mod data;
use std::{
	collections::HashMap,
	sync::{Arc, Mutex},
};

pub(crate) use data::Data;
use lru_cache::LruCache;
use ruma::{
	events::{
		room::{
			avatar::RoomAvatarEventContent,
			history_visibility::{HistoryVisibility, RoomHistoryVisibilityEventContent},
			member::{MembershipState, RoomMemberEventContent},
			name::RoomNameEventContent,
		},
		StateEventType,
	},
	EventId, OwnedServerName, OwnedUserId, RoomId, ServerName, UserId,
};
use serde_json::value::to_raw_value;
use tokio::sync::MutexGuard;
use tracing::{error, warn};

use crate::{service::pdu::PduBuilder, services, Error, PduEvent, Result};

pub(crate) struct Service {
	pub(crate) db: &'static dyn Data,
	pub(crate) server_visibility_cache: Mutex<LruCache<(OwnedServerName, u64), bool>>,
	pub(crate) user_visibility_cache: Mutex<LruCache<(OwnedUserId, u64), bool>>,
}

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))]
	pub(crate) async fn state_full_ids(&self, shortstatehash: u64) -> Result<HashMap<u64, Arc<EventId>>> {
		self.db.state_full_ids(shortstatehash).await
	}

	pub(crate) async fn state_full(
		&self, shortstatehash: u64,
	) -> 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))]
	pub(crate) fn state_get_id(
		&self, shortstatehash: u64, event_type: &StateEventType, state_key: &str,
	) -> Result<Option<Arc<EventId>>> {
		self.db.state_get_id(shortstatehash, event_type, state_key)
	}

	/// Returns a single PDU from `room_id` with key (`event_type`,
	/// `state_key`).
	pub(crate) fn state_get(
		&self, shortstatehash: u64, event_type: &StateEventType, state_key: &str,
	) -> Result<Option<Arc<PduEvent>>> {
		self.db.state_get(shortstatehash, event_type, state_key)
	}

	/// Get membership for given user in state
	fn user_membership(&self, shortstatehash: u64, user_id: &UserId) -> Result<MembershipState> {
		self.state_get(shortstatehash, &StateEventType::RoomMember, user_id.as_str())?
			.map_or(Ok(MembershipState::Leave), |s| {
				serde_json::from_str(s.content.get())
					.map(|c: RoomMemberEventContent| c.membership)
					.map_err(|_| Error::bad_database("Invalid room membership event in database."))
			})
	}

	/// The user was a joined member at this state (potentially in the past)
	fn user_was_joined(&self, shortstatehash: u64, user_id: &UserId) -> bool {
		self.user_membership(shortstatehash, user_id)
			.is_ok_and(|s| s == MembershipState::Join)
		// Return sensible default, i.e.
		// false
	}

	/// The user was an invited or joined room member at this state (potentially
	/// in the past)
	fn user_was_invited(&self, shortstatehash: u64, user_id: &UserId) -> bool {
		self.user_membership(shortstatehash, user_id)
			.is_ok_and(|s| s == MembershipState::Join || s == MembershipState::Invite)
		// Return sensible default, i.e. false
	}

	/// 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(crate) fn server_can_see_event(
		&self, origin: &ServerName, room_id: &RoomId, event_id: &EventId,
	) -> Result<bool> {
		let Some(shortstatehash) = self.pdu_shortstatehash(event_id)? else {
			return Ok(true);
		};

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

		let history_visibility = self
			.state_get(shortstatehash, &StateEventType::RoomHistoryVisibility, "")?
			.map_or(Ok(HistoryVisibility::Shared), |s| {
				serde_json::from_str(s.content.get())
					.map(|c: RoomHistoryVisibilityEventContent| c.history_visibility)
					.map_err(|e| {
						error!(
							"Invalid history visibility event in database for room {room_id}, assuming is \"shared\": \
							 {e}"
						);
						Error::bad_database("Invalid history visibility event in database.")
					})
			})
			.unwrap_or(HistoryVisibility::Shared);

		let mut current_server_members = services()
			.rooms
			.state_cache
			.room_members(room_id)
			.filter_map(Result::ok)
			.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))
			},
			HistoryVisibility::Joined => {
				// Allow if any member on requested server was joined, else deny
				current_server_members.any(|member| self.user_was_joined(shortstatehash, &member))
			},
			_ => {
				error!("Unknown history visibility {history_visibility}");
				false
			},
		};

		self.server_visibility_cache
			.lock()
			.unwrap()
			.insert((origin.to_owned(), shortstatehash), visibility);

		Ok(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(crate) fn user_can_see_event(&self, user_id: &UserId, room_id: &RoomId, event_id: &EventId) -> Result<bool> {
		let Some(shortstatehash) = self.pdu_shortstatehash(event_id)? else {
			return Ok(true);
		};

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

		let currently_member = services().rooms.state_cache.is_joined(user_id, room_id)?;

		let history_visibility = self
			.state_get(shortstatehash, &StateEventType::RoomHistoryVisibility, "")?
			.map_or(Ok(HistoryVisibility::Shared), |s| {
				serde_json::from_str(s.content.get())
					.map(|c: RoomHistoryVisibilityEventContent| c.history_visibility)
					.map_err(|e| {
						error!(
							"Invalid history visibility event in database for room {room_id}, assuming is \"shared\": \
							 {e}"
						);
						Error::bad_database("Invalid history visibility event in database.")
					})
			})
			.unwrap_or(HistoryVisibility::Shared);

		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)
			},
			HistoryVisibility::Joined => {
				// Allow if any member on requested server was joined, else deny
				self.user_was_joined(shortstatehash, user_id)
			},
			_ => {
				error!("Unknown history visibility {history_visibility}");
				false
			},
		};

		self.user_visibility_cache
			.lock()
			.unwrap()
			.insert((user_id.to_owned(), shortstatehash), visibility);

		Ok(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(crate) fn user_can_see_state_events(&self, user_id: &UserId, room_id: &RoomId) -> Result<bool> {
		let currently_member = services().rooms.state_cache.is_joined(user_id, room_id)?;

		let history_visibility = self
			.room_state_get(room_id, &StateEventType::RoomHistoryVisibility, "")?
			.map_or(Ok(HistoryVisibility::Shared), |s| {
				serde_json::from_str(s.content.get())
					.map(|c: RoomHistoryVisibilityEventContent| c.history_visibility)
					.map_err(|e| {
						error!(
							"Invalid history visibility event in database for room {room_id}, assuming is \"shared\": \
							 {e}"
						);
						Error::bad_database("Invalid history visibility event in database.")
					})
			})
			.unwrap_or(HistoryVisibility::Shared);

		Ok(currently_member || history_visibility == HistoryVisibility::WorldReadable)
	}

	/// Returns the state hash for this pdu.
	pub(crate) fn pdu_shortstatehash(&self, event_id: &EventId) -> Result<Option<u64>> {
		self.db.pdu_shortstatehash(event_id)
	}

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

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

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

	pub(crate) fn get_name(&self, room_id: &RoomId) -> Result<Option<String>> {
		services()
			.rooms
			.state_accessor
			.room_state_get(room_id, &StateEventType::RoomName, "")?
			.map_or(Ok(None), |s| {
				Ok(serde_json::from_str(s.content.get()).map_or_else(|_| None, |c: RoomNameEventContent| Some(c.name)))
			})
	}

	pub(crate) fn get_avatar(&self, room_id: &RoomId) -> Result<ruma::JsOption<RoomAvatarEventContent>> {
		services()
			.rooms
			.state_accessor
			.room_state_get(room_id, &StateEventType::RoomAvatar, "")?
			.map_or(Ok(ruma::JsOption::Undefined), |s| {
				serde_json::from_str(s.content.get())
					.map_err(|_| Error::bad_database("Invalid room avatar event in database."))
			})
	}

	pub(crate) fn get_member(&self, room_id: &RoomId, user_id: &UserId) -> Result<Option<RoomMemberEventContent>> {
		services()
			.rooms
			.state_accessor
			.room_state_get(room_id, &StateEventType::RoomMember, user_id.as_str())?
			.map_or(Ok(None), |s| {
				serde_json::from_str(s.content.get())
					.map_err(|_| Error::bad_database("Invalid room member event in database."))
			})
	}

	pub(crate) async fn user_can_invite(
		&self, room_id: &RoomId, sender: &UserId, target_user: &UserId, state_lock: &MutexGuard<'_, ()>,
	) -> Result<bool> {
		let content = to_raw_value(&RoomMemberEventContent::new(MembershipState::Invite))
			.expect("Event content always serializes");

		let new_event = PduBuilder {
			event_type: ruma::events::TimelineEventType::RoomMember,
			content,
			unsigned: None,
			state_key: Some(target_user.into()),
			redacts: None,
		};

		Ok(services()
			.rooms
			.timeline
			.create_hash_and_sign_event(new_event, sender, room_id, state_lock)
			.is_ok())
	}
}
