Determine if an author can edit a document

//Function to determine if user can edit a document 
//FIRST PARAMETER IS NotesDocument, SECOND PARAMETER IS Name of authors field 
function isAuthor( doc:NotesDocument, authorsFieldName ) { 
        var level = doc.getParentDatabase().getCurrentAccessLevel(); 
    if (level >= NotesACL.LEVEL_EDITOR) { 
        return true;        //editor or higher 
    } else if (level < NotesACL.LEVEL_AUTHOR) { 
        return false;        //reader or lower 
    } else {    //author 
                  var authors = doc.getItemValue(authorsFieldName);        //field containing all document authors 
                if (authors === null) { 
                                return false; 
                }        //no authors field present 
                var userName = @UserName().toLowerCase(); 
                var groupNames = context.getUser().getGroups(); //get the groups the user is in 
                var roles = context.getUser().getRoles(); 
                for (var i=0; i<authors.length; i++) { 
                            if (authors[i].substring(0,1) == "[") {        //is a role 
                                for (var j=0; j<roles.length; j++) { 
                                    if (authors[i].toLowerCase() == roles[j].toLowerCase()) {        //on of user's roles is in authors field 
                                                return true; 
                                    }//end test for role 
                                    }// end inner for 
                            }//end test for role entry 
                            else if (authors[i].toLowerCase() == userName ) {    //username matches one of the values in the authors field 
                                        return true; 
                            }         
                            else if (!groupNames.isEmpty()){ 
                            //test if group the user is in is in the authors field 
                                    for (var j=0; j<groupNames.length; j++ ){ 
                                            if (authors[i].toLowerCase()==groupNames[j].toLowerCase() ){ 
                                            return true; 
                                            } 
                                    } 
                            } 
                } 
            } 
    return false; 
}