luci-app-acme: Guess the system domain and pre-fill it to domains.

Check if the hostname is FQDN (e.g. has least one dot).
Check if the domain in the browser is not an IP and FQDN.

Signed-off-by: Sergey Ponomarev <stokito@gmail.com>

applications/luci-app-acme/htdocs/luci-static/resources/view/acme.js

@@ -19,6 +19,7 @@ return view.extend({
 			}),
 			L.resolveDefault(fs.exec_direct('/usr/libexec/acmesh-dnsinfo.sh'), ''),
 			L.resolveDefault(fs.stat('/usr/lib/acme/client/dnsapi'), null),
+			L.resolveDefault(fs.lines('/proc/sys/kernel/hostname'), ''),
 		]);
 	},
 
@@ -27,6 +28,8 @@ return view.extend({
 		let dnsApiInfoText = data[1];
 		let apiInfos = dnsapi.parseFile(dnsApiInfoText);
 		let hasDnsApi = data[2] != null;
+		let hostname = data[3];
+		let systemDomain = _guessDomain(hostname);
 		let wikiUrl = 'https://github.com/acmesh-official/acme.sh/wiki/';
 		let wikiInstructionUrl = wikiUrl + 'dnsapi';
 		let m, s, o;
@@ -97,6 +100,9 @@ return view.extend({
 				"The first name will be the subject name, subsequent names will be alt names. " +
 				"Note that all domain names must point at the router in the global DNS."));
 		o.datatype = "list(string)";
+		if (systemDomain) {
+			o.default = [systemDomain];
+		}
 		o.validate = function (section_id, value) {
 			if (!value) {
 				return true;
@@ -271,6 +277,15 @@ return view.extend({
 	}
 });
 
+function _isFqdn(domain) {
+	// Is not an IP i.e. starts from alphanumeric and has least one dot
+	return /[a-z0-9-]\..*$/.test(domain) && !/[0-9-]\..*$/.test(domain);
+}
+
+function _guessDomain(hostname) {
+	return _isFqdn(hostname) ? hostname : (_isFqdn(window.location.hostname) ? window.location.hostname : '');
+}
+
 
 function _addDnsProviderField(s, apiId, opt, isOptsAlt) {
 	let desc = '<code>' + opt.Name + '</code> ' + opt.Description;

applications/luci-app-acme/root/usr/share/rpcd/acl.d/luci-app-acme.json

@@ -4,6 +4,7 @@
                 "read": {
                         "cgi-io": [ "exec" ],
                         "file": {
+                                "/proc/sys/kernel/hostname": [ "read" ],
                                 "/etc/ssl/acme": [ "list" ],
                                 "/usr/libexec/acmesh-dnsinfo.sh": [ "exec" ]
                         },