Add basic support for username auto-completion

fixes #40

include/Config.h

@@ -15,6 +15,11 @@ static constexpr int emojiSize                  = 14;
 static constexpr int headerFontSize             = 21;
 static constexpr int typingNotificationFontSize = 11;
 
+namespace popup {
+static constexpr int font   = fontSize;
+static constexpr int avatar = 28;
+}
+
 namespace receipts {
 static constexpr int font = 12;
 }

include/SuggestionsPopup.hpp

@@ -0,0 +1,63 @@
+#pragma once
+
+#include <QHBoxLayout>
+#include <QLabel>
+#include <QPoint>
+#include <QWidget>
+
+class Avatar;
+
+struct SearchResult
+{
+        QString user_id;
+        QString display_name;
+};
+
+Q_DECLARE_METATYPE(SearchResult)
+Q_DECLARE_METATYPE(QVector<SearchResult>)
+
+class PopupItem : public QWidget
+{
+        Q_OBJECT
+
+        Q_PROPERTY(QColor hoverColor READ hoverColor WRITE setHoverColor)
+
+public:
+        PopupItem(QWidget *parent, const QString &user_id);
+
+        QColor hoverColor() const { return hoverColor_; }
+        void setHoverColor(QColor &color) { hoverColor_ = color; }
+
+protected:
+        void paintEvent(QPaintEvent *event) override;
+        void mousePressEvent(QMouseEvent *event) override;
+
+signals:
+        void clicked(const QString &display_name);
+
+private:
+        QHBoxLayout *topLayout_;
+
+        Avatar *avatar_;
+        QLabel *userName_;
+        QString user_id_;
+
+        QColor hoverColor_;
+};
+
+class SuggestionsPopup : public QWidget
+{
+        Q_OBJECT
+
+public:
+        explicit SuggestionsPopup(QWidget *parent = nullptr);
+
+public slots:
+        void addUsers(const QVector<SearchResult> &users);
+
+signals:
+        void itemSelected(const QString &user);
+
+private:
+        QVBoxLayout *layout_;
+};

include/TextInputWidget.h

@@ -18,7 +18,11 @@
 #pragma once
 
 #include <deque>
+#include <iterator>
+#include <map>
 
+#include <QApplication>
+#include <QDebug>
 #include <QHBoxLayout>
 #include <QPaintEvent>
 #include <QTextEdit>
@@ -26,15 +30,20 @@
 
 #include "FlatButton.h"
 #include "LoadingIndicator.h"
+#include "SuggestionsPopup.hpp"
 
 #include "dialogs/PreviewUploadOverlay.h"
 
 #include "emoji/PickButton.h"
 
+class RoomState;
+
 namespace dialogs {
 class PreviewUploadOverlay;
 }
 
+struct SearchResult;
+
 class FilteredTextEdit : public QTextEdit
 {
         Q_OBJECT
@@ -61,18 +70,45 @@ signals:
         void video(QSharedPointer<QIODevice> data, const QString &filename);
         void file(QSharedPointer<QIODevice> data, const QString &filename);
 
+        //! Trigger the suggestion popup.
+        void showSuggestions(const QString &query);
+        void resultsRetrieved(const QVector<SearchResult> &results);
+
+public slots:
+        void showResults(const QVector<SearchResult> &results);
+
 protected:
         void keyPressEvent(QKeyEvent *event) override;
         bool canInsertFromMimeData(const QMimeData *source) const override;
         void insertFromMimeData(const QMimeData *source) override;
+        void focusOutEvent(QFocusEvent *event) override
+        {
+                popup_.hide();
+                QWidget::focusOutEvent(event);
+        }
 
 private:
         std::deque<QString> true_history_, working_history_;
         size_t history_index_;
         QTimer *typingTimer_;
 
+        SuggestionsPopup popup_;
+
+        void closeSuggestions() { popup_.hide(); }
+        void resetAnchor() { atTriggerPosition_ = -1; }
+
+        QString query()
+        {
+                auto cursor = textCursor();
+                cursor.movePosition(QTextCursor::StartOfWord, QTextCursor::KeepAnchor);
+                return cursor.selectedText();
+        }
+
         dialogs::PreviewUploadOverlay previewDialog_;
 
+        //! Latest position of the '@' character that triggers the username completer.
+        int atTriggerPosition_ = -1;
+
         void textChanged();
         void uploadData(const QByteArray data, const QString &media, const QString &filename);
         void afterCompletion(int);
@@ -97,6 +133,7 @@ public slots:
         void openFileSelection();
         void hideUploadSpinner();
         void focusLineEdit() { input_->setFocus(); }
+        void setRoomState(QSharedPointer<RoomState> state) { currState_ = state; }
 
 private slots:
         void addSelectedEmoji(const QString &emoji);
@@ -132,5 +169,8 @@ private:
         FlatButton *sendMessageBtn_;
         emoji::PickButton *emojiBtn_;
 
+        //! State of the current room.
+        QSharedPointer<RoomState> currState_;
+
         QColor borderColor_;
 };

include/Utils.h

@@ -54,4 +54,8 @@ scaleDown(uint64_t max_width, uint64_t max_height, const ImageType &source)
         return source.scaled(
           final_width, final_height, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
 }
+
+//! Calculate the Levenshtein distance between two strings with character skipping.
+int
+levenshtein_distance(const std::string &s1, const std::string &s2);
 }