Add requireListener and hierarchical error.

app/src/main/java/org/thoughtcrime/securesms/util/fragments/ListenerExtensions.kt

@@ -0,0 +1,57 @@
+package org.thoughtcrime.securesms.util.fragments
+
+import androidx.fragment.app.Fragment
+import java.lang.Exception
+
+/**
+ * Given an input type [T], find an instance of it first looking through all
+ * parents, and then the activity.
+ *
+ * @return First instance found of type [T] or null
+ */
+inline fun <reified T> Fragment.findListener(): T? {
+  var parent: Fragment? = parentFragment
+  while (parent != null) {
+    if (parent is T) {
+      return parent
+    }
+    parent = parent.parentFragment
+  }
+
+  return requireActivity() as? T
+}
+
+/**
+ * Given an input type [T], find an instance of it first looking through all parents,
+ * and then the activity.
+ *
+ * @return First instance found of type [T]
+ * @throws ListenerNotFoundException with the hierarchy searched.
+ *
+ */
+inline fun <reified T> Fragment.requireListener(): T {
+  val hierarchy = mutableListOf<String>()
+  try {
+    var parent: Fragment? = parentFragment
+    while (parent != null) {
+      if (parent is T) {
+        return parent
+      }
+      hierarchy.add(parent::class.java.name)
+      parent = parent.parentFragment
+    }
+
+    return requireActivity() as T
+  } catch (e: ClassCastException) {
+    hierarchy.add(requireActivity()::class.java.name)
+    throw ListenerNotFoundException(hierarchy, e)
+  }
+}
+
+class ListenerNotFoundException(hierarchy: List<String>, cause: Throwable) : Exception(formatMessage(hierarchy), cause) {
+  companion object {
+    fun formatMessage(hierarchy: List<String>): String {
+      return "Hierarchy Searched: \n${hierarchy.joinToString("\n")}"
+    }
+  }
+}