add log local downloader

luasrc/view/AdGuardHome/log.htm

@@ -5,9 +5,24 @@
 <input type="checkbox" name="NAME" value="reverse" onclick=" return reverselog()" style="vertical-align:middle;height: auto;" checked>reverse</input><br>
 <textarea id="cbid.logview.1.conf" class="cbi-input-textarea" style="width: 100%;display:inline" data-update="change" name="vbid.logview.1.conf" rows="32" cols="60" readonly="readonly" > </textarea>
 <input class="cbi-button cbi-button-apply" name="apply_update_button" id="apply_update_button" value="dellog" onclick=" return apply_del_log() "/>
-
+<input class="cbi-button cbi-button-apply" name="backup" value="backup" style=" display:inline;" onclick=" return download_log()" />
 <script type="text/javascript">//<![CDATA[
 var islogreverse = true;
+function createAndDownloadFile(fileName, content) {
+    var aTag = document.createElement('a');
+    var blob = new Blob([content]);
+    aTag.download = fileName;
+    aTag.href = URL.createObjectURL(blob);
+    aTag.click();
+    URL.revokeObjectURL(blob);
+}
+function download_log(){
+	var lv = document.getElementById('cbid.logview.1.conf');
+	var dt = new Date();
+	var timestamp = dt.getMonth()+"-"+dt.getDay()+"-"+dt.getHours()+"_"+dt.getMinutes();
+	createAndDownloadFile("AdGuardHome"+timestamp+".log",lv.innerHTML)
+	return
+}
 function apply_del_log(){
 	XHR.get('<%=url([[admin]], [[services]], [[AdGuardHome]], [[dodellog]])%>',null,function(x, data){
 	var lv = document.getElementById('cbid.logview.1.conf');