// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2022 Benjamin Tissoires
 *
 * This program will morph the Microsoft Surface Dial into a mouse,
 * and depending on the chosen resolution enable or not the haptic feedback:
 * - a resolution (-r) of 3600 will report 3600 "ticks" in one full rotation
 *   without haptic feedback
 * - any other resolution will report N "ticks" in a full rotation with haptic
 *   feedback
 *
 * A good default for low resolution haptic scrolling is 72 (1 "tick" every 5
 * degrees), and set to 3600 for smooth scrolling.
 */

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>
#include <unistd.h>

#include <linux/bpf.h>
#include <linux/errno.h>

#include <bpf/bpf.h>
#include <bpf/libbpf.h>

#include "hid_surface_dial.skel.h"

static bool running = true;

struct haptic_syscall_args {
        unsigned int hid;
        int retval;
};

static void int_exit(int sig)
{
        running = false;
        exit(0);
}

static void usage(const char *prog)
{
        fprintf(stderr,
                "%s: %s [OPTIONS] /sys/bus/hid/devices/0BUS:0VID:0PID:00ID\n\n"
                "  OPTIONS:\n"
                "    -r N\t set the given resolution to the device (number of ticks per 360°)\n\n",
                __func__, prog);
        fprintf(stderr,
                "This program will morph the Microsoft Surface Dial into a mouse,\n"
                "and depending on the chosen resolution enable or not the haptic feedback:\n"
                "- a resolution (-r) of 3600 will report 3600 'ticks' in one full rotation\n"
                "  without haptic feedback\n"
                "- any other resolution will report N 'ticks' in a full rotation with haptic\n"
                "  feedback\n"
                "\n"
                "A good default for low resolution haptic scrolling is 72 (1 'tick' every 5\n"
                "degrees), and set to 3600 for smooth scrolling.\n");
}

static int get_hid_id(const char *path)
{
        const char *str_id, *dir;
        char uevent[1024];
        int fd;

        memset(uevent, 0, sizeof(uevent));
        snprintf(uevent, sizeof(uevent) - 1, "%s/uevent", path);

        fd = open(uevent, O_RDONLY | O_NONBLOCK);
        if (fd < 0)
                return -ENOENT;

        close(fd);

        dir = basename((char *)path);

        str_id = dir + sizeof("0003:0001:0A37.");
        return (int)strtol(str_id, NULL, 16);
}

static int set_haptic(struct hid_surface_dial *skel, int hid_id)
{
        struct haptic_syscall_args args = {
                .hid = hid_id,
                .retval = -1,
        };
        int haptic_fd, err;
        DECLARE_LIBBPF_OPTS(bpf_test_run_opts, tattr,
                            .ctx_in = &args,
                            .ctx_size_in = sizeof(args),
        );

        haptic_fd = bpf_program__fd(skel->progs.set_haptic);
        if (haptic_fd < 0) {
                fprintf(stderr, "can't locate haptic prog: %m\n");
                return 1;
        }

        err = bpf_prog_test_run_opts(haptic_fd, &tattr);
        if (err) {
                fprintf(stderr, "can't set haptic configuration to hid device %d: %m (err: %d)\n",
                        hid_id, err);
                return 1;
        }
        return 0;
}

int main(int argc, char **argv)
{
        struct hid_surface_dial *skel;
        const char *optstr = "r:";
        struct bpf_link *link;
        const char *sysfs_path;
        int err, opt, hid_id, resolution = 72;

        while ((opt = getopt(argc, argv, optstr)) != -1) {
                switch (opt) {
                case 'r':
                        {
                                char *endp = NULL;
                                long l = -1;

                                if (optarg) {
                                        l = strtol(optarg, &endp, 10);
                                        if (endp && *endp)
                                                l = -1;
                                }

                                if (l < 0) {
                                        fprintf(stderr,
                                                "invalid r option %s - expecting a number\n",
                                                optarg ? optarg : "");
                                        exit(EXIT_FAILURE);
                                };

                                resolution = (int) l;
                                break;
                        }
                default:
                        usage(basename(argv[0]));
                        return 1;
                }
        }

        if (optind == argc) {
                usage(basename(argv[0]));
                return 1;
        }

        sysfs_path = argv[optind];
        if (!sysfs_path) {
                perror("sysfs");
                return 1;
        }

        skel = hid_surface_dial__open();
        if (!skel) {
                fprintf(stderr, "%s  %s:%d", __func__, __FILE__, __LINE__);
                return -1;
        }

        hid_id = get_hid_id(sysfs_path);
        if (hid_id < 0) {
                fprintf(stderr, "can not open HID device: %m\n");
                return 1;
        }

        skel->struct_ops.surface_dial->hid_id = hid_id;

        err = hid_surface_dial__load(skel);
        if (err < 0) {
                fprintf(stderr, "can not load HID-BPF program: %m\n");
                return 1;
        }

        skel->data->resolution = resolution;
        skel->data->physical = (int)(resolution / 72);

        link = bpf_map__attach_struct_ops(skel->maps.surface_dial);
        if (!link) {
                fprintf(stderr, "can not attach HID-BPF program: %m\n");
                return 1;
        }

        signal(SIGINT, int_exit);
        signal(SIGTERM, int_exit);

        set_haptic(skel, hid_id);

        while (running)
                sleep(1);

        hid_surface_dial__destroy(skel);

        return 0;
}