Issue 4023 - Move storage of subscription lists to localStorage

lib/io.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 21 matching lines @@
     ext.storage.get([key], items =>
     {
       let entry = items[key];
       if (!entry)
       {
         // Check in localStorage
         try
         {
           entry = JSON.parse(window.localStorage.getItem(key));
         }
-        catch(err)
-        {
-          entry = null;          

[kzar, 2016/08/22 15:38:32]

Nit: `entry = null` seems redundant since we already know entry is falsey here.

[Oleksandr, 2016/08/31 21:54:35]

Done.

-        }
+        catch(err) {}
       }
       if (entry)
         resolve(entry);
       else
-      {

[kzar, 2016/08/22 15:38:32]

Nit: Please remove the braces for the else clause.

[Oleksandr, 2016/08/31 21:54:35]

Done.

         reject(new Error("File doesn't exist"));
-      }
     });
   });
 }
 
 exports.IO =
 {
   resolveFilePath: function(path)
   {
     return new FakeFile(path);
   },
 
   readFromFile: function(file, listener, callback)
   {
     function onLoaded(entry)
     {
       if ("content" in entry)
       {
-        if ("compressed" in entry)
+        if (entry["compressed"])
           entry.content = JSON.parse(LZString.decompressFromUTF16(entry.content));
         for (let line of entry.content)
           listener.process(line);
       }
       callback(null);
     }
 
     loadFile(file).then(onLoaded, callback);
   },
 
   writeToFile: function(file, data, callback)
   {
     let entry = {};
-    var key = fileToKey(file);

[kzar, 2016/08/22 15:38:32]

You seem to use let and var inconsistently throughout.

[Oleksandr, 2016/08/31 21:54:35]

Done.

+    let key = fileToKey(file);
 
-    // Edge cannot write files larger than 1Mb (500k string in UTF-16).
-    // However it does not always raise an exception when trying to do so.
     if (typeof browser == "undefined")

[kzar, 2016/08/22 15:38:32]

Since this code is for the adblockplusedge repository I wonder why we bother do
the `typeof browser == "undefined"` check at all. We already know this is Edge
right?

[Sebastian Noack, 2016/08/22 16:49:19]

As discussed on IRC, this should go into a bookmark in adblockpluschrome rather
than into a separate repo. Moreover, at some point we will merge those changes
upstream, using this code on Edge, Chrome, and Safari.

[Oleksandr, 2016/08/31 21:54:36]

Acknowledged.

     {
-      entry[key] = {lastModified: Date.now(), 
-                    content: data};
+      entry[key] = {lastModified: Date.now(), content: data};
       ext.storage.set(entry, callback);
     }
     else
     {
-      // Compress and fallback to localStorage
-      var dataString = JSON.stringify(data);

[kzar, 2016/08/22 15:38:32]

Perhaps do the JSON serialization and compression in one step? That would be
consistent with how you do the reverse process and I guess would avoid keeping a
reference to both. (Not sure that keeping a reference to both would matter, but
since they're both large strings maybe it would.)

[Oleksandr, 2016/08/31 21:54:35]

Done.

-      var processedData = LZString.compressToUTF16(dataString);
-      chrome.storage.local.remove(key);

[kzar, 2016/08/22 15:38:32]

Did you mean to use chrome.storage instead of ext.storage here?

[Oleksandr, 2016/08/31 21:54:36]

Done.

-      entry[key] = {lastModified: Date.now(), 
-                    content: processedData,
+      // Edge cannot write files larger than 1Mb (500k string in UTF-16) via 
+      // storage API. However it does not always raise an exception when trying
+      // to do so. The solution is to compress and fallback to localStorage.
+      let processedData = LZString.compressToUTF16(JSON.stringify(data));
+      ext.storage.remove(key);
+      entry[key] = {lastModified: Date.now(), content: processedData,
                     compressed: true};
       window.localStorage.setItem(key, JSON.stringify(entry[key]));
       callback();
     }
   },
 
   statFile: function(file, callback)
   {
     function onLoaded(entry)
     {
       callback(null, {
         exists: true,
         lastModified: entry.lastModified
       });
     }
 
     loadFile(file).then(onLoaded, callback);
   }
 };