From 8a3b07e537e853888a070fca34a8210b62e90fcc Mon Sep 17 00:00:00 2001
From: "Sebastian J. Wolf" <sebastian@ygriega.de>
Date: Wed, 26 Aug 2020 22:52:06 +0200
Subject: [PATCH] Load older chat messages if needed

---
 qml/pages/ChatPage.qml | 14 +++++++++++---
 src/chatmodel.cpp      | 17 ++++++++++++++++-
 src/chatmodel.h        |  3 +++
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/qml/pages/ChatPage.qml b/qml/pages/ChatPage.qml
index 5ca70e6..ade2a98 100644
--- a/qml/pages/ChatPage.qml
+++ b/qml/pages/ChatPage.qml
@@ -154,7 +154,7 @@ Page {
             chatView.positionViewAtEnd();
         }
         onNewMessageReceived: {
-            chatView.positionViewAtEnd();
+            // Notify user about new messages...
         }
     }
 
@@ -244,17 +244,25 @@ Page {
                 clip: true
                 visible: count > 0
 
-                onMovementEnded: {
+                function handleScrollPositionChanged() {
                     tdLibWrapper.viewMessage(chatInformation.id, chatView.itemAt(chatView.contentX, ( chatView.contentY + chatView.height - Theme.horizontalPageMargin )).myMessage.id);
+                    if (chatView.indexAt(chatView.contentX, chatView.contentY) < 10) {
+                        chatModel.triggerLoadMoreHistory();
+                    }
+                }
+
+                onMovementEnded: {
+                    handleScrollPositionChanged();
                 }
 
                 onQuickScrollAnimatingChanged: {
                     if (!quickScrollAnimating) {
-                        tdLibWrapper.viewMessage(chatInformation.id, chatView.itemAt(chatView.contentX, ( chatView.contentY + chatView.height - Theme.horizontalPageMargin )).myMessage.id);
+                        handleScrollPositionChanged();
                     }
                 }
 
                 onCurrentIndexChanged: {
+                    console.log("Current index: " + currentIndex);
                     tdLibWrapper.viewMessage(chatInformation.id, currentItem.myMessage.id);
                 }
 
diff --git a/src/chatmodel.cpp b/src/chatmodel.cpp
index 22289d9..e050f29 100644
--- a/src/chatmodel.cpp
+++ b/src/chatmodel.cpp
@@ -6,6 +6,7 @@ ChatModel::ChatModel(TDLibWrapper *tdLibWrapper)
 {
     this->tdLibWrapper = tdLibWrapper;
     this->inReload = false;
+    this->inIncrementalUpdate = false;
     connect(this->tdLibWrapper, SIGNAL(messagesReceived(QVariantList)), this, SLOT(handleMessagesReceived(QVariantList)));
     connect(this->tdLibWrapper, SIGNAL(newMessageReceived(QString, QVariantMap)), this, SLOT(handleNewMessageReceived(QString, QVariantMap)));
 }
@@ -51,6 +52,15 @@ void ChatModel::initialize(const QString &chatId)
     this->messagesToBeAdded.clear();
 }
 
+void ChatModel::triggerLoadMoreHistory()
+{
+    qDebug() << "[ChatModel] Trigger loading older history...";
+    if (!this->inIncrementalUpdate) {
+        this->inIncrementalUpdate = true;
+        this->tdLibWrapper->getChatHistory(this->chatId, this->messages.first().toMap().value("id").toLongLong());
+    }
+}
+
 bool compareMessages(const QVariant &message1, const QVariant &message2)
 {
     QVariantMap messageMap1 = message1.toMap();
@@ -93,7 +103,12 @@ void ChatModel::handleMessagesReceived(const QVariantList &messages)
     } else {
         qDebug() << "[ChatModel] Messages loaded, notifying chat UI...";
         this->inReload = false;
-        emit messagesReceived();
+        if (this->inIncrementalUpdate) {
+            this->inIncrementalUpdate = false;
+            emit messagesIncrementalUpdate();
+        } else {
+            emit messagesReceived();
+        }
     }
 }
 
diff --git a/src/chatmodel.h b/src/chatmodel.h
index 41cbd9a..f3b44d6 100644
--- a/src/chatmodel.h
+++ b/src/chatmodel.h
@@ -18,9 +18,11 @@ public:
     virtual bool insertRows(int row, int count, const QModelIndex &parent = QModelIndex()) override;
 
     Q_INVOKABLE void initialize(const QString &chatId);
+    Q_INVOKABLE void triggerLoadMoreHistory();
 
 signals:
     void messagesReceived();
+    void messagesIncrementalUpdate();
     void noMessagesAvailable();
     void newMessageReceived();
 
@@ -37,6 +39,7 @@ private:
     QMutex messagesMutex;
     QString chatId;
     bool inReload;
+    bool inIncrementalUpdate;
 
     void insertMessages();
 };