refactor: The update checker has become the announcements checker

Replaces June's endpoint with a continuwuity endpoint.
Adds a JSON schema.

Closes #89
Closes #760

src/service/announcements/mod.rs

@@ -0,0 +1,169 @@
+//! # Announcements service
+//!
+//! This service is responsible for checking for announcements and sending them
+//! to the client.
+//!
+//! It is used to send announcements to the admin room and logs.
+//! Annuncements are stored in /docs/static/announcements right now.
+//! The highest seen announcement id is stored in the database. When the
+//! announcement check is run, all announcements with an ID higher than those
+//! seen before are printed to the console and sent to the admin room.
+//!
+//! Old announcements should be deleted to avoid spamming the room on first
+//! install.
+//!
+//! Announcements are displayed as markdown in the admin room, but plain text in
+//! the console.
+
+use std::{sync::Arc, time::Duration};
+
+use async_trait::async_trait;
+use conduwuit::{Result, Server, debug, info, warn};
+use database::{Deserialized, Map};
+use ruma::events::room::message::RoomMessageEventContent;
+use serde::Deserialize;
+use tokio::{
+	sync::Notify,
+	time::{MissedTickBehavior, interval},
+};
+
+use crate::{Dep, admin, client, globals};
+
+pub struct Service {
+	interval: Duration,
+	interrupt: Notify,
+	db: Arc<Map>,
+	services: Services,
+}
+
+struct Services {
+	admin: Dep<admin::Service>,
+	client: Dep<client::Service>,
+	globals: Dep<globals::Service>,
+	server: Arc<Server>,
+}
+
+#[derive(Debug, Deserialize)]
+struct CheckForAnnouncementsResponse {
+	announcements: Vec<CheckForAnnouncementsResponseEntry>,
+}
+
+#[derive(Debug, Deserialize)]
+struct CheckForAnnouncementsResponseEntry {
+	id: u64,
+	date: Option<String>,
+	message: String,
+}
+
+const CHECK_FOR_ANNOUNCEMENTS_URL: &str =
+	"https://continuwuity.org/.well-known/continuwuity/announcements";
+const CHECK_FOR_ANNOUNCEMENTS_INTERVAL: u64 = 7200; // 2 hours
+const LAST_CHECK_FOR_ANNOUNCEMENTS_ID: &[u8; 25] = b"last_seen_announcement_id";
+// In conduwuit, this was under b"a"
+
+#[async_trait]
+impl crate::Service for Service {
+	fn build(args: crate::Args<'_>) -> Result<Arc<Self>> {
+		Ok(Arc::new(Self {
+			interval: Duration::from_secs(CHECK_FOR_ANNOUNCEMENTS_INTERVAL),
+			interrupt: Notify::new(),
+			db: args.db["global"].clone(),
+			services: Services {
+				globals: args.depend::<globals::Service>("globals"),
+				admin: args.depend::<admin::Service>("admin"),
+				client: args.depend::<client::Service>("client"),
+				server: args.server.clone(),
+			},
+		}))
+	}
+
+	#[tracing::instrument(skip_all, name = "announcements", level = "debug")]
+	async fn worker(self: Arc<Self>) -> Result<()> {
+		if !self.services.globals.allow_announcements_check() {
+			debug!("Disabling announcements check");
+			return Ok(());
+		}
+
+		let mut i = interval(self.interval);
+		i.set_missed_tick_behavior(MissedTickBehavior::Delay);
+		i.reset_after(self.interval);
+		loop {
+			tokio::select! {
+				() = self.interrupt.notified() => break,
+				_ = i.tick() => (),
+			}
+
+			if let Err(e) = self.check().await {
+				warn!(%e, "Failed to check for announcements");
+			}
+		}
+
+		Ok(())
+	}
+
+	fn interrupt(&self) { self.interrupt.notify_waiters(); }
+
+	fn name(&self) -> &str { crate::service::make_name(std::module_path!()) }
+}
+
+impl Service {
+	#[tracing::instrument(skip_all)]
+	async fn check(&self) -> Result<()> {
+		debug_assert!(self.services.server.running(), "server must not be shutting down");
+
+		let response = self
+			.services
+			.client
+			.default
+			.get(CHECK_FOR_ANNOUNCEMENTS_URL)
+			.send()
+			.await?
+			.text()
+			.await?;
+
+		let response = serde_json::from_str::<CheckForAnnouncementsResponse>(&response)?;
+		for announcement in &response.announcements {
+			if announcement.id > self.last_check_for_announcements_id().await {
+				self.handle(announcement).await;
+				self.update_check_for_announcements_id(announcement.id);
+			}
+		}
+
+		Ok(())
+	}
+
+	#[tracing::instrument(skip_all)]
+	async fn handle(&self, announcement: &CheckForAnnouncementsResponseEntry) {
+		if let Some(date) = &announcement.date {
+			info!("[announcements] {date} {:#}", announcement.message);
+		} else {
+			info!("[announcements] {:#}", announcement.message);
+		}
+
+		self.services
+			.admin
+			.send_message(RoomMessageEventContent::text_markdown(format!(
+				"### New announcement{}\n\n{}",
+				announcement
+					.date
+					.as_ref()
+					.map_or_else(String::new, |date| format!(" - `{date}`")),
+				announcement.message
+			)))
+			.await
+			.ok();
+	}
+
+	#[inline]
+	pub fn update_check_for_announcements_id(&self, id: u64) {
+		self.db.raw_put(LAST_CHECK_FOR_ANNOUNCEMENTS_ID, id);
+	}
+
+	pub async fn last_check_for_announcements_id(&self) -> u64 {
+		self.db
+			.get(LAST_CHECK_FOR_ANNOUNCEMENTS_ID)
+			.await
+			.deserialized()
+			.unwrap_or(0_u64)
+	}
+}