match.clj

(ns match)

(defn nest [m]
  "Converts a flat map with keys using underscore 
   nesting to proper nested maps"
  (reduce (fn [m [k v]] 
	    (let [ks (map keyword 
			  (.split (if (keyword? k) (name k) k) "__"))] 
	      (assoc-in m ks v))) {} m))

(defn- points [k v1 v2]
  "Given a key and two values, determine how many
   match points this pair is worth, adjusting for 
   special key weighting (todo: custom weights)"
  (if (= v1 v2) 
    (cond (= :id k) 100
	  :else 1) 
    0))

(defn- rank 
  "Returns the number of matching elements 
   between the candidate and master"
  ([candidate master] (rank candidate master (vector)))
  ([candidate master ks]
     (if (empty? master) 0
	 (let [e (first master) k (key e) v (val e) ks (conj ks k)]
	     (+ (if (map? v) 
		  (rank candidate v ks) 
		  (points k (get-in candidate ks) v))
		(rank candidate (rest master) (vec (drop-last ks))))))))

(defn convert [query]
  "Converts the query value strings to native types"
  (zipmap (keys query) 
	  (replace {"true" true 
		    "false" false} (vals query))))

(defn best-match [query coordinates]
  "Select the best matching coordinate given 
   the user selected query parameters"
  (let [candidate (nest (convert query))]
    (reduce #(if (> (rank candidate %1) 
		    (rank candidate %2)) %1 %2)
	    coordinates)))