Method backspace

src/components/modules/blockEvents.ts:347–425

* Handle backspace keydown on Block * * @param {KeyboardEvent} event - keydown

(event: KeyboardEvent)

   * @param {KeyboardEvent} event - keydown
   */
  private backspace(event: KeyboardEvent): void {
    const { BlockManager, Caret } = this.Editor;
    const { currentBlock, previousBlock } = BlockManager;

    if (currentBlock === undefined) {
      return;
    }

    /**
     * If some fragment is selected, leave native behaviour
     */
    if (!SelectionUtils.isCollapsed) {
      return;
    }

    /**
     * If caret is not at the start, leave native behaviour
     */
    if (!currentBlock.currentInput || !caretUtils.isCaretAtStartOfInput(currentBlock.currentInput)) {
      return;
    }
    /**
     * All the cases below have custom behaviour, so we don't need a native one
     */
    event.preventDefault();
    this.Editor.Toolbar.close();

    const isFirstInputFocused = currentBlock.currentInput === currentBlock.firstInput;

    /**
     * For example, caret at the start of the Quote second input (caption) — just navigate previous input
     */
    if (!isFirstInputFocused) {
      Caret.navigatePrevious();

      return;
    }

    /**
     * Backspace at the start of the first Block should do nothing
     */
    if (previousBlock === null) {
      return;
    }

    /**
     * If prev Block is empty, it should be removed just like a character
     */
    if (previousBlock.isEmpty) {
      BlockManager.removeBlock(previousBlock);

      return;
    }

    /**
     * If current Block is empty, just remove it and set cursor to the previous Block (like we're removing line break char)
     */
    if (currentBlock.isEmpty) {