--Myles

On Tue, Jan 31, 2012 at 6:37 PM, Myles C. Maxfield <myles.maxfield@gmail.com> wrote:

Here are my initial ideas about supporting cookies. Note that I'm using Chrome for ideas since it's open source.

Network/HTTP/Conduit/Cookies.hs file
Exporting the following symbols:
type StuffedCookie = SetCookie
A regular SetCookie can have Nothing for its Domain and Path attributes. A StuffedCookie has to have these fields set.
type CookieJar = [StuffedCookie]
Chrome's cookie jar is implemented as (the C++ equivalent of) Map W.Ascii StuffedCookie. The key is the "eTLD+1" of the domain, so lookups for all cookies for a given domain are fast.

I think I'll stay with just a list of StuffedCookies just to keep it simple. Perhaps a later revision can implement the faster map.
getRelevantCookies :: Request m -> CookieJar -> UTCTime -> (CookieJar, Cookies)

Gets all the cookies from the cookie jar that should be set for the given Request.
The time argument is whatever "now" is (it's pulled out of the function so the function can remain pure and easily testable)

The function will also remove expired cookies from the cookie jar (given what "now" is) and return the filtered cookie jar
putRelevantCookies :: Request m -> CookieJar -> [StuffedCookie] -> CookieJar

Insert cookies from a server response into the cookie jar.
The first argument is only used for checking to see which cookies are valid (which cookies match the requested domain, etc, so site1.com can't set a cookie for site2.com)

stuffCookie :: Request m -> SetCookie -> StuffedCookie
If the SetCookie's fields are Nothing, fill them in given the Request from which it originated
getCookies :: Response a -> ([SetCookie], Response a)

Pull cookies out of a server response. Return the response with the Set-Cookie headers filtered out
putCookies :: Request a -> Cookies -> Request a
A wrapper around renderCookies. Inserts some cookies into a request.

Doesn't overwrite cookies that are already set in the request
These functions will be exported from Network.HTTP.Conduit as well, so callers can use them to re-implement redirection chains
I won't implement a cookie filtering function (like what Network.Browser has)
If you want to have arbitrary handling of cookies, re-implement redirection following. It's not very difficult if you use the API provided, and the 'http' function is open source so you can use that as a reference.

I will implement the functions according to RFC 6265
I will also need to write the following functions. Should they also be exported?
canonicalizeDomain :: W.Ascii -> W.Ascii
turns "..a.b.c..d.com..." to "a.b.c.d.com"

Technically necessary for domain matching (Chrome does it)
Perhaps unnecessary for a first pass? Perhaps we can trust users for now?
domainMatches :: W.Ascii -> W.Ascii -> Maybe W.Ascii

Does the first domain match against the second domain?
If so, return the prefix of the first that isn't in the second
pathMatches :: W.Ascii -> W.Ascii -> Bool
Do the paths match?

In order to implement domain matching, I have to have knowledge of the Public Suffix List so I know that sub1.sub2.pvt.k12.wy.us can set a cookie for sub2.pvt.k12.wy.us but not for k12.wy.us (because pvt.k12.wy.us is a "suffix"). There are a variety of ways to implement this.

As far as I can tell, Chrome does it by using a script (which a human periodically runs) which parses the list at creates a .cc file that is included in the build.
I might be wrong about the execution of the script; it might be a build step. If it is a build step, however, it is suspicious that a build target would try to download a file...

Any more elegant ideas?
Feedback on any/all of the above would be very helpful before I go off into the weeds on this project.

Thanks,
Myles C. Maxfield

On Sat, Jan 28, 2012 at 8:17 PM, Michael Snoyman <michael@snoyman.com> wrote:
Thanks, looks great! I've merged it into the Github tree.

On Sat, Jan 28, 2012 at 8:36 PM, Myles C. Maxfield

<myles.maxfield@gmail.com> wrote:
> Ah, yes, you're completely right. I completely agree that moving the
> function into the Maybe monad increases readability. This kind of function
> is what the Maybe monad was designed for.
>
> Here is a revised patch.
>
>
> On Sat, Jan 28, 2012 at 8:28 AM, Michael Snoyman <michael@snoyman.com>
> wrote:
>>
>> On Sat, Jan 28, 2012 at 1:20 AM, Myles C. Maxfield
>> <myles.maxfield@gmail.com> wrote:
>> > the fromJust should never fail, beceause of the guard statement:
>> >
>> > | 300 <= code && code < 400 && isJust l'' && isJust l' = Just $ req
>> >
>> > Because of the order of the && operators, it will only evaluate fromJust
>> > after it makes sure that the argument isJust. That function in
>> > particular
>> > shouldn't throw any exceptions - it should only return Nothing.
>> >
>> > Knowing that, I don't quite think I understand what your concern is. Can
>> > you
>> > elaborate?
>>
>> You're right, but I had to squint really hard to prove to myself that
>> you're right. That's the kind of code that could easily be broken in
>> future updates by an unwitting maintainer (e.g., me). To protect the
>> world from me, I'd prefer if the code didn't have the fromJust. This
>> might be a good place to leverage the Monad instance of Maybe.
>>
>> Michael
>
>