Add UserAvatarHelper and UserAvatarHelperTest class.

rocket-chat-android-widgets/src/main/java/chat/rocket/android/widget/helper/UserAvatarHelper.kt

+package chat.rocket.android.widget.helper
+
+import android.content.Context
+import android.graphics.Typeface
+import android.graphics.drawable.Drawable
+import chat.rocket.android.widget.AbsoluteUrl
+import com.amulyakhare.textdrawable.TextDrawable
+import java.net.URLEncoder
+
+object UserAvatarHelper {
+
+    /**
+     * Returns the user avatar URI.
+     *
+     * REMARK: This is often a SVG image (Rocket.Chat:server/startup/avatar.js).
+     *
+     * @param hostname The server's hostname.
+     * @param username The username.
+     * @return The user avatar URI.
+     */
+    fun getUri(hostname : String, username: String): String {
+        return "https://" +
+                hostname.replace("http://", "").replace("https://", "") +
+                "/avatar/" +
+                URLEncoder.encode(username, "UTF-8")
+    }
+
+    /**
+     * Returns the user avatar absolute URI.
+     *
+     * REMARK: This is often a SVG image (Rocket.Chat:server/startup/avatar.js).
+     *
+     * @param absoluteUrl The AbsoluteUrl.
+     * @param username The username.
+     * @return The user avatar absolute URI.
+     */
+    fun getAbsoluteUri(absoluteUrl: AbsoluteUrl, username: String): String {
+        val avatarUri = "/avatar/" + URLEncoder.encode(username, "UTF-8")
+        return absoluteUrl.from(avatarUri)
+    }
+
+    /**
+     * Returns a drawable with username initials.
+     *
+     * @param username The username.
+     * @param context The context.
+     * @return A drawable with username initials.
+     * @see getUsernameInitials
+     */
+    fun getTextDrawable(username: String, context: Context): Drawable {
+        val round = (4 * context.resources.displayMetrics.density).toInt()
+
+        return TextDrawable.builder()
+                .beginConfig()
+                .useFont(Typeface.SANS_SERIF)
+                .endConfig()
+                .buildRoundRect(getUsernameInitials(username), getUserAvatarBackgroundColor(username), round)
+    }
+
+    /**
+     * Returns a string with the username initials. For example: username John Doe returns JD initials.
+     *
+     * @param username The username.
+     * @return A string with username initials.
+     */
+    fun getUsernameInitials(username: String): String {
+        if (username.isEmpty()) {
+            return "?"
+        }
+
+        val splitUsername = username.split(".")
+        if (splitUsername.size > 1) {
+            return (splitUsername[0].substring(0, 1) + splitUsername[splitUsername.size - 1].substring(0, 1)).toUpperCase()
+        } else {
+            if (username.length > 1) {
+                return username.substring(0, 2).toUpperCase()
+            } else {
+                return username.substring(0, 1).toUpperCase()
+            }
+        }
+    }
+
+    /**
+     * Returns a background color to be rendered on the user avatar (Rocket.Chat:server/startup/avatar.js).
+     *
+     * @param username The username.
+     * @return A hexadecimal color.
+     */
+    fun getUserAvatarBackgroundColor(username: String): Int {
+        return COLORS[username.length % COLORS.size]
+    }
+
+    private val COLORS = intArrayOf(
+            0xFFF44336.toInt(), 0xFFE91E63.toInt(), 0xFF9C27B0.toInt(), 0xFF673AB7.toInt(), 0xFF3F51B5.toInt(),
+            0xFF2196F3.toInt(), 0xFF03A9F4.toInt(), 0xFF00BCD4.toInt(), 0xFF009688.toInt(), 0xFF4CAF50.toInt(),
+            0xFF8BC34A.toInt(), 0xFFCDDC39.toInt(), 0xFFFFC107.toInt(), 0xFFFF9800.toInt(), 0xFFFF5722.toInt(),
+            0xFF795548.toInt(), 0xFF9E9E9E.toInt(), 0xFF607D8B.toInt())
+}
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rocket-chat-android-widgets/src/test/kotlin/UserAvatarHelperTest.kt

+import chat.rocket.android.widget.helper.UserAvatarHelper
+import org.junit.Test
+
+class UserAvatarHelperTest {
+
+    @Test
+    fun getUsernameInitialsTest() {
+        assert(UserAvatarHelper.getUsernameInitials("") == "?")
+        assert(UserAvatarHelper.getUsernameInitials("?") == "?")
+        assert(UserAvatarHelper.getUsernameInitials("f") == "F")
+        assert(UserAvatarHelper.getUsernameInitials("B") == "B")
+        assert(UserAvatarHelper.getUsernameInitials("fo") == "FO")
+        assert(UserAvatarHelper.getUsernameInitials("FO") == "FO")
+        assert(UserAvatarHelper.getUsernameInitials("fOo") == "FO")
+        assert(UserAvatarHelper.getUsernameInitials("FOO") == "FO")
+        assert(UserAvatarHelper.getUsernameInitials("F.O") == "FO")
+        assert(UserAvatarHelper.getUsernameInitials("F.o") == "FO")
+        assert(UserAvatarHelper.getUsernameInitials("Foo.bar") == "FB")
+        assert(UserAvatarHelper.getUsernameInitials("Foobar.bar") == "FB")
+        assert(UserAvatarHelper.getUsernameInitials("Foobar.bar.zab") == "FZ")
+    }
+}
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