story-1.clj

(ns bank-ocr.core
  (:require [clojure.set :as set]
            [clojure.java.io :as io]))

;; SEE: http://codingdojo.org/cgi-bin/wiki.pl?KataBankOCR

(def top
  {"   " #{1 4}
   " _ " #{0 2 3 5 6 7 8 9}})

(def middle
  {"| |" #{0}
   "  |" #{1 7}
   " _|" #{2 3}
   "|_|" #{4 8 9}
   "|_ " #{5 6}})

(def bottom
  {"  |" #{1 4 7}
   "|_ " #{2}
   " _|" #{3 5 9}
   "|_|" #{0 6 8}})

(defn parse-number [[t m b]]
  (->> [(top t) (middle m) (bottom b)]
        (reduce set/intersection)
        first))

(defn read-account-number [file-lines]
  (->> (take 3 file-lines)
       (map #(re-seq #"..." %))
       (apply interleave)
       (partition 3)
       (reduce
        (fn [number parts]
          (str number (or (parse-number parts) \?)))
        "")))

(defn read-account-numbers [file]
  (->> (io/file file)
       io/reader
       line-seq
       (partition-all 4)
       (map read-account-number)))