allow to remove all messages from current chat

res/menu/conversation_clear.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <item android:title="@string/menu_clear_chat"
+          android:id="@+id/menu_clear_chat"/>
+
+</menu>

res/values/strings.xml

@@ -192,6 +192,7 @@
     <string name="menu_add_attachment">Add Attachment</string>
     <string name="menu_leave_group">Leave Group</string>
     <string name="menu_delete_chat">Delete Chat</string>
+    <string name="menu_clear_chat">Clear Chat</string>
     <string name="ask_delete_named_chat">Are you sure you want to delete \"%1$s\"?</string>
     <string name="menu_delete_messages">Delete Messages</string>
     <string name="delete_contact">Delete Contact</string>

src/org/thoughtcrime/securesms/ConversationActivity.java

@@ -483,6 +483,7 @@ public boolean onPrepareOptionsMenu(Menu menu) {
       menu.findItem(R.id.menu_archive_chat).setTitle(R.string.menu_unarchive_chat);
     }
 
+    inflater.inflate(R.menu.conversation_clear, menu);
     inflater.inflate(R.menu.conversation_delete, menu);
 
     try {
@@ -533,6 +534,7 @@ public boolean onOptionsItemSelected(MenuItem item) {
       case R.id.menu_add_attachment:        handleAddAttachment();             return true;
       case R.id.menu_leave:                 handleLeaveGroup();                return true;
       case R.id.menu_archive_chat:          handleArchiveChat();               return true;
+      case R.id.menu_clear_chat:            fragment.handleClearChat();        return true;
       case R.id.menu_delete_chat:           handleDeleteChat();                return true;
       case R.id.menu_mute_notifications:    handleMuteNotifications();         return true;
       case R.id.menu_show_map:              handleShowMap();                   return true;

src/org/thoughtcrime/securesms/ConversationAdapter.java

@@ -331,6 +331,10 @@ public Set<DcMsg> getSelectedItems() {
     return Collections.unmodifiableSet(new HashSet<>(batchSelected));
   }
 
+  public int[] getMessageIds() {
+    return dcMsgList;
+  }
+
   public void pulseHighlightItem(int position) {
     if (position>=0 && position < getItemCount()) {
       positionToPulseHighlight = position;

src/org/thoughtcrime/securesms/ConversationFragment.java

@@ -357,6 +357,10 @@ static boolean canReplyToMsg(DcMsg dcMsg) {
         return !dcMsg.isInfo() && dcMsg.getType() != DcMsg.DC_MSG_VIDEOCHAT_INVITATION;
     }
 
+    public void handleClearChat() {
+        handleDeleteMessages((int) chatId, getListAdapter().getMessageIds());
+    }
+
     private ConversationAdapter getListAdapter() {
         return (ConversationAdapter) list.getAdapter();
     }

src/org/thoughtcrime/securesms/MessageSelectorFragment.java

@@ -55,19 +55,21 @@ protected void handleDisplayDetails(DcMsg dcMsg) {
   }
 
   protected void handleDeleteMessages(int chatId, final Set<DcMsg> messageRecords) {
-    int messagesCount = messageRecords.size();
+    handleDeleteMessages(chatId, DcMsg.msgSetToIds(messageRecords));
+  }
+
+  protected void handleDeleteMessages(int chatId, final int[] messageIds) {
     DcChat dcChat = DcHelper.getContext(getActivity()).getChat(chatId);
 
     String text = getActivity().getResources().getQuantityString(
       dcChat.isDeviceTalk()? R.plurals.ask_delete_messages_simple : R.plurals.ask_delete_messages,
-      messagesCount, messagesCount);
+      messageIds.length, messageIds.length);
 
     new AlertDialog.Builder(getActivity())
             .setMessage(text)
             .setCancelable(true)
             .setPositiveButton(R.string.delete, (dialog, which) -> {
-                int[] ids = DcMsg.msgSetToIds(messageRecords);
-                dcContext.deleteMsgs(ids);
+                dcContext.deleteMsgs(messageIds);
                 if (actionMode != null) actionMode.finish();
             })
             .setNegativeButton(android.R.string.cancel, null)