From cc0072df0e6907aa3dd3a97a6acad31f86549f38 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Mon, 11 Jun 2018 22:43:19 -0700
Subject: [PATCH] modules: Add preliminary m_room_canonical_alias protocol
 suite.

---
 modules/Makefile.am               |   2 +
 modules/m_room_canonical_alias.cc | 119 ++++++++++++++++++++++++++++++
 modules/vm.cc                     |   6 +-
 3 files changed, 126 insertions(+), 1 deletion(-)
 create mode 100644 modules/m_room_canonical_alias.cc

diff --git a/modules/Makefile.am b/modules/Makefile.am
index 11215ab75..50fa90046 100644
--- a/modules/Makefile.am
+++ b/modules/Makefile.am
@@ -89,6 +89,7 @@ m_room_create_la_SOURCES = m_room_create.cc
 m_room_member_la_SOURCES = m_room_member.cc
 m_room_join_rules_la_SOURCES = m_room_join_rules.cc
 m_room_history_visibility_la_SOURCES = m_room_history_visibility.cc
+m_room_canonical_alias_la_SOURCES = m_room_canonical_alias.cc
 
 m_module_LTLIBRARIES = \
 	m_noop.la \
@@ -100,6 +101,7 @@ m_module_LTLIBRARIES = \
 	m_room_member.la \
 	m_room_join_rules.la \
 	m_room_history_visibility.la \
+	m_room_canonical_alias.la \
 	###
 
 ###############################################################################
diff --git a/modules/m_room_canonical_alias.cc b/modules/m_room_canonical_alias.cc
new file mode 100644
index 000000000..e8c02aa42
--- /dev/null
+++ b/modules/m_room_canonical_alias.cc
@@ -0,0 +1,119 @@
+// Matrix Construct
+//
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2018 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.
+
+using namespace ircd;
+
+mapi::header
+IRCD_MODULE
+{
+	"Matrix m.room.canonical_alias"
+};
+
+const m::room::id::buf
+alias_room_id
+{
+	"alias", ircd::my_host()
+};
+
+const m::room
+alias_room
+{
+	alias_room_id
+};
+
+void
+_changed_canonical_alias(const m::event &event)
+{
+	const m::room::alias &alias
+	{
+		unquote(at<"content"_>(event).at("alias"))
+	};
+
+	const m::room::id &room_id
+	{
+		at<"room_id"_>(event)
+	};
+
+	const auto event_id
+	{
+		send(alias_room, m::me.user_id, "ircd.alias", alias, json::strung{event})
+	};
+
+	log::info
+	{
+		"Changed canonical alias of %s to %s by %s with %s => %s",
+		string_view{room_id},
+		string_view{alias},
+		json::get<"sender"_>(event),
+		json::get<"event_id"_>(event),
+		string_view{event_id}
+	};
+}
+
+const m::hookfn<>
+_changed_canonical_alias_hookfn
+{
+	_changed_canonical_alias,
+	{
+		{ "_site",    "vm.notify"               },
+		{ "type",     "m.room.canonical_alias"  },
+	}
+};
+
+void
+_can_change_canonical_alias(const m::event &event)
+{
+	const m::room::id &room_id
+	{
+		at<"room_id"_>(event)
+	};
+
+	const m::room::alias &alias
+	{
+		unquote(at<"content"_>(event).at("alias"))
+	};
+
+	const m::room room
+	{
+		room_id
+	};
+
+	bool has_alias{false};
+	room.get(std::nothrow, "m.room.aliases", alias.host(), [&alias, &has_alias]
+	(const m::event &event)
+	{
+		const json::array &aliases
+		{
+			json::get<"content"_>(event).at("aliases")
+		};
+
+		for(auto it(begin(aliases)); it != end(aliases) && !has_alias; ++it)
+			if(unquote(*it) == alias)
+				has_alias = true;
+	});
+
+	if(!has_alias)
+		throw m::ACCESS_DENIED
+		{
+			"Cannot set canonical alias '%s' because it is not an alias in '%s'",
+			string_view{alias},
+			string_view{room_id}
+		};
+}
+
+const m::hookfn<>
+_can_change_canonical_alias_hookfn
+{
+	_can_change_canonical_alias,
+	{
+		{ "_site",    "vm.eval"                 },
+		{ "type",     "m.room.canonical_alias"  },
+	}
+};
diff --git a/modules/vm.cc b/modules/vm.cc
index 70073025f..e026b8250 100644
--- a/modules/vm.cc
+++ b/modules/vm.cc
@@ -78,6 +78,7 @@ void
 ircd::m::vm::fini()
 {
 	m::modules.erase("vm_fetch"s);
+	assert(eval::list.empty());
 
 	id::event::buf event_id;
 	const auto current_sequence
@@ -114,6 +115,7 @@ ircd::m::vm::eval__commit_room(eval &eval,
 
 	// Note that the regular opts is unconditionally overridden because the
 	// user should have provided copts instead.
+	assert(!eval.opts || eval.opts == eval.copts);
 	eval.opts = eval.copts;
 
 	// Set a member pointer to the json::iov currently being composed. This
@@ -256,6 +258,7 @@ ircd::m::vm::eval__commit(eval &eval,
 
 	// Note that the regular opts is unconditionally overridden because the
 	// user should have provided copts instead.
+	assert(!eval.opts || eval.opts == eval.copts);
 	eval.opts = eval.copts;
 
 	// Set a member pointer to the json::iov currently being composed. This
@@ -648,7 +651,7 @@ ircd::m::vm::_eval_pdu(eval &eval,
 	};
 
 	eval.txn = &txn;
-	const unwind cleartxn{[&eval]
+	const unwind clear{[&eval]
 	{
 		eval.txn = nullptr;
 	}};
@@ -736,6 +739,7 @@ ircd::m::vm::_eval_pdu(eval &eval,
 void
 ircd::m::vm::write(eval &eval)
 {
+	assert(eval.txn);
 	auto &txn(*eval.txn);
 	if(eval.opts->debuglog_accept)
 		log::debug