Show target domains for non-mention/non-hashtag links where the target domain is not provided or differs from the domain in the text (#2698)

* Show target domains for non-mention/non-hashtag links where the target domain is not provided or differs from the domain in the text.
Addresses #2694

* Add link signifier to the marked-up domain

* Back down on validating hashtags and mentions, don't markup _any_ urls where the text starts with #/@

app/src/main/java/com/keylesspalace/tusky/util/LinkHelper.kt

@@ -57,7 +57,9 @@ fun getDomain(urlString: String?): String {
  * @param listener to notify about particular spans that are clicked
  */
 fun setClickableText(view: TextView, content: CharSequence, mentions: List<Mention>, tags: List<HashTag>?, listener: LinkListener) {
-    view.text = SpannableStringBuilder.valueOf(content).apply {
+    val spannableContent = markupHiddenUrls(view.context, content, mentions, tags, listener)
+
+    view.text = spannableContent.apply {
         getSpans(0, content.length, URLSpan::class.java).forEach {
             setClickableText(it, this, mentions, tags, listener)
         }
@@ -65,6 +67,29 @@ fun setClickableText(view: TextView, content: CharSequence, mentions: List<Menti
     view.movementMethod = LinkMovementMethod.getInstance()
 }
 
+@VisibleForTesting
+fun markupHiddenUrls(context: Context, content: CharSequence, mentions: List<Mention>, tags: List<HashTag>?, listener: LinkListener): SpannableStringBuilder {
+    val spannableContent = SpannableStringBuilder.valueOf(content)
+    val originalSpans = spannableContent.getSpans(0, content.length, URLSpan::class.java)
+    val obscuredLinkSpans = originalSpans.filter {
+        val text = spannableContent.subSequence(spannableContent.getSpanStart(it), spannableContent.getSpanEnd(it))
+        val firstCharacter = text[0]
+        firstCharacter != '#' &&
+            firstCharacter != '@' &&
+            getDomain(text.toString()) != getDomain(it.url)
+    }
+
+    for (span in obscuredLinkSpans) {
+        val start = spannableContent.getSpanStart(span)
+        val end = spannableContent.getSpanEnd(span)
+        val originalText = spannableContent.subSequence(start, end)
+        val replacementText = context.getString(R.string.url_domain_notifier, originalText, getDomain(span.url))
+        spannableContent.replace(start, end, replacementText) // this also updates the span locations
+    }
+
+    return spannableContent
+}
+
 @VisibleForTesting
 fun setClickableText(
     span: URLSpan,

app/src/main/res/values/strings.xml

@@ -658,6 +658,7 @@
     <string name="tips_push_notification_migration">Re-login all accounts to enable push notification support.</string>
     <string name="dialog_push_notification_migration">In order to use push notifications via UnifiedPush, Tusky needs permission to subscribe to notifications on your Mastodon server. This requires a re-login to change the OAuth scopes granted to Tusky. Using the re-login option here or in Account Preferences will preserve all of your local drafts and cache.</string>
     <string name="dialog_push_notification_migration_other_accounts">You have re-logged into your current account to grant push subscription permission to Tusky. However, you still have other accounts that have not been migrated this way. Switch to them and re-login one by one in order to enable UnifiedPush notifications support.</string>
+    <string name="url_domain_notifier">%s (🔗 %s)</string>
 
 
 </resources>

app/src/test/java/com/keylesspalace/tusky/util/LinkHelperTest.kt

@@ -1,8 +1,11 @@
 package com.keylesspalace.tusky.util
 
+import android.content.Context
 import android.text.SpannableStringBuilder
 import android.text.style.URLSpan
 import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.platform.app.InstrumentationRegistry
+import com.keylesspalace.tusky.R
 import com.keylesspalace.tusky.entity.HashTag
 import com.keylesspalace.tusky.entity.Status
 import com.keylesspalace.tusky.interfaces.LinkListener
@@ -29,6 +32,9 @@ class LinkHelperTest {
         HashTag("mastodev", "https://example.com/Tags/mastodev"),
     )
 
+    private val context: Context
+        get() = InstrumentationRegistry.getInstrumentation().targetContext
+
     @Test
     fun whenSettingClickableText_mentionUrlsArePreserved() {
         val builder = SpannableStringBuilder()
@@ -140,4 +146,94 @@ class LinkHelperTest {
             Assert.assertEquals(domain, getDomain(url))
         }
     }
+
+    @Test
+    fun hiddenDomainsAreMarkedUp() {
+        val displayedContent = "This is a good place to go"
+        val maliciousDomain = "malicious.place"
+        val maliciousUrl = "https://$maliciousDomain/to/go"
+        val content = SpannableStringBuilder()
+        content.append(displayedContent, URLSpan(maliciousUrl), 0)
+        Assert.assertEquals(context.getString(R.string.url_domain_notifier, displayedContent, maliciousDomain), markupHiddenUrls(context, content, listOf(), listOf(), listener).toString())
+    }
+
+    @Test
+    fun fraudulentDomainsAreMarkedUp() {
+        val displayedContent = "https://tusky.app/"
+        val maliciousDomain = "malicious.place"
+        val maliciousUrl = "https://$maliciousDomain/to/go"
+        val content = SpannableStringBuilder()
+        content.append(displayedContent, URLSpan(maliciousUrl), 0)
+        Assert.assertEquals(context.getString(R.string.url_domain_notifier, displayedContent, maliciousDomain), markupHiddenUrls(context, content, listOf(), listOf(), listener).toString())
+    }
+
+    @Test fun multipleHiddenDomainsAreMarkedUp() {
+        val domains = listOf("one.place", "another.place", "athird.place")
+        val displayedContent = "link"
+        val content = SpannableStringBuilder()
+        for (domain in domains) {
+            content.append(displayedContent, URLSpan("https://$domain/foo/bar"), 0)
+        }
+
+        val markedUpContent = markupHiddenUrls(context, content, listOf(), listOf(), listener)
+        for (domain in domains) {
+            Assert.assertTrue(markedUpContent.contains(context.getString(R.string.url_domain_notifier, displayedContent, domain)))
+        }
+    }
+
+    @Test
+    fun validMentionsAreNotMarkedUp() {
+        val builder = SpannableStringBuilder()
+        for (mention in mentions) {
+            builder.append("@${mention.username}", URLSpan(mention.url), 0)
+            builder.append(" ")
+        }
+
+        val markedUpContent = markupHiddenUrls(context, builder, mentions, tags, listener)
+        for (mention in mentions) {
+            Assert.assertFalse(markedUpContent.contains("${getDomain(mention.url)})"))
+        }
+    }
+
+    @Test
+    fun invalidMentionsAreNotMarkedUp() {
+        val builder = SpannableStringBuilder()
+        for (mention in mentions) {
+            builder.append("@${mention.username}", URLSpan(mention.url), 0)
+            builder.append(" ")
+        }
+
+        val markedUpContent = markupHiddenUrls(context, builder, listOf(), tags, listener)
+        for (mention in mentions) {
+            Assert.assertFalse(markedUpContent.contains("${getDomain(mention.url)})"))
+        }
+    }
+
+    @Test
+    fun validTagsAreNotMarkedUp() {
+        val builder = SpannableStringBuilder()
+        for (tag in tags) {
+            builder.append("#${tag.name}", URLSpan(tag.url), 0)
+            builder.append(" ")
+        }
+
+        val markedUpContent = markupHiddenUrls(context, builder, mentions, tags, listener)
+        for (tag in tags) {
+            Assert.assertFalse(markedUpContent.contains("${getDomain(tag.url)})"))
+        }
+    }
+
+    @Test
+    fun invalidTagsAreNotMarkedUp() {
+        val builder = SpannableStringBuilder()
+        for (tag in tags) {
+            builder.append("#${tag.name}", URLSpan(tag.url), 0)
+            builder.append(" ")
+        }
+
+        val markedUpContent = markupHiddenUrls(context, builder, mentions, listOf(), listener)
+        for (tag in tags) {
+            Assert.assertFalse(markedUpContent.contains("${getDomain(tag.url)})"))
+        }
+    }
 }