ircd:Ⓜ️:dbs: Make blacklist a write option rather than API call.

include/ircd/m/dbs/dbs.h

@@ -30,7 +30,6 @@ namespace ircd::m::dbs
 
 	// [SET (txn)] Basic write suite
 	string_view write(db::txn &, const event &, const write_opts &);
-	void blacklist(db::txn &, const event::id &, const write_opts &);
 }
 
 /// Database description

include/ircd/m/dbs/write_opts.h

@@ -22,7 +22,8 @@ struct ircd::m::dbs::write_opts
 	/// actual transaction.
 	db::op op {db::op::SET};
 
-	/// Principal's index number. Most codepaths do not permit zero; must set.
+	/// Principal's index number. Most codepaths do not permit zero. This may
+	/// be zero for blacklisting, but the blacklist option must be set.
 	uint64_t event_idx {0};
 
 	/// The state btree root to perform the update on.
@@ -69,4 +70,15 @@ struct ircd::m::dbs::write_opts
 	/// made indepdently; this is slow and requires external synchronization
 	/// to not introduce inconsistent data into the txn.
 	bool allow_queries {true};
+
+	/// Setting to true allows the event_idx to be 0 which allows the insertion
+	/// of the event_id into a "blacklist" to mark it as unprocessable; this
+	/// prevents the server from repeatedly trying to process an event.
+	///
+	/// Note for now this just creates an entry in _event_idx of 0 for the
+	/// event_id which also means "not found" for most codepaths, a reasonable
+	/// default. But for codepaths that must distinguish between "not found"
+	/// and "blacklist" they must know that `event_id => 0` was *found* to be
+	/// zero.
+	bool blacklist {false};
 };

ircd/m_dbs.cc

@@ -204,6 +204,38 @@ ircd::m::dbs::write_opts::appendix_all{[]
 // Basic write suite
 //
 
+namespace ircd::m::dbs
+{
+	static void blacklist(db::txn &txn, const event::id &, const write_opts &);
+}
+
+ircd::string_view
+ircd::m::dbs::write(db::txn &txn,
+                    const event &event,
+                    const write_opts &opts)
+{
+	if(opts.event_idx == 0 && opts.blacklist)
+	{
+		blacklist(txn, at<"event_id"_>(event), opts);
+		return {};
+	}
+
+	if(unlikely(opts.event_idx == 0))
+		throw panic
+		{
+			"Cannot write to database: no index specified for event."
+		};
+
+	if(opts.appendix.test(appendix::EVENT))
+		_index_event(txn, event, opts);
+
+	if(opts.appendix.test(appendix::ROOM))
+		if(json::get<"room_id"_>(event))
+			return _index_room(txn, event, opts);
+
+	return {};
+}
+
 void
 ircd::m::dbs::blacklist(db::txn &txn,
                         const event::id &event_id,
@@ -232,27 +264,6 @@ ircd::m::dbs::blacklist(db::txn &txn,
 	};
 }
 
-ircd::string_view
-ircd::m::dbs::write(db::txn &txn,
-                    const event &event,
-                    const write_opts &opts)
-{
-	if(unlikely(opts.event_idx == 0))
-		throw panic
-		{
-			"Cannot write to database: no index specified for event."
-		};
-
-	if(opts.appendix.test(appendix::EVENT))
-		_index_event(txn, event, opts);
-
-	if(opts.appendix.test(appendix::ROOM))
-		if(json::get<"room_id"_>(event))
-			return _index_room(txn, event, opts);
-
-	return {};
-}
-
 //
 // Internal interface
 //