3 files changed, 137 insertions, 47 deletions

diff --git a/Userland/Libraries/LibGUI/EditingEngine.cpp b/Userland/Libraries/LibGUI/EditingEngine.cpp
index 5f2d6cfc0d..028a7bb24e 100644
--- a/Userland/Libraries/LibGUI/EditingEngine.cpp
+++ b/Userland/Libraries/LibGUI/EditingEngine.cpp
@@ -259,8 +259,11 @@ EditingEngine::DidMoveALine EditingEngine::move_one_up(KeyEvent const& event)
 {
     if (m_editor->cursor().line() > 0 || m_editor->is_wrapping_enabled()) {
         if (event.ctrl() && event.shift()) {
-            move_selected_lines_up();
-            return DidMoveALine::Yes;
+            if (MoveLineUpOrDownCommand::valid_operation(*this, VerticalDirection::Up)) {
+                m_editor->execute<MoveLineUpOrDownCommand>(Badge<EditingEngine> {}, event, *this);
+                return DidMoveALine::Yes;
+            }
+            return DidMoveALine::No;
         }
         TextPosition new_cursor;
         if (m_editor->is_wrapping_enabled()) {
@@ -280,8 +283,11 @@ EditingEngine::DidMoveALine EditingEngine::move_one_down(KeyEvent const& event)
 {
     if (m_editor->cursor().line() < (m_editor->line_count() - 1) || m_editor->is_wrapping_enabled()) {
         if (event.ctrl() && event.shift()) {
-            move_selected_lines_down();
-            return DidMoveALine::Yes;
+            if (MoveLineUpOrDownCommand::valid_operation(*this, VerticalDirection::Down)) {
+                m_editor->execute<MoveLineUpOrDownCommand>(Badge<EditingEngine> {}, event, *this);
+                return DidMoveALine::Yes;
+            }
+            return DidMoveALine::No;
         }
         TextPosition new_cursor;
         if (m_editor->is_wrapping_enabled()) {
@@ -353,6 +359,11 @@ void EditingEngine::move_to_last_line()
     m_editor->set_cursor(m_editor->line_count() - 1, m_editor->lines()[m_editor->line_count() - 1].length());
 };
 
+void EditingEngine::get_selection_line_boundaries(Badge<MoveLineUpOrDownCommand>, size_t& first_line, size_t& last_line)
+{
+    get_selection_line_boundaries(first_line, last_line);
+}
+
 void EditingEngine::get_selection_line_boundaries(size_t& first_line, size_t& last_line)
 {
     auto selection = m_editor->normalized_selection();
@@ -367,67 +378,119 @@ void EditingEngine::get_selection_line_boundaries(size_t& first_line, size_t& la
         last_line -= 1;
 }
 
-void EditingEngine::move_selected_lines_up()
+void EditingEngine::delete_char()
 {
     if (!m_editor->is_editable())
         return;
-    size_t first_line;
-    size_t last_line;
-    get_selection_line_boundaries(first_line, last_line);
+    m_editor->do_delete();
+};
 
-    if (first_line == 0)
+void EditingEngine::delete_line()
+{
+    if (!m_editor->is_editable())
         return;
+    m_editor->delete_current_line();
+};
 
-    auto& lines = m_editor->document().lines();
-    lines.insert((int)last_line, lines.take((int)first_line - 1));
-    m_editor->set_cursor({ m_editor->cursor().line() - 1, m_editor->cursor().column() });
+MoveLineUpOrDownCommand::MoveLineUpOrDownCommand(TextDocument& document, KeyEvent event, EditingEngine& engine)
+    : TextDocumentUndoCommand(document)
+    , m_event(move(event))
+    , m_direction(key_code_to_vertical_direction(m_event.key()))
+    , m_engine(engine)
+    , m_selection(m_engine.editor().selection())
+    , m_cursor(m_engine.editor().cursor())
+{
+}
 
-    if (m_editor->has_selection()) {
-        m_editor->selection().start().set_line(m_editor->selection().start().line() - 1);
-        m_editor->selection().end().set_line(m_editor->selection().end().line() - 1);
-    }
+void MoveLineUpOrDownCommand::redo()
+{
+    move_lines(m_direction);
+}
 
-    m_editor->did_change();
-    m_editor->update();
+void MoveLineUpOrDownCommand::undo()
+{
+    move_lines(!m_direction);
 }
 
-void EditingEngine::move_selected_lines_down()
+bool MoveLineUpOrDownCommand::merge_with(GUI::Command const&)
 {
-    if (!m_editor->is_editable())
-        return;
-    size_t first_line;
-    size_t last_line;
-    get_selection_line_boundaries(first_line, last_line);
+    return false;
+}
 
-    auto& lines = m_editor->document().lines();
-    VERIFY(lines.size() != 0);
-    if (last_line >= lines.size() - 1)
-        return;
+String MoveLineUpOrDownCommand::action_text() const
+{
+    return "Move a line";
+}
+
+bool MoveLineUpOrDownCommand::valid_operation(EditingEngine& engine, VerticalDirection direction)
+{
 
-    lines.insert((int)first_line, lines.take((int)last_line + 1));
-    m_editor->set_cursor({ m_editor->cursor().line() + 1, m_editor->cursor().column() });
+    VERIFY(engine.editor().line_count() != 0);
 
-    if (m_editor->has_selection()) {
-        m_editor->selection().start().set_line(m_editor->selection().start().line() + 1);
-        m_editor->selection().end().set_line(m_editor->selection().end().line() + 1);
-    }
+    auto const& selection = engine.editor().selection().normalized();
+    if (selection.is_valid()) {
+        if ((direction == VerticalDirection::Up && selection.start().line() == 0) || (direction == VerticalDirection::Down && selection.end().line() >= engine.editor().line_count() - 1))
+            return false;
+    } else {
+        size_t first_line;
+        size_t last_line;
+        engine.get_selection_line_boundaries(Badge<MoveLineUpOrDownCommand> {}, first_line, last_line);
 
-    m_editor->did_change();
-    m_editor->update();
+        if ((direction == VerticalDirection::Up && first_line == 0) || (direction == VerticalDirection::Down && last_line >= engine.editor().line_count() - 1))
+            return false;
+    }
+    return true;
 }
 
-void EditingEngine::delete_char()
+TextRange MoveLineUpOrDownCommand::retrieve_selection(VerticalDirection direction)
 {
-    if (!m_editor->is_editable())
-        return;
-    m_editor->do_delete();
-};
+    if (direction == m_direction)
+        return m_selection;
 
-void EditingEngine::delete_line()
+    auto const offset_selection = [this](auto const offset) {
+        auto tmp = m_selection;
+        tmp.start().set_line(tmp.start().line() + offset);
+        tmp.end().set_line(tmp.end().line() + offset);
+
+        return tmp;
+    };
+
+    if (direction == VerticalDirection::Up)
+        return offset_selection(1);
+    if (direction == VerticalDirection::Down)
+        return offset_selection(-1);
+    VERIFY_NOT_REACHED();
+}
+
+void MoveLineUpOrDownCommand::move_lines(VerticalDirection direction)
 {
-    if (!m_editor->is_editable())
+    if (m_event.shift() && m_selection.is_valid()) {
+        m_engine.editor().set_selection(retrieve_selection(direction));
+        m_engine.editor().did_update_selection();
+    }
+
+    if (!m_engine.editor().is_editable())
         return;
-    m_editor->delete_current_line();
-};
+
+    size_t first_line;
+    size_t last_line;
+    m_engine.get_selection_line_boundaries(Badge<MoveLineUpOrDownCommand> {}, first_line, last_line);
+
+    auto const offset = direction == VerticalDirection::Up ? -1 : 1;
+    auto const insertion_index = direction == VerticalDirection::Up ? last_line : first_line;
+    auto const moved_line_index = offset + (direction != VerticalDirection::Up ? last_line : first_line);
+
+    auto moved_line = m_document.take_line(moved_line_index);
+    m_document.insert_line(insertion_index, move(moved_line));
+
+    m_engine.editor().set_cursor({ m_engine.editor().cursor().line() + offset, m_engine.editor().cursor().column() });
+    if (m_engine.editor().has_selection()) {
+        m_engine.editor().selection().start().set_line(m_engine.editor().selection().start().line() + offset);
+        m_engine.editor().selection().end().set_line(m_engine.editor().selection().end().line() + offset);
+    }
+
+    m_engine.editor().did_change();
+    m_engine.editor().update();
+}
 
 }
diff --git a/Userland/Libraries/LibGUI/EditingEngine.h b/Userland/Libraries/LibGUI/EditingEngine.h
index 13c71a3dca..d6dacb1205 100644
--- a/Userland/Libraries/LibGUI/EditingEngine.h
+++ b/Userland/Libraries/LibGUI/EditingEngine.h
@@ -22,6 +22,8 @@ enum EngineType {
     Vim,
 };
 
+class MoveLineUpOrDownCommand;
+
 class EditingEngine {
     AK_MAKE_NONCOPYABLE(EditingEngine);
     AK_MAKE_NONMOVABLE(EditingEngine);
@@ -45,6 +47,8 @@ public:
     bool is_regular() const { return engine_type() == EngineType::Regular; }
     bool is_vim() const { return engine_type() == EngineType::Vim; }
 
+    void get_selection_line_boundaries(Badge<MoveLineUpOrDownCommand>, size_t& first_line, size_t& last_line);
+
 protected:
     EditingEngine() = default;
 
@@ -80,10 +84,27 @@ protected:
     void delete_char();
 
     virtual EngineType engine_type() const = 0;
+};
+
+class MoveLineUpOrDownCommand : public TextDocumentUndoCommand {
+public:
+    MoveLineUpOrDownCommand(TextDocument&, KeyEvent event, EditingEngine&);
+    virtual void undo() override;
+    virtual void redo() override;
+    bool merge_with(GUI::Command const&) override;
+    String action_text() const override;
+
+    static bool valid_operation(EditingEngine& engine, VerticalDirection direction);
 
 private:
-    void move_selected_lines_up();
-    void move_selected_lines_down();
+    void move_lines(VerticalDirection);
+    TextRange retrieve_selection(VerticalDirection);
+
+    KeyEvent m_event;
+    VerticalDirection m_direction;
+    EditingEngine& m_engine;
+    TextRange m_selection;
+    TextPosition m_cursor;
 };
 
 }
diff --git a/Userland/Libraries/LibGUI/TextEditor.h b/Userland/Libraries/LibGUI/TextEditor.h
index b5b8dd374f..547ac759a3 100644
--- a/Userland/Libraries/LibGUI/TextEditor.h
+++ b/Userland/Libraries/LibGUI/TextEditor.h
@@ -229,6 +229,12 @@ public:
 
     virtual Optional<UISize> calculated_min_size() const override;
 
+    template<class T, class... Args>
+    inline void execute(Badge<EditingEngine>, Args&&... args)
+    {
+        execute<T>(forward<Args>(args)...);
+    }
+
 protected:
     explicit TextEditor(Type = Type::MultiLine);