@Nullable
  private PsiElement findCommentAtCaret() {
    int offset = myCaret.getOffset();
    TextRange range = new TextRange(myCaret.getSelectionStart(), myCaret.getSelectionEnd());
    if (offset == range.getEndOffset()) {
      offset--;
    }
    if (offset <= range.getStartOffset()) {
      offset++;
    }
    PsiElement elt = myFile.getViewProvider().findElementAt(offset);
    if (elt == null) return null;
    PsiElement comment = PsiTreeUtil.getParentOfType(elt, PsiComment.class, false);
    if (comment == null || myCaret.hasSelection() && !range.contains(comment.getTextRange())) {
      return null;
    }

    return comment;
  }
  public static void verifyCaretAndSelectionState(
      Editor editor, CaretAndSelectionState caretState, String message) {
    boolean hasChecks = false;
    for (int i = 0; i < caretState.carets.size(); i++) {
      EditorTestUtil.CaretInfo expected = caretState.carets.get(i);
      if (expected.position != null || expected.selection != null) {
        hasChecks = true;
        break;
      }
    }
    if (!hasChecks) {
      return; // nothing to check, so we skip caret/selection assertions
    }
    String messageSuffix = message == null ? "" : (message + ": ");
    CaretModel caretModel = editor.getCaretModel();
    List<Caret> allCarets = new ArrayList<Caret>(caretModel.getAllCarets());
    assertEquals(
        messageSuffix + " Unexpected number of carets", caretState.carets.size(), allCarets.size());
    for (int i = 0; i < caretState.carets.size(); i++) {
      String caretDescription =
          caretState.carets.size() == 1
              ? ""
              : "caret " + (i + 1) + "/" + caretState.carets.size() + " ";
      Caret currentCaret = allCarets.get(i);
      int actualCaretLine = editor.getDocument().getLineNumber(currentCaret.getOffset());
      int actualCaretColumn =
          currentCaret.getOffset() - editor.getDocument().getLineStartOffset(actualCaretLine);
      LogicalPosition actualCaretPosition = new LogicalPosition(actualCaretLine, actualCaretColumn);
      int selectionStart = currentCaret.getSelectionStart();
      int selectionEnd = currentCaret.getSelectionEnd();
      LogicalPosition actualSelectionStart = editor.offsetToLogicalPosition(selectionStart);
      LogicalPosition actualSelectionEnd = editor.offsetToLogicalPosition(selectionEnd);
      CaretInfo expected = caretState.carets.get(i);
      if (expected.position != null) {
        assertEquals(
            messageSuffix + caretDescription + "unexpected caret position",
            expected.position,
            actualCaretPosition);
      }
      if (expected.selection != null) {
        LogicalPosition expectedSelectionStart =
            editor.offsetToLogicalPosition(expected.selection.getStartOffset());
        LogicalPosition expectedSelectionEnd =
            editor.offsetToLogicalPosition(expected.selection.getEndOffset());

        assertEquals(
            messageSuffix + caretDescription + "unexpected selection start",
            expectedSelectionStart,
            actualSelectionStart);
        assertEquals(
            messageSuffix + caretDescription + "unexpected selection end",
            expectedSelectionEnd,
            actualSelectionEnd);
      } else {
        assertFalse(
            messageSuffix
                + caretDescription
                + "should has no selection, but was: ("
                + actualSelectionStart
                + ", "
                + actualSelectionEnd
                + ")",
            currentCaret.hasSelection());
      }
    }
  }
  @Override
  public void invoke(
      @NotNull Project project,
      @NotNull Editor editor,
      @NotNull Caret caret,
      @NotNull PsiFile file) {
    if (!CodeInsightUtilBase.prepareEditorForWrite(editor)) return;
    myProject = project;
    myEditor = editor;
    myCaret = caret;
    myFile = file;

    myDocument = editor.getDocument();

    if (!FileDocumentManager.getInstance().requestWriting(myDocument, project)) {
      return;
    }
    FeatureUsageTracker.getInstance().triggerFeatureUsed("codeassists.comment.block");
    final Commenter commenter = findCommenter(myFile, myEditor, caret);
    if (commenter == null) return;

    final String prefix;
    final String suffix;

    if (commenter instanceof SelfManagingCommenter) {
      final SelfManagingCommenter selfManagingCommenter = (SelfManagingCommenter) commenter;
      mySelfManagedCommenterData =
          selfManagingCommenter.createBlockCommentingState(
              caret.getSelectionStart(), caret.getSelectionEnd(), myDocument, myFile);

      if (mySelfManagedCommenterData == null) {
        mySelfManagedCommenterData = SelfManagingCommenter.EMPTY_STATE;
      }

      prefix =
          selfManagingCommenter.getBlockCommentPrefix(
              caret.getSelectionStart(), myDocument, mySelfManagedCommenterData);
      suffix =
          selfManagingCommenter.getBlockCommentSuffix(
              caret.getSelectionEnd(), myDocument, mySelfManagedCommenterData);
    } else {
      prefix = commenter.getBlockCommentPrefix();
      suffix = commenter.getBlockCommentSuffix();
    }

    if (prefix == null || suffix == null) return;

    TextRange commentedRange = findCommentedRange(commenter);
    if (commentedRange != null) {
      final int commentStart = commentedRange.getStartOffset();
      final int commentEnd = commentedRange.getEndOffset();
      int selectionStart = commentStart;
      int selectionEnd = commentEnd;
      if (myCaret.hasSelection()) {
        selectionStart = myCaret.getSelectionStart();
        selectionEnd = myCaret.getSelectionEnd();
      }
      if ((commentStart < selectionStart || commentStart >= selectionEnd)
          && (commentEnd <= selectionStart || commentEnd > selectionEnd)) {
        commentRange(selectionStart, selectionEnd, prefix, suffix, commenter);
      } else {
        uncommentRange(commentedRange, trim(prefix), trim(suffix), commenter);
      }
    } else {
      if (myCaret.hasSelection()) {
        int selectionStart = myCaret.getSelectionStart();
        int selectionEnd = myCaret.getSelectionEnd();
        if (commenter instanceof IndentedCommenter) {
          final Boolean value = ((IndentedCommenter) commenter).forceIndentedLineComment();
          if (value != null && value == Boolean.TRUE) {
            selectionStart =
                myDocument.getLineStartOffset(myDocument.getLineNumber(selectionStart));
            selectionEnd = myDocument.getLineEndOffset(myDocument.getLineNumber(selectionEnd));
          }
        }
        commentRange(selectionStart, selectionEnd, prefix, suffix, commenter);
      } else {
        EditorUtil.fillVirtualSpaceUntilCaret(editor);
        int caretOffset = myCaret.getOffset();
        if (commenter instanceof IndentedCommenter) {
          final Boolean value = ((IndentedCommenter) commenter).forceIndentedLineComment();
          if (value != null && value == Boolean.TRUE) {
            final int lineNumber = myDocument.getLineNumber(caretOffset);
            final int start = myDocument.getLineStartOffset(lineNumber);
            final int end = myDocument.getLineEndOffset(lineNumber);
            commentRange(start, end, prefix, suffix, commenter);
            return;
          }
        }
        myDocument.insertString(caretOffset, prefix + suffix);
        myCaret.moveToOffset(caretOffset + prefix.length());
      }
    }
  }
  @Nullable
  private TextRange findCommentedRange(final Commenter commenter) {
    final CharSequence text = myDocument.getCharsSequence();
    final FileType fileType = myFile.getFileType();
    if (fileType instanceof CustomSyntaxTableFileType) {
      Lexer lexer =
          new CustomFileTypeLexer(((CustomSyntaxTableFileType) fileType).getSyntaxTable());
      final int caretOffset = myCaret.getOffset();
      int commentStart =
          CharArrayUtil.lastIndexOf(text, commenter.getBlockCommentPrefix(), caretOffset);
      if (commentStart == -1) return null;

      lexer.start(text, commentStart, text.length());
      if (lexer.getTokenType() == CustomHighlighterTokenType.MULTI_LINE_COMMENT
          && lexer.getTokenEnd() >= caretOffset) {
        return new TextRange(commentStart, lexer.getTokenEnd());
      }
      return null;
    }

    final String prefix;
    final String suffix;
    // Custom uncommenter is able to find commented block inside of selected text
    final String selectedText = myCaret.getSelectedText();
    if ((commenter instanceof CustomUncommenter) && selectedText != null) {
      final TextRange commentedRange =
          ((CustomUncommenter) commenter).findMaximumCommentedRange(selectedText);
      if (commentedRange == null) {
        return null;
      }
      // Uncommenter returns range relative to text start, so we need to shift it to make abosolute.
      return commentedRange.shiftRight(myCaret.getSelectionStart());
    }

    if (commenter instanceof SelfManagingCommenter) {
      SelfManagingCommenter selfManagingCommenter = (SelfManagingCommenter) commenter;

      prefix =
          selfManagingCommenter.getBlockCommentPrefix(
              myCaret.getSelectionStart(), myDocument, mySelfManagedCommenterData);
      suffix =
          selfManagingCommenter.getBlockCommentSuffix(
              myCaret.getSelectionEnd(), myDocument, mySelfManagedCommenterData);
    } else {
      prefix = trim(commenter.getBlockCommentPrefix());
      suffix = trim(commenter.getBlockCommentSuffix());
    }
    if (prefix == null || suffix == null) return null;

    TextRange commentedRange;

    if (commenter instanceof SelfManagingCommenter) {
      commentedRange =
          ((SelfManagingCommenter) commenter)
              .getBlockCommentRange(
                  myCaret.getSelectionStart(),
                  myCaret.getSelectionEnd(),
                  myDocument,
                  mySelfManagedCommenterData);
    } else {
      if (!testSelectionForNonComments()) {
        return null;
      }

      commentedRange = getSelectedComments(text, prefix, suffix);
    }
    if (commentedRange == null) {
      PsiElement comment = findCommentAtCaret();
      if (comment != null) {

        String commentText = comment.getText();
        if (commentText.startsWith(prefix) && commentText.endsWith(suffix)) {
          commentedRange = comment.getTextRange();
        }
      }
    }
    return commentedRange;
  }