For having had all they could do to repulse an enemy

"As for the Macedonians, however, their struggle with https://en.wikipedia.org/wiki/King_Porus blunted their courage and stayed their further advance into India. For having had all they could do to repulse an enemy who mustered only twenty thousand infantry and two thousand horse, they violently opposed Alexander when he insisted on crossing the river Ganges also, the width of which, as they learned, was thirty-two furlongs, its depth a hundred fathoms, while its banks on the further side were covered with multitudes of men-at-arms and horsemen and elephants. For they were told that the kings of the Ganderites and Praesii were awaiting them with eighty thousand horsemen, two hundred thousand footmen, eight thousand chariots, and six thousand fighting elephants. And there was no boasting in these reports. For Androcottus, who reigned there not long afterwards, made a present to Seleucus of five hundred elephants, and with an army of six hundred thousand men overran and subdued all India."
<Source: "Chandragupta Maurya" in WIKIPEDIA https://en.wikipedia.org/wiki/Chandragupta_Maurya>
I'd like to know if "done" is implied "done" after "having had."
And I'd like to know if "they violently opposed Alexander" is the result of "For they were told that~."
Thank you in advance for your help.