Get older messages

lib/helpers/conversations_helper.dart

@@ -29,21 +29,16 @@ class ConversationsHelper {
   ///
   /// Return the ID of the newly created conversation or -1 in case of failure
   Future<int> createConversation(ConversationSettings settings) async {
+    final response =
+        await APIRequest(uri: "conversations/create", needLogin: true, args: {
+      "name": settings.hasName ? settings.name : "false",
+      "follow": settings.following ? "true" : "false",
+      "users": settings.members.join(",")
+    }).exec();
 
-    final response = await APIRequest(
-      uri: "conversations/create",
-      needLogin: true,
-      args: {
-        "name" : settings.hasName ? settings.name : "false",
-        "follow" : settings.following ? "true" : "false",
-        "users": settings.members.join(",")
-      }
-    ).exec();
-
-    if(response.code != 200) return -1;
+    if (response.code != 200) return -1;
 
     return response.getObject()["conversationID"];
-
   }
 
   /// Download the list of conversations from the server
@@ -156,6 +151,28 @@ class ConversationsHelper {
     );
   }
 
+  /// Parse a list of messages given by the server
+  Future<ConversationMessagesList> _parseConversationMessageFromServer(
+      int conversationID, APIResponse response) async {
+    if (response.code != 200) return null;
+
+    // Parse the response of the server
+    ConversationMessagesList list = ConversationMessagesList();
+    response.getArray().forEach((f) {
+      list.add(
+        _apiToConversationMessage(
+          conversationID: conversationID,
+          map: f,
+        ),
+      );
+    });
+
+    // Save messages in the cache
+    _conversationMessagesDatabaseHelper.insertOrUpdateAll(list);
+
+    return list;
+  }
+
   /// Refresh the list of messages of a conversation
   ///
   /// Set [lastMessageID] to 0 to specify that we do not have any message of the
@@ -172,24 +189,26 @@ class ConversationsHelper {
           "last_message_id": lastMessageID.toString()
         }).exec();
 
-    if (response.code != 200) return null;
+    return await _parseConversationMessageFromServer(conversationID, response);
+  }
 
-    // Parse the response of the server
-    ConversationMessagesList list = ConversationMessagesList();
-    response.getArray().forEach((f) {
-      list.add(ConversationMessage(
-          id: f["ID"],
-          conversationID: conversationID,
-          userID: f["ID_user"],
-          timeInsert: f["time_insert"],
-          message: f["message"],
-          imageURL: f["image_path"]));
-    });
+  /// Get older messages for a given conversation from an online source
+  Future<ConversationMessagesList> getOlderMessages({
+    @required int conversationID,
+    @required int oldestMessagesID,
+    int limit = 15,
+  }) async {
+    // Perform the request online
+    final response = await APIRequest(
+        uri: "conversations/get_older_messages",
+        needLogin: true,
+        args: {
+          "conversationID": conversationID.toString(),
+          "oldest_message_id": oldestMessagesID.toString(),
+          "limit": limit.toString()
+        }).exec();
 
-    // Save messages in the cache
-    _conversationMessagesDatabaseHelper.insertOrUpdateAll(list);
-
-    return list;
+    return await _parseConversationMessageFromServer(conversationID, response);
   }
 
   /// Get new messages for a given conversation
@@ -237,4 +256,19 @@ class ConversationsHelper {
 
     return SendMessageResult.SUCCESS;
   }
+
+  /// Turn an API response into a ConversationMessage object
+  ConversationMessage _apiToConversationMessage({
+    @required int conversationID,
+    @required Map<String, dynamic> map,
+  }) {
+    return ConversationMessage(
+      id: map["ID"],
+      conversationID: conversationID,
+      userID: map["ID_user"],
+      timeInsert: map["time_insert"],
+      message: map["message"],
+      imageURL: map["image_path"],
+    );
+  }
 }

lib/lists/conversation_messages_list.dart

@@ -40,4 +40,12 @@ class ConversationMessagesList extends ListBase<ConversationMessage> {
       if (message.id > lastMessageID) lastMessageID = message.id;
     return lastMessageID;
   }
+
+  /// Get the ID of the first message present in this list
+  int get firstMessageID {
+    int firstMessageID = this[0].id;
+    for (ConversationMessage message in this)
+      if (message.id < firstMessageID) firstMessageID = message.id;
+    return firstMessageID;
+  }
 }

lib/ui/screens/conversation_screen.dart

@@ -6,6 +6,7 @@ import 'package:comunic/lists/conversation_messages_list.dart';
 import 'package:comunic/lists/users_list.dart';
 import 'package:comunic/models/new_conversation_message.dart';
 import 'package:comunic/ui/tiles/conversation_message_tile.dart';
+import 'package:comunic/ui/widgets/scroll_watcher.dart';
 import 'package:comunic/utils/files_utils.dart';
 import 'package:comunic/utils/intl_utils.dart';
 import 'package:comunic/utils/list_utils.dart';
@@ -17,6 +18,7 @@ import 'package:flutter/material.dart';
 /// @author Pierre HUBERT
 
 enum ErrorLevel { NONE, MINOR, MAJOR }
+enum _OlderMessagesLevel { NONE, LOADING, NO_MORE_AVAILABLE }
 
 class ConversationScreen extends StatefulWidget {
   final int conversationID;
@@ -42,6 +44,14 @@ class _ConversationScreenState extends State<ConversationScreen> {
   bool _isSendingMessage = false;
   TextEditingController _textEditingController = TextEditingController();
   Timer _refreshTime;
+  ScrollWatcher _scrollController;
+  _OlderMessagesLevel _loadingOlderMessages = _OlderMessagesLevel.NONE;
+
+  @override
+  void initState() {
+    super.initState();
+    _scrollController = ScrollWatcher(onReachBottom: _loadOlderMessages);
+  }
 
   @override
   void didChangeDependencies() {
@@ -59,6 +69,10 @@ class _ConversationScreenState extends State<ConversationScreen> {
 
   void _setSending(bool sending) => setState(() => _isSendingMessage = sending);
 
+  void _setLoadingOlderMessagesState(_OlderMessagesLevel state) => setState(() {
+        _loadingOlderMessages = state;
+      });
+
   /// Method called when an error occurred while loading messages
   void _errorLoading() {
     _setError(_messages == null ? ErrorLevel.MAJOR : ErrorLevel.MINOR);
@@ -89,6 +103,47 @@ class _ConversationScreenState extends State<ConversationScreen> {
     // anything (we wait for the online request)
     if (messages.length == 0 && !online) return;
 
+    await _applyNewMessages(messages);
+  }
+
+  /// Get older messages
+  Future<void> _loadOlderMessages() async {
+    if (_loadingOlderMessages != _OlderMessagesLevel.NONE ||
+        _messages == null ||
+        _messages.length == 0) return;
+
+    // Let's start to load older messages
+    _setLoadingOlderMessagesState(_OlderMessagesLevel.LOADING);
+
+    final messages = await _conversationsHelper.getOlderMessages(
+        conversationID: widget.conversationID,
+        oldestMessagesID: _messages.firstMessageID);
+
+    // Mark as not loading anymore
+    _setLoadingOlderMessagesState(_OlderMessagesLevel.NONE);
+
+    // Check for errors
+    if (messages == null) {
+      _errorLoading();
+      return;
+    }
+
+    // Check if there is no more unread messages
+    if (messages.length == 0) {
+      _setLoadingOlderMessagesState(_OlderMessagesLevel.NO_MORE_AVAILABLE);
+      return;
+    }
+
+    // Apply the messages
+    _applyNewMessages(messages);
+  }
+
+  /// Apply new messages [messages] must not be null
+  Future<void> _applyNewMessages(ConversationMessagesList messages) async {
+
+    // We ignore new messages once the area is no longer visible
+    if(!this.mounted) return;
+
     //Then get information about users
     final usersToGet =
         findMissingFromList(_usersInfo.usersID, messages.getUsersID());
@@ -204,10 +259,19 @@ class _ConversationScreenState extends State<ConversationScreen> {
     return buildErrorCard(tr("Could not load the list of messages!"));
   }
 
+  /// Widget shown when loading older messages
+  Widget _buildLoadingOlderMessage() {
+    return Container(
+      padding: EdgeInsets.all(8.0),
+      child: CircularProgressIndicator(),
+    );
+  }
+
   /// Messages list
   Widget _buildMessagesList() {
     return Expanded(
       child: ListView.builder(
+          controller: _scrollController,
           reverse: true,
           itemCount: _messages.length,
           itemBuilder: (c, i) {
@@ -221,7 +285,7 @@ class _ConversationScreenState extends State<ConversationScreen> {
     );
   }
 
-  /// Send message from
+  /// Send message form
   Widget _buildSendMessageForm() {
     return new Container(
       margin: const EdgeInsets.symmetric(horizontal: 8.0),
@@ -244,6 +308,7 @@ class _ConversationScreenState extends State<ConversationScreen> {
           // Message area
           new Flexible(
             child: new TextField(
+              keyboardType: TextInputType.text,
               maxLines: null,
               maxLength: 200,
               maxLengthEnforced: true,
@@ -302,10 +367,17 @@ class _ConversationScreenState extends State<ConversationScreen> {
         Container(
           child: _error == ErrorLevel.MINOR ? _buildError() : null,
         ),
+        Container(
+          child: _loadingOlderMessages == _OlderMessagesLevel.LOADING
+              ? _buildLoadingOlderMessage()
+              : null,
+        ),
         _buildMessagesList(),
         Divider(),
         _buildSendMessageForm()
       ],
     );
   }
+
+
 }

lib/ui/widgets/scroll_watcher.dart

@@ -0,0 +1,27 @@
+import 'package:flutter/material.dart';
+
+/// Scroll watcher
+///
+/// @author Pierre HUBERT
+
+typedef OnReachBottomCallback = void Function();
+
+class ScrollWatcher extends ScrollController {
+
+  // Callbacks
+  OnReachBottomCallback onReachBottom;
+
+  ScrollWatcher({this.onReachBottom}) {
+    addListener(_updatePosition);
+  }
+
+
+
+  void _updatePosition() {
+
+    // Refresh bottom position
+    if(position.pixels.floor() == position.maxScrollExtent.floor())
+      onReachBottom();
+
+  }
+}