fix(external-source): disallow to select multiple files when multiple…

… mode is off (#589)

Co-authored-by: nd0ut <[email protected]>

blocks/ExternalSource/ExternalSource.js

@@ -43,6 +43,7 @@ export class ExternalSource extends UploaderBlock {
       activityCaption: '',
       selectedList: [],
       counter: 0,
+      multiple: false,
       onDone: () => {
         for (const message of this.$.selectedList) {
           const url = this.extractUrlFromMessage(message);
@@ -87,6 +88,9 @@ export class ExternalSource extends UploaderBlock {
     this.sub('selectedList', (list) => {
       this.$.counter = list.length;
     });
+    this.subConfigValue('multiple', (multiple) => {
+      this.$.multiple = multiple;
+    });
   }
 
   /**
@@ -122,7 +126,15 @@ export class ExternalSource extends UploaderBlock {
    * @param {SelectedFileMessage} message
    */
   async handleFileSelected(message) {
+    if (!this.$.multiple && this.$.selectedList.length) {
+      return;
+    }
+
     this.$.selectedList = [...this.$.selectedList, message];
+
+    if (!this.$.multiple) {
+      this.$.onDone();
+    }
   }
 
   /** @private */
@@ -235,7 +247,7 @@ ExternalSource.template = /* HTML */ `
     <div class="toolbar">
       <button type="button" class="cancel-btn secondary-btn" set="onclick: onCancel" l10n="cancel"></button>
       <div></div>
-      <div class="selected-counter"><span l10n="selected-count"></span>{{counter}}</div>
+      <div set="@hidden: !multiple" class="selected-counter"><span l10n="selected-count"></span>{{counter}}</div>
       <button type="button" class="done-btn primary-btn" set="onclick: onDone; @disabled: !counter">
         <lr-icon name="check"></lr-icon>
       </button>