Constant voltage regulator to charge lithium ion cell

[Kimly]

Hi All, I am very new to electronics so please excuse my stupid questions.
I am trying to design a solar powered light to assist people in rural areas who don't have electricity. I have the following components, a solar panel which can put out 170mA and 5.5V at max performance. I have a lithium ion cell which is 4.2v 2600mA and an LED which offers max performance at 3.7v and 350mA.

What I need is a voltage regulator which will allow the lithium cell to be charged at a constant 4.2v. Also, it must not be over charged.

I also need a protection circuit which must prevent over discharge of the lithium ion cell by the LED. (this I think I may be able to arrange with the purchase of the Lithium ion cell)

any help will be appreciated
thanks