Improved handling for URLs that are composed of mixed character sets.

test/unitTest/java/org/thoughtcrime/securesms/linkpreview/LinkPreviewUtilTest.java

@@ -0,0 +1,24 @@
+package org.thoughtcrime.securesms.linkpreview;
+
+import org.junit.Test;
+
+import static junit.framework.TestCase.assertFalse;
+import static junit.framework.TestCase.assertTrue;
+
+public class LinkPreviewUtilTest {
+
+  @Test
+  public void isLegal_allLatin() {
+    assertTrue(LinkPreviewUtil.isLegalUrl("https://signal.org"));
+  }
+
+  @Test
+  public void isLegal_latinAndCyrillic() {
+    assertFalse(LinkPreviewUtil.isLegalUrl("https://www.аmazon.com"));
+  }
+
+  @Test
+  public void isLegal_latinAndGreek() {
+    assertFalse(LinkPreviewUtil.isLegalUrl("https://www.αpple.com"));
+  }
+}