harry potter - Was the casting of Alan Rickman as Snape based on the full knowledge of the future of that character?

Casting Alan Rickman (a great actor) in the role of Snape would make a great deal of sense if one considers the depth of the character as exposed by all the books up to the seventh one.

A great example is the deleted scene from the HBP movie:

The still – which does absolutely no justice to Rickman's talent – is on HP Wikia. I'd prefer not to post the links to the video as that might violate copyright.

The scene shows the choir singing 'In Noctem` and then Snape looking out at the approaching darkness.

But it seems a mite of an overkill (shades of Alec Guinness here) if one merely needs to portray an somewhat evilly guy from "The Philosopher's Stone" – yes, Rickman played those before (e.g. Die Hard), but still an overkill – and he's been known to turn down blockbuster roles before (he turned down the villain role in 007 movie Goldeneye.

Is there any support for the theory that the casting of Alan Rickman was done based on at least a rough idea of his full story and depth as a character in JKR's mind?

Ideally I'd like an explicit statement from someone involved; but circumstantial evidence based on timelines would also be OK if the former doesn't exist.

Answer

From wikipedia:

Severus Snape appears in all eight Harry Potter films, portrayed by British actor Alan Rickman. Rickman was Rowling's personal choice to portray the character. He had conversations with Rowling about his character and is one of the few Harry Potter actors that she spoke to prior to the completion of the book series about the future direction of the character. "He knew very early on that he'd been in love with Lily," said Rowling. "He needed to understand […] where this bitterness towards this boy who's the living example of her preference for another man came from."

Also from a Time article:

Rowling also had a hand in choosing most of the adult cast members. She specifically requested Coltrane. Others, like Richard Harris as Dumbledore, Maggie Smith as Professor McGonagall and Alan Rickman as Professor Snape came straight from a wish list of actors that Rowling provided the producers. She gave Rickman and Coltrane precious bits of information about their characters' futures.

And, from a much later Time article, Alan Rickman is quote as saying:

"Three children have become adults since a phone call with Jo Rowling, containing one small clue, persuaded me that there was more to Snape than an unchanging costume, and that even though only three of the books were out at that time, she held the entire massive but delicate narrative in the surest of hands."