#pragma once

#include <memory>
#include "Time.hpp"
#include "Common/Casts.hpp"
#include "Common/Sizes.hpp"
#include "Common/Pure.hpp"
#include "GFX/Window.hpp"
#include "Math/Vector.hpp"

namespace MC {

// TODO: Add some more keys.
// TODO: I think some of these keys are "modifiers" under GLFW, and should be handled differently.
enum class Key {
    A, B, C, D, E, F, G, H, I, J, K, L, M,
    N, O, P, Q, R, S, T, U, V, W, X, Y, Z,
    Zero, One, Two, Three, Four, Five, Six, Seven, Eight, Nine,
    Escape, Enter, Tab, Backspace, Insert, Delete, Right, Left, Down, Up,
    LeftShift, RightShift, LeftControl, RightControl, LeftAlt, RightAlt,
    Space, F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11, F12,
};

constexpr USize KeyCount = 65;
static_assert(KeyCount == TO(USize, Key::F12) + 1, "Key count mismatch.");

enum class Mouse {
    Left, Right, Middle,
};

constexpr USize MouseCount = 3;
static_assert(MouseCount == TO(USize, Mouse::Middle) + 1, "Mouse count mismatch.");

// The simple input system.
// All methods are thread safe, except the initial registration of the input callbacks
// and the state update. Both must be called from the main thread.
class Input {
public:
    explicit Input() = default;

    // Registers the input callbacks for the given window.
    // This function must be called from the main thread.
    static void register_callbacks(GFX::Window const& window);

    // Updates the input state from the callback buffers.
    // This function must be called from the main thread.
    void update(Time::Timestamp current_time);

    // Returns true if the key was pressed during the last frame.
    PURE Bool pressed(Key key) const;
    // Returns true if the mouse button was pressed during the last frame.
    PURE Bool pressed(Mouse button) const;

    // Returns true if the key is currently held down.
    PURE Bool held(Key key) const;
    // Returns true if the mouse button is currently held down.
    PURE Bool held(Mouse button) const;

    // Returns true if the key was released during the last frame.
    PURE Bool released(Key key) const;
    // Returns true if the mouse button was released during the last frame.
    PURE Bool released(Mouse button) const;

    // Returns true if the key was double pressed during the last frame.
    // A double press is defined as two presses within a certain time frame.
    PURE Bool double_pressed(Key key) const;
    // Returns true if the mouse button was double pressed during the last frame.
    // A double press is defined as two presses within a certain time frame.
    PURE Bool double_pressed(Mouse button) const;

    // Returns the position of the mouse cursor in the window.
    PURE Vector<2> mouse_position() const;

    // Returns the change in the position of the mouse cursor since the last frame.
    PURE Vector<2> mouse_movement() const;

private:
    template <typename T>
    struct ButtonMap {
        T keys[KeyCount] = { 0 };
        T mouse_buttons[MouseCount] = { 0 };
    };

    struct FrameState {
        ButtonMap<Bool> map;
        Vec2 mouse_position = { 0, 0 };
    };

    std::unique_ptr<FrameState> m_state = std::make_unique<FrameState>();
    std::unique_ptr<FrameState> m_previous_state = std::make_unique<FrameState>();

    std::unique_ptr<ButtonMap<Time::Timestamp>> m_last_key_release = std::make_unique<ButtonMap<Time::Timestamp>>();
    std::unique_ptr<ButtonMap<Bool>> m_double_press = std::make_unique<ButtonMap<Bool>>();

    static Bool key_pressed(std::unique_ptr<FrameState> const& current, std::unique_ptr<FrameState> const& previous, Key key);
    static Bool mouse_button_pressed(std::unique_ptr<FrameState> const& current, std::unique_ptr<FrameState> const& previous, Mouse mouse);
    static Bool key_released(std::unique_ptr<FrameState> const& current, std::unique_ptr<FrameState> const& previous, Key key);
    static Bool mouse_button_released(std::unique_ptr<FrameState> const& current, std::unique_ptr<FrameState> const& previous, Mouse mouse);

    static Bool s_key_buffer[KeyCount];
    static Bool s_mouse_buffer[MouseCount];
    static Vec2 s_mouse_position;
    enum class MouseEventType { None, First, Subsequent };
    static MouseEventType s_mouse_event_type;

    static USize key_value(Key key);
    static USize mouse_button_value(Mouse button);

    static Key from_glfw_key(I32 key);
    static Mouse from_glfw_mouse(I32 button);

    static void key_callback(GLFWwindow* _window, I32 key, I32 _scancode, I32 action, I32 _mods);
    static void cursor_position_callback(GLFWwindow* _window, F64 x, F64 y);
    static void mouse_button_callback(GLFWwindow* _window, I32 button, I32 action, I32 _mods);
};

}