How may I make n and k in terms of x and y in this equation?:

$$\frac{1-n-i k}{1+n+i k}=\sqrt{x} e^{i y}$$

I have tried separating the real and imaginary terms on the left hand side using complex expand so that I can have 2 sets of equations now but I have no idea how to continue?

ComplexExpand[((1 - n - I k)/(1 + n + I k))]