#ifndef PLAYER_INPUT_HPP
#define 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:
        // the two actions, evaluated as positive - negative
        gd::String actionNegative{""};
        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};
        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;
    };
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};

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

    void listen_to(Listener const &listener);
    void listen_to(gd::String action, gd::Callable callable);
    void listen_to(gd::String negative, gd::String positive, gd::Callable callable);

    void stop_listening(Node *node);
    void stop_listening(Listener const &listener);
    void clear_listeners();
};
}


#endif // !PLAYER_INPUT_HPP