Handle downloads correctly in Cordova environment

client/assets.js

@@ -29,6 +29,52 @@ const kLoaded = new Promise((resolve, _) => onAssetsLoaded = resolve);
 
 const kStartup = new Promise((resolve, _) => Meteor.startup(resolve));
 
+const base64 = {
+  decode: (uri) => {
+    const d = (ch) => '%' + ('00' + ch.charCodeAt(0).toString(16)).slice(-2);
+    return decodeURIComponent(Array.from(atob(uri)).map(d).join(''));
+  },
+  encode: (data) => {
+    return btoa(encodeURIComponent(data).replace(
+        /%([0-9A-F]{2})/g, (match, x) => String.fromCharCode('0x' + x)));
+  },
+};
+
+// Input: a target filename and the data to download to it.
+// Output: a Promise that resolves to a description of where to find the
+//         downloaded file: in Downloads, on web, or in ~/Inkstone on mobile.
+const download = (filename, data) => {
+  return kStartup.then(() => new Promise((resolve, reject) => {
+    if (Meteor.isCordova) {
+      const fragments = [cordova.file.externalRootDirectory, 'Inkstone'];
+      const target =  `${fragments.join('')}/${filename}`;
+      const success = () => resolve(target.substr('file://'.length));
+      fileWriteHelper(fragments, filename, data, success, reject);
+    } else {
+      const link = document.createElement('a');
+      link.href = `data:text/plain;charset:utf-8;base64,${base64.encode(data)}`;
+      link.download = filename;
+      link.click();
+      resolve('Downloads folder.');
+    }
+  }));
+}
+
+// Input: a list of path fragments in a Cordova filesystem, a file to write
+//        at the directory given by those fragments, the data to write to it,
+//        and two Promise "resolve/reject" callbacks to execute on completion.
+const fileWriteHelper = (fragments, filename, data, resolve, reject) => {
+  getDirectoryEntry(fragments).then((entry) => {
+    entry.getFile(filename, {create: true}, (file) => {
+      file.createWriter((writer) => {
+        writer.onerror = reject;
+        writer.onwriteend = () => resolve(true);
+        writer.write(new Blob([data]), {type: 'text/plain'});
+      }, reject);
+    }, reject);
+  }).catch(reject);
+}
+
 const isImportedAsset = (asset) => {
   return asset.startsWith('characters/') || asset.startsWith('lists/s/');
 }
@@ -192,15 +238,7 @@ const writeAsset = (path, data) => {
         const prefix = [cordova.file.dataDirectory, 'www', 'assets'];
         const fragments = prefix.concat(path.split('/'));
         const filename = fragments.pop();
-        return getDirectoryEntry(fragments).then((entry) => {
-          entry.getFile(filename, {create: true}, (file) => {
-            file.createWriter((writer) => {
-              writer.onerror = reject;
-              writer.onwriteend = () => resolve(true);
-              writer.write(new Blob([data]), {type: 'text/plain'});
-            }, reject);
-          }, reject);
-        }).catch(reject);
+        fileWriteHelper(fragments, filename, data, resolve, reject);
       } catch (e) {
         reject(e);
       }
@@ -276,6 +314,7 @@ const kRadicals = readAsset('radicals.json')
 
 export {
   kCharacters,
+  download,
   onAssetsLoaded,
   readCharacter,
   readItem,

client/templates/settings/code.js

@@ -17,7 +17,7 @@
  *  along with Inkstone.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-import {readList, writeList} from '/client/assets';
+import {download, readList, writeList} from '/client/assets';
 import {Backdrop} from '/client/backdrop';
 import {Lists} from '/client/model/lists';
 import {clearTables} from '/client/model/persistence';
@@ -74,16 +74,6 @@ const confirmWithCode = (title, action) => {
   Popup.show({title: title, template: template, buttons: buttons});
 }
 
-const decodeBase64 = window.decodeBase64 = (uri) => {
-  const d = (ch) => '%' + ('00' + ch.charCodeAt(0).toString(16)).slice(-2);
-  return decodeURIComponent(Array.from(atob(uri)).map(d).join(''));
-}
-
-const encodeBase64 = window.encodeBase64 = (data) => {
-  return btoa(encodeURIComponent(data).replace(
-      /%([0-9A-F]{2})/g, (match, x) => String.fromCharCode('0x' + x)));
-}
-
 const getDateString = () => {
   const d = new Date();
   const p = (x) => { const y = '' + x; return (y.length < 2 ? '0' : '') + y; }
@@ -101,13 +91,6 @@ const onError = (title) => (error) => {
   Popup.show({buttons: buttons, text: `${error}`, title: title});
 }
 
-const startDownload = (data, filename) => {
-  const link = document.createElement('a');
-  link.href = `data:text/plain;charset:utf-8;base64,${encodeBase64(data)}`;
-  link.download = filename;
-  link.click();
-}
-
 const submitBackup = () => {
   const filename = $('.popup input[type="text"]').val();
   const database = JSON.parse(JSON.stringify(localStorage));
@@ -118,7 +101,7 @@ const submitBackup = () => {
   const lists = _.keys(Lists.getImportedLists());
   Promise.all(lists.map(readList)).then((values) => {
     lists.map((x, i) => data.lists[x] = values[i]);
-    startDownload(JSON.stringify(data), filename);
+    download(filename, JSON.stringify(data));
     Popup.hide();
   }).catch(onError('Backup failed'));
 }