Don't destroy formatting when editing previous messages

Adds a few new methods to grab the markdown/slightly rich text from the
message, and will intelligently re-insert user mentions as needed.

src/chatbarcache.cpp

@@ -3,6 +3,7 @@
 
 #include "chatbarcache.h"
 
+#include "chatdocumenthandler.h"
 #include "eventhandler.h"
 #include "neochatroom.h"
 
@@ -117,7 +118,7 @@ QString ChatBarCache::relationMessage() const
 
     if (auto event = room->findInTimeline(m_relationId); event != room->historyEdge()) {
         EventHandler eventhandler(room, &**event);
-        return eventhandler.getPlainBody();
+        return eventhandler.getMarkdownBody();
     }
     return {};
 }
@@ -163,6 +164,54 @@ QList<Mention> *ChatBarCache::mentions()
     return &m_mentions;
 }
 
+void ChatBarCache::updateMentions(QQuickTextDocument *document, ChatDocumentHandler *documentHandler)
+{
+    documentHandler->setDocument(document);
+
+    if (parent() == nullptr) {
+        qWarning() << "ChatBarCache created with no parent, a NeoChatRoom must be set as the parent on creation.";
+        return;
+    }
+    if (m_relationId.isEmpty()) {
+        return;
+    }
+    auto room = dynamic_cast<NeoChatRoom *>(parent());
+    if (room == nullptr) {
+        qWarning() << "ChatBarCache created with incorrect parent, a NeoChatRoom must be set as the parent on creation.";
+        return;
+    }
+
+    if (auto event = room->findInTimeline(m_relationId); event != room->historyEdge()) {
+        if (const auto &roomMessageEvent = &*event->viewAs<Quotient::RoomMessageEvent>()) {
+            // Replaces the mentions that are baked into the HTML but plaintext in the original markdown
+            const QRegularExpression re(QStringLiteral(R"lit(<a\shref="https:\/\/matrix.to\/#\/([\S]*)"\s?>([\S]*)<\/a>)lit"));
+
+            m_mentions.clear();
+
+            int linkSize = 0;
+            auto matches = re.globalMatch(EventHandler::rawMessageBody(*roomMessageEvent));
+            while (matches.hasNext()) {
+                const QRegularExpressionMatch match = matches.next();
+                if (match.hasMatch()) {
+                    const QString id = match.captured(1);
+                    const QString name = match.captured(2);
+
+                    const int position = match.capturedStart(0) - linkSize;
+                    const int end = position + name.length();
+                    linkSize += match.capturedLength(0) - name.length();
+
+                    QTextCursor cursor(documentHandler->document()->textDocument());
+                    cursor.setPosition(position);
+                    cursor.setPosition(end, QTextCursor::KeepAnchor);
+                    cursor.setKeepPositionOnInsert(true);
+
+                    m_mentions.push_back(Mention{.cursor = cursor, .text = name, .start = position, .position = end, .id = id});
+                }
+            }
+        }
+    }
+}
+
 QString ChatBarCache::savedText() const
 {
     return m_savedText;

src/chatbarcache.h

@@ -5,8 +5,11 @@
 
 #include <QObject>
 #include <QQmlEngine>
+#include <QQuickTextDocument>
 #include <QTextCursor>
 
+class ChatDocumentHandler;
+
 /**
  * @brief Defines a user mention in the current chat or edit text.
  */
@@ -174,6 +177,11 @@ public:
      */
     QList<Mention> *mentions();
 
+    /**
+     * @brief Update the mentions in @p document when editing a message.
+     */
+    Q_INVOKABLE void updateMentions(QQuickTextDocument *document, ChatDocumentHandler *documentHandler);
+
     /**
      * @brief Get the saved chat bar text.
      */

src/eventhandler.cpp

@@ -280,6 +280,22 @@ QString EventHandler::getPlainBody(bool stripNewlines) const
     return getBody(m_event, Qt::PlainText, stripNewlines);
 }
 
+QString EventHandler::getMarkdownBody() const
+{
+    if (m_event == nullptr) {
+        qCWarning(EventHandling) << "getMarkdownBody called with m_event set to nullptr.";
+        return {};
+    }
+
+    if (!m_event->is<RoomMessageEvent>()) {
+        qCWarning(EventHandling) << "getMarkdownBody called when m_event isn't a RoomMessageEvent.";
+        return {};
+    }
+
+    const auto roomMessageEvent = eventCast<const RoomMessageEvent>(m_event);
+    return roomMessageEvent->plainBody();
+}
+
 QString EventHandler::getBody(const Quotient::RoomEvent *event, Qt::TextFormat format, bool stripNewlines) const
 {
     if (event->isRedacted()) {

src/eventhandler.h

@@ -185,6 +185,13 @@ public:
      */
     QString getPlainBody(bool stripNewlines = false) const;
 
+    /**
+     * @brief Output the original body for the message content, useful for editing the original message.
+     *
+     * The event type must be a room message event.
+     */
+    QString getMarkdownBody() const;
+
     /**
      * @brief Output a generic string for the message content ready for display.
      *

src/qml/MessageEditComponent.qml

@@ -170,8 +170,11 @@ QQC2.TextArea {
         onChatBarCacheChanged: documentHandler.chatBarCache = chatBarCache
 
         function updateEditText() {
+            // This could possibly be undefined due to some esoteric QtQuick issue. Referencing it somewhere in JS is enough.
+            documentHandler.textDocument;
             if (chatBarCache?.isEditing && chatBarCache.relationMessage.length > 0) {
                 root.text = chatBarCache.relationMessage;
+                chatBarCache.updateMentions(root.textDocument, documentHandler);
                 root.forceActiveFocus();
                 root.cursorPosition = root.length;
             }