From 465712c1e4c91780dc34be9849e154f1b853bdfe Mon Sep 17 00:00:00 2001
From: Daniel Compton <desk@danielcompton.net>
Date: Fri, 25 Aug 2017 11:00:36 +1200
Subject: [PATCH] Add local-store get default value, save ls keys with a safe
 prefix

---
 src/day8/re_frame/trace.cljs              |  3 +--
 src/day8/re_frame/trace/localstorage.cljs | 26 +++++++++++++++--------
 2 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/src/day8/re_frame/trace.cljs b/src/day8/re_frame/trace.cljs
index 896e274..ddf9343 100644
--- a/src/day8/re_frame/trace.cljs
+++ b/src/day8/re_frame/trace.cljs
@@ -188,8 +188,7 @@
 
 (defn render-trace-panel []
   (let [filter-input               (r/atom "")
-        filter-items               (r/atom (or (localstorage/get "filter-items")
-                                               []))
+        filter-items               (r/atom (localstorage/get "filter-items" []))
         filter-type                (r/atom :contains)
         input-error                (r/atom false)
         trace-detail-expansions    (r/atom {:show-all? false :overrides {}})]
diff --git a/src/day8/re_frame/trace/localstorage.cljs b/src/day8/re_frame/trace/localstorage.cljs
index df6cf08..c1ff29c 100644
--- a/src/day8/re_frame/trace/localstorage.cljs
+++ b/src/day8/re_frame/trace/localstorage.cljs
@@ -4,15 +4,23 @@
             [cljs.reader :as reader])
   (:refer-clojure :exclude [get]))
 
-(def mech (goog.storage.mechanism.HTML5LocalStorage.))
+(def storage (goog.storage.Storage. (goog.storage.mechanism.HTML5LocalStorage.)))
 
-(defn- storage []
-  (goog.storage.Storage. mech))
+(defn- safe-key [key]
+  "Adds a unique prefix to keys to ensure they don't collide with the host application"
+  (str "day8.re-frame.trace." key))
 
-(defn get [key]
-  (when-let [value (.get (storage) key)]
-    (cljs.reader/read-string value)))
+(defn get
+  "Gets a re-frame-trace value from local storage."
+  ([key]
+   (get key nil))
+  ([key not-found]
+   (let [value (.get storage (safe-key key))]
+     (if (undefined? value)
+       not-found
+       (reader/read-string value)))))
 
-(defn save! [key value]
-  (let [store (storage)]
-    (.set store key (pr-str value))))
+(defn save!
+  "Saves a re-frame-trace value to local storage."
+  [key value]
+  (.set storage (safe-key key) (pr-str value)))