This piece is very scalar, except for the arpeggiated notes in the accompaniment. It follows a mostly I-V-I pattern throughout the entire piece. It then modulates using sequential modulation. I noticed there were several instances of a breakup of the I-V-I using a half diminished 7th chord. It's always followed by a I chord as a restatement of the theme.
On its second modulation, this time to a minor, and this phrase modulation displays the dependancy of this key in the whole piece. The third and final modulation returns back to the first key, ending on a perfect authentic cadence.