(ns outliner.boundaries.dom.image-utils)

(defn resize-image [file max-dim]
  (js/Promise.
   (fn [resolve reject]
     (let [reader (js/FileReader.)]
       (set! (.-onload reader)
             (fn [e]
               (let [img (js/Image.)]
                 (set! (.-onload img)
                       (fn []
                         (let [canvas (js/document.createElement "canvas")
                               ctx (.getContext canvas "2d")
                               w (.-width img)
                               h (.-height img)
                               scale (if (> (max w h) max-dim)
                                       (/ max-dim (max w h))
                                       1)
                               new-w (* w scale)
                               new-h (* h scale)]
                           (set! (.-width canvas) new-w)
                           (set! (.-height canvas) new-h)
                           (.drawImage ctx img 0 0 new-w new-h)
                           (resolve (.toDataURL canvas "image/jpeg" 0.8)))))
                 (set! (.-onerror img) #(reject %))
                 (set! (.-src img) (.. e -target -result)))))
       (set! (.-onerror reader) #(reject %))
       (.readAsDataURL reader file)))))