#ifndef UTILS_PLAYER_INPUT_HPP
#define UTILS_PLAYER_INPUT_HPP

#include <optional>
#include <godot_cpp/classes/input.hpp>
#include <godot_cpp/classes/input_event.hpp>
#include <godot_cpp/classes/node.hpp>
#include <godot_cpp/templates/vector.hpp>
#include <godot_cpp/variant/callable.hpp>

namespace gd = godot;

namespace utils {
/*! An event-driven input observer.
 *
 * Listen for events with `listen_to`, registering godot input action names to callbacks. It's possible to register an "axis" by registering a listener with a positive and negative action.
 */
class PlayerInput : public gd::Node {
    GDCLASS(PlayerInput, gd::Node)
    static void _bind_methods();
public:
    /*! A PlayerInput action listener.
     *
     * A listener is a combination of a positive and negative action and a callable.
     * The expected callable signature is `void (godot::Ref<godot::InputEvent> event, float value)`
     * actions can also be "special" actions prefixed with `_`.
     * Special actions include `_mouse_up`, `_mouse_down`, `_mouse_left`, and `_mouse_right`.
     */
    struct Listener {
        friend class PlayerInput;
    private:
        //! Negative action on axis, evaluates to -1.
        gd::String actionNegative{""};
        //! Positive action on axis, evaluates to +1.
        gd::String actionPositive{""};
        /*! The last cached action.
         *
         * If the newest result matches this, the event will be considered duplicate and ignored (not passed to listener)
         */
        float lastCached{0.f};
        //! The listening function.
        gd::Callable callable;
        //! If either actionNegative or actionPositive is a _mouse_ event this will be true
        bool isMouseEvent{false};

    public:
        Listener() = default;
        Listener(gd::String negative, gd::String positive, gd::Callable callable);
        Listener(gd::String action, gd::Callable callable);
        // evaluate the current state of an action.
        static std::optional<float> evaluate_action(gd::String const &action);
        /*! Check if this event has any chance to result in a trigger.
         *
         * Does not evaluate the event or poll current input state
         */
        bool has_changed(gd::Ref<gd::InputEvent> const &event);
        //! evaluate the event for changes to either actionPositive or actionNegative
        float evaluate(gd::Ref<gd::InputEvent> const &event);
        bool operator==(PlayerInput::Listener const& b) const;
    };
public:
    //! Returns the last stored mouse delta.
    static gd::Vector2 get_last_mouse_motion();

    virtual void _enter_tree() override;
    virtual void _exit_tree() override;
    virtual void _unhandled_input(gd::Ref<gd::InputEvent> const &event) override;
    virtual void _process(double deltaTime) override;

    //! Start listening for action.
    void listen_to(Listener const &listener);
    /*! Start listening for action.
     *
     * Shorthand for `listen_to(Listener(action, callable))`.
     */
    void listen_to(gd::String action, gd::Callable callable);
    /*! Start listening for action.
     *
     * Shorthand for `listen_to(Listener(negative, positive, callable))`.
     */
    void listen_to(gd::String negative, gd::String positive, gd::Callable callable);

    //! Remove any listeners related to node.
    void stop_listening(Node *node);
    //! Remove listeners exactly equal to listener.
    void stop_listening(Listener const &listener);
    //! Remove all listeners.
    void clear_listeners();
    //! set the device observe events from.
    void set_device(int id);
private:
    //! The last mouse motion, updated by the primary instance
    static gd::Vector2 lastMouseMotion;
    //! Does a primary instance exist
    static bool primaryExists;
    /*! Is this the primary instance.
     *
     * The primary instance is responsible for updating static variables like lastMouseMotion.
     */
    bool isPrimary{false};
    //! which device to observe events from.
    int device{-1}; 

    //! current listeners for this instance
    gd::Vector<Listener> listeners{};
};
}


#endif // !UTILS_PLAYER_INPUT_HPP