use std::{
	collections::{BTreeMap, HashMap},
	error::Error as StdError,
	fs,
	future::{self, Future},
	iter,
	net::{IpAddr, SocketAddr},
	path::PathBuf,
	sync::{
		atomic::{self, AtomicBool},
		Arc, RwLock as StdRwLock,
	},
	time::{Duration, Instant},
};

use argon2::Argon2;
use base64::{engine::general_purpose, Engine as _};
pub use data::Data;
use futures_util::FutureExt;
use hickory_resolver::TokioAsyncResolver;
use hyper::{
	client::connect::dns::{GaiResolver, Name},
	service::Service as HyperService,
};
use regex::RegexSet;
use reqwest::dns::{Addrs, Resolve, Resolving};
use ruma::{
	api::{
		client::sync::sync_events,
		federation::discovery::{ServerSigningKeys, VerifyKey},
	},
	serde::Base64,
	DeviceId, OwnedDeviceId, OwnedEventId, OwnedRoomId, OwnedServerName, OwnedServerSigningKeyId, OwnedUserId,
	RoomVersionId, ServerName, UserId,
};
use tokio::sync::{broadcast, watch::Receiver, Mutex, RwLock, Semaphore};
use tracing::{error, info};

use crate::{api::server_server::FedDest, services, Config, Error, Result};

mod data;

type WellKnownMap = HashMap<OwnedServerName, (FedDest, String)>;
type TlsNameMap = HashMap<String, (Vec<IpAddr>, u16)>;
type RateLimitState = (Instant, u32); // Time if last failed try, number of failed tries
type SyncHandle = (
	Option<String>,                                      // since
	Receiver<Option<Result<sync_events::v3::Response>>>, // rx
);

pub struct Service<'a> {
	pub db: &'static dyn Data,

	pub actual_destination_cache: Arc<RwLock<WellKnownMap>>, // actual_destination, host
	pub tls_name_override: Arc<StdRwLock<TlsNameMap>>,
	pub config: Config,
	keypair: Arc<ruma::signatures::Ed25519KeyPair>,
	dns_resolver: TokioAsyncResolver,
	jwt_decoding_key: Option<jsonwebtoken::DecodingKey>,
	url_preview_client: reqwest::Client,
	federation_client: reqwest::Client,
	default_client: reqwest::Client,
	pub stable_room_versions: Vec<RoomVersionId>,
	pub unstable_room_versions: Vec<RoomVersionId>,
	pub bad_event_ratelimiter: Arc<RwLock<HashMap<OwnedEventId, RateLimitState>>>,
	pub bad_signature_ratelimiter: Arc<RwLock<HashMap<Vec<String>, RateLimitState>>>,
	pub bad_query_ratelimiter: Arc<RwLock<HashMap<OwnedServerName, RateLimitState>>>,
	pub servername_ratelimiter: Arc<RwLock<HashMap<OwnedServerName, Arc<Semaphore>>>>,
	pub sync_receivers: RwLock<HashMap<(OwnedUserId, OwnedDeviceId), SyncHandle>>,
	pub roomid_mutex_insert: RwLock<HashMap<OwnedRoomId, Arc<Mutex<()>>>>,
	pub roomid_mutex_state: RwLock<HashMap<OwnedRoomId, Arc<Mutex<()>>>>,
	pub roomid_mutex_federation: RwLock<HashMap<OwnedRoomId, Arc<Mutex<()>>>>, // this lock will be held longer
	pub roomid_federationhandletime: RwLock<HashMap<OwnedRoomId, (OwnedEventId, Instant)>>,
	pub stateres_mutex: Arc<Mutex<()>>,
	pub(crate) rotate: RotationHandler,

	pub shutdown: AtomicBool,
	pub argon: Argon2<'a>,
}

/// Handles "rotation" of long-polling requests. "Rotation" in this context is
/// similar to "rotation" of log files and the like.
///
/// This is utilized to have sync workers return early and release read locks on
/// the database.
pub(crate) struct RotationHandler(broadcast::Sender<()>, ());

impl RotationHandler {
	pub fn new() -> Self {
		let (s, _r) = broadcast::channel(1);
		Self(s, ())
	}

	pub fn watch(&self) -> impl Future<Output = ()> {
		let mut r = self.0.subscribe();

		async move {
			let _ = r.recv().await;
		}
	}

	pub fn fire(&self) { let _ = self.0.send(()); }
}

impl Default for RotationHandler {
	fn default() -> Self { Self::new() }
}

struct Resolver {
	inner: GaiResolver,
	overrides: Arc<StdRwLock<TlsNameMap>>,
}

impl Resolver {
	fn new(overrides: Arc<StdRwLock<TlsNameMap>>) -> Self {
		Resolver {
			inner: GaiResolver::new(),
			overrides,
		}
	}
}

impl Resolve for Resolver {
	fn resolve(&self, name: Name) -> Resolving {
		self.overrides
			.read()
			.unwrap()
			.get(name.as_str())
			.and_then(|(override_name, port)| {
				override_name.first().map(|first_name| {
					let x: Box<dyn Iterator<Item = SocketAddr> + Send> =
						Box::new(iter::once(SocketAddr::new(*first_name, *port)));
					let x: Resolving = Box::pin(future::ready(Ok(x)));
					x
				})
			})
			.unwrap_or_else(|| {
				let this = &mut self.inner.clone();
				Box::pin(HyperService::<Name>::call(this, name).map(|result| {
					result
						.map(|addrs| -> Addrs { Box::new(addrs) })
						.map_err(|err| -> Box<dyn StdError + Send + Sync> { Box::new(err) })
				}))
			})
	}
}

impl Service<'_> {
	pub fn load(db: &'static dyn Data, config: Config) -> Result<Self> {
		let keypair = db.load_keypair();

		let keypair = match keypair {
			Ok(k) => k,
			Err(e) => {
				error!("Keypair invalid. Deleting...");
				db.remove_keypair()?;
				return Err(e);
			},
		};

		let tls_name_override = Arc::new(StdRwLock::new(TlsNameMap::new()));

		let jwt_decoding_key =
			config.jwt_secret.as_ref().map(|secret| jsonwebtoken::DecodingKey::from_secret(secret.as_bytes()));

		let url_preview_client = url_preview_reqwest_client_builder(&config)?.build()?;
		let default_client = reqwest_client_builder(&config)?.build()?;
		let federation_client = reqwest_client_builder(&config)?
			.dns_resolver(Arc::new(Resolver::new(tls_name_override.clone())))
			.build()?;

		// Supported and stable room versions
		let stable_room_versions = vec![
			RoomVersionId::V6,
			RoomVersionId::V7,
			RoomVersionId::V8,
			RoomVersionId::V9,
			RoomVersionId::V10,
		];
		// Experimental, partially supported room versions
		let unstable_room_versions = vec![
			RoomVersionId::V2,
			RoomVersionId::V3,
			RoomVersionId::V4,
			RoomVersionId::V5,
			RoomVersionId::V11,
		];
		// 19456 Kib blocks, iterations = 2, parallelism = 1 for more info https://cheatsheetseries.owasp.org/cheatsheets/Password_Storage_Cheat_Sheet.html#argon2id
		let argon = Argon2::new(
			argon2::Algorithm::Argon2id,
			argon2::Version::default(),
			argon2::Params::new(19456, 2, 1, None).expect("valid parameters"),
		);
		let mut s = Self {
			db,
			config,
			keypair: Arc::new(keypair),
			dns_resolver: TokioAsyncResolver::tokio_from_system_conf().map_err(|e| {
				error!("Failed to set up trust dns resolver with system config: {}", e);
				Error::bad_config("Failed to set up trust dns resolver with system config.")
			})?,
			actual_destination_cache: Arc::new(RwLock::new(WellKnownMap::new())),
			tls_name_override,
			url_preview_client,
			federation_client,
			default_client,
			jwt_decoding_key,
			stable_room_versions,
			unstable_room_versions,
			bad_event_ratelimiter: Arc::new(RwLock::new(HashMap::new())),
			bad_signature_ratelimiter: Arc::new(RwLock::new(HashMap::new())),
			bad_query_ratelimiter: Arc::new(RwLock::new(HashMap::new())),
			servername_ratelimiter: Arc::new(RwLock::new(HashMap::new())),
			roomid_mutex_state: RwLock::new(HashMap::new()),
			roomid_mutex_insert: RwLock::new(HashMap::new()),
			roomid_mutex_federation: RwLock::new(HashMap::new()),
			roomid_federationhandletime: RwLock::new(HashMap::new()),
			stateres_mutex: Arc::new(Mutex::new(())),
			sync_receivers: RwLock::new(HashMap::new()),
			rotate: RotationHandler::new(),
			shutdown: AtomicBool::new(false),
			argon,
		};

		fs::create_dir_all(s.get_media_folder())?;

		if !s.supported_room_versions().contains(&s.config.default_room_version) {
			error!(config=?s.config.default_room_version, fallback=?crate::config::default_default_room_version(), "Room version in config isn't supported, falling back to default version");
			s.config.default_room_version = crate::config::default_default_room_version();
		};

		Ok(s)
	}

	/// Returns this server's keypair.
	pub fn keypair(&self) -> &ruma::signatures::Ed25519KeyPair { &self.keypair }

	/// Returns a reqwest client which can be used to send requests for URL
	/// previews This is the same as `default_client()` except a redirect policy
	/// of max 2 is set
	pub fn url_preview_client(&self) -> reqwest::Client {
		// Client is cheap to clone (Arc wrapper) and avoids lifetime issues
		self.url_preview_client.clone()
	}

	/// Returns a reqwest client which can be used to send requests
	pub fn default_client(&self) -> reqwest::Client {
		// Client is cheap to clone (Arc wrapper) and avoids lifetime issues
		self.default_client.clone()
	}

	/// Returns a client used for resolving .well-knowns
	pub fn federation_client(&self) -> reqwest::Client {
		// Client is cheap to clone (Arc wrapper) and avoids lifetime issues
		self.federation_client.clone()
	}

	#[tracing::instrument(skip(self))]
	pub fn next_count(&self) -> Result<u64> { self.db.next_count() }

	#[tracing::instrument(skip(self))]
	pub fn current_count(&self) -> Result<u64> { self.db.current_count() }

	#[tracing::instrument(skip(self))]
	pub fn last_check_for_updates_id(&self) -> Result<u64> { self.db.last_check_for_updates_id() }

	#[tracing::instrument(skip(self))]
	pub fn update_check_for_updates_id(&self, id: u64) -> Result<()> { self.db.update_check_for_updates_id(id) }

	pub async fn watch(&self, user_id: &UserId, device_id: &DeviceId) -> Result<()> {
		self.db.watch(user_id, device_id).await
	}

	pub fn cleanup(&self) -> Result<()> { self.db.cleanup() }

	pub fn flush(&self) -> Result<()> { self.db.flush() }

	pub fn server_name(&self) -> &ServerName { self.config.server_name.as_ref() }

	pub fn max_request_size(&self) -> u32 { self.config.max_request_size }

	pub fn max_fetch_prev_events(&self) -> u16 { self.config.max_fetch_prev_events }

	pub fn allow_registration(&self) -> bool { self.config.allow_registration }

	pub fn allow_guest_registration(&self) -> bool { self.config.allow_guest_registration }

	pub fn allow_encryption(&self) -> bool { self.config.allow_encryption }

	pub fn allow_federation(&self) -> bool { self.config.allow_federation }

	pub fn allow_public_room_directory_over_federation(&self) -> bool {
		self.config.allow_public_room_directory_over_federation
	}

	pub fn allow_public_room_directory_without_auth(&self) -> bool {
		self.config.allow_public_room_directory_without_auth
	}

	pub fn allow_device_name_federation(&self) -> bool { self.config.allow_device_name_federation }

	pub fn allow_room_creation(&self) -> bool { self.config.allow_room_creation }

	pub fn allow_unstable_room_versions(&self) -> bool { self.config.allow_unstable_room_versions }

	pub fn default_room_version(&self) -> RoomVersionId { self.config.default_room_version.clone() }

	pub fn new_user_displayname_suffix(&self) -> &String { &self.config.new_user_displayname_suffix }

	pub fn allow_check_for_updates(&self) -> bool { self.config.allow_check_for_updates }

	pub fn trusted_servers(&self) -> &[OwnedServerName] { &self.config.trusted_servers }

	pub fn query_trusted_key_servers_first(&self) -> bool { self.config.query_trusted_key_servers_first }

	pub fn dns_resolver(&self) -> &TokioAsyncResolver { &self.dns_resolver }

	pub fn jwt_decoding_key(&self) -> Option<&jsonwebtoken::DecodingKey> { self.jwt_decoding_key.as_ref() }

	pub fn turn_password(&self) -> &String { &self.config.turn_password }

	pub fn turn_ttl(&self) -> u64 { self.config.turn_ttl }

	pub fn turn_uris(&self) -> &[String] { &self.config.turn_uris }

	pub fn turn_username(&self) -> &String { &self.config.turn_username }

	pub fn turn_secret(&self) -> &String { &self.config.turn_secret }

	pub fn auto_join_rooms(&self) -> &[OwnedRoomId] { &self.config.auto_join_rooms }

	pub fn notification_push_path(&self) -> &String { &self.config.notification_push_path }

	pub fn emergency_password(&self) -> &Option<String> { &self.config.emergency_password }

	pub fn url_preview_domain_contains_allowlist(&self) -> &Vec<String> {
		&self.config.url_preview_domain_contains_allowlist
	}

	pub fn url_preview_domain_explicit_allowlist(&self) -> &Vec<String> {
		&self.config.url_preview_domain_explicit_allowlist
	}

	pub fn url_preview_url_contains_allowlist(&self) -> &Vec<String> { &self.config.url_preview_url_contains_allowlist }

	pub fn url_preview_max_spider_size(&self) -> usize { self.config.url_preview_max_spider_size }

	pub fn url_preview_check_root_domain(&self) -> bool { self.config.url_preview_check_root_domain }

	pub fn forbidden_alias_names(&self) -> &RegexSet { &self.config.forbidden_alias_names }

	pub fn forbidden_usernames(&self) -> &RegexSet { &self.config.forbidden_usernames }

	pub fn allow_local_presence(&self) -> bool { self.config.allow_local_presence }

	pub fn allow_incoming_presence(&self) -> bool { self.config.allow_incoming_presence }

	pub fn allow_outgoing_presence(&self) -> bool { self.config.allow_outgoing_presence }

	pub fn presence_idle_timeout_s(&self) -> u64 { self.config.presence_idle_timeout_s }

	pub fn presence_offline_timeout_s(&self) -> u64 { self.config.presence_offline_timeout_s }

	pub fn allow_incoming_read_receipts(&self) -> bool { self.config.allow_incoming_read_receipts }

	pub fn rocksdb_log_level(&self) -> &String { &self.config.rocksdb_log_level }

	pub fn rocksdb_max_log_file_size(&self) -> usize { self.config.rocksdb_max_log_file_size }

	pub fn rocksdb_log_time_to_roll(&self) -> usize { self.config.rocksdb_log_time_to_roll }

	pub fn rocksdb_optimize_for_spinning_disks(&self) -> bool { self.config.rocksdb_optimize_for_spinning_disks }

	pub fn rocksdb_parallelism_threads(&self) -> usize { self.config.rocksdb_parallelism_threads }

	pub fn rocksdb_compression_algo(&self) -> &String { &self.config.rocksdb_compression_algo }

	pub fn rocksdb_compression_level(&self) -> i32 { self.config.rocksdb_compression_level }

	pub fn rocksdb_bottommost_compression_level(&self) -> i32 { self.config.rocksdb_bottommost_compression_level }

	pub fn prevent_media_downloads_from(&self) -> &[OwnedServerName] { &self.config.prevent_media_downloads_from }

	pub fn ip_range_denylist(&self) -> &[String] { &self.config.ip_range_denylist }

	pub fn block_non_admin_invites(&self) -> bool { self.config.block_non_admin_invites }

	pub fn supported_room_versions(&self) -> Vec<RoomVersionId> {
		let mut room_versions: Vec<RoomVersionId> = vec![];
		room_versions.extend(self.stable_room_versions.clone());
		if self.allow_unstable_room_versions() {
			room_versions.extend(self.unstable_room_versions.clone());
		};
		room_versions
	}

	/// TODO: the key valid until timestamp (`valid_until_ts`) is only honored
	/// in room version > 4
	///
	/// Remove the outdated keys and insert the new ones.
	///
	/// This doesn't actually check that the keys provided are newer than the
	/// old set.
	pub fn add_signing_key(
		&self, origin: &ServerName, new_keys: ServerSigningKeys,
	) -> Result<BTreeMap<OwnedServerSigningKeyId, VerifyKey>> {
		self.db.add_signing_key(origin, new_keys)
	}

	/// This returns an empty `Ok(BTreeMap<..>)` when there are no keys found
	/// for the server.
	pub fn signing_keys_for(&self, origin: &ServerName) -> Result<BTreeMap<OwnedServerSigningKeyId, VerifyKey>> {
		let mut keys = self.db.signing_keys_for(origin)?;
		if origin == self.server_name() {
			keys.insert(
				format!("ed25519:{}", services().globals.keypair().version())
					.try_into()
					.expect("found invalid server signing keys in DB"),
				VerifyKey {
					key: Base64::new(self.keypair.public_key().to_vec()),
				},
			);
		}

		Ok(keys)
	}

	pub fn database_version(&self) -> Result<u64> { self.db.database_version() }

	pub fn bump_database_version(&self, new_version: u64) -> Result<()> { self.db.bump_database_version(new_version) }

	pub fn get_media_folder(&self) -> PathBuf {
		let mut r = PathBuf::new();
		r.push(self.config.database_path.clone());
		r.push("media");
		r
	}

	/// new SHA256 file name media function, requires "sha256_media" feature
	/// flag enabled and database migrated uses SHA256 hash of the base64 key as
	/// the file name
	#[cfg(feature = "sha256_media")]
	pub fn get_media_file_new(&self, key: &[u8]) -> PathBuf {
		let mut r = PathBuf::new();
		r.push(self.config.database_path.clone());
		r.push("media");
		// Using the hash of the base64 key as the filename
		// This is to prevent the total length of the path from exceeding the maximum
		// length in most filesystems
		r.push(general_purpose::URL_SAFE_NO_PAD.encode(<sha2::Sha256 as sha2::Digest>::digest(key)));
		r
	}

	/// old base64 file name media function
	/// This is the old version of `get_media_file` that uses the full base64
	/// key as the filename.
	pub fn get_media_file(&self, key: &[u8]) -> PathBuf {
		let mut r = PathBuf::new();
		r.push(self.config.database_path.clone());
		r.push("media");
		r.push(general_purpose::URL_SAFE_NO_PAD.encode(key));
		r
	}

	pub fn well_known_client(&self) -> &Option<String> { &self.config.well_known_client }

	pub fn well_known_server(&self) -> &Option<String> { &self.config.well_known_server }

	pub fn unix_socket_path(&self) -> &Option<PathBuf> { &self.config.unix_socket_path }

	pub fn shutdown(&self) {
		self.shutdown.store(true, atomic::Ordering::Relaxed);
		// On shutdown

		if self.unix_socket_path().is_some() {
			match &self.unix_socket_path() {
				Some(path) => {
					fs::remove_file(path).unwrap();
				},
				None => error!(
					"Unable to remove socket file at {:?} during shutdown.",
					&self.unix_socket_path()
				),
			};
		};

		info!(target: "shutdown-sync", "Received shutdown notification, notifying sync helpers...");
		services().globals.rotate.fire();
	}
}

fn reqwest_client_builder(config: &Config) -> Result<reqwest::ClientBuilder> {
	let redirect_policy = reqwest::redirect::Policy::custom(|attempt| {
		if attempt.previous().len() > 6 {
			attempt.error("Too many redirects (max is 6)")
		} else {
			attempt.follow()
		}
	});

	let mut reqwest_client_builder = reqwest::Client::builder()
		.hickory_dns(true)
		.pool_max_idle_per_host(1)
		.pool_idle_timeout(Duration::from_secs(50))
		.connect_timeout(Duration::from_secs(60))
		.timeout(Duration::from_secs(60 * 5))
		.redirect(redirect_policy)
		.user_agent("Conduwuit".to_owned() + "/" + env!("CARGO_PKG_VERSION"));

	if let Some(proxy) = config.proxy.to_proxy()? {
		reqwest_client_builder = reqwest_client_builder.proxy(proxy);
	}

	Ok(reqwest_client_builder)
}

fn url_preview_reqwest_client_builder(config: &Config) -> Result<reqwest::ClientBuilder> {
	// for security reasons (e.g. malicious open redirect), we do not want to follow
	// too many redirects when generating URL previews. let's keep it at least 2 to
	// account for HTTP -> HTTPS upgrades, if it becomes an issue we can consider
	// raising it to 3.
	let redirect_policy = reqwest::redirect::Policy::custom(|attempt| {
		if attempt.previous().len() > 2 {
			attempt.error("Too many redirects (max is 2)")
		} else {
			attempt.follow()
		}
	});

	let mut reqwest_client_builder = reqwest::Client::builder()
		.hickory_dns(true)
		.pool_max_idle_per_host(0)
		.connect_timeout(Duration::from_secs(20))
		.timeout(Duration::from_secs(30))
		.redirect(redirect_policy)
		.user_agent("Conduwuit".to_owned() + "/" + env!("CARGO_PKG_VERSION"));

	if let Some(proxy) = config.proxy.to_proxy()? {
		reqwest_client_builder = reqwest_client_builder.proxy(proxy);
	}

	Ok(reqwest_client_builder)
}