Sort is made inside Vocabulary class

app/src/main/java/com/paktalin/vocabularynotebook/VocabularyAdapter.kt

@@ -72,30 +72,12 @@ class VocabularyAdapter(private val vocabulary: Vocabulary, private val activity
         this.sort()
     }
 
-    private fun sortByTranslation() {
-        vocabulary.words.sortWith(Comparator { item1, item2 ->
-            item1.pojo.translation.compareTo(item2.pojo.translation) })
-    }
-
-    private fun sortByWord() {
-        vocabulary.words.sortWith(Comparator { item1, item2 ->
-            item1.pojo.word.compareTo(item2.pojo.word) })
-    }
-
-    private fun sortByTime() {
-        vocabulary.words.sortWith(Comparator { item1, item2 ->
-            -item1.pojo.time!!.compareTo(item2.pojo.time) })
-    }
-
     fun sort() {
+        // update SortOrder
         if (sortOrder == 2) sortOrder = 0
         else sortOrder++
 
-        when(sortOrder) {
-            0 -> sortByTime()
-            1 -> sortByWord()
-            2 -> sortByTranslation()
-        }
+        vocabulary.sort(sortOrder)
         this.notifyDataSetChanged()
     }
 

app/src/main/java/com/paktalin/vocabularynotebook/firestoreitems/Vocabulary.kt

@@ -2,6 +2,8 @@ package com.paktalin.vocabularynotebook.firestoreitems
 
 class Vocabulary(var words: MutableList<WordItem>) {
     companion object {
+        private val TAG = "VN/" + Vocabulary::class.java.simpleName
+
         private const val SORT_BY_TIME = 0
         private const val SORT_BY_WORD = 1
         private const val SORT_BY_TRANSLATION = 2
@@ -19,16 +21,25 @@ class Vocabulary(var words: MutableList<WordItem>) {
         pojo = Pojo(null)
     }
 
-    fun sort(index:Int) {
-        when(index) {
+    fun sort(sortOrder:Int) {
+        when(sortOrder) {
             SORT_BY_TIME -> sortByTime()
             SORT_BY_WORD -> sortByWord()
             SORT_BY_TRANSLATION -> sortByTranslation()
         }
     }
 
-    private fun sortByTime() { }
-    private fun sortByWord() { }
-    private fun sortByTranslation() { }
+    private fun sortByTime() {
+        words.sortWith(Comparator { item1, item2 ->
+            -item1.pojo.time!!.compareTo(item2.pojo.time) })
+    }
+    private fun sortByWord() {
+        words.sortWith(Comparator { item1, item2 ->
+            item1.pojo.word.compareTo(item2.pojo.word) })
+    }
+    private fun sortByTranslation() {
+        words.sortWith(Comparator { item1, item2 ->
+            item1.pojo.translation.compareTo(item2.pojo.translation) })
+    }
 
 }

app/src/main/java/com/paktalin/vocabularynotebook/ui/MainActivity.kt

@@ -69,6 +69,7 @@ class MainActivity : AppCompatActivity() {
         userDocument.get()
                 .addOnSuccessListener { task ->
                     hideProgressBar()
+                    //todo move Firestore logic and collections names to a separate class
                     if (task.get("vocabularies") != null) {
                         val vocabularies: List<DocumentReference> = task.get("vocabularies") as List<DocumentReference>
                         val vocabulary = db.collection("vocabularies").document(vocabularies[0].id)