Parsing Keyboard Shortcuts from CGEvent

I'm trying to parse a CGEvent from myCGEventCallback for keyboard events. I can get access to modifier flags, keycode, UniChar.

So far I managed to get it to work for some combinations like command+shift+f, but I have a couple of problems for some other combinations.

1. Control and option seem to give me a UniChar of some symbols instead of alphabet. For example, option+g will give me option+copyright symbol instead of option+g.
2. I can't get function keys and cursors from UniChar.

What's the best way to interpret the result? For example, I want to get a result like control+g, option+control+g, or option+shift+f1, and so on. Here is the code for myCGEventCallback. Thanks!

func myCGEventCallback(proxy : CGEventTapProxy, type : CGEventType, event : CGEvent, refcon : UnsafeMutableRawPointer?) -> Unmanaged<CGEvent>? {
    if type == .keyDown {
        let flags = event.flags
        var msg = ""
        if flags.contains(.maskAlphaShift) {
            msg+="caps+"
        }
        if flags.contains(.maskShift) {
            msg+="shift+"
        }
        if flags.contains(.maskControl) {
            msg+="control+"
        }
        if flags.contains(.maskAlternate) {
            msg+="option+"
        }
        if flags.contains(.maskCommand) {
            msg += "command+"
        }
        if flags.contains(.maskSecondaryFn) {
            msg += "function+"
        }

        var keyCode = event.getIntegerValueField(.keyboardEventKeycode)
        var char = UniChar()
        var length = 0
        event.keyboardGetUnicodeString(maxStringLength: 1, actualStringLength: &length, unicodeString: &char)

        msg+="\(Character(UnicodeScalar(char)!))"
        debugPrint(msg)
    }
    return Unmanaged.passRetained(event)
}

I ended up just converting CGEvent to NSEvent by initializing NSEvent with CGEvent, and get charactersIgnoringModifiers. Non-characters like escape and backspace won't work though. Here's the entire CGEventCallback.

func myCGEventCallback(proxy : CGEventTapProxy, type : CGEventType, event : CGEvent, refcon : UnsafeMutableRawPointer?) -> Unmanaged<CGEvent>? {
    if type == .keyDown {
        let flags = event.flags
        var msg = ""
        if flags.contains(.maskAlphaShift) {
            msg+="caps+"
        }
        if flags.contains(.maskShift) {
            msg+="shift+"
        }
        if flags.contains(.maskControl) {
            msg+="control+"
        }
        if flags.contains(.maskAlternate) {
            msg+="option+"
        }
        if flags.contains(.maskCommand) {
            msg += "command+"
        }
        if flags.contains(.maskSecondaryFn) {
            msg += "function+"
        }
        if let other = NSEvent(cgEvent: event), let chars = other.charactersIgnoringModifiers {
           msg += chars
            debugPrint(msg)
        }
    }
    return Unmanaged.passRetained(event)
}