Support for GetAchievementAndUnlockTime

[Yanrishatum]

This method takes two pointers, bool with unlocked state and uint32 with unlock time in unix timestamp.
This issue is more about how to format it for Haxe code, I can implement it and make a pull request myself.
Unlock time may be 0, even if achievement already unlocked (if it was unlocked before December 2009).
So there a several ways:

1. getAchievementUnlockTime(id:String):Int
   Will return 0 if achievement is not unlocked, and non-zero value otherwise. This will automatically cease the support for 2009< achievements, but I think this is not very bad in current case. (We're not making some sort of achievement unlocker, yes? :) )
2. getAchievementAndUnlockTime(id:String):{ achieved:Bool, unlockTime:Int }
   E.g. object/typedef with both values.
3. Make both methods :)

[larsiusprime]

Another approach is to return a sentinel value like -1 for "is unlocked, but we can't determine the time (ie it was before December 2009)". Then you wouldn't need two functions or a typedef. Any reason this wouldn't work?

Like you said it really doesn't seem like it will be an issue for us as the only case I can really imagine it mattering for is if someone wanted to rewrite their pre-2010 game in Haxe or something and re-use the same steam ID.

[Yanrishatum]

Then it's better to return -1 as "not unlocked"? It would make more sense, as "not unlocked" is a state without time at all.
UPD: Plus it's defined as unsigned int in steam API, so -1 would be more dangerous, no?

[larsiusprime]

Yeah sure, whatever makes the most sense, as long as the function documentation explains it. So:

-1: not unlocked
 0: unlocked, but we don't know when
 X: unlocked at time X

0 seems like an appropriate "unknown time" sentinel value since it's literally impossible for a Steam Game to have an achievement unlocked in the 70's. Since it's a unix timestamp the value for the int is milliseconds, right? Is -1 safe for us to use in that case? I'm not sure if DateTime is going to be wanting to interpret that value as an unsigned integer, and thus -1 is actually representing some valid amount of time. If it's not safe to use -1 as a sentinel value, then maybe we do need to have the two functions after all.

[Yanrishatum]

It's in seconds. Time is seconds since January 1, 1970. - from isteamuserstats.h.
And condition for 0 time is: If the return value is true, but the unlock time is zero, that means it was unlocked before Steam began tracking achievement unlock times (December 2009).

[larsiusprime]

Okay, cool, so we've got a 32 bit integer here which only going off the positive value will let us get to 2038? Seems good to me.