Parse a comma-separated parameter list like those used in HTTP headers.

auth-params.clj

;; From RFC 2616, section 2.2: token "=" quoted-string
(def head-re #"([^\p{Cntrl}()<>@,;:\\\"\/\[\]?={} \t]+)=\"((?:[^\"\\]|\\.)*)\"")

;; Same as above, with a prepended comma optionally surrounded by whitespace
(def tail-re #"\s*,\s*([^\p{Cntrl}()<>@,;:\\\"\/\[\]?={} \t]+)=\"((?:[^\"\\]|\\.)*)\"")

(defn parse-params [input]
  (loop [input input regex head-re params nil]
    (let [matcher (re-matcher regex input)]
      (if (.lookingAt matcher)
        (let [kv (rest (re-groups matcher))
              params (apply assoc params kv)
              rest (subs input (.end matcher))]
          (if (= (count rest) 0) ; end of input
            params
            (recur rest tail-re params)))))))

;; The following string:
;;    "realm=\"testrealm@host.com\",qop=\"auth,auth-int\",nonce=\"dcd98b7102dd\\\"2f0e8b11d0f600bfb0c093\",opaque=\"5ccc069c403ebaf9f0171e9517f40e41\""
;; Should parse into:
;;    {"opaque" "5ccc069c403ebaf9f0171e9517f40e41", "nonce" "dcd98b7102dd\\\"2f0e8b11d0f600bfb0c093", "qop" "auth,auth-int", "realm" "testrealm@host.com"}