mod data;

use std::{
	collections::HashMap,
	fmt::Write,
	sync::{Arc, Mutex as StdMutex, Mutex},
};

use conduit::{
	err, error,
	pdu::PduBuilder,
	utils::{math::usize_from_f64, ReadyExt},
	Err, Error, Event, PduEvent, Result,
};
use futures::StreamExt;
use lru_cache::LruCache;
use ruma::{
	events::{
		room::{
			avatar::RoomAvatarEventContent,
			canonical_alias::RoomCanonicalAliasEventContent,
			create::RoomCreateEventContent,
			encryption::RoomEncryptionEventContent,
			guest_access::{GuestAccess, RoomGuestAccessEventContent},
			history_visibility::{HistoryVisibility, RoomHistoryVisibilityEventContent},
			join_rules::{AllowRule, JoinRule, RoomJoinRulesEventContent, RoomMembership},
			member::{MembershipState, RoomMemberEventContent},
			name::RoomNameEventContent,
			power_levels::{RoomPowerLevels, RoomPowerLevelsEventContent},
			topic::RoomTopicEventContent,
		},
		StateEventType, TimelineEventType,
	},
	room::RoomType,
	space::SpaceRoomJoinRule,
	EventEncryptionAlgorithm, EventId, JsOption, OwnedRoomAliasId, OwnedRoomId, OwnedServerName, OwnedUserId, RoomId,
	ServerName, UserId,
};
use serde::Deserialize;

use self::data::Data;
use crate::{
	rooms,
	rooms::{
		short::{ShortEventId, ShortStateHash, ShortStateKey},
		state::RoomMutexGuard,
	},
	Dep,
};

pub struct Service {
	services: Services,
	db: Data,
	pub server_visibility_cache: Mutex<LruCache<(OwnedServerName, ShortStateHash), bool>>,
	pub user_visibility_cache: Mutex<LruCache<(OwnedUserId, ShortStateHash), bool>>,
}

struct Services {
	state_cache: Dep<rooms::state_cache::Service>,
	timeline: Dep<rooms::timeline::Service>,
}

impl crate::Service for Service {
	fn build(args: crate::Args<'_>) -> Result<Arc<Self>> {
		let config = &args.server.config;
		let server_visibility_cache_capacity =
			f64::from(config.server_visibility_cache_capacity) * config.cache_capacity_modifier;
		let user_visibility_cache_capacity =
			f64::from(config.user_visibility_cache_capacity) * config.cache_capacity_modifier;

		Ok(Arc::new(Self {
			services: Services {
				state_cache: args.depend::<rooms::state_cache::Service>("rooms::state_cache"),
				timeline: args.depend::<rooms::timeline::Service>("rooms::timeline"),
			},
			db: Data::new(&args),
			server_visibility_cache: StdMutex::new(LruCache::new(usize_from_f64(server_visibility_cache_capacity)?)),
			user_visibility_cache: StdMutex::new(LruCache::new(usize_from_f64(user_visibility_cache_capacity)?)),
		}))
	}

	fn memory_usage(&self, out: &mut dyn Write) -> Result<()> {
		let server_visibility_cache = self.server_visibility_cache.lock().expect("locked").len();
		writeln!(out, "server_visibility_cache: {server_visibility_cache}")?;

		let user_visibility_cache = self.user_visibility_cache.lock().expect("locked").len();
		writeln!(out, "user_visibility_cache: {user_visibility_cache}")?;

		Ok(())
	}

	fn clear_cache(&self) {
		self.server_visibility_cache.lock().expect("locked").clear();
		self.user_visibility_cache.lock().expect("locked").clear();
	}

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

impl Service {
	/// Builds a StateMap by iterating over all keys that start
	/// with state_hash, this gives the full state for the given state_hash.
	#[tracing::instrument(skip(self), level = "debug")]
	pub async fn state_full_ids(&self, shortstatehash: ShortStateHash) -> Result<HashMap<u64, Arc<EventId>>> {
		self.db.state_full_ids(shortstatehash).await
	}

	#[inline]
	pub async fn state_full_shortids(
		&self, shortstatehash: ShortStateHash,
	) -> Result<Vec<(ShortStateKey, ShortEventId)>> {
		self.db.state_full_shortids(shortstatehash).await
	}

	pub async fn state_full(
		&self, shortstatehash: ShortStateHash,
	) -> Result<HashMap<(StateEventType, String), Arc<PduEvent>>> {
		self.db.state_full(shortstatehash).await
	}

	/// Returns a single PDU from `room_id` with key (`event_type`,
	/// `state_key`).
	#[tracing::instrument(skip(self), level = "debug")]
	pub async fn state_get_id(
		&self, shortstatehash: ShortStateHash, event_type: &StateEventType, state_key: &str,
	) -> Result<Arc<EventId>> {
		self.db
			.state_get_id(shortstatehash, event_type, state_key)
			.await
	}

	/// Returns a single PDU from `room_id` with key (`event_type`,
	/// `state_key`).
	#[inline]
	pub async fn state_get(
		&self, shortstatehash: ShortStateHash, event_type: &StateEventType, state_key: &str,
	) -> Result<Arc<PduEvent>> {
		self.db
			.state_get(shortstatehash, event_type, state_key)
			.await
	}

	/// Returns a single PDU from `room_id` with key (`event_type`,`state_key`).
	pub async fn state_get_content<T>(
		&self, shortstatehash: ShortStateHash, event_type: &StateEventType, state_key: &str,
	) -> Result<T>
	where
		T: for<'de> Deserialize<'de> + Send,
	{
		self.state_get(shortstatehash, event_type, state_key)
			.await
			.and_then(|event| event.get_content())
	}

	/// Get membership for given user in state
	async fn user_membership(&self, shortstatehash: ShortStateHash, user_id: &UserId) -> MembershipState {
		self.state_get_content(shortstatehash, &StateEventType::RoomMember, user_id.as_str())
			.await
			.map_or(MembershipState::Leave, |c: RoomMemberEventContent| c.membership)
	}

	/// The user was a joined member at this state (potentially in the past)
	#[inline]
	async fn user_was_joined(&self, shortstatehash: ShortStateHash, user_id: &UserId) -> bool {
		self.user_membership(shortstatehash, user_id).await == MembershipState::Join
	}

	/// The user was an invited or joined room member at this state (potentially
	/// in the past)
	#[inline]
	async fn user_was_invited(&self, shortstatehash: ShortStateHash, user_id: &UserId) -> bool {
		let s = self.user_membership(shortstatehash, user_id).await;
		s == MembershipState::Join || s == MembershipState::Invite
	}

	/// Whether a server is allowed to see an event through federation, based on
	/// the room's history_visibility at that event's state.
	#[tracing::instrument(skip(self, origin, room_id, event_id))]
	pub async fn server_can_see_event(&self, origin: &ServerName, room_id: &RoomId, event_id: &EventId) -> bool {
		let Ok(shortstatehash) = self.pdu_shortstatehash(event_id).await else {
			return true;
		};

		if let Some(visibility) = self
			.server_visibility_cache
			.lock()
			.expect("locked")
			.get_mut(&(origin.to_owned(), shortstatehash))
		{
			return *visibility;
		}

		let history_visibility = self
			.state_get_content(shortstatehash, &StateEventType::RoomHistoryVisibility, "")
			.await
			.map_or(HistoryVisibility::Shared, |c: RoomHistoryVisibilityEventContent| {
				c.history_visibility
			});

		let current_server_members = self
			.services
			.state_cache
			.room_members(room_id)
			.ready_filter(|member| member.server_name() == origin);

		let visibility = match history_visibility {
			HistoryVisibility::WorldReadable | HistoryVisibility::Shared => true,
			HistoryVisibility::Invited => {
				// Allow if any member on requesting server was AT LEAST invited, else deny
				current_server_members
					.any(|member| self.user_was_invited(shortstatehash, member))
					.await
			},
			HistoryVisibility::Joined => {
				// Allow if any member on requested server was joined, else deny
				current_server_members
					.any(|member| self.user_was_joined(shortstatehash, member))
					.await
			},
			_ => {
				error!("Unknown history visibility {history_visibility}");
				false
			},
		};

		self.server_visibility_cache
			.lock()
			.expect("locked")
			.insert((origin.to_owned(), shortstatehash), visibility);

		visibility
	}

	/// Whether a user is allowed to see an event, based on
	/// the room's history_visibility at that event's state.
	#[tracing::instrument(skip(self, user_id, room_id, event_id))]
	pub async fn user_can_see_event(&self, user_id: &UserId, room_id: &RoomId, event_id: &EventId) -> bool {
		let Ok(shortstatehash) = self.pdu_shortstatehash(event_id).await else {
			return true;
		};

		if let Some(visibility) = self
			.user_visibility_cache
			.lock()
			.expect("locked")
			.get_mut(&(user_id.to_owned(), shortstatehash))
		{
			return *visibility;
		}

		let currently_member = self.services.state_cache.is_joined(user_id, room_id).await;

		let history_visibility = self
			.state_get_content(shortstatehash, &StateEventType::RoomHistoryVisibility, "")
			.await
			.map_or(HistoryVisibility::Shared, |c: RoomHistoryVisibilityEventContent| {
				c.history_visibility
			});

		let visibility = match history_visibility {
			HistoryVisibility::WorldReadable => true,
			HistoryVisibility::Shared => currently_member,
			HistoryVisibility::Invited => {
				// Allow if any member on requesting server was AT LEAST invited, else deny
				self.user_was_invited(shortstatehash, user_id).await
			},
			HistoryVisibility::Joined => {
				// Allow if any member on requested server was joined, else deny
				self.user_was_joined(shortstatehash, user_id).await
			},
			_ => {
				error!("Unknown history visibility {history_visibility}");
				false
			},
		};

		self.user_visibility_cache
			.lock()
			.expect("locked")
			.insert((user_id.to_owned(), shortstatehash), visibility);

		visibility
	}

	/// Whether a user is allowed to see an event, based on
	/// the room's history_visibility at that event's state.
	#[tracing::instrument(skip(self, user_id, room_id))]
	pub async fn user_can_see_state_events(&self, user_id: &UserId, room_id: &RoomId) -> bool {
		if self.services.state_cache.is_joined(user_id, room_id).await {
			return true;
		}

		let history_visibility = self
			.room_state_get_content(room_id, &StateEventType::RoomHistoryVisibility, "")
			.await
			.map_or(HistoryVisibility::Shared, |c: RoomHistoryVisibilityEventContent| {
				c.history_visibility
			});

		match history_visibility {
			HistoryVisibility::Invited => self.services.state_cache.is_invited(user_id, room_id).await,
			HistoryVisibility::WorldReadable => true,
			_ => false,
		}
	}

	/// Returns the state hash for this pdu.
	pub async fn pdu_shortstatehash(&self, event_id: &EventId) -> Result<ShortStateHash> {
		self.db.pdu_shortstatehash(event_id).await
	}

	/// Returns the full room state.
	#[tracing::instrument(skip(self), level = "debug")]
	pub async fn room_state_full(&self, room_id: &RoomId) -> Result<HashMap<(StateEventType, String), Arc<PduEvent>>> {
		self.db.room_state_full(room_id).await
	}

	/// Returns the full room state pdus
	#[tracing::instrument(skip(self), level = "debug")]
	pub async fn room_state_full_pdus(&self, room_id: &RoomId) -> Result<Vec<Arc<PduEvent>>> {
		self.db.room_state_full_pdus(room_id).await
	}

	/// Returns a single PDU from `room_id` with key (`event_type`,
	/// `state_key`).
	#[tracing::instrument(skip(self), level = "debug")]
	pub async fn room_state_get_id(
		&self, room_id: &RoomId, event_type: &StateEventType, state_key: &str,
	) -> Result<Arc<EventId>> {
		self.db
			.room_state_get_id(room_id, event_type, state_key)
			.await
	}

	/// Returns a single PDU from `room_id` with key (`event_type`,
	/// `state_key`).
	#[tracing::instrument(skip(self), level = "debug")]
	pub async fn room_state_get(
		&self, room_id: &RoomId, event_type: &StateEventType, state_key: &str,
	) -> Result<Arc<PduEvent>> {
		self.db.room_state_get(room_id, event_type, state_key).await
	}

	/// Returns a single PDU from `room_id` with key (`event_type`,`state_key`).
	pub async fn room_state_get_content<T>(
		&self, room_id: &RoomId, event_type: &StateEventType, state_key: &str,
	) -> Result<T>
	where
		T: for<'de> Deserialize<'de> + Send,
	{
		self.room_state_get(room_id, event_type, state_key)
			.await
			.and_then(|event| event.get_content())
	}

	pub async fn get_name(&self, room_id: &RoomId) -> Result<String> {
		self.room_state_get_content(room_id, &StateEventType::RoomName, "")
			.await
			.map(|c: RoomNameEventContent| c.name)
	}

	pub async fn get_avatar(&self, room_id: &RoomId) -> JsOption<RoomAvatarEventContent> {
		let content = self
			.room_state_get_content(room_id, &StateEventType::RoomAvatar, "")
			.await
			.ok();

		JsOption::from_option(content)
	}

	pub async fn get_member(&self, room_id: &RoomId, user_id: &UserId) -> Result<RoomMemberEventContent> {
		self.room_state_get_content(room_id, &StateEventType::RoomMember, user_id.as_str())
			.await
	}

	pub async fn user_can_invite(
		&self, room_id: &RoomId, sender: &UserId, target_user: &UserId, state_lock: &RoomMutexGuard,
	) -> bool {
		self.services
			.timeline
			.create_hash_and_sign_event(
				PduBuilder::state(target_user.into(), &RoomMemberEventContent::new(MembershipState::Invite)),
				sender,
				room_id,
				state_lock,
			)
			.await
			.is_ok()
	}

	/// Checks if guests are able to view room content without joining
	pub async fn is_world_readable(&self, room_id: &RoomId) -> bool {
		self.room_state_get_content(room_id, &StateEventType::RoomHistoryVisibility, "")
			.await
			.map(|c: RoomHistoryVisibilityEventContent| c.history_visibility == HistoryVisibility::WorldReadable)
			.unwrap_or(false)
	}

	/// Checks if guests are able to join a given room
	pub async fn guest_can_join(&self, room_id: &RoomId) -> bool {
		self.room_state_get_content(room_id, &StateEventType::RoomGuestAccess, "")
			.await
			.map(|c: RoomGuestAccessEventContent| c.guest_access == GuestAccess::CanJoin)
			.unwrap_or(false)
	}

	/// Gets the primary alias from canonical alias event
	pub async fn get_canonical_alias(&self, room_id: &RoomId) -> Result<OwnedRoomAliasId> {
		self.room_state_get_content(room_id, &StateEventType::RoomCanonicalAlias, "")
			.await
			.and_then(|c: RoomCanonicalAliasEventContent| {
				c.alias
					.ok_or_else(|| err!(Request(NotFound("No alias found in event content."))))
			})
	}

	/// Gets the room topic
	pub async fn get_room_topic(&self, room_id: &RoomId) -> Result<String> {
		self.room_state_get_content(room_id, &StateEventType::RoomTopic, "")
			.await
			.map(|c: RoomTopicEventContent| c.topic)
	}

	/// Checks if a given user can redact a given event
	///
	/// If federation is true, it allows redaction events from any user of the
	/// same server as the original event sender
	pub async fn user_can_redact(
		&self, redacts: &EventId, sender: &UserId, room_id: &RoomId, federation: bool,
	) -> Result<bool> {
		let redacting_event = self.services.timeline.get_pdu(redacts).await;

		if redacting_event
			.as_ref()
			.is_ok_and(|event| event.event_type() == &TimelineEventType::RoomCreate)
		{
			return Err!(Request(Forbidden("Redacting m.room.create is not safe, forbidding.")));
		}

		if let Ok(pl_event_content) = self
			.room_state_get_content::<RoomPowerLevelsEventContent>(room_id, &StateEventType::RoomPowerLevels, "")
			.await
		{
			let pl_event: RoomPowerLevels = pl_event_content.into();
			Ok(pl_event.user_can_redact_event_of_other(sender)
				|| pl_event.user_can_redact_own_event(sender)
					&& if let Ok(redacting_event) = redacting_event {
						if federation {
							redacting_event.sender.server_name() == sender.server_name()
						} else {
							redacting_event.sender == sender
						}
					} else {
						false
					})
		} else {
			// Falling back on m.room.create to judge power level
			if let Ok(room_create) = self
				.room_state_get(room_id, &StateEventType::RoomCreate, "")
				.await
			{
				Ok(room_create.sender == sender
					|| redacting_event
						.as_ref()
						.is_ok_and(|redacting_event| redacting_event.sender == sender))
			} else {
				Err(Error::bad_database(
					"No m.room.power_levels or m.room.create events in database for room",
				))
			}
		}
	}

	/// Returns the join rule (`SpaceRoomJoinRule`) for a given room
	pub async fn get_join_rule(&self, room_id: &RoomId) -> Result<(SpaceRoomJoinRule, Vec<OwnedRoomId>)> {
		self.room_state_get_content(room_id, &StateEventType::RoomJoinRules, "")
			.await
			.map(|c: RoomJoinRulesEventContent| (c.join_rule.clone().into(), self.allowed_room_ids(c.join_rule)))
			.or_else(|_| Ok((SpaceRoomJoinRule::Invite, vec![])))
	}

	/// Returns an empty vec if not a restricted room
	pub fn allowed_room_ids(&self, join_rule: JoinRule) -> Vec<OwnedRoomId> {
		let mut room_ids = Vec::with_capacity(1);
		if let JoinRule::Restricted(r) | JoinRule::KnockRestricted(r) = join_rule {
			for rule in r.allow {
				if let AllowRule::RoomMembership(RoomMembership {
					room_id: membership,
				}) = rule
				{
					room_ids.push(membership.clone());
				}
			}
		}
		room_ids
	}

	pub async fn get_room_type(&self, room_id: &RoomId) -> Result<RoomType> {
		self.room_state_get_content(room_id, &StateEventType::RoomCreate, "")
			.await
			.and_then(|content: RoomCreateEventContent| {
				content
					.room_type
					.ok_or_else(|| err!(Request(NotFound("No type found in event content"))))
			})
	}

	/// Gets the room's encryption algorithm if `m.room.encryption` state event
	/// is found
	pub async fn get_room_encryption(&self, room_id: &RoomId) -> Result<EventEncryptionAlgorithm> {
		self.room_state_get_content(room_id, &StateEventType::RoomEncryption, "")
			.await
			.map(|content: RoomEncryptionEventContent| content.algorithm)
	}

	pub async fn is_encrypted_room(&self, room_id: &RoomId) -> bool {
		self.room_state_get(room_id, &StateEventType::RoomEncryption, "")
			.await
			.is_ok()
	}
}