add copy tooltip and fix reply

src/Flows.css

@@ -155,3 +155,18 @@
 .box-id {
     color: #666666;
 }
+.box-id a:hover::before {
+    content: "复制全文";
+    position: relative;
+    width: 5em;
+    height: 1.3em;
+    line-height: 1.3em;
+    margin-bottom: -1.3em;
+    border-radius: 3px;
+    text-align: center;
+    top: -1.5em;
+    display: block;
+    color: white;
+    background-color: rgba(0,0,0,.6);
+    pointer-events: none;
+}

src/Flows.js

@@ -10,7 +10,7 @@ import {TokenCtx, ReplyForm} from './UserAction';
 import {API} from './flows_api';
 
 const IMAGE_BASE='http://www.pkuhelper.com:10301/services/pkuhole/images/';
-const AUDIO_BASE='/audio_proxy/';
+const AUDIO_BASE='http://www.pkuhelper.com:10301/services/pkuhole/audios/';
 
 const SEARCH_PAGESIZE=50;
 const CLICKABLE_TAGS={a: true, audio: true};
@@ -256,7 +256,8 @@ class FlowSidebar extends PureComponent {
     do_reply(name,event) {
         if(event.target.tagName.toLowerCase()!=='a') {
             let text=this.reply_ref.current.get();
-            this.reply_ref.current.set_and_focus('Re '+name+': ');
+            if(/^\s*(Re (洞主|\b[A-Z][a-z]+){0,2}:)?\s*$/.test(text)) // text is nearly empty so we can replace it
+                this.reply_ref.current.set_and_focus('Re '+name+': ');
         }
     }