* Fixing `Chunk upload` problems:

* Use of `FormData` to send the content of the chunks
  * Better handle of errors from server

src/chunk/ChunkUploadHandler.js

@@ -1,4 +1,8 @@
-import { default as request, createRequest, sendRequest } from '../utils/request'
+import {
+  default as request,
+  createRequest,
+  sendFormRequest
+} from '../utils/request'
 
 export default class ChunkUploadHandler {
   /**
@@ -204,7 +208,9 @@ export default class ChunkUploadHandler {
   start () {
     request({
       method: 'POST',
-      headers: this.headers,
+      headers: Object.assign(this.headers, {
+        'Content-Type': 'application/json'
+      }),
       url: this.action,
       body: Object.assign(this.startBody, {
         phase: 'start',
@@ -213,7 +219,8 @@ export default class ChunkUploadHandler {
       })
     }).then(res => {
       if (res.status !== 'success') {
-        return this.reject(res.message)
+        this.file.response = res
+        return this.reject('server')
       }
 
       this.sessionId = res.data.session_id
@@ -221,7 +228,10 @@ export default class ChunkUploadHandler {
 
       this.createChunks()
       this.startChunking()
-    }).catch(error => this.reject(error))
+    }).catch(res => {
+      this.file.response = res
+      this.reject('server')
+    })
   }
 
   /**
@@ -265,17 +275,19 @@ export default class ChunkUploadHandler {
     this.updateFileProgress()
     chunk.xhr = createRequest({
       method: 'POST',
-      headers: this.headers,
+      headers: Object.assign(this.headers, {
+        'Content-Type': 'multipart/form-data'
+      }),
       url: this.action
     })
 
-    chunk.xhr.upload.addEventListener('progress', function(evt) {
+    chunk.xhr.upload.addEventListener('progress', function (evt) {
       if (evt.lengthComputable) {
         chunk.progress = Math.round(evt.loaded / evt.total * 100)
       }
     }, false)
 
-    sendRequest(chunk.xhr, Object.assign(this.uploadBody, {
+    sendFormRequest(chunk.xhr, Object.assign(this.uploadBody, {
       phase: 'upload',
       session_id: this.sessionId,
       start_offset: chunk.startOffset,
@@ -287,7 +299,7 @@ export default class ChunkUploadHandler {
       } else {
         if (chunk.retries-- <= 0) {
           this.pause()
-          return this.reject('File upload failed')
+          return this.reject('upload')
         }
       }
 
@@ -296,7 +308,7 @@ export default class ChunkUploadHandler {
       chunk.active = false
       if (chunk.retries-- <= 0) {
         this.pause()
-        return this.reject('File upload failed')
+        return this.reject('upload')
       }
 
       this.uploadNextChunk()
@@ -312,18 +324,24 @@ export default class ChunkUploadHandler {
 
     request({
       method: 'POST',
-      headers: this.headers,
+      headers: Object.assign(this.headers, {
+        'Content-Type': 'application/json'
+      }),
       url: this.action,
       body: Object.assign(this.finishBody, {
         phase: 'finish',
         session_id: this.sessionId
       })
     }).then(res => {
+      this.file.response = res
       if (res.status !== 'success') {
-        return this.reject(res.message)
+        return this.reject('server')
       }
 
       this.resolve(res)
-    }).catch(error => this.reject(error))
+    }).catch(res => {
+      this.file.response = res
+      this.reject('server')
+    })
   }
 }

src/utils/chunkUpload.js

@@ -42,6 +42,10 @@ const chunkUploadFinish = (req, res) => {
 }
 
 module.exports = (req, res) => {
+  if (!req.body.phase) {
+    return chunkUploadPart(req, res)
+  }
+
   switch (req.body.phase) {
     case 'start':
       return chunkUploadStart(req, res)

src/utils/request.js

@@ -28,14 +28,39 @@ export const sendRequest = (xhr, body) => {
       if (xhr.status >= 200 && xhr.status < 300) {
         resolve(xhr.response)
       } else {
-        reject(xhr.statusText)
+        reject(xhr.response)
       }
     }
-    xhr.onerror = () => reject(xhr.statusText)
+    xhr.onerror = () => reject(xhr.response)
     xhr.send(JSON.stringify(body))
   })
 }
 
+/**
+ * Sends a XHR request with certain form data
+ *
+ * @param {XMLHttpRequest} xhr
+ * @param {Object} data
+ */
+export const sendFormRequest = (xhr, data) => {
+  const body = new FormData()
+  for (var name in data) {
+    body.append(name, data[name])
+  }
+
+  return new Promise((resolve, reject) => {
+    xhr.onload = () => {
+      if (xhr.status >= 200 && xhr.status < 300) {
+        resolve(xhr.response)
+      } else {
+        reject(xhr.response)
+      }
+    }
+    xhr.onerror = () => reject(xhr.response)
+    xhr.send(body)
+  })
+}
+
 /**
  * Creates and sends XHR request
  *