degesch: Lua: allow simulating user input

Also added UTF-8 validation to buffer:log() while I'm at it.

degesch.c

@@ -7432,6 +7432,15 @@ lua_plugin_handle_string_filter_result (struct lua_plugin *self,
 	return true;
 }
 
+static const char *
+lua_plugin_check_utf8 (lua_State *L, int arg)
+{
+	size_t len;
+	const char *s = luaL_checklstring (L, arg, &len);
+	luaL_argcheck (L, utf8_validate (s, len), 1, "must be valid UTF-8");
+	return s;
+}
+
 static void
 lua_plugin_log_error
 	(struct lua_plugin *self, const char *where, struct error *error)
@@ -7548,7 +7557,7 @@ lua_buffer_log (lua_State *L)
 {
 	struct lua_buffer *wrapper = luaL_checkudata (L, 1, XLUA_BUFFER_METATABLE);
 	luaL_argcheck (L, wrapper->buffer, 1, "dead reference used");
-	const char *message = luaL_checkstring (L, 2);
+	const char *message = lua_plugin_check_utf8 (L, 2);
 
 	struct buffer *buffer = wrapper->buffer;
 	log_full (wrapper->plugin->ctx, buffer->server, buffer,
@@ -7556,12 +7565,25 @@ lua_buffer_log (lua_State *L)
 	return 0;
 }
 
+static int
+lua_buffer_execute (lua_State *L)
+{
+	struct lua_buffer *wrapper = luaL_checkudata (L, 1, XLUA_BUFFER_METATABLE);
+	luaL_argcheck (L, wrapper->buffer, 1, "dead reference used");
+	const char *line = lua_plugin_check_utf8 (L, 2);
+
+	struct buffer *buffer = wrapper->buffer;
+	process_input_utf8 (wrapper->plugin->ctx, buffer, line, 0);
+	return 0;
+}
+
 static luaL_Reg lua_buffer_table[] =
 {
 	// TODO: some useful methods or values
 	{ "__gc",       lua_buffer_gc         },
 	{ "get_server", lua_buffer_get_server },
 	{ "log",        lua_buffer_log        },
+	{ "execute",    lua_buffer_execute    },
 	{ NULL,         NULL                  }
 };