ircd:Ⓜ️ Elaborate the event::prev interface with pattern conveniences.

include/ircd/m/event.h

@@ -99,6 +99,14 @@ struct ircd::m::event::prev
 {
 	enum cond :int;
 
+	std::tuple<event::id, string_view> auth_events(const uint &idx) const;
+	std::tuple<event::id, string_view> prev_states(const uint &idx) const;
+	std::tuple<event::id, string_view> prev_events(const uint &idx) const;
+
+	event::id auth_event(const uint &idx) const;
+	event::id prev_state(const uint &idx) const;
+	event::id prev_event(const uint &idx) const;
+
 	using super_type::tuple;
 	using super_type::operator=;
 };

ircd/m/event.cc

@@ -337,6 +337,76 @@ ircd::m::event::event(const id &id,
 	new (this) m::event(obj);
 }
 
+//
+// event::prev
+//
+
+ircd::m::event::id
+ircd::m::event::prev::auth_event(const uint &idx)
+const
+{
+	return std::get<0>(auth_events(idx));
+}
+
+ircd::m::event::id
+ircd::m::event::prev::prev_state(const uint &idx)
+const
+{
+	return std::get<0>(prev_states(idx));
+}
+
+ircd::m::event::id
+ircd::m::event::prev::prev_event(const uint &idx)
+const
+{
+	return std::get<0>(prev_events(idx));
+}
+
+std::tuple<ircd::m::event::id, ircd::string_view>
+ircd::m::event::prev::auth_events(const uint &idx)
+const
+{
+	const json::array &auth_event
+	{
+		at<"auth_events"_>(*this).at(idx)
+	};
+
+	return
+	{
+		unquote(auth_event.at(0)), unquote(auth_event[1])
+	};
+}
+
+std::tuple<ircd::m::event::id, ircd::string_view>
+ircd::m::event::prev::prev_states(const uint &idx)
+const
+{
+	const json::array &state_event
+	{
+		at<"prev_state"_>(*this).at(idx)
+	};
+
+	return
+	{
+		unquote(state_event.at(0)), unquote(state_event[1])
+	};
+}
+
+std::tuple<ircd::m::event::id, ircd::string_view>
+ircd::m::event::prev::prev_events(const uint &idx)
+const
+{
+	const json::array &prev_event
+	{
+		at<"prev_events"_>(*this).at(idx)
+	};
+
+	return
+	{
+		unquote(prev_event.at(0)), unquote(prev_event[1])
+	};
+}
+
 //
 // event::fetch
 //