(defmacro defcolumn [header records]
  `(def ~header
     (let [header-str# (str (quote ~header))
           size# (+ 3 (apply max (map count (cons header-str# ~records))))
           hoffset# (int (- (/ size# 2) (/ (count header-str#) 2)))
           size# (if (< hoffset# 2) (inc size#) size#)
           hoffset# (if (< hoffset# 2) 2 hoffset#)]
       {:header header-str# :records ~records :size size# :offset hoffset#})))

(defn pad [len c] (apply str (repeat len c)))

(defn col-rep [column]
  (letfn [(rec-rep [siz off rec]
                   (let [len (- siz (+ off (count rec)))]
                     (str (pad off \ ) rec (pad len \ ) "|")))]
    (let [grec-rep1 (partial rec-rep (:size column))
          grec-rep2 (partial grec-rep1 1)
          nil-rep (grec-rep2 "nil")
          recs-rep (cons (grec-rep1 (:offset column) (:header column))
                         (map grec-rep2 (:records column)))]
      {:nil-rep nil-rep :recs-rep recs-rep})))

(defn table [cols]
  (letfn [(get-record [col]
                      (if (empty? (:recs-rep col)) (:nil-rep col)
                        (first (:recs-rep col))))]
    (if (empty? (remove #(< (count %) 2) (map :recs-rep cols)))
      [(map get-record cols)]
      (lazy-cat [(map get-record cols)]
                (table (map #(assoc % :recs-rep (rest (:recs-rep %)))
                            cols))))))

(defmacro deftable [name columns] `(def ~name (table (map col-rep ~columns))))

(defn prn-table [t]
  (let [header (apply str (first t))
        len (count header)
        border (str "+" (pad (- len 1) \-) "+")
        prn-rec (fn [rec] (prn (apply str "|" rec)))]
    (doall
      ((prn border)
      (prn-rec header)
      (prn border)
      (doall (map prn-rec (rest t)))
      (prn border)))))

(comment
(use 'programthis.table)
(defcolumn ingredients ["milk" "eggs" "butter"])

(defcolumn substitutes ["splenda"])
(deftable t [ingredients substitutes])
(prn-table t)
(defcolumn small ["short" "a really long record" "short again"])
(deftable t [ingredients substitutes small])
(prn-table t)
)