/**
 * Author: Jason White
 *
 * Description:
 * Reads joystick/gamepad events and displays them.
 *
 * Compile:
 * gcc joystick.c -o joystick
 *
 * Run:
 * ./joystick [/dev/input/jsX]
 *
 * See also:
 * https://www.kernel.org/doc/Documentation/input/joystick-api.txt
 */

#include <fcntl.h>
#include <cstdio>
#include <unistd.h>
#include <linux/joystick.h>
#include <cstdint>
#include <cstring>
#include <string>
#include <iostream>
#include <filesystem>
#include <format>

enum class XBoxButton : uint8_t
{
    ButtonA = 0,
    ButtonB = 1,
    ButtonX = 2,
    ButtonY = 3,
    BumperL = 4,
    BumperR = 5,
    Back    = 6,
    Start   = 7,
    TheBigOne = 8,
    ThumbL = 9,
    ThumbR = 10,
};

/// Reads a joystick event from the joystick device.
/// @returns 0 on success. Otherwise -1 is returned.
int read_event(int fd, struct js_event *event)
{
    ssize_t bytes;

    bytes = read(fd, event, sizeof(*event));

    if (bytes == sizeof(*event))
        return 0;

    /// Error, could not read full event.
    return -1;
}

/// @returns the number of axes on the controller or 0 if an error occurs.
size_t get_axis_count(int fd)
{
    __u8 axes;

    if (ioctl(fd, JSIOCGAXES, &axes) == -1)
        return 0;

    return axes;
}

/// @returns the number of buttons on the controller or 0 if an error occurs.
size_t get_button_count(int fd)
{
    __u8 buttons;
    if (ioctl(fd, JSIOCGBUTTONS, &buttons) == -1)
        return 0;

    return buttons;
}

/// Current state of an axis.


struct Axes {
    short LeftThumbX = 0;
    short LeftThumbY = 0;
    short RightThumbX = 0;
    short RightThumbY = 0;
    short DPadX = 0;
    short DPadY = 0;
    // TODO Left & Right triggers should start at -32767 because 0 would be pressed half way.
    short LeftTrigger = 0;
    short RightTrigger = 0;
};


/// Keeps track of the current axis state.
/// @note This function assumes that axes are numbered starting from 0, and that
/// the X axis is an even number, and the Y axis is an odd number. However, this
/// is usually a safe assumption.
/// @returns the axis that the event indicated.
size_t get_axis_state(struct js_event *event, struct Axes& axes)
{
    /// Mappings on my device, meaning these assumptions are incorrect.
    // LStick X = 0
    // LStick Y = 1
    // LTrigger = 2
    // RStick X = 3
    // RStick Y = 4
    // RTrigger = 5
    // DirPad X = 6
    // DirPad Y = 7

    size_t axis = event->number;
    short value = event->value;

    // X-Box 360 & X-Box One are the same.
    if (axis == 0) axes.LeftThumbX = value;
    if (axis == 1) axes.LeftThumbY = value;
    if (axis == 2) axes.LeftTrigger = value;
    if (axis == 3) axes.RightThumbX = value;
    if (axis == 4) axes.RightThumbY = value;
    if (axis == 5) axes.RightTrigger = value;
    if (axis == 6) axes.DPadX = value;
    if (axis == 7) axes.DPadY = value;

    // "Sony PLAYSTATION(R)3 Controller", Has 6 axes.
    /*
    // D-PAD UP -> Button 12
    // D-Pad DOWN -> Button 13
    // D-Pad LEFT -> Button 14
    // D-Pad RIGHT -> Button 15
    if (axis == 0) axes.LeftThumbX = value;
    if (axis == 1) axes.LeftThumbY = value;
    if (axis == 3) axes.RightThumbX = value;
    if (axis == 4) axes.RightThumbY = value;
    if (axis == 2) axes.LeftTrigger = value;
    if (axis == 5) axes.RightTrigger = value;
    */


    // Playstation 4
    /*
    if (axis == 0) axes.LeftThumbX = value;
    if (axis == 1) axes.LeftThumbY = value;
    if (axis == 3) axes.RightThumbX = value;
    if (axis == 4) axes.RightThumbY = value;
    if (axis == 2) axes.LeftTrigger = value;
    if (axis == 5) axes.RightTrigger = value;
    if (axis == 6) axes.DPadX = value;
    if (axis == 7) axes.DPadY = value;
    */

    // "8BitDo Pro 2" in Direct Input mode. This controller also supports the Xbox mode.
    /*
    if (axis == 0) axes.LeftThumbX = value;
    if (axis == 1) axes.LeftThumbY = value;
    if (axis == 2) axes.RightThumbX = value;
    if (axis == 3) axes.RightThumbY = value;
    if (axis == 4) axes.RightTrigger = value;
    if (axis == 5) axes.LeftTrigger = value;
    if (axis == 6) axes.DPadX = value;
    if (axis == 7) axes.DPadY = value;
    */


    std::cout << std::format("axis_index: {}, val: {}", axis, value) << std::endl;
    std::cout << std::format("lthumb: {},{} ltrigger: {}, rthumb: {},{}, rtrigger: {}, dp: {},{}",  axes.LeftThumbX, axes.LeftThumbY, axes.LeftTrigger, axes.RightThumbX, axes.RightThumbY, axes.RightTrigger, axes.DPadX, axes.DPadY) << std::endl;

    /*size_t axis = event->number / 2;

    if (axis < 3)
    {
        if (event->number % 2 == 0)
            axes[axis].x = event->value;
        else
            axes[axis].y = event->value;
    }

    return axis;*/
    return axis;
}

uint8_t get_num_axes(int joystick_handle) {
    char num_axes;
    ioctl(joystick_handle, JSIOCGAXES, &num_axes);
    return num_axes;
}

std::string get_joystick_name(int joystick_handle)
{
    char name_buf[128];
    if (ioctl(joystick_handle, JSIOCGNAME(sizeof(name_buf)), name_buf) < 0)
        strncpy(name_buf, "Unknown", sizeof(name_buf));
    return std::string(name_buf);
}

int get_joystick_driver_ver(int joystick_handle)
{
    int version;
    ioctl(joystick_handle, JSIOCGVERSION, &version);
    return version;
}

bool check_for_joystick_device()
{
    return std::filesystem::exists("/dev/input/js0");
}

int js;
bool device_open;

bool connect_device() {
    js = open("/dev/input/js0", O_NONBLOCK);

    if (js == -1)
        perror("Could not open joystick");


    std::cout << get_joystick_name(js) << std::endl;
    std::cout << get_joystick_driver_ver(js) << std::endl;
    std::cout << get_axis_count(js) << std::endl;
}

void disconnect_device() {
    close(js);
}

#define ENUM_TO_STRING(var) (#var)

int main(int argc, char *argv[])
{
    const char *device;

    struct js_event event;
    struct Axes axes = {};
    size_t axis;

    if (argc > 1)
        device = argv[1];
    else
        device = "/dev/input/js0";

    js = open(device, O_NONBLOCK);

    if (js == -1)
        perror("Could not open joystick");
    else
    {
        std::cout << get_joystick_name(js) << std::endl;
        std::cout << get_joystick_driver_ver(js) << std::endl;
        std::cout << get_axis_count(js) << std::endl;
    }



    /// This loop will exit if the controller is unplugged.

    bool had = false;

    while (1)
    {
        bool has_file = check_for_joystick_device();

        if (has_file && !had) {
            if (js == -1)
            {
                std::cout << "Controller plugged in!" << std::endl;
                js = open(device, O_NONBLOCK);

                if (js == -1)
                    perror("Could not open joystick");
            }

        } else if (!has_file && had) {
            std::cout << "Controller unplugged!" << std::endl;
            if (js != -1) {
                close(js);
                js = -1;
            }


        }

        had = has_file;


        while (read_event(js, &event) == 0)
        {
            switch (event.type)
            {
                case JS_EVENT_BUTTON:
                    printf("Button %u %s\n", event.number, event.value ? "pressed" : "released");
                    break;
                case JS_EVENT_AXIS:
                    axis = get_axis_state(&event, axes);
                    //if (axis < 3)
                        //printf("Axis %zu at (%6d, %6d)\n", axis, axes[axis].x, axes[axis].y);
                    break;
                case JS_EVENT_INIT:
                default:
                    /// Ignore init events.
                    break;
            }

            fflush(stdout);
        }
    }


    close(js);
    return 0;
}