Toward abstracting Pdu into trait Event.

Co-authored-by: Jade Ellis <jade@ellis.link>
Signed-off-by: Jason Volk <jason@zemos.net>

src/core/matrix/event/redact.rs

@@ -0,0 +1,86 @@
+use ruma::{
+	OwnedEventId, RoomVersionId,
+	events::{TimelineEventType, room::redaction::RoomRedactionEventContent},
+};
+use serde::Deserialize;
+use serde_json::value::{RawValue as RawJsonValue, to_raw_value};
+
+use super::Event;
+
+/// Copies the `redacts` property of the event to the `content` dict and
+/// vice-versa.
+///
+/// This follows the specification's
+/// [recommendation](https://spec.matrix.org/v1.10/rooms/v11/#moving-the-redacts-property-of-mroomredaction-events-to-a-content-property):
+///
+/// > For backwards-compatibility with older clients, servers should add a
+/// > redacts property to the top level of m.room.redaction events in when
+/// > serving such events over the Client-Server API.
+///
+/// > For improved compatibility with newer clients, servers should add a
+/// > redacts property to the content of m.room.redaction events in older
+/// > room versions when serving such events over the Client-Server API.
+#[must_use]
+pub(super) fn copy<E: Event>(event: &E) -> (Option<OwnedEventId>, Box<RawJsonValue>) {
+	if *event.event_type() != TimelineEventType::RoomRedaction {
+		return (event.redacts().map(ToOwned::to_owned), event.content().to_owned());
+	}
+
+	let Ok(mut content) = event.get_content::<RoomRedactionEventContent>() else {
+		return (event.redacts().map(ToOwned::to_owned), event.content().to_owned());
+	};
+
+	if let Some(redacts) = content.redacts {
+		return (Some(redacts), event.content().to_owned());
+	}
+
+	if let Some(redacts) = event.redacts().map(ToOwned::to_owned) {
+		content.redacts = Some(redacts);
+		return (
+			event.redacts().map(ToOwned::to_owned),
+			to_raw_value(&content).expect("Must be valid, we only added redacts field"),
+		);
+	}
+
+	(event.redacts().map(ToOwned::to_owned), event.content().to_owned())
+}
+
+#[must_use]
+pub(super) fn is_redacted<E: Event>(event: &E) -> bool {
+	let Some(unsigned) = event.unsigned() else {
+		return false;
+	};
+
+	let Ok(unsigned) = ExtractRedactedBecause::deserialize(unsigned) else {
+		return false;
+	};
+
+	unsigned.redacted_because.is_some()
+}
+
+#[must_use]
+pub(super) fn redacts_id<E: Event>(
+	event: &E,
+	room_version: &RoomVersionId,
+) -> Option<OwnedEventId> {
+	use RoomVersionId::*;
+
+	if *event.kind() != TimelineEventType::RoomRedaction {
+		return None;
+	}
+
+	match *room_version {
+		| V1 | V2 | V3 | V4 | V5 | V6 | V7 | V8 | V9 | V10 =>
+			event.redacts().map(ToOwned::to_owned),
+		| _ =>
+			event
+				.get_content::<RoomRedactionEventContent>()
+				.ok()?
+				.redacts,
+	}
+}
+
+#[derive(Deserialize)]
+struct ExtractRedactedBecause {
+	redacted_because: Option<serde::de::IgnoredAny>,
+}