Easiest way to go to Nainital from delhi?

Hello what's the easiest and cheapest way to travel to Nainital from delhi? I am visiting alone and a safe mode of public transport will be best for me. But so far I don't know about any buses/ trains directly to Nainital. Is there a way to access a public transport from haldwani? If yes exactly where do I need to go to access the bus? Can anyone please let me know in comments.. thank you!