(ns microtables-frontend.core
    (:require
      [reagent.core :as r]
      ["mathjs" :as mathjs]))

; to generate random values
;for(let i = 0, s = new Set(); i < 10; i++){ let r = Math.floor(Math.random() * 15)+1, c = a[Math.floor(Math.random() * a.length)], k = `${c}${r}`; if(s.has(k)){ i--; continue; } s.add(k); v.push(`{:row ${r} :col "${c}" :value "${Math.floor(Math.random() * 10000)}"}`); }
(def sample-data [{:row 1 :col "A" :value "59" :view :display}
                  {:row 5 :col "C" :value "269" :view :display}
                  {:row 4 :col "B" :value "7893" :view :display}
                  {:row 2 :col "F" :value "8650" :view :display}
                  {:row 6 :col "D" :value "4065" :view :display}
                  {:row 7 :col "F" :value "5316" :view :display}
                  {:row 12 :col "A" :value "2405" :view :display}
                  {:row 5 :col "B" :value "7863" :view :display}
                  {:row 9 :col "E" :value "3144" :view :display}
                  {:row 10 :col "D" :value "8272" :view :display}
                  {:row 11 :col "D" :value "2495" :view :display}
                  {:row 15 :col "E" :value "8968" :view :display}
                  {:row 7 :col "B" :value "=C5 + D6" :view :display}
                  {:row 8 :col "B" :value "=B7 * 2" :view :display}
                  {:row 7 :col "C" :value "=D1" :view :display}
                  {:row 12 :col "B" :value "=C12" :view :display}])

(defonce data-atom (r/atom sample-data))

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

; COLUMN NAMES
(defn upgrade-letter-code [s]
  (let [l (last s)]
    (cond
      (empty? s) [65]
      (= l 90) (conj (upgrade-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 (upgrade-letter-code (mapv #(.charCodeAt % 0) lc)))))
(def col-letters (iterate next-letter "A"))


; CHANGE VALUE FUNCTIONS
(defn update-value [c r existing-datum value]
  (if (nil? existing-datum)
    (swap! data-atom conj {:row r :col c :value value :dirty true})
    (swap! data-atom (partial map #(if (and (= r (:row %)) (= c (:col %))) (assoc (assoc % :dirty true) :value value) %)))))

;TODO: consider changing this for a single "view" atom which points to zero or one cells, which will determine whether to show the formula or evaluation
(defn toggle-display [data c r view-mode]
  (println (str "  toggling " c r " to " view-mode))
  (map #(if (and (= r (:row %)) (= c (:col %))) (assoc % :view view-mode) %) data))

; CALCULATION / FORMULA EVALUATION FUNCTIONS

(def parse-variables (memoize (fn [expression]
                                (js->clj (.getVariables mathjs expression)))))
(def evaluate-expression (memoize (fn [expression variables]
                                    (.evaluate mathjs expression (clj->js variables)))))

(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}))))

;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: figure out how to re-evaluate only when the cell modified affects other cells
(defn re-evaluate [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] (assoc datum :inputs (apply hash-map (interleave (:vars datum) (:found datum))))) 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)]
        (if (nil? not-ready)
          updated-values
          (recur updated-values not-ready))))))

(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))

(defn on-enter-cell [c r e]
  (println (str "entering cell " c r))
  (swap! data-atom #(toggle-display % c r :value)))
(defn on-leave-cell [c r e]
  (println (str "leaving cell " c r))
  (swap! data-atom #(as-> % data
                      (toggle-display data c r :display)
                      (add-parsed-variables-to-specific-datum c r data)
                      (re-evaluate data))))


;; -------------------------
;; Views

(defn cell [c r data]
  (let [datum (some #(if (and (= c (:col %)) (= r (:row %))) %) data)]
    ^{:key (str c r)} [:td [:input {:value (if (= (get datum :view nil) :value)
                                             (get datum :value "")
                                             (get datum :error (get datum :display (get datum :value ""))))
                                    :on-change #(update-value c r datum (.. % -target -value))
                                    :on-blur (partial on-leave-cell c r)
                                    :on-focus (partial on-enter-cell c r)}]]))
(defn row [r cols data]
  ^{:key (str "row-" r)} [:tr
                          (cons
                            ^{:key (str "row-head-" r)} [:th (str r)]
                            (map #(cell % r data) cols))])
(defn header-row [cols]
  ^{:key "header"} [:tr
   (cons
     ^{:key "corner"} [:th]
     (map (fn [c] ^{:key (str "col-head-" c)} [:th c]) cols))])

(defn sheet [data]
  [:table [:tbody
           (let [maxrow (highest :row data)
                 cols (take-while (partial not= (next-letter (highest :col data))) col-letters)]
             (cons
               (header-row cols)
               (map #(row % cols data) (range 1 (inc maxrow)))))]])

(defn app []
  [:div
   [:h3 "Microtables"]
   [sheet @data-atom]])

;; -------------------------
;; Initialize app

(swap! data-atom #(->> % (map add-parsed-variables) (re-evaluate))) ; evalutate any formulas the first time

(defn mount-root []
  (r/render [app] (.getElementById js/document "app")))

(defn init! []
  (mount-root))