Rewrite SpanFormatter for more kotlin

mobile/src/main/java/be/mygod/vpnhotspot/util/Utils.kt

@@ -12,9 +12,7 @@ import android.os.RemoteException
 import android.system.ErrnoException
 import android.system.Os
 import android.system.OsConstants
-import android.text.Spannable
-import android.text.SpannableString
-import android.text.SpannableStringBuilder
+import android.text.*
 import android.view.MenuItem
 import android.view.View
 import android.widget.ImageView
@@ -39,6 +37,7 @@ import java.lang.reflect.Method
 import java.net.InetAddress
 import java.net.NetworkInterface
 import java.net.SocketException
+import java.util.*
 
 tailrec fun Throwable.getRootCause(): Throwable {
     if (this is InvocationTargetException || this is RemoteException) return (cause ?: return this).getRootCause()
@@ -80,6 +79,53 @@ fun setVisibility(view: View, value: Boolean) {
     view.isVisible = value
 }
 
+private val formatSequence = "%([0-9]+\\$|<?)([^a-zA-z%]*)([[a-zA-Z%]&&[^tT]]|[tT][a-zA-Z])".toPattern()
+/**
+ * Version of [String.format] that works on [Spanned] strings to preserve rich text formatting.
+ * Both the `format` as well as any `%s args` can be Spanned and will have their formatting preserved.
+ * Due to the way [Spannable]s work, any argument's spans will can only be included **once** in the result.
+ * Any duplicates will appear as text only.
+ *
+ * See also: https://github.com/george-steel/android-utils/blob/289aff11e53593a55d780f9f5986e49343a79e55/src/org/oshkimaadziig/george/androidutils/SpanFormatter.java
+ *
+ * @param locale
+ * the locale to apply; `null` value means no localization.
+ * @param format the format string (see [java.util.Formatter.format])
+ * @param args
+ * the list of arguments passed to the formatter.
+ * @return the formatted string (with spans).
+ * @see String.format
+ * @author George T. Steel
+ */
+fun CharSequence.format(locale: Locale, vararg args: Any) = SpannableStringBuilder(this).apply {
+    var i = 0
+    var argAt = -1
+    while (i < length) {
+        val m = formatSequence.matcher(this)
+        if (!m.find(i)) break
+        i = m.start()
+        val exprEnd = m.end()
+        val argTerm = m.group(1)!!
+        val modTerm = m.group(2)
+        val cookedArg = when (val typeTerm = m.group(3)) {
+            "%" -> "%"
+            "n" -> "\n"
+            else -> {
+                val argItem = args[when (argTerm) {
+                    "" -> ++argAt
+                    "<" -> argAt
+                    else -> Integer.parseInt(argTerm.substring(0, argTerm.length - 1)) - 1
+                }]
+                if (typeTerm == "s" && argItem is Spanned) argItem else {
+                    String.format(locale, "%$modTerm$typeTerm", argItem)
+                }
+            }
+        }
+        replace(i, exprEnd, cookedArg)
+        i += cookedArg.length
+    }
+}
+
 fun makeIpSpan(ip: InetAddress) = ip.hostAddress.let {
     // exclude all bogon IP addresses supported by Android APIs
     if (!app.hasTouch || ip.isMulticastAddress || ip.isAnyLocalAddress || ip.isLoopbackAddress ||