Modeling Combat

I'm trying to do some modeling of Pokemon GO combat, and am stuck at a few places. The Damage Mechanics page here (bottom left, below Gym Mechanics) is helpful in explaining the damage formulas. But how about energy? Where is this explained? How much energy does it take to fill one's bar? I know it's generated by the Energy of the quick attack, and by damage taken. Yet in battle, I see it jumping around all the time. Where are these mechanics spelled out? Any resources appreciated.