(ns microtables-frontend.utils
  (:require
   ["mathjs" :as mathjs]))

; to add an npm package to shadow-cljs:
; https://clojureverse.org/t/guide-on-how-to-use-import-npm-modules-packages-in-clojurescript/2298
; https://shadow-cljs.github.io/docs/UsersGuide.html#npm

(defn highest [dir data] (apply max (map dir data)))

(defn increment-letter-code [s]
  (let [l (last s)]
    (cond
      (empty? s) [65]
      (= l 90) (conj (increment-letter-code (subvec s 0 (dec (count s)))) 65)
      :else (conj (subvec s 0 (dec (count s))) (inc l)))))


(defn next-letter [lc]
  (apply str (map char (increment-letter-code (mapv #(.charCodeAt % 0) lc)))))


(def col-letters (iterate next-letter "A"))

(defn get-datum [data c r]
  (some #(if (and (= c (:col %)) (= r (:row %))) %) data))

(def parse-variables (memoize (fn [expression]
                                (as-> (js->clj (.parse mathjs expression)) $
                                  (.filter $ #(true? (.-isSymbolNode %)))
                                  (map #(.-name %) $)
                                  (map #(.toUpperCase %) $)
                                  (filter #(re-matches #"[A-Z]+[0-9]+" %) $)))))

(def str->rc (memoize (fn [s]
                        (let [c (re-find #"^[A-Z]+" s)
                              r (.parseInt js/window (re-find #"[0-9]+$" s))]
                          {:row r :col c}))))

(defn add-parsed-variables [datum]
  (if (= (first (:value datum)) "=")
    (let [vars (parse-variables (subs (:value datum) 1))
          refs (map str->rc vars)]
      (-> datum (assoc :vars vars) (assoc :refs refs) (dissoc :error)))
    (-> datum (dissoc :vars) (dissoc :refs) (dissoc :display) (dissoc :error))))

(defn add-parsed-variables-to-specific-datum
  "Parse variables from the value of a datum and add in :vars and :refs (for swap! data-atom).
  If the value does not contain a fomula, remove any :vars and :refs that may have been there."
  [c r data] (map #(if (and (= (:col %) c) (= (:row %) r))
                     (add-parsed-variables %)
                     %) data))


(def evaluate-expression (memoize (fn [expression variables]
                                    (try
                                      (.evaluate mathjs expression (clj->js variables))
                                      (catch js/Error e
                                        (println "mathjs evaluation error" (.-message e) e)
                                        :calc-error)))))

;TODO: deal with lowercase cell references
(defn find-cell [data c r]
  (some #(if (and (= (:col %) c) (= (:row %) r)) %) data))
(defn find-ref [data cell-ref]
  (some (fn [{:keys [row col] :as datum}] (if (and (= row (:row cell-ref)) (= col (:col cell-ref))) datum)) data))
(defn copy-display-values [data display-values]
  (let [original (map #(dissoc % :dirty) data)
        removed (map #(-> % (dissoc :found) (dissoc :inputs) (dissoc :dirty)) display-values)]
    (into original removed)))

;TODO: memoize dynamically? probably not worth memoizing directly, and could take up too much memory over time
;      https://stackoverflow.com/a/13123571/8172807
(defn find-cycle
  ([data datum] (find-cycle data datum #{}))
  ([data datum ances]
   (let [cur {:row (:row datum) :col (:col datum)}
         this-and-above (conj ances cur)
         refs (:refs datum)
         found (not (empty? (clojure.set/intersection this-and-above (set refs))))]
     (if found
       :cycle-error
       (some (fn [cell]
               (find-cycle data (find-ref data cell) this-and-above)) refs)))))

(defn find-val [data c r]
  (let [l (find-cell data c r)
        v (get l :display (get l :value))
        formula? (and (string? v) (= (first v) "="))]
    (cond
      (nil? v) 0
      ;(contains? l :error) :ref-error
      formula? :not-yet
      :else v)))

;TODO: ADD DOCSTRINGS TO ALL CONNECTED FUNCTIONS AND RENAME VARIABLES WHERE NEEDED
;TODO: figure out how to re-evaluate only when the cell modified affects other cells
(defn re-evaluate [data]
  (println "re-evaluating" data)
  (let [{has-formula true original-values false} (group-by #(= (first (:value %)) "=") data)
        found-cycles (map #(let [found (find-cycle data %)] (if found (assoc % :error found) %)) has-formula)
        {eligible true ineligible false} (group-by #(not (contains? %  :error)) found-cycles)]
    ; 
    (loop [values (into original-values ineligible)
           mapped-cell-keys eligible]
      (let [search-values (map (fn [datum]
                                 (assoc datum :found (map #(find-val
                                                             (concat values mapped-cell-keys)
                                                             (:col %)
                                                             (:row %))
                                                          (:refs datum))))
                               mapped-cell-keys)
            {not-ready true ready nil} (group-by (fn [datum]
                                                   (some #(= :not-yet %) (:found datum)))
                                                 search-values)
            prepped-for-eval (map (fn [datum]
                                    (let [hash-map-of-vars-to-vals (apply hash-map (interleave (:vars datum) (:found datum)))]
                                      (assoc datum :inputs hash-map-of-vars-to-vals)))
                                  ready)
            evaluated (map (fn [datum]
                             (assoc datum :display (evaluate-expression
                                                     (subs (:value datum) 1)
                                                     (:inputs datum))))
                           prepped-for-eval)
            updated-values (copy-display-values values evaluated)]
        (println "EVALUATED" evaluated)
        (if (nil? not-ready)
          updated-values
          (recur updated-values not-ready))))))