Basic shell working.

Command.h

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+/*
+ * Command.h - command model and registry for editor actions
+ */
+#ifndef KTE_COMMAND_H
+#define KTE_COMMAND_H
+
+#include <functional>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+class Editor;
+
+// Identifiers for editor commands. This is intentionally small for now and
+// will grow as features are implemented.
+enum class CommandId {
+    Save,
+    SaveAs,
+    // Placeholders for future commands from ke's model
+    Quit,
+    SaveAndQuit,
+    Refresh,    // force redraw
+    FindStart,  // begin incremental search (placeholder)
+    // Editing
+    InsertText,   // arg: text to insert at cursor (UTF-8, no newlines)
+    Newline,      // insert a newline at cursor
+    Backspace,    // delete char before cursor (may join lines)
+    DeleteChar,   // delete char at cursor (may join lines)
+    // Navigation (basic)
+    MoveLeft,
+    MoveRight,
+    MoveUp,
+    MoveDown,
+    MoveHome,
+    MoveEnd,
+};
+
+
+// Context passed to command handlers.
+struct CommandContext {
+    Editor &editor;
+
+    // Optional argument string (e.g., filename for SaveAs).
+    std::string arg;
+
+    // Optional repeat count (C-u support). 0 means not provided.
+    int count = 0;
+};
+
+
+using CommandHandler = std::function<bool(CommandContext &)>; // return true on success
+
+
+struct Command {
+    CommandId id;
+    std::string name; // stable, unique name (e.g., "save", "save-as")
+    std::string help; // short help/description
+    CommandHandler handler;
+};
+
+
+// Simple global registry. Not thread-safe; suitable for this app.
+class CommandRegistry {
+public:
+    static void Register(const Command &cmd);
+
+    static const Command *FindById(CommandId id);
+
+    static const Command *FindByName(const std::string &name);
+
+    static const std::vector<Command> &All();
+
+private:
+    static std::vector<Command> &storage_();
+};
+
+
+// Built-in command installers
+void InstallDefaultCommands();
+
+// Dispatcher entry points for the input layer
+// Returns true if the command executed successfully.
+bool Execute(Editor &ed, CommandId id, const std::string &arg = std::string(), int count = 0);
+bool Execute(Editor &ed, const std::string &name, const std::string &arg = std::string(), int count = 0);
+
+#endif // KTE_COMMAND_H