I have managed to create a function that will read an ATOM feed
indefinitely and now need a way to stop it ;-)
(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]
(let [chunk (fetch-atom-chunk feed-url)]
(lazy-seq
(cons chunk (fetch-atom-feed (:HREF (:PREVIOUS_LINK chunk)))))))
(defn after?
"Returns true if first-date is after second-date"
[first-date second-date]
(> (.getTime first-date) (.getTime second-date)))
(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 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))))
(def date-from (.parse (java.text.SimpleDateFormat. "yyyy-MM-dd")
"2013-05-27"))
(take-while #(more-feed-chunks-needed? date-from %) (fetch-atom-feed
"some-url"))
; example of the feed
; {: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"}, .....
If I run without the take-while it runs forever (so I am happy that its
generating data) but when I add the take-while I get an empty list.
I guess I'm missing something simple and would welcome suggestions.
Thanks
Ray
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