Add download chat feature to server chat (#10481)

* Add download chat feature to server chat

Add a download feature next to the delete chat feature in the server vue chat interface.

* code style

---------

Co-authored-by: Xuan Son Nguyen <son@huggingface.co>

examples/server/public/index.html

@@ -81,7 +81,13 @@
               <path d="M14.5 3a1 1 0 0 1-1 1H13v9a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2V4h-.5a1 1 0 0 1-1-1V2a1 1 0 0 1 1-1H6a1 1 0 0 1 1-1h2a1 1 0 0 1 1 1h3.5a1 1 0 0 1 1 1zM4.118 4 4 4.059V13a1 1 0 0 0 1 1h6a1 1 0 0 0 1-1V4.059L11.882 4zM2.5 3h11V2h-11z"/>
             </svg>
           </button>
-
+          <button v-if="messages.length > 0" class="btn mr-1" @click="downloadConv(viewingConvId)" :disabled="isGenerating">
+              <!-- download conversation button -->
+              <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-download" viewBox="0 0 16 16">
+                  <path d="M.5 9.9a.5.5 0 0 1 .5.5v2.5a1 1 0 0 0 1 1h12a1 1 0 0 0 1-1v-2.5a.5.5 0 0 1 1 0v2.5a2 2 0 0 1-2 2H2a2 2 0 0 1-2-2v-2.5a.5.5 0 0 1 .5-.5"/>
+                  <path d="M7.646 11.854a.5.5 0 0 0 .708 0l3-3a.5.5 0 0 0-.708-.708L8.5 10.293V1.5a.5.5 0 0 0-1 0v8.793L5.354 8.146a.5.5 0 1 0-.708.708z"/>
+            </svg>
+          </button>
           <button class="btn" @click="showConfigDialog = true" :disabled="isGenerating">
             <!-- edit config button -->
             <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-gear" viewBox="0 0 16 16">
@@ -526,6 +532,23 @@
             this.fetchMessages();
           }
         },
+        downloadConv(convId) {
+          const conversation = StorageUtils.getOneConversation(convId);
+          if (!conversation) {
+            alert('Conversation not found.');
+            return;
+          }
+          const conversationJson = JSON.stringify(conversation, null, 2);
+          const blob = new Blob([conversationJson], { type: 'application/json' });
+          const url = URL.createObjectURL(blob);
+          const a = document.createElement('a');
+          a.href = url;
+          a.download = `conversation_${convId}.json`;
+          document.body.appendChild(a);
+          a.click();
+          document.body.removeChild(a);
+          URL.revokeObjectURL(url);
+        },
         async sendMessage() {
           if (!this.inputMsg) return;
           const currConvId = this.viewingConvId;