From fa0365fa3114cb260ac93ee5bb2f8465c5bbea18 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Tue, 18 Apr 2023 11:47:49 -0700
Subject: [PATCH] ircd::m: Add convenience interface for querying m.replace
 relation.

---
 include/ircd/m/m.h        |  1 +
 include/ircd/m/replaced.h | 80 +++++++++++++++++++++++++++++++++++++++
 matrix/room_messages.cc   |  9 ++---
 3 files changed, 85 insertions(+), 5 deletions(-)
 create mode 100644 include/ircd/m/replaced.h

diff --git a/include/ircd/m/m.h b/include/ircd/m/m.h
index b2a2b6c0a..a30841619 100644
--- a/include/ircd/m/m.h
+++ b/include/ircd/m/m.h
@@ -89,6 +89,7 @@ namespace ircd::m
 #include "direct_to_device.h"
 #include "visible.h"
 #include "redacted.h"
+#include "replaced.h"
 #include "feds.h"
 #include "app.h"
 #include "bridge.h"
diff --git a/include/ircd/m/replaced.h b/include/ircd/m/replaced.h
new file mode 100644
index 000000000..7da29df5d
--- /dev/null
+++ b/include/ircd/m/replaced.h
@@ -0,0 +1,80 @@
+// Matrix Construct
+//
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2023 Jason Volk <jason@zemos.net>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies. The
+// full license for this software is available in the LICENSE file.
+
+#pragma once
+#define HAVE_IRCD_M_REPLACED_H
+
+namespace ircd::m
+{
+	struct replaced;
+}
+
+class ircd::m::replaced
+:public returns<event::idx>
+{
+	m::relates relates;
+
+  public:
+	IRCD_OVERLOAD(latest);
+
+	replaced(const event::idx &, latest_t);
+	replaced(const event::idx &);
+
+	replaced(const event::id &, latest_t);
+	replaced(const event::id &);
+
+	explicit replaced(const event &, latest_t);
+	explicit replaced(const event &);
+};
+
+inline
+ircd::m::replaced::replaced(const event &event)
+:replaced{event.event_id}
+{}
+
+inline
+ircd::m::replaced::replaced(const event &event,
+                            latest_t)
+:replaced{event.event_id, latest}
+{}
+
+inline
+ircd::m::replaced::replaced(const event::id &event_id)
+:replaced{index(std::nothrow, event_id)}
+{}
+
+inline
+ircd::m::replaced::replaced(const event::id &event_id,
+                            latest_t)
+:replaced{index(std::nothrow, event_id), latest}
+{}
+
+inline
+ircd::m::replaced::replaced(const event::idx &event_idx)
+:relates
+{
+	.refs = event_idx,
+	.match_sender = true,
+}
+{
+	this->returns::ret = relates.has("m.replace")? -1UL: 0UL;
+}
+
+inline
+ircd::m::replaced::replaced(const event::idx &event_idx,
+                            latest_t)
+:relates
+{
+	.refs = event_idx,
+	.match_sender = true,
+}
+{
+	this->returns::ret = relates.latest("m.replace");
+}
diff --git a/matrix/room_messages.cc b/matrix/room_messages.cc
index 3bfb35ecb..885acaef3 100644
--- a/matrix/room_messages.cc
+++ b/matrix/room_messages.cc
@@ -54,15 +54,14 @@ ircd::m::replace(room::message &msg,
                  const event::idx &event_idx)
 {
 	// Find the latest edit of this; otherwise stick with the original.
-	const m::relates relates
+	const m::replaced replaced
 	{
-		.refs = event_idx,
-		.match_sender = true,
+		event_idx, m::replaced::latest
 	};
 
-	const event::idx replace_idx
+	const event::idx &replace_idx
 	{
-		relates.latest("m.replace")
+		replaced
 	};
 
 	if(!replace_idx)