Ignore "@instance..." part of username when computing status length (#3392)

* Move compose.* tests to own namespace

* Ignore "@instance..." part of username when computing status length

In a status with a mention ("@foo@example.org") only the "@foo" part should
be included in the calculated status length. It wasn't, so the app was
prevening people from posting statuses that should have been allowed.

Fix this.

- Lift the length calculation code in to a separate static function (easier
  and faster to test)
- Add a `MentionSpan` type, to reuse existing code for detecting mentions
- Fix a bug in `FakeSpannable.getSpans()` (it was returning the outer type,
  not the wrapped inner span)
- Add additional fast tests

The tests made sense under the `components.compose.ComposeActivity` package,
so I also created that and moved the existing ComposeActivity tests there.

Fixes https://github.com/tuskyapp/Tusky/issues/3339

* Static import assertEquals

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

@@ -156,7 +156,7 @@ private fun getCustomSpanForMention(mentions: List<Mention>, span: URLSpan, list
 }
 
 private fun getCustomSpanForMentionUrl(url: String, mentionId: String, listener: LinkListener): ClickableSpan {
-    return object : NoUnderlineURLSpan(url) {
+    return object : MentionSpan(url) {
         override fun onClick(view: View) = listener.onViewAccount(mentionId)
     }
 }

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

@@ -19,9 +19,14 @@ import android.text.TextPaint
 import android.text.style.URLSpan
 import android.view.View
 
-open class NoUnderlineURLSpan(
-    url: String
-) : URLSpan(url) {
+open class NoUnderlineURLSpan constructor(val url: String) : URLSpan(url) {
+
+    // This should not be necessary. But if you don't do this the [StatusLengthTest] tests
+    // fail. Without this, accessing the `url` property, or calling `getUrl()` (which should
+    // automatically call through to [UrlSpan.getURL]) returns null.
+    override fun getURL(): String {
+        return url
+    }
 
     override fun updateDrawState(ds: TextPaint) {
         super.updateDrawState(ds)
@@ -32,3 +37,8 @@ open class NoUnderlineURLSpan(
         view.context.openLink(url)
     }
 }
+
+/**
+ * Mentions of other users ("@user@example.org")
+ */
+open class MentionSpan(url: String) : NoUnderlineURLSpan(url)

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

@@ -131,6 +131,7 @@ private fun getSpan(matchType: FoundMatchType, string: String, colour: Int, star
     return when (matchType) {
         FoundMatchType.HTTP_URL -> NoUnderlineURLSpan(string.substring(start, end))
         FoundMatchType.HTTPS_URL -> NoUnderlineURLSpan(string.substring(start, end))
+        FoundMatchType.MENTION -> MentionSpan(string.substring(start, end))
         else -> ForegroundColorSpan(colour)
     }
 }