feat(tui): add reusable text input component

1 files changed, 169 insertions, 0 deletions

diff --git a/src/tui/editor.hh b/src/tui/editor.hh
new file mode 100644
index 0000000..457b0ca
--- /dev/null
+++ b/src/tui/editor.hh
@@ -0,0 +1,169 @@
+/*
+ * Ricochet - A minimalist CLI web browser for fast, distraction-free navigation.
+ * Copyright (C) 2026  Richard Qin
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "paint.hh"
+#include "text.hh"
+
+#include <chrono>
+#include <optional>
+
+namespace ricochet::tui::detail {
+
+enum class EditorKind : std::uint8_t
+{
+  SingleLine,
+  MultiLine,
+  Password
+};
+
+struct EditorOptions
+{
+  EditorKind kind { EditorKind::SingleLine };
+  // The owner supplies history; password and multiline editors never request it.
+  bool history { false };
+};
+
+enum class EditorCommand : std::uint8_t
+{
+  Left,
+  Right,
+  Up,
+  Down,
+  LineStart,
+  LineEnd,
+  PreviousWord,
+  NextWord,
+  Backspace,
+  Delete,
+  KillToStart,
+  KillToEnd,
+  KillWord,
+  Yank,
+  BeginSelection,
+  SelectAll,
+  CancelSelection,
+  Clear,
+  Newline,
+  Undo,
+  Redo
+};
+
+// Enter/Tab/Escape are context decisions, never implicit submit/finish operations.
+// The owner may translate Enter into Newline for a multiline field.
+// Unhandled keys stay with the owning editor context, never fall through to Browse.
+enum class EditorIntent : std::uint8_t
+{
+  Consumed,
+  Unhandled,
+  Enter,
+  Tab,
+  BackTab,
+  Escape,
+  Cancel,
+  Menu,
+  Redraw,
+  HistoryPrevious,
+  HistoryNext
+};
+
+// One editing session. Owners recreate it when changing fields; its text, undo
+// history and kill buffer are never shared with another editor or a view snapshot.
+class TextEditor
+{
+public:
+  TextEditor( std::string value, EditorOptions options, const TextService& text, ScreenSize viewport );
+  TextEditor( const TextEditor& ) = delete;
+  TextEditor& operator=( const TextEditor& ) = delete;
+  TextEditor( TextEditor&& ) = delete;
+  TextEditor& operator=( TextEditor&& ) = delete;
+  ~TextEditor() = default;
+
+  // Business value for the owning field; rendering and copying use the methods below.
+  const std::string& value() const;
+  std::uint64_t revision() const;
+  std::size_t cursor() const;
+  ByteRange selection() const;
+  std::optional<std::string> copy_selection();
+  std::optional<std::chrono::steady_clock::time_point> prefix_deadline() const;
+
+  void resize( ScreenSize viewport );
+  void insert( std::u32string_view input );
+  // Host history replacement is one undoable edit, not a new editing session.
+  void replace_value( std::string value );
+  void execute( EditorCommand command, bool extend = false );
+  EditorIntent handle( const InputEvent& event,
+                       std::chrono::steady_clock::time_point now = std::chrono::steady_clock::now() );
+  // Region-local mouse positioning, with extend=true while selecting/dragging.
+  void place( CellPoint point, bool extend );
+  void draw( Frame& frame, CellPoint origin ) const;
+
+private:
+  struct State
+  {
+    std::string value {};
+    std::size_t cursor { 0 };
+    std::optional<std::size_t> anchor {};
+    bool selecting { false };
+  };
+  struct Point
+  {
+    std::size_t row { 0 };
+    std::int64_t column { 0 };
+  };
+  struct Glyph
+  {
+    Point point {};
+    int columns { 0 };
+  };
+
+  std::string normalize( std::string_view value ) const;
+  std::size_t unit_index() const;
+  std::size_t boundary( std::size_t index ) const;
+  std::size_t line_start() const;
+  std::size_t line_end() const;
+  std::size_t nearest( Point point ) const;
+  void analyze();
+  void layout();
+  void reveal();
+  void move( std::size_t destination, bool extend, bool preserve_column );
+  void replace( ByteRange range, std::string_view replacement );
+  void kill( ByteRange range );
+  void undo( bool redo );
+  EditorIntent key( const Key& key, std::chrono::steady_clock::time_point now );
+
+  EditorOptions options_;
+  const TextService& text_;
+  ScreenSize viewport_;
+  State state_ {};
+  TextAnalysis analysis_ {};
+  std::vector<Glyph> glyphs_ {};
+  std::vector<Point> carets_ {};
+  std::size_t top_row_ { 0 };
+  std::int64_t left_column_ { 0 };
+  std::int64_t desired_column_ { 0 };
+  std::vector<State> past_ {};
+  std::vector<State> future_ {};
+  std::string killed_ {};
+  bool killing_ { false };
+  std::uint64_t revision_ { 0 };
+  std::optional<std::chrono::steady_clock::time_point> prefix_ {};
+};
+
+} // namespace ricochet::tui::detail