#pragma once

#include "lumacs/buffer.hpp"
#include "lumacs/window.hpp"
#include "lumacs/kill_ring.hpp"
#include <memory>
#include <functional>
#include <vector>
#include <list>

namespace lumacs {

/// Editor state change events
enum class EditorEvent {
    BufferModified,
    CursorMoved,
        ViewportChanged,
        WindowLayoutChanged, // New event
        WindowFocused,       // New event: a different window gained focus
        Message,             // New event
        CommandMode,         // Trigger command mode (minibuffer)
        BufferSwitchMode,    // Trigger buffer switch mode
        KillBufferMode,      // Trigger kill buffer mode
    Quit
};

struct LayoutNode;

/// Core editor logic, independent of UI framework
class EditorCore {
public:
    EditorCore();
    ~EditorCore() = default;

    // Disable copy, allow move
    EditorCore(const EditorCore&) = delete;
    EditorCore& operator=(const EditorCore&) = delete;
    EditorCore(EditorCore&&) noexcept = default;
    EditorCore& operator=(EditorCore&&) noexcept = default;

    // === Message System ===
    void set_message(std::string msg) {
        last_message_ = std::move(msg);
        emit_event(EditorEvent::Message);
    }
    
    const std::string& last_message() const { return last_message_; }

    // === Actions ===
    void enter_command_mode() {
        emit_event(EditorEvent::CommandMode);
    }

    void enter_buffer_switch_mode() {
        emit_event(EditorEvent::BufferSwitchMode);
    }

    void enter_kill_buffer_mode() {
        emit_event(EditorEvent::KillBufferMode);
    }

    // === Buffer Management ===

    /// Get the current buffer (of the active window)
    [[nodiscard]] const Buffer& buffer() const noexcept;
    [[nodiscard]] Buffer& buffer() noexcept;

    /// Load a file into the current window
    bool load_file(const std::filesystem::path& path);

    /// Create a new empty buffer in current window
    void new_buffer(std::string name = "*scratch*");

    /// Get list of all buffer names
    [[nodiscard]] std::vector<std::string> get_buffer_names() const;

    /// Get buffer by name (returns nullptr if not found)
    [[nodiscard]] std::shared_ptr<Buffer> get_buffer_by_name(const std::string& name);

    /// Switch active window to buffer by name
    bool switch_buffer_in_window(const std::string& name);

    /// Close buffer by name (returns false if buffer is displayed or doesn't exist)
    bool close_buffer(const std::string& name);

    /// Buffer information for list display
    struct BufferInfo {
        std::string name;
        size_t size;
        bool modified;
        std::string mode;
        std::optional<std::filesystem::path> filepath;
    };

    /// Get information about all buffers
    [[nodiscard]] std::vector<BufferInfo> get_all_buffer_info() const;

    // === Window Management ===

    /// Split the current window horizontally (active window becomes top, new one bottom)
    void split_horizontally();

    /// Split the current window vertically (active window becomes left, new one right)
    void split_vertically();

    /// Close the current window
    void close_active_window();

    /// Move focus to the next window
    void next_window();

    /// Get the active window
    std::shared_ptr<Window> active_window() const { return active_window_; }

    /// Get the root of the layout tree (for rendering)
    std::shared_ptr<LayoutNode> root_layout() const { return root_node_; }

    // === Cursor Management (Proxies to active window) ===

    [[nodiscard]] Position cursor() const noexcept;
    void set_cursor(Position pos);

    // === Cursor Movement (Proxies to active window) ===

    void move_up();
    void move_down();
    void move_left();
    void move_right();
    void move_to_line_start();
    void move_to_line_end();
    void move_forward_word();
    void move_backward_word();
    void page_up();
    void page_down();
    void goto_beginning();
    void goto_end();
    void goto_line(size_t line);

    // === Viewport Management (Proxies to active window) ===
    
    const Viewport& viewport() const noexcept;
    void set_viewport_size(int width, int height);
    void adjust_scroll();
    std::pair<size_t, size_t> visible_line_range() const;

    // === Event Callbacks ===

    using EventCallback = std::function<void(EditorEvent)>;

    void on_event(EventCallback callback) {
        event_callbacks_.push_back(std::move(callback));
    }

    // === Actions ===

    void request_quit() {
        emit_event(EditorEvent::Quit);
    }

    // === Undo/Redo ===

    bool undo();
    bool redo();
    bool can_undo() const;
    bool can_redo() const;

    // === Kill Ring ===

    /// Get the kill ring
    [[nodiscard]] KillRing& kill_ring() noexcept { return kill_ring_; }
    [[nodiscard]] const KillRing& kill_ring() const noexcept { return kill_ring_; }

    /// Kill (cut) text from position to end of line
    void kill_line();

    /// Kill (cut) the active region
    void kill_region();

    /// Copy the active region to kill ring (without deleting)
    void copy_region_as_kill();

    /// Yank (paste) from kill ring
    void yank();

    /// Yank and pop to previous kill ring entry
    void yank_pop();

private:
    // All open buffers
    std::list<std::shared_ptr<Buffer>> buffers_;

    // Window layout
    std::shared_ptr<LayoutNode> root_node_;
    std::shared_ptr<Window> active_window_;

    std::string last_message_;

    std::vector<EventCallback> event_callbacks_;

    // Kill ring for cut/copy/paste
    KillRing kill_ring_;

    // Last yank position (for yank-pop)
    std::optional<Position> last_yank_start_;
    std::optional<Position> last_yank_end_;

    void emit_event(EditorEvent event);
    
    // Helper to find a node containing the active window
    LayoutNode* find_parent_node(LayoutNode* root, std::shared_ptr<Window> target);
    
    // Helper to collect all windows in traversal order
    void collect_windows(LayoutNode* node, std::vector<std::shared_ptr<Window>>& windows);
};

struct LayoutNode {
    enum class Type { Leaf, HorizontalSplit, VerticalSplit };
    Type type;
    
    // If Leaf
    std::shared_ptr<Window> window;
    
    // If Split
    std::shared_ptr<LayoutNode> child1;
    std::shared_ptr<LayoutNode> child2;
    float ratio = 0.5f; // For future resizing
    
    LayoutNode(std::shared_ptr<Window> w) : type(Type::Leaf), window(w) {}
    LayoutNode(Type t, std::shared_ptr<LayoutNode> c1, std::shared_ptr<LayoutNode> c2)
        : type(t), child1(c1), child2(c2) {}
};

} // namespace lumacs