(ns batch-pmap-wide-finder
  "A basic map/reduce approach to the wide finder using agents.
  Optimized for being idiomatic and readable rather than speed.
  Updated to deal with batches of lines instead of individual lines.
  "
  (:use [clojure.contrib.duck-streams :only [reader]]
        [clojure.contrib.seq-utils :only [partition-all]]))

(def *batch-size* 50)

;;(def re #"GET /\S+-(\d+)-\S+ ")
(def re #"GET /(\d+) ")


(defn tally [line]
  (if-let [[_ hit] (re-find re line)]
    {hit 1}
    {}))


(defn count-lines
  [lines]
  (apply merge-with + (map tally lines)))


(defn find-widely
  "Return a map of pages to hit counts in filename."
  [filename]
  ;; each agent begins as an empty map.
  (apply merge-with +
         (pmap count-lines (partition *batch-size*
                                      (line-seq (reader filename))))))

;; Main
(. System/out println
   (str (find-widely (first (rest *command-line-args*)))))