            // we're not currently navigating the history; NOP.
                        return;
                    } else if (this.historyIndex < this.history.length - 1) {
                        this.historyIndex += 1;
                        this.input = this.historyBuffer[this.historyIndex];
                    } else if (this.historyIndex == this.history.length - 1) {
                        // we're coming back from the last history value; reset
                        // the input to whatever it was