ircd:Ⓜ️:dbs: Add event_horizon resolver.

include/ircd/m/dbs/appendix.h

@@ -54,6 +54,9 @@ enum ircd::m::dbs::appendix::index
 	/// properly complete the event_refs graph to all the referencing events.
 	EVENT_HORIZON,
 
+	/// Resolves unresolved references for this event left in event_horizon.
+	EVENT_HORIZON_RESOLVE,
+
 	/// Involves the event_sender column (reverse index on the event sender).
 	EVENT_SENDER,
 
@@ -108,6 +111,7 @@ namespace ircd::m::dbs
 	string_view _index_room(db::txn &, const event &, const write_opts &);
 	void _index_event_type(db::txn &, const event &, const write_opts &);
 	void _index_event_sender(db::txn &, const event &, const write_opts &);
+	void _index_event_horizon_resolve(db::txn &, const event &, const write_opts &);
 	void _index_event_horizon(db::txn &, const event &, const write_opts &, const id::event &);
 	void _index_event_refs_m_room_redaction(db::txn &, const event &, const write_opts &);
 	void _index_event_refs_m_receipt_m_read(db::txn &, const event &, const write_opts &);

include/ircd/m/dbs/write_opts.h

@@ -41,6 +41,10 @@ struct ircd::m::dbs::write_opts
 	/// by clearing a bit.
 	std::bitset<256> event_refs {event_refs_all};
 
+	/// Selection of what reference types to resolve and delete from the
+	/// event_horizon for this event.
+	std::bitset<256> horizon_resolve {event_refs_all};
+
 	/// Whether the present state table `room_state` should be updated by
 	/// this operation if appropriate.
 	bool present {true};

ircd/m_dbs.cc

@@ -271,6 +271,9 @@ ircd::m::dbs::_index_event(db::txn &txn,
 	if(opts.appendix.test(appendix::EVENT_JSON))
 		_index_event_json(txn, event, opts);
 
+	if(opts.appendix.test(appendix::EVENT_HORIZON_RESOLVE) && opts.horizon_resolve.any())
+		_index_event_horizon_resolve(txn, event, opts);
+
 	if(opts.appendix.test(appendix::EVENT_REFS) && opts.event_refs.any())
 		_index_event_refs(txn, event, opts);
 
@@ -827,6 +830,7 @@ ircd::m::dbs::_index_event_horizon(db::txn &txn,
                                    const m::event::id &unresolved_id)
 {
 	thread_local char buf[EVENT_HORIZON_KEY_MAX_SIZE];
+	assert(opts.appendix.test(appendix::EVENT_HORIZON));
 	assert(opts.event_idx != 0 && unresolved_id);
 	const string_view &key
 	{
@@ -842,6 +846,75 @@ ircd::m::dbs::_index_event_horizon(db::txn &txn,
 	};
 }
 
+void
+ircd::m::dbs::_index_event_horizon_resolve(db::txn &txn,
+                                           const event &event,
+                                           const write_opts &opts)
+{
+	thread_local char buf[EVENT_HORIZON_KEY_MAX_SIZE];
+	assert(opts.appendix.test(appendix::EVENT_HORIZON_RESOLVE));
+	assert(opts.event_idx != 0);
+	const string_view &key
+	{
+		event_horizon_key(buf, at<"event_id"_>(event), 0UL)
+	};
+
+	auto it
+	{
+		dbs::event_horizon.begin(key)
+	};
+
+	for(; it; ++it)
+	{
+		const auto parts
+		{
+			event_horizon_key(it->first)
+		};
+
+		const auto &event_idx
+		{
+			std::get<0>(parts)
+		};
+
+		assert(event_idx != opts.event_idx);
+		const event::fetch _event
+		{
+			event_idx, std::nothrow
+		};
+
+		if(!_event.valid)
+			continue;
+
+		// Make the references on behalf of the future event
+		write_opts _opts;
+		_opts.op = opts.op;
+		_opts.event_idx = event_idx;
+		_opts.appendix.reset();
+		_opts.appendix.set(appendix::EVENT);
+		_opts.appendix.set(appendix::EVENT_REFS);
+		_opts.event_refs = opts.horizon_resolve;
+		write(txn, _event, _opts);
+
+		// Delete the event_horizon entry after resolving.
+		thread_local char buf[EVENT_HORIZON_KEY_MAX_SIZE];
+		const string_view &key
+		{
+			event_horizon_key(buf, at<"event_id"_>(event), event_idx)
+		};
+
+		db::txn::append
+		{
+			txn, dbs::event_horizon,
+			{
+				opts.op == db::op::SET?
+					db::op::DELETE:
+					db::op::SET,
+				key
+			}
+		};
+	}
+}
+
 void
 ircd::m::dbs::_index_event_sender(db::txn &txn,
                                   const event &event,

modules/console.cc

@@ -6416,6 +6416,48 @@ console_cmd__event__bad(opt &out, const string_view &line)
 	return true;
 }
 
+bool
+console_cmd__event__horizon(opt &out, const string_view &line)
+{
+	const params param{line, " ",
+	{
+		"event_id",
+	}};
+
+	const m::event::id &event_id
+	{
+		param.at("event_id")
+	};
+
+	char buf[m::dbs::EVENT_HORIZON_KEY_MAX_SIZE];
+	const string_view &key
+	{
+		m::dbs::event_horizon_key(buf, event_id, 0UL)
+	};
+
+	for(auto it(m::dbs::event_horizon.begin(key)); it; ++it)
+	{
+		const auto &event_idx
+		{
+			std::get<0>(m::dbs::event_horizon_key(it->first))
+		};
+
+		const auto _event_id
+		{
+			m::event_id(event_idx, std::nothrow)
+		};
+
+		out << event_id
+		    << " -> "
+		    << event_idx
+		    << " "
+		    << _event_id
+		    << std::endl;
+	}
+
+	return true;
+}
+
 bool
 console_cmd__event__cached(opt &out, const string_view &line)
 {