Continue file upload (#1012)

* changes to support continuing a previous upload job that was interrupted but not canceled/deleted
* keep track of chunk start index. Make sure we factor in startchunk idx for resuming upload jobs to ensure completion
* add more comments and jsdoc info, change one implementation detail that didn't need to be conditional in updateProgressBar

js/hatrac.js

@@ -320,6 +320,10 @@ var ERMrest = (function(module) {
         this.uploadingSize = 0;
 
         this.chunks = [];
+         // array of true values for tracking which chunks are uploaded so far
+         // used to determine what chunk to resume upload from if needed
+        this.chunkTracker = [];
+        this.startChunkIdx = 0;
 
         this.log = console.log;
 
@@ -409,9 +413,13 @@ var ERMrest = (function(module) {
      * @desc Call this function to determine file exists on the server
      * If it doesn't then resolve the promise with url.
      * If it does then set isPaused, completed and jobDone to true
+     * @param {string} jobUrl - if an existing job is being tracked locally and the checksum for current `upload` 
+     *     matches that matched job, return the stored previousJobUrl to be used if a 409 is returned
+     *       - a 409 could mean the namespace already exists and we have an existing job for that namespace we know is partially uplaoded
+     *       - if all the above is true, set the `upload.chunkUrl` to the jobUrl we were tracking locally
      * @returns {Promise}
      */
-    upload.prototype.fileExists = function(contextHeaderParams) {
+    upload.prototype.fileExists = function(previousJobUrl, contextHeaderParams) {
         var self = this;
 
         var deferred = module._q.defer();
@@ -480,10 +488,16 @@ var ERMrest = (function(module) {
             // 403 - file exists but user can't read it -> create a new one
             // 404 - file doesn't exist -> create new one
             // 409 - The parent path does not denote a namespace OR the namespace already exists (from hatrac docs)
-            if (response.status == 403 || response.status == 404 || response.status == 409) {
-              deferred.resolve(self.url);
+            if (response.status == 403 || response.status == 404) {
+                deferred.resolve(self.url);
+            } else if (response.status == 409) {
+                // the namespace might exist with no content, maybe there is a partial upload
+                // set the chunkUrl to the previousJobUrl that we stored in chaise with a partial upload
+                // previousJobUrl = self.url + ';upload/' + job.hash
+                if (previousJobUrl) self.chunkUrl = previousJobUrl;
+                deferred.resolve(self.url);
             } else {
-              deferred.reject(module.responseToError(response));
+                deferred.reject(module.responseToError(response));
             }
         });
 
@@ -568,11 +582,12 @@ var ERMrest = (function(module) {
      * If the completed flag is true, then this means that all chunks were already uploaded, thus it will resolve the promize with url
      * else it will start uploading the chunks. If the job was paused then resume by uploading just those chunks which were not completed.
      *
+     * @param {number} startChunkIdx - the index of the chunk to start uploading from in case of resuming a found incomplete upload job
      * @returns {Promise} A promise resolved with a url where we uploaded the file
      * or rejected with error if unable to upload any chunk
      * and notified with a progress handler, sending number in bytes uploaded uptil now
      */
-    upload.prototype.start = function() {
+    upload.prototype.start = function(startChunkIdx) {
         var self = this;
 
         this.erred = false;
@@ -610,6 +625,13 @@ var ERMrest = (function(module) {
                     this.chunks.push(chunk);
                     start = end;
                 }
+
+                this.startChunkIdx = startChunkIdx || 0;
+                // intialize array to the same length as the number of chunks we have
+                // this initializes every index to `Empty`
+                this.chunkTracker = Array(this.chunks.length);
+                // set index in array to true for each chunk we know is already uploaded 
+                for (var j = 0; j < startChunkIdx; j++) this.chunkTracker[j] = true;
             }
         }
 
@@ -618,7 +640,10 @@ var ERMrest = (function(module) {
 
         this.chunkQueue = [];
 
-        this.chunks.forEach(function(chunk) {
+        this.chunks.forEach(function(chunk, idx) {
+            // check the startChunkIdx before uploading the chunk in the case we are resuming an upload job
+            if (idx < startChunkIdx) return;
+
             chunk.retryCount = 0;
             self.chunkQueue.push(chunk);
             part++;
@@ -913,9 +938,9 @@ var ERMrest = (function(module) {
         var config = {
             headers: _generateContextHeader(contextHeaderParams)
         };
-        // If chunkUrl is not null then fetch  the status of the uploadJob
+        // If chunkUrl is not null then fetch the status of the uploadJob
         // and resolve promise with it.
-        // else just resolved it without any response
+        // else resolve it without any response
         if (this.chunkUrl) {
             this.http.get(this._getAbsoluteUrl(this.chunkUrl), config).then(function(response) {
                 deferred.resolve(response);
@@ -956,13 +981,14 @@ var ERMrest = (function(module) {
      * @private
      * @desc This function should be called to update the progress of upload
      * It calls the onProgressChanged callback that the user subscribes
-     * In addition if the upload has been combleted then it will call onUploadCompleted for regular upload
+     * In addition if the upload has been completed then it will call onUploadCompleted for regular upload
      * and completeUpload to complete the chunk upload
      */
     upload.prototype._updateProgressBar = function() {
         var length = this.chunks.length;
-        var progressDone = 0;
-        var chunksComplete = 0;
+        // progressDone and chunksComplete should be intiialized if we had an existing upload job
+        var progressDone = this.startChunkIdx * this.PART_SIZE;
+        var chunksComplete = this.startChunkIdx;
         for (var i = 0; i < length; i++) {
             progressDone = progressDone + this.chunks[i].progress;
             if (this.chunks[i].completed) chunksComplete++;
@@ -1130,6 +1156,8 @@ var ERMrest = (function(module) {
 
             deferred.resolve();
 
+            // this chunk was successfully uploaded, update the chunkTracker
+            upload.chunkTracker[self.index] = true;
             upload._updateProgressBar();
         }, function(response) {
             self.progress = 0;