Use DiffUtil with thread recyclerview

Also added a progress indicator at the top while fetching older messages

app/src/main/kotlin/com/simplemobiletools/smsmessenger/models/Message.kt

@@ -27,4 +27,21 @@ data class Message(
     fun isReceivedMessage() = type == Telephony.Sms.MESSAGE_TYPE_INBOX
 
     fun millis() = date * 1000L
+
+    companion object {
+        fun areItemsTheSame(old: Message, new: Message): Boolean {
+            return old.id == new.id
+        }
+
+        fun areContentsTheSame(old: Message, new: Message): Boolean {
+            return old.body == new.body &&
+                old.type == new.type &&
+                old.threadId == new.threadId &&
+                old.isMMS == new.isMMS &&
+                old.attachment == new.attachment &&
+                old.senderName == new.senderName &&
+                old.senderPhotoUri == new.senderPhotoUri &&
+                old.isScheduled == new.isScheduled
+        }
+    }
 }

app/src/main/kotlin/com/simplemobiletools/smsmessenger/models/ThreadDateTime.kt

@@ -1,3 +0,0 @@
-package com.simplemobiletools.smsmessenger.models
-
-data class ThreadDateTime(val date: Int, val simID: String) : ThreadItem()

app/src/main/kotlin/com/simplemobiletools/smsmessenger/models/ThreadError.kt

@@ -1,3 +0,0 @@
-package com.simplemobiletools.smsmessenger.models
-
-data class ThreadError(val messageId: Long, val messageText: String) : ThreadItem()

app/src/main/kotlin/com/simplemobiletools/smsmessenger/models/ThreadItem.kt

@@ -1,3 +0,0 @@
-package com.simplemobiletools.smsmessenger.models
-
-open class ThreadItem

app/src/main/kotlin/com/simplemobiletools/smsmessenger/models/ThreadItems.kt

@@ -0,0 +1,12 @@
+package com.simplemobiletools.smsmessenger.models
+
+/**
+ * Thread item representations for the main thread recyclerview. [Message] is also a [ThreadItem]
+ */
+sealed class ThreadItem {
+    data class ThreadLoading(val id: Long) : ThreadItem()
+    data class ThreadDateTime(val date: Int, val simID: String) : ThreadItem()
+    data class ThreadError(val messageId: Long, val messageText: String) : ThreadItem()
+    data class ThreadSent(val messageId: Long, val delivered: Boolean) : ThreadItem()
+    data class ThreadSending(val messageId: Long) : ThreadItem()
+}

app/src/main/kotlin/com/simplemobiletools/smsmessenger/models/ThreadSending.kt

@@ -1,3 +0,0 @@
-package com.simplemobiletools.smsmessenger.models
-
-data class ThreadSending(val messageId: Long) : ThreadItem()

app/src/main/kotlin/com/simplemobiletools/smsmessenger/models/ThreadSent.kt

@@ -1,5 +0,0 @@
-package com.simplemobiletools.smsmessenger.models
-
-// show a check after the latest message, if it is a sent one and succeeded,
-// show a double check if it is delivered
-data class ThreadSent(val messageID: Long, val delivered: Boolean) : ThreadItem()