Add lobby list request filtering

[wyvernbw]

closes #140

Summary

added 7 functions for filtering out lobby requests:

• set_lobby_list_filter: adds filters defined in a LobbyListFilter struct.
• set_request_lobby_list_string_filter: adds filters for key value pairs of strings.
• set_request_lobby_list_numerical_filter: adds filters for key value pairs of string number types.
• set_request_lobby_list_near_value_filter: adds sorting based on which value is closer to the filter
• set_request_lobby_list_distance_filter: adds filtering based on geographical distance
• set_request_lobby_list_slots_available_filter: adds filtering based on how many open slots a lobby has
• set_request_lobby_list_result_count_filter: adds the maximum number of results a request can resolve to.

added 1 struct:

• LobbyListFilter: struct that holds every option possible for filtering

added 1 enum:

• DistanceFilter: thin wrapper over ELobbyDistanceFilter
  I included documentation for everything I added and one code example.

[wyvernbw]

I omitted comparison types for the filters as they don't seem very useful imho. I'm open to changing this, ofc

[TrustNoOneElse]

First pretty cool that you are working on this!

I just wanted to note that you can have a List/Array of String-, Numeric- and NearValueFilters, that why i would update the LobbyListFilter struct to actually support it.

Another point on which im not certain about but the keyof those filters cannot exceed 255 chars. For setting the metadata of a lobby the function itself already returns a bool, if thats the case. In this case of the filter functions, we could maybe implement a safety check for the user, because he may be not aware of this or to add this to the docs.

[wyvernbw]

Thanks for the kind words!

I didnt know you can pass in multiple key value pairs, i assumed you have to call the function multiple times. Is this done by passing a pointer to the array to the underlying steamworks-sys call?

I just checked and you are correct, you can only pass in keys shorter than 256 characters

[TrustNoOneElse]

That is correct, you have to call the function multiple times. What i meant was your helper type LobbyListFilter, which currently only suppports one times of String, Numeric and Nearfilters. Thats why i would suggest the change to take in a Array of key/value pairs for this 3 types of filter.

And to the comparison types:
For String i can't see the use too, besides Equal and NotEqual. Also i don't know anyone which used besides this two comparision types any other comparision. But for numeric you can do quite a lot with this things.
Some examples:
NotEqual: Could be a metadata with a playerid matched against last time, so you could filter out that they don't play again, to have variation.
For the other cases (Greater then, Less Then, Equal Less, Equal Greater), the best example is level matchmaking or elo/skill matchmaking.

[wyvernbw]

ok so ive added a few things as you suggested and some qol changes

• multiple key-value pair filters
  • LobbyListFilter now takes a slices of key-value pairs
• newtype pattern for filters
  • filters take a LobbyKey struct instead of a simple str slice. This is done to restrict how a key is constructed so it can be validated.
  • new StringFilter, NumberFilter and NearFilter structs. Useful for giving a name to tuples
• comparison types
  • new ComparisonFilter enum that can be used with NumberFilter and NearFilter. Includes all options from steamworks
  • new StringFilterKind enum. Allows users to pass in whether they want to exclude or include a string value.
• lobby key validation (as mentioned)

[wyvernbw]

Ok so turns out &[T] cannot be deserialized in serde. At least i can't figure out how. So i just went ahead and changed it to use Vec. A more performant (i think) option would be Arc<[T]> but that would require the rc feature in serde