Initial work on proper undo/redu functionality.

That is based in in-memmory queue of more detailed changes
instead of relying on history log that is not pretty
detailed and requires explcit user confirmation on each
Ctrl+Z action that is counterintuitive.

src/uxbox/main/data/undo.cljs

@@ -0,0 +1,47 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) 2016 Andrey Antukh <niwi@niwi.nz>
+
+(ns uxbox.main.data.undo
+  (:require [cuerdas.core :as str]
+            [promesa.core :as p]
+            [beicon.core :as rx]
+            [lentes.core :as l]
+            [uxbox.util.rstore :as rs]
+            [uxbox.util.router :as r]
+            [uxbox.main.repo :as rp]
+            [uxbox.util.i18n :refer (tr)]
+            [uxbox.util.schema :as sc]
+            [uxbox.main.data.pages :as udp]
+            [uxbox.main.state :as st]
+            [uxbox.util.datetime :as dt]
+            [uxbox.util.data :refer (without-keys
+                                     replace-by-id
+                                     index-by)]))
+
+(defrecord SaveUndoEntry [id]
+  rs/UpdateEvent
+  (-apply-update [_ state]
+    (let [page (udp/pack-page state id)]
+      (update-in state [:undo id :stack] (fnil conj []) page)))
+
+  rs/EffectEvent
+  (-apply-effect [_ state]
+    (let [undo (get-in state [:undo id])]
+      (println (pr-str undo)))))
+
+(defn watch-page-changes
+  "A function that starts watching for `IPageUpdate`
+  events emited to the global event stream and just
+  reacts on them emiting an other event that just
+  persists the state of the page in an undo stack."
+  [id]
+  (letfn [(on-value []
+            (rs/emit! (->SaveUndoEntry id)))]
+    (as-> rs/stream $
+      (rx/filter #(satisfies? udp/IPageUpdate %) $)
+      (rx/debounce 500 $)
+      (rx/on-next $ on-value))))
+

src/uxbox/main/state.cljs

@@ -30,6 +30,7 @@
    :route nil
    :auth (:uxbox/auth storage nil)
    :clipboard #queue []
+   :undo {}
    :profile nil
    :workspace nil
    :shapes-by-id {}

src/uxbox/main/ui/workspace.cljs

@@ -14,6 +14,7 @@
             [uxbox.main.data.workspace :as dw]
             [uxbox.main.data.pages :as udp]
             [uxbox.main.data.history :as udh]
+            [uxbox.main.data.undo :as udu]
             [uxbox.util.dom :as dom]
             [uxbox.main.geom.point :as gpt]
             [uxbox.util.data :refer (classnames)]
@@ -47,6 +48,7 @@
         sub1 (scroll/watch-scroll-interactions own)
         sub2 (udp/watch-page-changes pageid)
         sub3 (udh/watch-page-changes)
+        sub4 (udu/watch-page-changes pageid)
         dom (mx/ref-node own "workspace-canvas")]
 
     ;; Set initial scroll position
@@ -56,7 +58,8 @@
     (assoc own
            ::sub1 sub1
            ::sub2 sub2
-           ::sub3 sub3)))
+           ::sub3 sub3
+           ::sub4 sub4)))
 
 (defn- workspace-will-unmount
   [own]
@@ -64,7 +67,8 @@
   (.close (::sub1 own))
   (.close (::sub2 own))
   (.close (::sub3 own))
-  (dissoc own ::sub1 ::sub2 ::sub3))
+  (.close (::sub4 own))
+  (dissoc own ::sub1 ::sub2 ::sub3 ::sub4))
 
 (defn- workspace-did-remount
   [old-state state]