diff --git a/common/app/common/data.cljc b/common/app/common/data.cljc
index 12b58d619..da478337a 100644
--- a/common/app/common/data.cljc
+++ b/common/app/common/data.cljc
@@ -461,3 +461,9 @@
         kw     (if (keyword? kw) (name kw) kw)]
     (keyword (str prefix kw))))
 
+
+(defn tap
+  "Simpilar to the tap in rxjs but for plain collections"
+  [f coll]
+  (f coll)
+  coll)
diff --git a/common/app/common/pages.cljc b/common/app/common/pages.cljc
index 2776e8168..8282cf12c 100644
--- a/common/app/common/pages.cljc
+++ b/common/app/common/pages.cljc
@@ -11,6 +11,7 @@
    [app.common.pages.changes :as changes]
    [app.common.pages.common :as common]
    [app.common.pages.helpers :as helpers]
+   [app.common.pages.indices :as indices]
    [app.common.pages.init :as init]
    [app.common.pages.spec :as spec]
    [clojure.spec.alpha :as s]))
@@ -42,7 +43,6 @@
 (d/export helpers/is-shape-grouped)
 (d/export helpers/get-parent)
 (d/export helpers/get-parents)
-(d/export helpers/generate-child-parent-index)
 (d/export helpers/clean-loops)
 (d/export helpers/calculate-invalid-targets)
 (d/export helpers/valid-frame-target)
@@ -60,13 +60,17 @@
 (d/export helpers/get-base-shape)
 (d/export helpers/is-parent?)
 (d/export helpers/get-index-in-parent)
-(d/export helpers/calculate-z-index)
-(d/export helpers/generate-child-all-parents-index)
 (d/export helpers/parse-path-name)
 (d/export helpers/merge-path-item)
 (d/export helpers/compact-path)
 (d/export helpers/compact-name)
 
+;; Indices
+(d/export indices/calculate-z-index)
+(d/export indices/generate-child-all-parents-index)
+(d/export indices/generate-child-parent-index)
+(d/export indices/create-mask-index)
+
 ;; Process changes
 (d/export changes/process-changes)
 
diff --git a/common/app/common/pages/helpers.cljc b/common/app/common/pages/helpers.cljc
index 39597788d..f3a52cbc9 100644
--- a/common/app/common/pages/helpers.cljc
+++ b/common/app/common/pages/helpers.cljc
@@ -160,27 +160,6 @@
     (when parent-id
       (lazy-seq (cons parent-id (get-parents parent-id objects))))))
 
-(defn generate-child-parent-index
-  [objects]
-  (reduce-kv
-   (fn [index id obj]
-     (assoc index id (:parent-id obj)))
-   {} objects))
-
-(defn generate-child-all-parents-index
-  "Creates an index where the key is the shape id and the value is a set
-  with all the parents"
-  ([objects]
-   (generate-child-all-parents-index objects (vals objects)))
-
-  ([objects shapes]
-   (let [shape->parents
-         (fn [shape]
-           (->> (get-parents (:id shape) objects)
-                (into [])))]
-     (->> shapes
-          (map #(vector (:id %) (shape->parents %)))
-          (into {})))))
 
 (defn clean-loops
   "Clean a list of ids from circular references."
@@ -347,40 +326,7 @@
               (reduce red-fn cur-idx (reverse (:shapes object)))))]
     (into {} (rec-index '() uuid/zero))))
 
-(defn calculate-z-index
-  "Given a collection of shapes calculates their z-index. Greater index
-  means is displayed over other shapes with less index."
-  [objects]
 
-  (let [is-frame? (fn [id] (= :frame (get-in objects [id :type])))
-        root-children (get-in objects [uuid/zero :shapes])
-        num-frames (->> root-children (filter is-frame?) count)]
-    (when (seq root-children)
-      (loop [current (peek root-children)
-             pending (pop root-children)
-             current-idx (+ (count objects) num-frames -1)
-             z-index {}]
-
-        (let [children (->> (get-in objects [current :shapes]))
-              children (cond
-                         (and (is-frame? current) (contains? z-index current))
-                         []
-
-                         (and (is-frame? current)
-                              (not (contains? z-index current)))
-                         (into [current] children)
-
-                         :else
-                         children)
-              pending (into (vec pending) children)]
-          (if (empty? pending)
-            (assoc z-index current current-idx)
-
-            (let []
-              (recur (peek pending)
-                     (pop pending)
-                     (dec current-idx)
-                     (assoc z-index current current-idx)))))))))
 
 (defn expand-region-selection
   "Given a selection selects all the shapes between the first and last in
diff --git a/common/app/common/pages/indices.cljc b/common/app/common/pages/indices.cljc
new file mode 100644
index 000000000..d58accd00
--- /dev/null
+++ b/common/app/common/pages/indices.cljc
@@ -0,0 +1,83 @@
+;; 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) UXBOX Labs SL
+
+(ns app.common.pages.indices
+  (:require
+   [app.common.data :as d]
+   [app.common.geom.shapes :as gsh]
+   [app.common.pages.helpers :as helpers]
+   [app.common.uuid :as uuid]))
+
+(defn calculate-z-index
+  "Given a collection of shapes calculates their z-index. Greater index
+  means is displayed over other shapes with less index."
+  [objects]
+  (let [is-frame? (fn [id] (= :frame (get-in objects [id :type])))
+        root-children (or (get-in objects [uuid/zero :shapes]) [])
+        num-frames (->> root-children (filterv is-frame?) count)]
+
+    (when-not (empty? root-children)
+      (loop [current (peek root-children)
+             pending (pop root-children)
+             current-idx (+ (count objects) num-frames -1)
+             z-index (transient {})]
+
+        (let [children (get-in objects [current :shapes])
+              assigned? (contains? z-index current)
+              is-frame? (is-frame? current)
+
+              pending (cond
+                        (not is-frame?)
+                        (d/concat pending children)
+
+                        (not assigned?)
+                        (d/concat pending [current] children)
+
+                        :else
+                        pending)]
+
+          (if (empty? pending)
+            (-> (assoc! z-index current current-idx)
+                (persistent!))
+            (recur (peek pending)
+                   (pop pending)
+                   (dec current-idx)
+                   (assoc! z-index current current-idx))))))))
+
+(defn generate-child-parent-index
+  [objects]
+  (reduce-kv
+   (fn [index id obj]
+     (assoc index id (:parent-id obj)))
+   {} objects))
+
+(defn generate-child-all-parents-index
+  "Creates an index where the key is the shape id and the value is a set
+  with all the parents"
+  ([objects]
+   (generate-child-all-parents-index objects (vals objects)))
+
+  ([objects shapes]
+   (let [shape->parents
+         (fn [shape]
+           (->> (helpers/get-parents (:id shape) objects)
+                (into [])))]
+     (->> shapes
+          (map #(vector (:id %) (shape->parents %)))
+          (into {})))))
+
+(defn create-mask-index
+  "Retrieves the mask information for an object"
+  [objects parents-index]
+  (let [retrieve-masks
+        (fn [id parents]
+          (->> parents
+               (map #(get objects %))
+               (filter #(:masked-group? %))
+               ;; Retrieve the masking element
+               (mapv #(get objects (->> % :shapes first)))))]
+    (->> parents-index
+         (d/mapm retrieve-masks))))
diff --git a/frontend/src/app/main/data/workspace/transforms.cljs b/frontend/src/app/main/data/workspace/transforms.cljs
index 279682c2f..cd86cb48f 100644
--- a/frontend/src/app/main/data/workspace/transforms.cljs
+++ b/frontend/src/app/main/data/workspace/transforms.cljs
@@ -264,7 +264,7 @@
                               :index (cp/get-index-in-parent objects (:id shape))
                               :shapes [(:id shape)]})))]
 
-        (when-not (empty? rch)
+        (when-not (empty? uch)
           (rx/of dwu/pop-undo-into-transaction
                  (dch/commit-changes rch uch {:commit-local? true})
                  (dwu/commit-undo-transaction)
@@ -294,12 +294,15 @@
                            (rx/take-until stopper)
                            (rx/map #(gpt/to-vec from-position %)))
 
-             snap-delta (->> position
-                             (rx/throttle 20)
-                             (rx/switch-map
-                              (fn [pos]
-                                (->> (snap/closest-snap-move page-id shapes objects layout zoom pos)
-                                     (rx/map #(vector pos %))))))]
+             snap-delta (rx/concat
+                         ;; We send the nil first so the stream is not waiting for the first value
+                         (rx/of nil)
+                         (->> position
+                              (rx/throttle 20)
+                              (rx/switch-map
+                               (fn [pos]
+                                 (->> (snap/closest-snap-move page-id shapes objects layout zoom pos)
+                                      (rx/map #(vector pos %)))))))]
          (if (empty? shapes)
            (rx/empty)
            (rx/concat
diff --git a/frontend/src/app/main/snap.cljs b/frontend/src/app/main/snap.cljs
index 021d2528a..b8e700b6b 100644
--- a/frontend/src/app/main/snap.cljs
+++ b/frontend/src/app/main/snap.cljs
@@ -19,7 +19,7 @@
    [beicon.core :as rx]
    [clojure.set :as set]))
 
-(defonce ^:private snap-accuracy 10)
+(defonce ^:private snap-accuracy 5)
 (defonce ^:private snap-path-accuracy 10)
 (defonce ^:private snap-distance-accuracy 10)
 
@@ -337,13 +337,15 @@
   "Snaps a position given an old snap to a different position. We use this to provide a temporal
   snap while the new is being processed."
   [[position [snap-pos snap-delta]]]
-  (let [dx (if (not= 0 (:x snap-delta))
-             (- (+ (:x snap-pos) (:x snap-delta)) (:x position))
-             0)
-        dy (if (not= 0 (:y snap-delta))
-             (- (+ (:y snap-pos) (:y snap-delta)) (:y position))
-             0)]
+  (if (some? snap-delta)
+    (let [dx (if (not= 0 (:x snap-delta))
+               (- (+ (:x snap-pos) (:x snap-delta)) (:x position))
+               0)
+          dy (if (not= 0 (:y snap-delta))
+               (- (+ (:y snap-pos) (:y snap-delta)) (:y position))
+               0)]
 
-    (cond-> position
-      (<= (mth/abs dx) snap-accuracy) (update :x + dx)
-      (<= (mth/abs dy) snap-accuracy) (update :y + dy))))
+      (cond-> position
+        (<= (mth/abs dx) snap-accuracy) (update :x + dx)
+        (<= (mth/abs dy) snap-accuracy) (update :y + dy)))
+    position))
diff --git a/frontend/src/app/util/quadtree.js b/frontend/src/app/util/quadtree.js
index a6f904c10..000ae7c42 100644
--- a/frontend/src/app/util/quadtree.js
+++ b/frontend/src/app/util/quadtree.js
@@ -32,12 +32,16 @@
 "use strict";
 
 goog.provide("app.util.quadtree");
+goog.require("cljs.core");
 
 goog.scope(function() {
   const self = app.util.quadtree;
+  const eq = cljs.core._EQ_;
+  const contains = cljs.core.contains_QMARK_;
 
   class Node {
-    constructor(bounds, data) {
+    constructor(id, bounds, data) {
+      this.id = id;
       this.bounds = bounds;
       this.data = data;
     }
@@ -51,8 +55,8 @@ goog.scope(function() {
       this.level = level || 0;
       this.bounds = bounds;
 
-      this.objects    = [];
-      this.indexes      = [];
+      this.objects = [];
+      this.indexes = [];
     }
 
     split() {
@@ -183,14 +187,18 @@ goog.scope(function() {
       this.objects = [];
       this.indexes = [];
     }
+
+    getObjects() {
+      return this.objects;
+    }
   }
 
   self.create = function(rect) {
     return new Quadtree(rect, 10, 4, 0);
   };
 
-  self.insert = function(index, bounds, data) {
-    const node = new Node(bounds, data);
+  self.insert = function(index, id, bounds, data) {
+    const node = new Node(id, bounds, data);
     index.insert(node);
     return index;
   };
@@ -210,4 +218,29 @@ goog.scope(function() {
     }
   };
 
+  self.remove = function(index, id) {
+    const result = self.create(index.bounds);
+
+    for (let node of index.objects) {
+      if (!eq(id, node.id)) {
+        self.insert(result, node.id, node.bounds, node.data);
+      }
+    }
+
+    return result;
+  }
+
+  // FIXME: Inefficient to recreate the index. Needs to be improved
+  self.remove_all = function(index, ids) {
+    const result = self.create(index.bounds);
+
+    for (let node of self.search(index, index.bounds)) {
+      if (!contains(ids, node.id)) {
+        self.insert(result, node.id, node.bounds, node.data);
+      }
+    }
+
+    return result;
+  }
+
 });
diff --git a/frontend/src/app/util/range_tree.js b/frontend/src/app/util/range_tree.js
index ed62a0200..64e3d3fdd 100644
--- a/frontend/src/app/util/range_tree.js
+++ b/frontend/src/app/util/range_tree.js
@@ -13,7 +13,7 @@
 "use strict";
 
 goog.provide("app.util.range_tree");
-goog.require("cljs.core")
+goog.require("cljs.core");
 
 goog.scope(function() {
     const eq = cljs.core._EQ_;
@@ -92,7 +92,7 @@ goog.scope(function() {
         }
 
         isEmpty() {
-            return this.root === null;
+            return !this.root;
         }
 
         toString() {
@@ -116,7 +116,7 @@ goog.scope(function() {
 
     // Insert recursively in the tree
     function recInsert (branch, value, data) {
-        if (branch === null) {
+        if (!branch) {
             const ret = new Node(value, data);
             ret.color = Color.RED;
             return ret;
@@ -144,7 +144,7 @@ goog.scope(function() {
 
     // Search for the min node
     function searchMin(branch) {
-        if (branch.left === null) {
+        if (!branch.left) {
             return branch;
         } else {
             return searchMin(branch.left);
@@ -153,7 +153,7 @@ goog.scope(function() {
 
     // Remove the lefmost node of the current branch
     function recRemoveMin(branch) {
-        if (branch.left === null) {
+        if (!branch.left) {
             return null;
         }
 
@@ -167,7 +167,7 @@ goog.scope(function() {
     // Remove the data element for the value given
     // this will not remove the node, we have to remove the empty node afterwards
     function recRemoveData(branch, value, data) {
-        if (branch === null) {
+        if (!branch) {
             // Not found
             return branch;
         } else if (branch.value === value) {
@@ -193,7 +193,7 @@ goog.scope(function() {
             if (isRed(branch.left)) {
                 branch = rotateRight(branch);
             }
-            if (value === branch.value && branch.right === null) {
+            if (value === branch.value && !branch.right) {
                 return null;
             }
             if (!isRed(branch.right) && !isRed(branch.right.left)) {
@@ -214,7 +214,7 @@ goog.scope(function() {
 
     // Retrieve all the data related to value
     function recGet(branch, value) {
-        if (branch === null) {
+        if (!branch) {
             return null;
         } else if (branch.value === value) {
             return branch.data;
@@ -226,7 +226,7 @@ goog.scope(function() {
     }
 
     function recUpdate(branch, value, oldData, newData) {
-        if (branch === null) {
+        if (!branch) {
             return branch;
         } else if (branch.value === value) {
             branch.data = branch.data.map((it) => (eq(it, oldData)) ? newData : it);
@@ -239,7 +239,7 @@ goog.scope(function() {
     }
 
     function recRangeQuery(branch, fromValue, toValue, result) {
-        if (branch === null) {
+        if (!branch) {
             return result;
         }
         if (fromValue < branch.value) {
@@ -329,7 +329,7 @@ goog.scope(function() {
     // This will return the string representation. We don't care about internal structure
     // only the data
     function recToString(branch, result) {
-        if (branch === null) {
+        if (!branch) {
             return;
         }
 
diff --git a/frontend/src/app/worker/impl.cljs b/frontend/src/app/worker/impl.cljs
index 107270387..77032133a 100644
--- a/frontend/src/app/worker/impl.cljs
+++ b/frontend/src/app/worker/impl.cljs
@@ -39,11 +39,15 @@
 (defmethod handler :update-page-indices
   [{:keys [page-id changes] :as message}]
 
-  (swap! state ch/process-changes changes false)
+  (let [old-objects (get-in @state [:pages-index page-id :objects])]
+    (swap! state ch/process-changes changes false)
 
-  (let [objects (get-in @state [:pages-index page-id :objects])
-        message (assoc message :objects objects)]
-    (handler (-> message
-                 (assoc :cmd :selection/update-index)))
-    (handler (-> message
-                 (assoc :cmd :snaps/update-index)))))
+    (let [new-objects (get-in @state [:pages-index page-id :objects])
+          message (assoc message
+                         :objects new-objects
+                         :new-objects new-objects
+                         :old-objects old-objects)]
+      (handler (-> message
+                   (assoc :cmd :selection/update-index)))
+      (handler (-> message
+                   (assoc :cmd :snaps/update-index))))))
diff --git a/frontend/src/app/worker/selection.cljs b/frontend/src/app/worker/selection.cljs
index 2d0ac3a5d..b49c2fe93 100644
--- a/frontend/src/app/worker/selection.cljs
+++ b/frontend/src/app/worker/selection.cljs
@@ -15,12 +15,110 @@
    [app.common.spec :as us]
    [app.common.uuid :as uuid]
    [app.util.quadtree :as qdt]
-   [app.worker.impl :as impl]))
+   [app.worker.impl :as impl]
+   [clojure.set :as set]))
 
 (defonce state (l/atom {}))
 
-(declare index-object)
-(declare create-index)
+(defn- index-object
+  [objects z-index parents-index masks-index index obj]
+  (let [{:keys [x y width height]} (:selrect obj)
+        shape-bound #js {:x x :y y :width width :height height}
+
+        parents (get parents-index (:id obj))
+        masks   (get masks-index (:id obj))
+        z       (get z-index (:id obj))
+
+        frame   (when (and (not= :frame (:type obj))
+                           (not= (:frame-id obj) uuid/zero))
+                  (get objects (:frame-id obj)))]
+    (qdt/insert index
+                (:id obj)
+                shape-bound
+                (assoc obj :frame frame :masks masks :parents parents :z z))))
+
+(defn- create-index
+  [objects]
+  (let [shapes        (-> objects (dissoc uuid/zero) (vals))
+        z-index       (cp/calculate-z-index objects)
+        parents-index (cp/generate-child-all-parents-index objects)
+        masks-index   (cp/create-mask-index objects parents-index)
+        bounds        (gsh/selection-rect shapes)
+        bounds #js {:x (:x bounds)
+                    :y (:y bounds)
+                    :width (:width bounds)
+                    :height (:height bounds)}]
+
+    (reduce (partial index-object objects z-index parents-index masks-index)
+            (qdt/create bounds)
+            shapes)))
+
+(defn- update-index
+  [index old-objects new-objects]
+
+  (let [changes? (fn [id]
+                   (not= (get old-objects id)
+                         (get new-objects id)))
+
+        changed-ids (into #{}
+                          (filter changes?)
+                          (set/union (keys old-objects)
+                                     (keys new-objects)))
+
+        shapes (->> changed-ids (mapv #(get new-objects %)) (filterv (comp not nil?)))
+        z-index       (cp/calculate-z-index new-objects)
+        parents-index (cp/generate-child-all-parents-index new-objects shapes)
+        masks-index   (cp/create-mask-index new-objects parents-index)
+
+        new-index (qdt/remove-all index changed-ids)]
+
+    (reduce (partial index-object new-objects z-index parents-index masks-index)
+            new-index
+            shapes)))
+
+(defn- query-index
+  [index rect frame-id include-frames? include-groups? disabled-masks reverse?]
+  (let [result (-> (qdt/search index (clj->js rect))
+                   (es6-iterator-seq))
+
+        ;; Check if the shape matches the filter criteria
+        match-criteria?
+        (fn [shape]
+          (and (not (:hidden shape))
+               (not (:blocked shape))
+               (or (not frame-id) (= frame-id (:frame-id shape)))
+               (case (:type shape)
+                 :frame   include-frames?
+                 :group   include-groups?
+                 true)))
+
+        overlaps?
+        (fn [shape]
+          (gsh/overlaps? shape rect))
+
+        overlaps-masks?
+        (fn [masks]
+          (->> masks
+               (some (comp not overlaps?))
+               not))
+
+        ;; Shapes after filters of overlapping and criteria
+        matching-shapes
+        (into []
+              (comp (map #(unchecked-get % "data"))
+                    (filter match-criteria?)
+                    (filter (comp overlaps? :frame))
+                    (filter (comp overlaps-masks? :masks))
+                    (filter overlaps?))
+              result)
+
+        keyfn (if reverse? (comp - :z) :z)]
+
+    (into (d/ordered-set)
+          (->> matching-shapes
+               (sort-by keyfn)
+               (map :id)))))
+
 
 (defmethod impl/handler :selection/initialize-index
   [{:keys [file-id data] :as message}]
@@ -35,96 +133,13 @@
     nil))
 
 (defmethod impl/handler :selection/update-index
-  [{:keys [page-id objects] :as message}]
-  (let [index (create-index objects)]
-    (swap! state update page-id (constantly index))
-    nil))
+  [{:keys [page-id old-objects new-objects] :as message}]
+  (swap! state update page-id update-index old-objects new-objects)
+  nil)
 
 (defmethod impl/handler :selection/query
   [{:keys [page-id rect frame-id include-frames? include-groups? disabled-masks reverse?]
     :or {include-groups? true disabled-masks #{} reverse? false} :as message}]
   (when-let [index (get @state page-id)]
-    (let [result (-> (qdt/search index (clj->js rect))
-                     (es6-iterator-seq))
-
-          ;; Check if the shape matches the filter criteria
-          match-criteria?
-          (fn [shape]
-            (and (not (:hidden shape))
-                 (not (:blocked shape))
-                 (or (not frame-id) (= frame-id (:frame-id shape)))
-                 (case (:type shape)
-                   :frame   include-frames?
-                   :group   include-groups?
-                   true)))
-
-          overlaps?
-          (fn [shape]
-            (gsh/overlaps? shape rect))
-
-          overlaps-masks?
-          (fn [masks]
-            (->> masks
-                 (some (comp not overlaps?))
-                 not))
-
-          ;; Shapes after filters of overlapping and criteria
-          matching-shapes
-          (into []
-                (comp (map #(unchecked-get % "data"))
-                      (filter match-criteria?)
-                      (filter (comp overlaps? :frame))
-                      (filter (comp overlaps-masks? :masks))
-                      (filter overlaps?))
-                result)
-
-          keyfn (if reverse? (comp - :z) :z)]
-
-      (into (d/ordered-set)
-            (->> matching-shapes
-                 (sort-by keyfn)
-                 (map :id))))))
-
-(defn create-mask-index
-  "Retrieves the mask information for an object"
-  [objects parents-index]
-  (let [retrieve-masks
-        (fn [id parents]
-          (->> parents
-               (map #(get objects %))
-               (filter #(:masked-group? %))
-               ;; Retrieve the masking element
-               (mapv #(get objects (->> % :shapes first)))))]
-    (->> parents-index
-         (d/mapm retrieve-masks))))
-
-(defn- create-index
-  [objects]
-  (let [shapes        (-> objects (dissoc uuid/zero) (vals))
-        z-index       (cp/calculate-z-index objects)
-        parents-index (cp/generate-child-all-parents-index objects)
-        masks-index   (create-mask-index objects parents-index)
-        bounds        (gsh/selection-rect shapes)
-        bounds #js {:x (:x bounds)
-                    :y (:y bounds)
-                    :width (:width bounds)
-                    :height (:height bounds)}]
-
-    (reduce (partial index-object objects z-index parents-index masks-index)
-            (qdt/create bounds)
-            shapes)))
-
-(defn- index-object
-  [objects z-index parents-index masks-index index obj]
-  (let [{:keys [x y width height]} (:selrect obj)
-        shape-bound #js {:x x :y y :width width :height height}
-        parents (get parents-index (:id obj))
-        masks   (get masks-index (:id obj))
-        z       (get z-index (:id obj))
-        frame   (when (and (not= :frame (:type obj))
-                           (not= (:frame-id obj) uuid/zero))
-                  (get objects (:frame-id obj)))]
-    (qdt/insert index
-                shape-bound
-                (assoc obj :frame frame :masks masks :parents parents :z z))))
+    (query-index index rect frame-id include-frames? include-groups? disabled-masks reverse?)))
 
diff --git a/frontend/src/app/worker/snaps.cljs b/frontend/src/app/worker/snaps.cljs
index 9da49438b..9cd78cec0 100644
--- a/frontend/src/app/worker/snaps.cljs
+++ b/frontend/src/app/worker/snaps.cljs
@@ -6,48 +6,105 @@
 
 (ns app.worker.snaps
   (:require
-   [okulary.core :as l]
-   [app.common.uuid :as uuid]
-   [app.common.pages :as cp]
    [app.common.data :as d]
-   [app.worker.impl :as impl]
-   [app.util.range-tree :as rt]
+   [app.common.pages :as cp]
+   [app.common.uuid :as uuid]
+   [app.util.geom.grid :as gg]
    [app.util.geom.snap-points :as snap]
-   [app.util.geom.grid :as gg]))
+   [app.util.range-tree :as rt]
+   [app.worker.impl :as impl]
+   [clojure.set :as set]
+   [okulary.core :as l]))
 
 (defonce state (l/atom {}))
 
-(defn- create-coord-data
-  "Initializes the range tree given the shapes"
-  [frame-id shapes coord]
-  (let [process-shape (fn [coord]
-                        (fn [shape]
-                          (concat
-                           (let [points (snap/shape-snap-points shape)]
-                             (map #(vector % (:id shape)) points))
+(defn process-shape [frame-id coord]
+  (fn [shape]
+    (let [points (snap/shape-snap-points shape)
+          shape-data (->> points (mapv #(vector % (:id shape))))]
+      (if (= (:id shape) frame-id)
+        (d/concat
+         shape-data
 
-                           ;; The grid points are only added by the "root" of the coord-dat
-                           (when (= (:id shape) frame-id)
-                             (let [points (gg/grid-snap-points shape coord)]
-                               (map #(vector % :layout) points))))))
-        into-tree (fn [tree [point _ :as data]]
-                    (rt/insert tree (coord point) data))]
+         ;; The grid points are only added by the "root" of the coord-dat
+         (->> (gg/grid-snap-points shape coord)
+              (map #(vector % :layout))))
+
+        shape-data))))
+
+(defn- add-coord-data
+  "Initializes the range tree given the shapes"
+  [data frame-id shapes coord]
+  (letfn [(into-tree [tree [point _ :as data]]
+            (rt/insert tree (coord point) data))]
     (->> shapes
-         (mapcat (process-shape coord))
-         (reduce into-tree (rt/make-tree)))))
+         (mapcat (process-shape frame-id coord))
+         (reduce into-tree data))))
+
+(defn remove-coord-data
+  [data frame-id shapes coord]
+
+  (letfn [(remove-tree [tree [point _ :as data]]
+            (rt/remove tree (coord point) data))]
+    (->> shapes
+         (mapcat (process-shape frame-id coord))
+         (reduce remove-tree data))))
+
+(defn aggregate-data
+  ([objects]
+   (aggregate-data objects (keys objects)))
+
+  ([objects ids]
+   (->> ids
+        (filter #(contains? objects %))
+        (map #(get objects %))
+        (filter :frame-id)
+        (group-by :frame-id)
+        ;; Adds the frame
+        (d/mapm #(conj %2 (get objects %1))))))
 
 (defn- initialize-snap-data
   "Initialize the snap information with the current workspace information"
   [objects]
-  (let [frame-shapes (->> (vals objects)
-                          (filter :frame-id)
-                          (group-by :frame-id))
-        frame-shapes (->> (cp/select-frames objects)
-                          (reduce #(update %1 (:id %2) conj %2) frame-shapes))]
+  (let [shapes-data (aggregate-data objects)
 
-    (d/mapm (fn [frame-id shapes] {:x (create-coord-data frame-id shapes :x)
-                                   :y (create-coord-data frame-id shapes :y)})
-            frame-shapes)))
+        create-index
+        (fn [frame-id shapes] {:x (add-coord-data (rt/make-tree) frame-id shapes :x)
+                               :y (add-coord-data (rt/make-tree) frame-id shapes :y)})]
+
+    (d/mapm create-index shapes-data)))
+
+(defn- update-snap-data
+  [snap-data old-objects new-objects]
+
+  (let [changed? #(not= (get old-objects %) (get new-objects %))
+
+        changed-ids (into #{}
+                          (filter changed?)
+                          (set/union (keys old-objects) (keys new-objects)))
+
+        to-delete (aggregate-data old-objects changed-ids)
+        to-add    (aggregate-data new-objects changed-ids)
+
+        delete-data
+        (fn [snap-data [frame-id shapes]]
+          (-> snap-data
+              (update-in [frame-id :x] remove-coord-data frame-id shapes :x)
+              (update-in [frame-id :y] remove-coord-data frame-id shapes :y)))
+
+        add-data
+        (fn [snap-data [frame-id shapes]]
+          (-> snap-data
+              (update-in [frame-id :x] add-coord-data frame-id shapes :x)
+              (update-in [frame-id :y] add-coord-data frame-id shapes :y)))
+
+        snap-data (->> to-delete
+                       (reduce delete-data snap-data))
+
+        snap-data (->> to-add
+                       (reduce add-data snap-data))]
+
+    snap-data))
 
 (defn- log-state
   "Helper function to print a friendly version of the snap tree. Debugging purposes"
@@ -60,6 +117,16 @@
   (let [snap-data (initialize-snap-data objects)]
     (assoc state page-id snap-data)))
 
+(defn- update-page [state page-id old-objects new-objects]
+  (let [changed? #(not= (get old-objects %) (get new-objects %))
+        changed-ids (into #{}
+                          (filter changed?)
+                          (set/union (keys old-objects) (keys new-objects)))
+
+        snap-data (get state page-id)
+        snap-data (update-snap-data snap-data old-objects new-objects)]
+    (assoc state page-id snap-data)))
+
 ;; Public API
 (defmethod impl/handler :snaps/initialize-index
   [{:keys [file-id data] :as message}]
@@ -74,9 +141,9 @@
     nil))
 
 (defmethod impl/handler :snaps/update-index
-  [{:keys [page-id objects] :as message}]
+  [{:keys [page-id old-objects new-objects] :as message}]
   ;; TODO: Check the difference and update the index acordingly
-  (swap! state index-page page-id objects)
+  (swap! state update-page page-id old-objects new-objects)
   ;; (log-state)
   nil)