Allow multiple files upload through web UI, including drag & drop (#9856)

* Allow drag and drop uploads of multiple files to compose

* Calculate aggregate upload progress for single action

* Allow multiple uploads to compose through traditional input, consolidate update file limit logic, provide file limit feedback

6 files changed, 43 insertions, 15 deletions

diff --git a/app/javascript/mastodon/actions/alerts.js b/app/javascript/mastodon/actions/alerts.js
index 3f5d7ef46..50cd48a9e 100644
--- a/app/javascript/mastodon/actions/alerts.js
+++ b/app/javascript/mastodon/actions/alerts.js
@@ -22,7 +22,7 @@ export function clearAlert() {
   };
 };
 
-export function showAlert(title, message) {
+export function showAlert(title = messages.unexpectedTitle, message = messages.unexpectedMessage) {
   return {
     type: ALERT_SHOW,
     title,
@@ -44,6 +44,6 @@ export function showAlertForError(error) {
     return showAlert(title, message);
   } else {
     console.error(error);
-    return showAlert(messages.unexpectedTitle, messages.unexpectedMessage);
+    return showAlert();
   }
 }
diff --git a/app/javascript/mastodon/actions/compose.js b/app/javascript/mastodon/actions/compose.js
index a4352faab..0be2a5cd4 100644
--- a/app/javascript/mastodon/actions/compose.js
+++ b/app/javascript/mastodon/actions/compose.js
@@ -8,6 +8,8 @@ import resizeImage from '../utils/resize_image';
 import { importFetchedAccounts } from './importer';
 import { updateTimeline } from './timelines';
 import { showAlertForError } from './alerts';
+import { showAlert } from './alerts';
+import { defineMessages } from 'react-intl';
 
 let cancelFetchComposeSuggestionsAccounts;
 
@@ -49,6 +51,10 @@ export const COMPOSE_UPLOAD_CHANGE_REQUEST     = 'COMPOSE_UPLOAD_UPDATE_REQUEST'
 export const COMPOSE_UPLOAD_CHANGE_SUCCESS     = 'COMPOSE_UPLOAD_UPDATE_SUCCESS';
 export const COMPOSE_UPLOAD_CHANGE_FAIL        = 'COMPOSE_UPLOAD_UPDATE_FAIL';
 
+const messages = defineMessages({
+  uploadErrorLimit: { id: 'upload_error.limit', defaultMessage: 'File upload limit exceeded.' },
+});
+
 export function changeCompose(text) {
   return {
     type: COMPOSE_CHANGE,
@@ -184,20 +190,32 @@ export function submitComposeFail(error) {
 
 export function uploadCompose(files) {
   return function (dispatch, getState) {
-    if (getState().getIn(['compose', 'media_attachments']).size > 3) {
+    const uploadLimit = 4;
+    const media  = getState().getIn(['compose', 'media_attachments']);
+    const total = Array.from(files).reduce((a, v) => a + v.size, 0);
+    const progress = new Array(files.length).fill(0);
+
+    if (files.length + media.size > uploadLimit) {
+      dispatch(showAlert(undefined, messages.uploadErrorLimit));
       return;
     }
-
     dispatch(uploadComposeRequest());
 
-    resizeImage(files[0]).then(file => {
-      const data = new FormData();
-      data.append('file', file);
-
-      return api(getState).post('/api/v1/media', data, {
-        onUploadProgress: ({ loaded, total }) => dispatch(uploadComposeProgress(loaded, total)),
-      }).then(({ data }) => dispatch(uploadComposeSuccess(data)));
-    }).catch(error => dispatch(uploadComposeFail(error)));
+    for (const [i, f] of Array.from(files).entries()) {
+      if (media.size + i > 3) break;
+
+      resizeImage(f).then(file => {
+        const data = new FormData();
+        data.append('file', file);
+
+        return api(getState).post('/api/v1/media', data, {
+          onUploadProgress: function({ loaded }){
+            progress[i] = loaded;
+            dispatch(uploadComposeProgress(progress.reduce((a, v) => a + v, 0), total));
+          },
+        }).then(({ data }) => dispatch(uploadComposeSuccess(data)));
+      }).catch(error => dispatch(uploadComposeFail(error)));
+    };
   };
 };
 
diff --git a/app/javascript/mastodon/features/compose/components/upload_button.js b/app/javascript/mastodon/features/compose/components/upload_button.js
index b6fe770ea..db55ad70b 100644
--- a/app/javascript/mastodon/features/compose/components/upload_button.js
+++ b/app/javascript/mastodon/features/compose/components/upload_button.js
@@ -63,7 +63,7 @@ class UploadButton extends ImmutablePureComponent {
             key={resetFileKey}
             ref={this.setRef}
             type='file'
-            multiple={false}
+            multiple
             accept={acceptContentTypes.toArray().join(',')}
             onChange={this.handleChange}
             disabled={disabled}
diff --git a/app/javascript/mastodon/features/ui/index.js b/app/javascript/mastodon/features/ui/index.js
index f01c2bf24..93e45678f 100644
--- a/app/javascript/mastodon/features/ui/index.js
+++ b/app/javascript/mastodon/features/ui/index.js
@@ -263,7 +263,7 @@ class UI extends React.PureComponent {
     this.setState({ draggingOver: false });
     this.dragTargets = [];
 
-    if (e.dataTransfer && e.dataTransfer.files.length === 1) {
+    if (e.dataTransfer && e.dataTransfer.files.length >= 1) {
       this.props.dispatch(uploadCompose(e.dataTransfer.files));
     }
   }
diff --git a/app/javascript/mastodon/locales/defaultMessages.json b/app/javascript/mastodon/locales/defaultMessages.json
index 6ac8160ba..89d4e6bba 100644
--- a/app/javascript/mastodon/locales/defaultMessages.json
+++ b/app/javascript/mastodon/locales/defaultMessages.json
@@ -15,6 +15,15 @@
   {
     "descriptors": [
       {
+        "defaultMessage": "File upload limit exceeded.",
+        "id": "upload_error.limit"
+      }
+    ],
+    "path": "app/javascript/mastodon/actions/compose.json"
+  },
+  {
+    "descriptors": [
+      {
         "defaultMessage": "{name} mentioned you",
         "id": "notification.mention"
       },
@@ -2285,4 +2294,4 @@
     ],
     "path": "app/javascript/mastodon/features/video/index.json"
   }
-]
\ No newline at end of file
+]
diff --git a/app/javascript/mastodon/locales/en.json b/app/javascript/mastodon/locales/en.json
index 1dbf28022..e840b17d8 100644
--- a/app/javascript/mastodon/locales/en.json
+++ b/app/javascript/mastodon/locales/en.json
@@ -342,6 +342,7 @@
   "ui.beforeunload": "Your draft will be lost if you leave Mastodon.",
   "upload_area.title": "Drag & drop to upload",
   "upload_button.label": "Add media (JPEG, PNG, GIF, WebM, MP4, MOV)",
+  "upload_error.limit": "File upload limit exceeded.",
   "upload_form.description": "Describe for the visually impaired",
   "upload_form.focus": "Change preview",
   "upload_form.undo": "Delete",