core.clj

(ns jk.core)

(defn get-text []
  (slurp "book.txt"))

(defn end-word? [word]
  (boolean
    (re-find #"\w+[.!?]" word)))

(defn get-words [text]
  (re-seq #"[\w',.!?]+" text))

(defn build-chain [words]
  (apply merge-with
         concat
         (map (fn [word next-word] {word [next-word]})
              words
              (next words))))

(defn build-words [chain]
  (let [[word next-words] (rand-nth (seq chain))
        next-word (rand-nth next-words)]
    (loop [words [word next-word]]
      (let [next-words (get chain (last words))]
        (if (nil? next-words)
          words
          (let [next-word (rand-nth next-words)
                words (conj words next-word)]
            (if (end-word? next-word)
              words
              (recur words))))))))

(defn build-sentence [words]
  (str
    (clojure.string/capitalize (first words))
    (clojure.string/join " " (rest words))))

(defn main []
  (println
    (->> (get-text)
         (get-words)
         (build-chain)
         (build-words)
         (build-sentence))))