Switch File Manager API to promise based methods

src/app/files/fileManager.js

@@ -119,39 +119,36 @@ class FileManager {
     return path ? path[1] : null
   }
 
-  getCurrentFile (cb) {
-    var path = this.currentFile()
-    if (!path) {
-      cb('no file selected')
-    } else {
-      cb(null, path)
-    }
+  async getCurrentFile () {
+    const path = this.currentFile()
+    if (!path) throw 'no file selected'
+    return path
   }
 
-  getFile (path, cb) {
-    var provider = this.fileProviderOf(path)
-    if (provider) {
-      // TODO add approval to user for external plugin to get the content of the given `path`
-      provider.get(path, (error, content) => {
-        cb(error, content)
+  getFile (path) {
+    const provider = this.fileProviderOf(path)
+    if (!provider) throw new Error(`${path} not available`)
+    // TODO: change provider to Promise
+    return new Promise((resolve, reject) => {
+      provider.get(path, (err, content) => {
+        if (err) reject(err)
+        resolve(content)
       })
-    } else {
-      cb(path + ' not available')
-    }
+    })
   }
 
-  setFile (path, content, cb) {
-    var provider = this.fileProviderOf(path)
-    if (provider) {
-      // TODO add approval to user for external plugin to set the content of the given `path`
+  setFile (path, content) {
+    const provider = this.fileProviderOf(path)
+    if (!provider) throw new Error(`${path} not availble`)
+    // TODO : Add permission
+    // TODO : Change Provider to Promise
+    return new Promise((resolve, reject) => {
       provider.set(path, content, (error) => {
-        if (error) return cb(error)
+        if (error) reject(error)
         this.syncEditor(path)
-        cb()
+        resolve(true)
       })
-    } else {
-      cb(path + ' not available')
-    }
+    })
   }
 
   removeTabsOf (provider) {