I am working on my first "real" Clojure application. I started building tools
and looking use cases for my daily work, so i would
have a direct benefit from using Clojure. The first application would be an
unpacking of an edn definition of access control lists
for Apache JackRabbit. The edn-acls vector represents such lists.
Privileges (:privilege i.e. "jcr:read", "jcr:all") to a path (:path i.e.
"/content") can be granted or denied (:primaryType "rep:GrantACE",
"rep:DenyACE") for principals (:principalName i.e. "admin" "workflow-editors").
I am currently stuck at the following questions:
1. How to (efficiently - that would be ) accumulate the data. It seems like
i am not getting the data returned from unpack-aces-for-path into a list or
vector. I tried to pass an accumulator to edn-acl-unpack but that didn't work
out.
2. There are a bunch of zip methods already available, but i didn't find one
which transforms a list/vector from a map {"jcr:read" ["anonymous"
"workflow-users"] into [["jcr:read" "anonymous"] ["jcr:read"
"workflow-users"]]. I didn't find an implementation in core, but i wonder if
there was something like that already.
3. Getting more idiomatic ...
The code ...
(def edn-acls [{"/content"
[{"rep:GrantACE"
[{"jcr:read" ["anonymous" "workflow-users"]}
{"jcr:all" ["admin" "workflow-editors"]}]}]}
{"/etc"
[{"rep:DenyACE"
[{"jcr:all" ["anonymous" "workflow-users"]}]}
{"rep:GrantACE"
[{"jcr:read" ["anonymous" "workflow-users"]}]}
{"rep:GrantACE"
[{"jcr:all" ["admin" "workflow-editors"]}]}]}])
(defn map-privileges-to-principals
[primary-type
privileges]
(for [privilege-for-principals privileges
[privilege principals] privilege-for-principals]
(for [principal principals]
(hash-map :primaryType primary-type
:privilege privilege
:principalName principal))))
(defn unpack-aces
[aces]
(flatten
(for [ace aces]
(for [[primary-type privileges] ace]
(map-privileges-to-principals primary-type privileges)))))
(defn unpack-aces-for-path
[aces-for-path]
(for [[path aces] aces-for-path]
(hash-map :path path
:acls (unpack-aces aces))))
(defn edn-acl-unpack
[policies]
(let [head (first policies)
tail (rest policies)]
(when (not (empty? head))
(let [entry (unpack-aces-for-path head)]
(when (not (empty? tail))
(recur tail))))))
(edn-acl-unpack edn-acls)
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