(ns advent.pathfind
  (:require [play-clj.core :refer :all]
            [play-clj.ui :refer :all]
            [play-clj.utils :refer :all]
            [play-clj.g2d :refer :all]
            [clojure.pprint]
            [clojure.data.priority-map :refer [priority-map]])
  (:import [com.badlogic.gdx.files FileHandle]
           [com.badlogic.gdx Files]
           [java.lang Math]
           [com.badlogic.gdx.graphics Camera Color GL20 OrthographicCamera
            PerspectiveCamera Pixmap Pixmap$Format PixmapIO Texture
            VertexAttributes$Usage]))

(def compare-count (atom 0))

(def scale 2)

(def cost-comparator (comparator (fn [{^long a :cost} {^long b :cost}] (< a b))))

(defn from-scale [[x y]]
  [(int (* scale x)) (int (* scale y))])

(defn to-scale [[x y]]
  [(int (/ x scale)) (int (/ y scale ))])

(defn printmap [my-map & [skip]]
  (let [skip (or skip 1)]
    (doseq [row (take-nth skip my-map)]
      (println (take-nth skip (map {1 \space 0 "W" "X" "X" "." "."} row))))))

(defn random-map [] (-> (vec (take 640 (repeatedly (fn [] (vec (take 480 (repeatedly  (fn [] (rand-nth [1  1  1  1 1  0])))))))))
                        (update-in [1 1] (constantly 1))
                        (update-in [639 479] (constantly 1))))


(defn neighbors [[^long x ^long y] my-map]
  (let [x (long x)
        y (long y)
        left-x (unchecked-subtract x 1)
        right-x (unchecked-add x 1)
        top-y (unchecked-subtract y 1)
        below-y (unchecked-add y 1)
        candidates [[left-x top-y] [x top-y] [right-x top-y]
                    [left-x y]                   [right-x y]
                    [left-x below-y] [x below-y] [right-x below-y]]
        height (count (first my-map))
        width (count my-map)]
    (remove #(= 0 (get-in my-map %))
            (filter (fn [[^long x ^long y]] (and (< -1 x width)
                                                (< -1 y height))) candidates))))


(defn resolve-path [came-from play-loc target-loc]
  (let [came-from (into {} came-from)]

    (if (nil? (came-from target-loc))
      nil
      (loop [path []
             current-node (vec target-loc)]
        (if (or (= current-node play-loc)
                (nil? current-node))
          (reverse (conj path (from-scale current-node)))
          (recur
           (conj path (from-scale current-node))
           (came-from (vec current-node))))))))

(def d2 ^double (- (Math/sqrt 2) 2))
(defn heuristic ^long [^long goal-x ^long goal-y ^long current-x ^long current-y]
  (let [dist-x (if (< goal-x current-x)
                       (unchecked-subtract current-x goal-x)
                       (unchecked-subtract goal-x current-x ))
        dist-y (if (< goal-y current-y)
                       (unchecked-subtract current-y goal-y)
                       (unchecked-subtract goal-y current-y))
        min-dist ^double (double (min dist-x dist-y))]
    (unchecked-add (unchecked-add dist-x dist-y )
                   (long (unchecked-multiply ^double d2 min-dist)))))


(defn visit-all [my-map play-loc target-loc]
  (let [play-loc (vec (to-scale play-loc))
        target-loc (vec (to-scale target-loc))]
    (if (= 0 (get-in my-map target-loc))
      nil
      (let [cost-so-far ^java.util.HashMap (java.util.HashMap. {play-loc 0}) 
            came-from ^java.util.HashMap (java.util.HashMap.)
            fronteir ^java.util.PriorityQueue (java.util.PriorityQueue. (/ (* 320 240) scale) cost-comparator)]
        (.offer fronteir {:cost 0 :loc play-loc})
        (loop [current-loc (.poll fronteir)]
          (if (or (nil? current-loc)
                  (= (:loc current-loc) target-loc))
            
            (resolve-path came-from play-loc target-loc)
            (do (doseq [neighbor (neighbors (:loc current-loc) my-map)]
                  (let [cost-for-neighbor (.get cost-so-far neighbor)
                        new-cost (+ (.get cost-so-far (:loc current-loc)) (get-in my-map neighbor))]
                    (when (or (nil? cost-for-neighbor)
                              (< new-cost cost-for-neighbor))
                      (.put came-from (vec neighbor) (vec (:loc current-loc)))
                      (.put cost-so-far (vec neighbor) new-cost)
                      (.offer fronteir {:cost (+ new-cost (heuristic (first target-loc) (second target-loc) (first neighbor) (second neighbor)))
                                        :loc neighbor}))))
                (recur (.poll fronteir)))))))))


(defn print-resolved [path my-map]
  (doseq [row (reduce (fn [acc path]
                        (if path
                          (update-in acc (reverse path) (constantly "X"))
                          acc))
                my-map
                path)]
    
    (println (map {1 \space 5 "." 0 "W" "X" "X"} row)))
  nil)

(defn test-pathfind []
  (let [my-map (random-map)
        path (visit-all my-map [1 1] [639 479 ])]
    (println "Test")
    (print-resolved path my-map)
    (println path)))

(defn map-from-resource [filename]
  (let [pm (pixmap filename)
        black (color 0 0 0 255)
        painful (color 255 0 0 255)]
    (vec (take-nth scale (for [x (range (pixmap! pm :get-width))]
                           (vec (take-nth scale (for [y (reverse (range (pixmap! pm :get-height)))
                                                      :let [current-color (color (pixmap! pm :get-pixel x y))]]
                                                  (cond
                                                   (color! current-color :equals black) 0
                                                   (color! current-color :equals painful) 2
                                                   :else 1)))))))))