the underlying call), potential resident
	/// servers are not returned
	#[inline]
	pub async fn resolve(&self, room: &RoomOrAliasId) -> Result<OwnedRoomId> {
		self.resolve_with_servers(room, None)
			.await
			.map(|(room_id, _)| room_id)
	}

	/// Resolves the given room ID or alias, returning the resolved room ID, and
	/// any servers that might be able to assist in fetching room data.
	///
	/// If the input is a room ID, this simply returns it and <servers>.
	/// If the input is an alias, this attempts to resolve it locally, then via
	/// appservices, and finally remotely if the alias is not local.
	/// If the alias is successfully resolved, the room ID and an empty list of
	/// servers is returned.
	pub async fn resolve_with_servers(
		&self,
		room: &RoomOrAliasId,
		servers: Option<Vec<OwnedServerName>>,
	) -> Result<(OwnedRoomId, Vec<OwnedServerName>)> {
		if room.is_room_id() {
			let room_id: &RoomId = room.try_into().expect("valid RoomId");
			Ok((room_id.to_owned(), servers.unwrap_or_default()))
		} else {
			let alias: &RoomAliasId = room.try_into().expect("valid RoomAliasId");
			self.resolve_alias(alias).await
		}
	}

	/// Resolves the given room alias, returning the resolved room ID and any
	/// servers that might be in the room.
	#[tracing::instrument(skip(self), name = "resolve")]
	pub async fn resolve_alias(
		&self,
		room_alias: &RoomAliasId,
	) -> Result<(OwnedRoomId, Vec<OwnedServerName>)> {
		let server_is_ours = self
			.services
			.globals
			.server_is_ours(room_alias.server_name());

		if !server_is_ours {
			// TODO: The spec advises servers may cache remote room aliases temporarily.
			// We might want to look at doing that.
			return self.remote_resolve(room_alias).await;
		}

		let room_id = match self.resolve_local_alias(room_alias).await {
			| Ok(r) => Some(r),
			| Err(_) => self.resolve_appservice_alias(room_alias).await?,
		};

		if let Some(room_id) = room_id {
			let servers: Vec<OwnedServerName> = self
				.services
				.state_cache
				.room_servers(&room_id)
				.collect()
				.await;
			return Ok((room_id, servers));
		}

		Err!(Request(NotFound("Alias does not exist.")))
	}

	#[tracing::instrument(skip(self), level = "debug")]
	pub async fn resolve_local_alias(&self, alias: &RoomAliasId) -> Result<OwnedRoomId> {
		self.db.alias_roomid.get(alias.alias()).await.deserialized()
	}

	#[tracing::instrument(skip(self), level = "debug")]
	pub fn local_aliases_for_room<'a>(
		&'a self,
		room_id: &'a RoomId,
	) -> impl Stream<Item = OwnedRoomAliasId> + Send + 'a {
		let prefix = (room_id, Interfix);
		self.db
			.aliasid_alias
			.stream_prefix(&prefix)
			.ignore_err()
			.map(|(_, alias): (Ignore, OwnedRoomAliasId)| alias)
	}

	#[tracing::instrument(skip(self), level = "debug")]
	pub fn all_local_aliases(&self) -> impl Stream<Item = (OwnedRoomId, &str)> + Send + '_ {
		self.db
			.alias_roomid
			.stream()
			.ignore_err()
			.map(|(alias_localpart, room_id): (&str, OwnedRoomId)| (room_id, alias_localpart))
	}

	async fn user_can_remove_alias(&self, alias: &RoomAliasId, user_id: &UserId) -> Result<bool> {
		let room_id = self
			.resolve_local_alias(alias)
			.await
			.map_err(|_| err!(Request(NotFound("Alias not found."))))?;

		let server_user = &self.services.globals.server_user;

		// The creator of an alias can remove it
		if self
			.who_created_alias(alias).await
			.is_ok_and(|user| user == user_id)
			// Server admins can remove any local alias
			|| self.services.admin.user_is_admin(user_id).await
			// Always allow the server service account to remove the alias, since there may not be an admin room
			|| server_user == user_id
		{
			return Ok(true);
		}

		// Checking whether the user is able to change canonical aliases of the room
		let can_change_canonical_alias = self
			.services
			.state_accessor
			.get_room_power_levels(&room_id)
			.await
			.user_can_send_state(user_id, StateEventType::RoomCanonicalAlias);

		Ok(can_change_canonical_alias)
	}

	async fn who_created_alias(&self, alias: &RoomAliasId) -> Result<OwnedUserId> {
		self.db.alias_userid.get(alias.alias()).await.deserialized()
	}

	async fn remove_aliasid_alias_entries(&self, room_id: &[u8], alias_full: &[u8]) {
		let prefix = (room_id, Interfix);
		let keys: Vec<Vec<u8>> = self
			.db
			.aliasid_alias
			.stream_prefix_raw(&prefix)
			.ignore_err()
			.ready_filter_map(|(key, value)| (value == alias_full).then_some(key.to_vec()))
			.collect()
			.await;

		for key in keys {
			self.db.aliasid_alias.remove(&key);
		}
	}

	async fn resolve_appservice_alias(
		&self,
		room_alias: &RoomAliasId,
	) -> Result<Option<OwnedRoomId>> {
		use ruma::api::appservice::query::query_room_alias;

		for appservice in self.services.appservice.read().await.values() {
			if appservice.aliases.is_match(room_alias.as_str())
				&& matches!(
					self.services
						.sending
						.send_appservice_request(
							appservice.registration.clone(),
							query_room_alias::v1::Request::new(room_alias.to_owned()),
						)
						.await,
					Ok(Some(_opt_result))
				) {
				return self
					.resolve_local_alias(room_alias)
					.await
					.map_err(|_| err!(Request(NotFound("Room does not exist."))))
					.map(Some);
			}
		}

		Ok(None)
	}

	pub async fn appservice_checks(
		&self,
		room_alias: &RoomAliasId,
		appservice_info: &Option<RegistrationInfo>,
	) -> Result<()> {
		if !self
			.services
			.globals
			.server_is_ours(room_alias.server_name())
		{
			return Err!(Request(InvalidParam("Alias is from another server.")));
		}

		if let Some(info) = appservice_info {
			if !info.aliases.is_match(room_alias.as_str()) {
				return Err!(Request(Exclusive("Room alias is not in namespace.")));
			}
		} else if self
			.services
			.appservice
			.is_exclusive_alias(room_alias)
			.await
		{
			return Err!(Request(Exclusive("Room alias reserved by appservice.")));
		}

		Ok(())
	}
}