coordinates.clj

(ns coordinates
  (:import [clojure.lang IPersistentVector IPersistentMap]))

(declare flatten)

(defmulti append 
  "Appends a given data structure to a flat map"
  #(class %3))

(defmethod append IPersistentVector [m k v]
  (assoc m k (vec (distinct (concat (m k) v)))))

(defmethod append IPersistentMap [m k v]
  (flatten m (str (name k) "__") v))

(defmethod append :default [m k v] 
  (assoc m k (if-let [vals (m k)]
	       (vec (distinct (conj vals v)))
	       (vector v))))

(defn flatten 
  "Reduces a nil-free coordinate c into the 
   taxonomy m using an optional key prefix p"
  ([c] (flatten {} "" c))
  ([m c] (flatten m "" c))
  ([m p c]
     (reduce #(append %1 
		      (keyword (str p (name (key %2)))) 
		      (val %2)) m 
	     (filter #(not (nil? (val %))) c))))

(defn taxonomy [coordinates]
  "Returns the available coordinate values"
  (reduce flatten {} coordinates))