Quite a few views but no bites ... what have I done wrong in asking this
question? If you can't help with the problem would you please take a moment
to help me understand what has put you off?
Too much code not enough data?
Problem too complex to grasp with the supplied info?
Too dull?
Am I asking too much ... in other words I have got this far and I should be
expected to know the answer (I really feel like I should too by the way!)
Use of the term Clojurians?
Something else?
Thanks
Ray
On Tuesday, 28 May 2013 13:44:57 UTC+2, Mond Ray wrote:
>
> Hi Clojurians,
>
> I have a program which generates a lazy sequence to read ATOM feed chunks.
> That part works OK but now I want to only take a limited number of the
> chunks based on some predicate. My predicate is currently returning an
> empty list so I think (hope!) I am missing something simple.
>
> Here is an excerpt from the feed (yes the feed is in JSON and I have used
> cheshire to map to Clojure data):
>
> {:FEED_ID "5650f3ad-b793-42c6-9fef-80ba105f847d", :TITLE "Delta Feed",
> :UPDATED "2013-05-28T11:15:34.860+02:00", :GENERATOR "Products", :LINK
> {:REL "Self", :HREF "http://some-url"}, :PREVIOUS_LINK {:REL
> "prev-archive", :HREF "http://another-url"}, .....
>
> Here is the sequence generator:
>
> (defn fetch-atom-chunk
> "Returns an ATOM chunk from the feed-url"
> [feed-url]
> (:ATOM_FEED (:body (client/get feed-url {:as :json}))))
>
> (defn fetch-atom-feed
> "Returns a list of ATOM chunks from the feed-url going back to the
> from-date"
> ; [feed-url from-date] (fetch-atom-feed feed-url from-date ())
> [feed-url]
> (let [chunk (fetch-atom-chunk feed-url)]
> (lazy-seq
> (cons chunk (fetch-atom-feed (:HREF (:PREVIOUS_LINK chunk)))))))
>
> Here is the predicate:
>
> (defn feed-date-to-clj-date
> "Patch for ATOM feed date formats like '2013-05-27T14:35:00.982+02:00'
> we have to remove the final ':' from the string to enable its
> conversion"
> [feed-date]
> (.parse (java.text.SimpleDateFormat. "yyyy-MM-dd'T'HH:mm:ss.SSSZ")
> (str/replace feed-date #"(.*)(\d\d):(\d\d)" "$1$2$3")))
>
> (defn after?
> "Returns true if first-date is after second-date"
> [first-date second-date]
> (> (.getTime first-date) (.getTime second-date)))
>
> (defn more-feed-chunks-needed?
> "Look at the atom chunk and decide if we have enough"
> [from-date atom-chunk]
> (after? from-date (feed-date-to-clj-date (:UPDATED atom-chunk))))
>
> And here is how I run it forever:
>
> (fetch-atom-feed "https://producta.blah.com/feed/current";)
>
> And here is how I run it with a predicate:
>
> (def date-from (.parse (java.text.SimpleDateFormat. "yyyy-MM-dd")
> "2013-05-27"))
> (take-while #(more-feed-chunks-needed? date-from %) (fetch-atom-feed "
> https://producta.blah.com/feed/current";))
>
> Maybe this is too detailed for the group (do let me know) but otherwise I
> would appreciate your advice / tips on what I could try.
>
> Thanks
>
> Ray
>
>
>
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