public static void initOffsets(final PsiFile file, final OffsetMap offsetMap) {
    int offset =
        Math.max(
            offsetMap.getOffset(CompletionInitializationContext.SELECTION_END_OFFSET),
            offsetMap.getOffset(CompletionInitializationContext.IDENTIFIER_END_OFFSET));

    PsiElement element = file.findElementAt(offset);
    if (element instanceof PsiWhiteSpace
        && (!element.textContains('\n')
            || CodeStyleSettingsManager.getSettings(file.getProject())
                .getCommonSettings(JavaLanguage.INSTANCE)
                .METHOD_PARAMETERS_LPAREN_ON_NEXT_LINE)) {
      element = file.findElementAt(element.getTextRange().getEndOffset());
    }
    if (element == null) return;

    if (LEFT_PAREN.accepts(element)) {
      offsetMap.addOffset(LPAREN_OFFSET, element.getTextRange().getStartOffset());
      PsiElement list = element.getParent();
      PsiElement last = list.getLastChild();
      if (last instanceof PsiJavaToken
          && ((PsiJavaToken) last).getTokenType() == JavaTokenType.RPARENTH) {
        offsetMap.addOffset(RPAREN_OFFSET, last.getTextRange().getStartOffset());
      }

      offsetMap.addOffset(ARG_LIST_END_OFFSET, list.getTextRange().getEndOffset());
    }
  }
  private static void deleteImportSpec(@Nullable GoImportSpec importSpec) {
    GoImportDeclaration importDeclaration =
        PsiTreeUtil.getParentOfType(importSpec, GoImportDeclaration.class);
    if (importSpec != null && importDeclaration != null) {
      PsiElement startElementToDelete = importSpec;
      PsiElement endElementToDelete = importSpec;
      if (importDeclaration.getImportSpecList().size() == 1) {
        startElementToDelete = importDeclaration;
        endElementToDelete = importDeclaration;

        PsiElement nextSibling = endElementToDelete.getNextSibling();
        if (nextSibling != null && nextSibling.getNode().getElementType() == GoTypes.SEMICOLON) {
          endElementToDelete = nextSibling;
        }
      }
      // todo: delete after proper formatter implementation
      PsiElement nextSibling = endElementToDelete.getNextSibling();
      if (nextSibling instanceof PsiWhiteSpace && nextSibling.textContains('\n')) {
        endElementToDelete = nextSibling;
      }
      startElementToDelete.getParent().deleteChildRange(startElementToDelete, endElementToDelete);
    }
  }
  public void invoke(@NotNull Project project, @NotNull Editor editor, @NotNull PsiFile file) {
    myProject = project;
    myFile = file.getViewProvider().getPsi(file.getViewProvider().getBaseLanguage());
    myEditor = editor;

    PsiElement context = myFile.getContext();

    if (context != null && (context.textContains('\'') || context.textContains('\"'))) {
      String s = context.getText();
      if (StringUtil.startsWith(s, "\"") || StringUtil.startsWith(s, "\'")) {
        myFile = context.getContainingFile();
        myEditor = editor instanceof EditorWindow ? ((EditorWindow) editor).getDelegate() : editor;
      }
    }

    myDocument = myEditor.getDocument();
    if (!FileDocumentManager.getInstance().requestWriting(myDocument, project)) {
      return;
    }

    PsiDocumentManager.getInstance(project).commitDocument(myDocument);

    FeatureUsageTracker.getInstance().triggerFeatureUsed("codeassists.comment.line");

    myCodeStyleManager = CodeStyleManager.getInstance(myProject);

    final SelectionModel selectionModel = myEditor.getSelectionModel();

    boolean hasSelection = selectionModel.hasSelection();
    myStartOffset = selectionModel.getSelectionStart();
    myEndOffset = selectionModel.getSelectionEnd();

    FoldRegion fold = myEditor.getFoldingModel().getCollapsedRegionAtOffset(myStartOffset);
    if (fold != null
        && fold.shouldNeverExpand()
        && fold.getStartOffset() == myStartOffset
        && fold.getEndOffset() == myEndOffset) {
      // Foldings that never expand are automatically selected, so the fact it is selected must not
      // interfer with commenter's logic
      hasSelection = false;
    }

    if (myDocument.getTextLength() == 0) return;

    while (true) {
      int lastLineEnd = myDocument.getLineEndOffset(myDocument.getLineNumber(myEndOffset));
      FoldRegion collapsedAt = myEditor.getFoldingModel().getCollapsedRegionAtOffset(lastLineEnd);
      if (collapsedAt != null) {
        final int endOffset = collapsedAt.getEndOffset();
        if (endOffset <= myEndOffset) {
          break;
        }
        myEndOffset = endOffset;
      } else {
        break;
      }
    }

    boolean wholeLinesSelected =
        !hasSelection
            || myStartOffset
                    == myDocument.getLineStartOffset(myDocument.getLineNumber(myStartOffset))
                && myEndOffset
                    == myDocument.getLineEndOffset(myDocument.getLineNumber(myEndOffset - 1)) + 1;

    boolean startingNewLineComment =
        !hasSelection
            && isLineEmpty(myDocument.getLineNumber(myStartOffset))
            && !Comparing.equal(
                IdeActions.ACTION_COMMENT_LINE,
                ActionManagerEx.getInstanceEx().getPrevPreformedActionId());
    doComment();

    if (startingNewLineComment) {
      final Commenter commenter = myCommenters[0];
      if (commenter != null) {
        String prefix;
        if (commenter instanceof SelfManagingCommenter) {
          prefix =
              ((SelfManagingCommenter) commenter)
                  .getCommentPrefix(
                      myStartLine,
                      myDocument,
                      myCommenterStateMap.get((SelfManagingCommenter) commenter));
          if (prefix == null) prefix = ""; // TODO
        } else {
          prefix = commenter.getLineCommentPrefix();
          if (prefix == null) prefix = commenter.getBlockCommentPrefix();
        }

        int lineStart = myDocument.getLineStartOffset(myStartLine);
        lineStart = CharArrayUtil.shiftForward(myDocument.getCharsSequence(), lineStart, " \t");
        lineStart += prefix.length();
        lineStart = CharArrayUtil.shiftForward(myDocument.getCharsSequence(), lineStart, " \t");
        if (lineStart > myDocument.getTextLength()) lineStart = myDocument.getTextLength();
        myEditor.getCaretModel().moveToOffset(lineStart);
        myEditor.getScrollingModel().scrollToCaret(ScrollType.RELATIVE);
      }
    } else {
      if (!hasSelection) {
        // Don't tweak caret position if we're already located on the last document line.
        LogicalPosition position = myEditor.getCaretModel().getLogicalPosition();
        if (position.line < myDocument.getLineCount() - 1) {
          int verticalShift =
              1
                  + myEditor.getSoftWrapModel().getSoftWrapsForLine(position.line).size()
                  - position.softWrapLinesOnCurrentLogicalLine;
          myEditor.getCaretModel().moveCaretRelatively(0, verticalShift, false, false, true);
        }
      } else {
        if (wholeLinesSelected) {
          selectionModel.setSelection(myStartOffset, selectionModel.getSelectionEnd());
        }
      }
    }
  }