feat: Add !admin debug show-auth-chain

Because why not am I right lads

src/admin/debug/commands.rs

@@ -1,29 +1,29 @@
 use std::{
-	collections::HashMap,
+	collections::{HashMap, HashSet},
 	fmt::Write,
 	iter::once,
 	time::{Instant, SystemTime},
 };
 
 use conduwuit::{
-	debug_error, err, info, matrix::{
+	Err, Result, debug_error, err, info,
-		pdu::{PduEvent, PduId, RawPduId},
+	matrix::{
 		Event,
-	}, trace,
+		pdu::{PduEvent, PduId, RawPduId},
-	utils,
+	},
+	trace, utils,
 	utils::{
 		stream::{IterStream, ReadyExt},
 		string::EMPTY,
-	}, warn,
+	},
-	Err,
+	warn,
-	Result,
 };
 use futures::{FutureExt, StreamExt, TryStreamExt};
 use lettre::message::Mailbox;
 use ruma::{
-	api::federation::event::get_room_state, events::AnyStateEvent, serde::Raw, CanonicalJsonObject, CanonicalJsonValue,
+	CanonicalJsonObject, CanonicalJsonValue, EventId, OwnedEventId, OwnedRoomId,
-	EventId, OwnedEventId, OwnedRoomId, OwnedRoomOrAliasId,
+	OwnedRoomOrAliasId, OwnedServerName, RoomId, RoomVersionId, UInt,
-	OwnedServerName, RoomId, RoomVersionId,
+	api::federation::event::get_room_state, events::AnyStateEvent, serde::Raw,
 };
 use service::rooms::{
 	short::{ShortEventId, ShortRoomId},
@@ -69,6 +69,189 @@ pub(super) async fn get_auth_chain(&self, event_id: OwnedEventId) -> Result {
 	self.write_str(&out).await
 }
 
+#[derive(Clone, Copy, Eq, PartialEq)]
+enum NodeStatus {
+	Normal(bool),
+	SoftFailed(bool),
+	Rejected(bool),
+}
+
+struct AuthChild {
+	node_id: String,
+	event_id: OwnedEventId,
+	depth: UInt,
+	ts: UInt,
+	first_seen: bool,
+	pdu: Option<PduEvent>,
+}
+
+fn render_node(
+	graph: &mut String,
+	node_id: &str,
+	event_id: &EventId,
+	status: NodeStatus,
+) -> Result {
+	let evt_str = event_id.to_string();
+
+	let status_label = match status {
+		| NodeStatus::Normal(false) => evt_str,
+		| NodeStatus::Normal(true) => format!("{evt_str} (missing locally)"),
+		| NodeStatus::SoftFailed(false) => format!("{evt_str} (soft-failed)"),
+		| NodeStatus::SoftFailed(true) => format!("{evt_str} (soft-failed & missing locally)"),
+		| NodeStatus::Rejected(false) => format!("{evt_str} (rejected)"),
+		| NodeStatus::Rejected(true) => format!("{evt_str} (rejected & missing locally)"),
+	};
+
+	writeln!(graph, "{node_id}[\"{}\"]", status_label.as_str())?;
+
+	match status {
+		| NodeStatus::Rejected(_) => writeln!(graph, "class {node_id} rejected;")?,
+		| NodeStatus::SoftFailed(_) => writeln!(graph, "class {node_id} soft_failed;")?,
+		| NodeStatus::Normal(_) => {},
+	}
+
+	Ok(())
+}
+
+#[admin_command]
+pub(super) async fn show_auth_chain(&self, event_id: OwnedEventId) -> Result {
+	let node_status = async |event_id: &EventId, missing: bool| -> NodeStatus {
+		if self
+			.services
+			.rooms
+			.pdu_metadata
+			.is_event_rejected(event_id)
+			.await
+		{
+			NodeStatus::Rejected(missing)
+		} else if self
+			.services
+			.rooms
+			.pdu_metadata
+			.is_event_soft_failed(event_id)
+			.await
+		{
+			NodeStatus::SoftFailed(missing)
+		} else {
+			NodeStatus::Normal(missing)
+		}
+	};
+
+	let Ok(root) = self.services.rooms.timeline.get_pdu(&event_id).await else {
+		return Err!("Event not found.");
+	};
+
+	let mut graph = String::from(
+		"```mermaid\n%% This is a mermaid graph. You can plug this output into\n\
+		%% https://mermaid.live/edit to visualise it on-the-fly.\nflowchart TD\n\
+		classDef rejected fill:#ffe5e5,stroke:#cc0000,stroke-width:2px,color:#000;\n\
+		classDef soft_failed fill:#fff6cc,stroke:#c9a400,stroke-width:2px,color:#000;\n"
+	);
+
+	let mut node_ids: HashMap<OwnedEventId, String> = HashMap::new();
+	let mut cached_events: HashMap<OwnedEventId, PduEvent> =
+		HashMap::from([(event_id.clone(), root.clone())]);
+	let mut scheduled: HashSet<OwnedEventId> = HashSet::from([event_id.clone()]);
+	let mut visited: HashSet<OwnedEventId> = HashSet::new();
+	let mut stack = vec![root];
+	let mut next_node_id = 0_usize;
+
+	let node_id_for = |event_id: &OwnedEventId,
+	                   node_ids: &mut HashMap<OwnedEventId, String>,
+	                   next_node_id: &mut usize| {
+		node_ids
+			.entry(event_id.clone())
+			.or_insert_with(|| {
+				let id = format!("n{}", *next_node_id);
+				*next_node_id = next_node_id.saturating_add(1);
+				id
+			})
+			.clone()
+	};
+
+	while let Some(event) = stack.pop() {
+		let current_event_id = event.event_id().to_owned();
+		if !visited.insert(current_event_id.clone()) {
+			continue;
+		}
+
+		let current_node_id = node_id_for(&current_event_id, &mut node_ids, &mut next_node_id);
+		let current_status = node_status(&current_event_id, false).await;
+
+		render_node(&mut graph, &current_node_id, &current_event_id, current_status)?;
+
+		let mut children = Vec::with_capacity(event.auth_events.len());
+		for auth_event_id in event.auth_events().rev() {
+			let auth_event_id = auth_event_id.to_owned();
+			let auth_node_id = node_id_for(&auth_event_id, &mut node_ids, &mut next_node_id);
+			writeln!(graph, "{current_node_id} --> {auth_node_id}")?;
+
+			let first_seen = scheduled.insert(auth_event_id.clone());
+			let auth_pdu = if let Some(auth_pdu) = cached_events.get(&auth_event_id) {
+				// NOTE: events might be referenced multiple times (like the create event)
+				// so this saves some cheeky db lookup time
+				Some(auth_pdu.clone())
+			} else if first_seen {
+				match self.services.rooms.timeline.get_pdu(&auth_event_id).await {
+					| Ok(auth_event) => {
+						cached_events.insert(auth_event_id.clone(), auth_event.clone());
+						Some(auth_event)
+					},
+					| Err(_) => None,
+				}
+			} else {
+				None
+			};
+
+			// NOTE: Depth is used as the primary sorting key here, even though it has no
+			// bearing on state resolution or anything. Timestamp is used as a
+			// tiebreaker, failing back to lexicographical comparison.
+			let (depth, ts) = auth_pdu
+				.as_ref()
+				.map_or((UInt::MAX, UInt::MAX), |pdu| (pdu.depth, pdu.origin_server_ts));
+
+			children.push(AuthChild {
+				node_id: auth_node_id,
+				event_id: auth_event_id,
+				depth,
+				ts,
+				first_seen,
+				pdu: auth_pdu,
+			});
+		}
+
+		children.sort_by(|a, b| {
+			a.depth
+				.cmp(&b.depth)
+				.then(a.ts.cmp(&b.ts))
+				.then(a.event_id.as_str().cmp(b.event_id.as_str()))
+		});
+
+		for child in children.into_iter().rev() {
+			if !child.first_seen {
+				continue;
+			}
+
+			if let Some(child_pdu) = child.pdu {
+				// We have this PDU so will want to traverse it.
+				stack.push(child_pdu);
+			} else {
+				// We don't have this PDU locally so we can't traverse its auth events,
+				// but we can still render it as a node.
+				render_node(
+					&mut graph,
+					&child.node_id,
+					&child.event_id,
+					node_status(&child.event_id, true).await,
+				)?;
+			}
+		}
+	}
+
+	graph.push_str("```\n");
+	self.write_str(&graph).await
+}
+
 #[admin_command]
 pub(super) async fn parse_pdu(&self) -> Result {
 	if self.body.len() < 2
@@ -111,8 +294,18 @@ pub(super) async fn get_pdu(&self, event_id: OwnedEventId) -> Result {
 		outlier = true;
 		pdu_json = self.services.rooms.timeline.get_pdu_json(&event_id).await;
 	}
-	let rejected = self.services.rooms.pdu_metadata.is_event_rejected(&event_id).await;
+	let rejected = self
-	let soft_failed = self.services.rooms.pdu_metadata.is_event_soft_failed(&event_id).await;
+		.services
+		.rooms
+		.pdu_metadata
+		.is_event_rejected(&event_id)
+		.await;
+	let soft_failed = self
+		.services
+		.rooms
+		.pdu_metadata
+		.is_event_soft_failed(&event_id)
+		.await;
 
 	match pdu_json {
 		| Err(_) => return Err!("PDU not found locally."),

src/admin/debug/mod.rs

@@ -17,12 +17,21 @@ pub enum DebugCommand {
 		message: Vec<String>,
 	},
 
-	/// Get the auth_chain of a PDU
+	/// Loads the auth_chain of a PDU, reporting how long it took.
 	GetAuthChain {
 		/// An event ID (the $ character followed by the base64 reference hash)
 		event_id: OwnedEventId,
 	},
 
+	/// Walks & displays the auth_chain of a PDU in a mermaid graph format.
+	///
+	/// This is useless to basically anyone but developers, and is also probably
+	/// slow and memory hungry.
+	ShowAuthChain {
+		/// The root event ID to start walking back from.
+		event_id: OwnedEventId,
+	},
+
 	/// Parse and print a PDU from a JSON
 	///
 	/// The PDU event is only checked for validity and is not added to the