#ifndef XTC_GRAPH_WIDGET_HPP
#define XTC_GRAPH_WIDGET_HPP
#include <FL/Fl_Widget.H>
#include <array>
#include "xtc/xtc_engine.h"

class Fl_Box;

/* GUI positions/selection only. Domain snapshots and edits stay in the C API. */
class GraphWidget : public Fl_Widget {
  public:
    /**
     * @brief Applies a graph edit using an opaque context and optional added-node output.
     *
     * The handler receives the context, edit command, and output identifier in that order.
     * @return XTC_OK on success, or an edit error.
     */
    using EditHandler = xtc_result (*)(void *, const xtc_graph_edit &, size_t *);
    /**
     * @brief Constructs a graph widget bound to a graph and an edit callback.
     *
     * The widget stores the graph, handler, context, and feedback box without
     * taking ownership of any of them.
     *
     * @param x Left coordinate in FLTK screen space.
     * @param y Top coordinate in FLTK screen space.
     * @param width Widget width in pixels.
     * @param height Widget height in pixels.
     * @param graph Borrowed graph snapshot; must outlive the widget's use of it.
     * @param handler Edit callback invoked for every graph mutation.
     * @param context Opaque pointer passed back to @p handler; may be NULL.
     * @param feedback Borrowed label used to report edit results; must outlive the widget.
     */
    GraphWidget(int x, int y, int width, int height, const xtc_graph *graph, EditHandler handler, void *context,
                Fl_Box *feedback);

    /**
     * @brief Clears cached node positions, selection, and interaction state.
     *
     * Does not change the borrowed graph pointer or the graph's own layout.
     */
    void reset_layout()
    {
        count_ = 0;
        selected_node_ = SIZE_MAX;
        edge_selected_ = dragging_ = wiring_ = false;
    }

    /**
     * @brief Replaces the graph snapshot and rebuilds cached node positions.
     *
     * Existing positions are preserved by node ID; new nodes are placed on a grid
     * that avoids overlapping previously known nodes. Selections that no longer
     * exist are cleared. The widget does not take ownership of @p graph.
     *
     * @param graph Borrowed graph that must outlive the widget's use of it.
     */
    void set_graph(const xtc_graph *graph);

    /**
     * @brief Returns the graph snapshot currently displayed.
     *
     * The returned pointer is borrowed and valid for GUI thread use only.
     *
     * @return Borrowed graph pointer; may be NULL when none was supplied.
     */
    const xtc_graph *graph() const
    {
        return graph_;
    } // Borrowed, GUI thread only.

    /**
     * @brief Requests creation of a node through the edit handler.
     *
     * Selects the new node when the edit succeeds.
     *
     * @param type Kind of node to add.
     * @return Result reported by the edit handler.
     */
    xtc_result add_node(xtc_node_type type);

    /**
     * @brief Requests a connection between two ports through the edit handler.
     *
     * @param connection Connection describing the source and destination node/port pairs.
     * @return Result reported by the edit handler.
     */
    xtc_result connect_ports(const xtc_connection_info &connection);

    /**
     * @brief Requests removal of the selected wire or node through the edit handler.
     *
     * @return Result reported by the edit handler, or XTC_ERR_INVALID_STATE when
     *         nothing is selected.
     */
    xtc_result delete_selected();

    /**
     * @brief Selects a node by ID and clears any wire selection.
     *
     * @param id Stable node identifier.
     * @return True when the node has a cached position, false otherwise.
     */
    bool select_node(size_t id);

    /**
     * @brief Selects a wire between two nodes and clears the node selection.
     *
     * @param source Source node identifier.
     * @param destination Destination node identifier.
     * @return True when a matching connection exists, false otherwise.
     */
    bool select_connection(size_t source, size_t destination);

    /**
     * @brief Moves a node within the widget, clamped to the visible bounds.
     *
     * @param id Stable node identifier.
     * @param left Requested left position in widget-local coordinates.
     * @param top Requested top position in widget-local coordinates.
     * @return True when the node has a cached position, false otherwise.
     */
    bool move_node(size_t id, int left, int top);

    /**
     * @brief Looks up the cached position of a node.
     *
     * @param id Stable node identifier.
     * @param left Receives the left position in widget-local coordinates.
     * @param top Receives the top position in widget-local coordinates.
     * @return True when the node has a cached position, false otherwise.
     */
    bool node_position(size_t id, int &left, int &top) const;

    /**
     * @brief Handles mouse and keyboard events for selection, dragging, and wiring.
     *
     * @param event FLTK event code.
     * @return 1 when the event was consumed, 0 for unsupported left-button input,
     *         or the result of Fl_Widget::handle() for unhandled events.
     */
    int handle(int event) override;

  protected:
    /**
     * @brief Draws the background, wires, nodes, ports, and any pending wire.
     */
    void draw() override;

  private:
    struct Position {
        size_t id = SIZE_MAX;
        int left = 0, top = 0;
    };

    std::array<Position, 256> positions_{};
    size_t count_ = 0U;
    const xtc_graph *graph_;
    EditHandler handler_;
    void *context_;
    Fl_Box *feedback_;
    size_t selected_node_ = SIZE_MAX;
    xtc_connection_info selected_edge_{};
    bool edge_selected_ = false;
    bool dragging_ = false, wiring_ = false;
    size_t wire_node_ = SIZE_MAX, wire_port_ = 0U;
    int drag_x_ = 0, drag_y_ = 0, mouse_x_ = 0, mouse_y_ = 0;
    /**
     * @brief Shows the outcome of an edit in the feedback label.
     *
     * @param result Result returned by the edit handler.
     * @param success Text shown when @p result is XTC_OK; must be valid then and is ignored otherwise.
     */
    void feedback(xtc_result result, const char *success);

    /**
     * @brief Finds the port nearest to a widget-local point.
     *
     * Searches nodes in reverse draw order and accepts points within 9 pixels of a
     * port center.
     *
     * @param left Widget-local x coordinate to test.
     * @param top Widget-local y coordinate to test.
     * @param node Receives the matching node ID when true is returned.
     * @param port Receives the matching port index (0 input, 1 output) when true is returned.
     * @return True when a port is within range, false otherwise.
     */
    bool hit_port(int left, int top, size_t &node, size_t &port) const;

    /**
     * @brief Computes the widget-local center of a node port.
     *
     * @param id Stable node identifier.
     * @param port Port index; 0 selects the input and 1 the output.
     * @param left Receives the port center x coordinate.
     * @param top Receives the port center y coordinate.
     * @return True when the node and port exist, false otherwise.
     */
    bool port_position(size_t id, size_t port, int &left, int &top) const;
};
#endif