private _handleOpenKeydown()

in src/material/select/select.ts [743:787]
38 lines of code
21 McCabe index (conditional complexity)

  private _handleOpenKeydown(event: KeyboardEvent): void {
    const manager = this._keyManager;
    const keyCode = event.keyCode;
    const isArrowKey = keyCode === DOWN_ARROW || keyCode === UP_ARROW;
    const isTyping = manager.isTyping();

    if (isArrowKey && event.altKey) {
      // Close the select on ALT + arrow key to match the native <select>
      event.preventDefault();
      this.close();
      // Don't do anything in this case if the user is typing,
      // because the typing sequence can include the space key.
    } else if (
      !isTyping &&
      (keyCode === ENTER || keyCode === SPACE) &&
      manager.activeItem &&
      !hasModifierKey(event)
    ) {
      event.preventDefault();
      manager.activeItem._selectViaInteraction();
    } else if (!isTyping && this._multiple && keyCode === A && event.ctrlKey) {
      event.preventDefault();
      const hasDeselectedOptions = this.options.some(opt => !opt.disabled && !opt.selected);

      this.options.forEach(option => {
        if (!option.disabled) {
          hasDeselectedOptions ? option.select() : option.deselect();
        }
      });
    } else {
      const previouslyFocusedIndex = manager.activeItemIndex;

      manager.onKeydown(event);

      if (
        this._multiple &&
        isArrowKey &&
        event.shiftKey &&
        manager.activeItem &&
        manager.activeItemIndex !== previouslyFocusedIndex
      ) {
        manager.activeItem._selectViaInteraction();
      }
    }
  }