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(ns tictactoe.core)
(declare generate-moves-memo new-boards-memo turn get-input ranking-memo)
(defn game-state [player-who-just-moved board]
{:player player-who-just-moved
:board board
:moves (generate-moves-memo player-who-just-moved board)})
(def game-state-memo (memoize game-state))
;; TODO ensure that this returns a vector
(defn generate-moves [player-who-just-moved board]
(let [next-player (* -1 player-who-just-moved)]
(map (partial game-state next-player) (new-boards-memo next-player board))))
(def generate-moves-memo (memoize generate-moves))
(defn new-boards [player-making-move board]
"given a board, generates new boards for every empty cell"
(let [nil-positions (map first (filter #(nil? (second %)) (map-indexed vector board)))]
(map #(assoc board % player-making-move) nil-positions)))
(def new-boards-memo (memoize new-boards))
(defn x? [player]
(= player 1))
(defmacro with-gs-vars [[game-state & vars] & body]
"Example usage: (with-gs-vars (game-state moves vars) (body))"
(let [evald-game-state-name (gensym)]
`(let [~evald-game-state-name ~game-state
~@(reduce into [] (map (fn [var] `(~var (~(keyword var) ~evald-game-state-name))) vars))]
(defn cell-for-display [cell]
(cond (= cell 1) " X "
(= cell -1) " O "
true (str " " cell " ")))
(defn rows [board]
(partition 3 board))
;; TODO use this in winner?
(defn cols [board]
(vals (group-by #(mod % 3) board)))
(defn row-display [row]
(str (apply str (interpose \| (map cell-for-display row))) "\n"))
(defn board-display [board]
(apply str (interpose "-----------\n" (map row-display (rows (add-position-numbers board))))))
(defn add-position-numbers [board]
(let [counter (atom 0)]
(map (fn [cell] (swap! counter inc) (or cell (str @counter))) board)))
(defn print-board [board]
(print (board-display board)))
;; Ranking
(defn board-full? [board]
(not-any? nil? board))
(defn win-condition-met? [board win-condition]
(let [p1 (board (first win-condition))
p2 (board (second win-condition))
p3 (board (last win-condition))]
(and p1 p2 p3 (= p1 p2 p3))))
(defn winner [board]
(let [win-conditions '(;; horizontal wins
(0 1 2)
(3 4 5)
(6 7 8)
;; vertical wins
(0 3 6)
(1 4 7)
(2 5 8)
;; diagonal wins
(0 4 8)
(6 4 2))]
(or (when-let [win (first (drop-while (complement (partial win-condition-met? board)) win-conditions))]
(board (first win)))
(if (board-full? board) 0))))
(defn ranking [game-state]
(with-gs-vars [game-state moves player board]
(let [win (winner board)]
(cond win win
(not (empty? moves)) (let [rank-fun (if (x? player) min max)]
(apply rank-fun (remove nil? (map ranking-memo moves))))))))
(def ranking-memo (memoize ranking))
;; Game Flow
(defn start []
(turn "" (game-state-memo -1 (vec (repeat 9 nil)))))
(defn play-again-prompt []
(println "Play again, puny ape?")
(let [answer (get-input)]
(if (= answer "y")
(defn handle-win [game-state]
(with-gs-vars [game-state board]
(let [w (winner board)]
(if (x? w)
(println "You lost, you sad, fleshy creature!")
(println "You won... this time!"))))
(defn handle-draw [game-state]
(println "It was a draw! How about that.")
(defn ai-choose-move [game-state]
(first (sort-by ranking-memo > (:moves game-state))))
(defn parse-int [s]
(Integer. (re-find #"[0-9]*" s)))
(defn human-choose-move [game-state]
(println "Enter your move, human:")
(with-gs-vars [game-state moves]
(let [selection (dec (parse-int (get-input)))]
(if ((:board game-state) selection)
(do (println "That position is already taken, stupid meat machine!")
(human-choose-move game-state))
(first (filter (fn [move] (= -1 ((:board move) selection))) moves))))))
(defn turn [current-player game-state]
(if (= "q" game-state)
(println "Goodbye, weakling!")
(do (with-gs-vars [game-state board]
(print-board board)
(cond (winner board) (handle-win game-state)
(board-full? board) (handle-draw game-state)
true (if (= "ai" current-player)
(turn "human" (human-choose-move game-state))
(turn "ai" (ai-choose-move game-state))))))))
(defn get-input []
(clojure.string/trim (read-line)))
;; TODO how do I make this work in lein repl?
(try (defn get-input []
(clojure.string/trim (swank.core/with-read-line-support (read-line))))
(catch ClassNotFoundException e))
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