#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <asm/termbits.h> /* struct termios2 */
#include <time.h>
#include <ctype.h>
#include <signal.h>
#include <sys/time.h>

#define CANUSB_INJECT_SLEEP_GAP_DEFAULT 200 /* ms */
#define CANUSB_TTY_BAUD_RATE_DEFAULT 2000000

typedef enum {
  CANUSB_SPEED_1000000 = 0x01,
  CANUSB_SPEED_800000  = 0x02,
  CANUSB_SPEED_500000  = 0x03,
  CANUSB_SPEED_400000  = 0x04,
  CANUSB_SPEED_250000  = 0x05,
  CANUSB_SPEED_200000  = 0x06,
  CANUSB_SPEED_125000  = 0x07,
  CANUSB_SPEED_100000  = 0x08,
  CANUSB_SPEED_50000   = 0x09,
  CANUSB_SPEED_20000   = 0x0a,
  CANUSB_SPEED_10000   = 0x0b,
  CANUSB_SPEED_5000    = 0x0c,
} CANUSB_SPEED;

typedef enum {
  CANUSB_MODE_NORMAL          = 0x00,
  CANUSB_MODE_LOOPBACK        = 0x01,
  CANUSB_MODE_SILENT          = 0x02,
  CANUSB_MODE_LOOPBACK_SILENT = 0x03,
} CANUSB_MODE;

typedef enum {
  CANUSB_FRAME_STANDARD = 0x01,
  CANUSB_FRAME_EXTENDED = 0x02,
} CANUSB_FRAME;

typedef enum {
    CANUSB_INJECT_PAYLOAD_MODE_RANDOM      = 0,
    CANUSB_INJECT_PAYLOAD_MODE_INCREMENTAL = 1,
    CANUSB_INJECT_PAYLOAD_MODE_FIXED       = 2,
} CANUSB_PAYLOAD_MODE;



static int terminate_after = 0;
static int program_running = 1;
static int inject_payload_mode = CANUSB_INJECT_PAYLOAD_MODE_FIXED;
static float inject_sleep_gap = CANUSB_INJECT_SLEEP_GAP_DEFAULT;
static int print_traffic = 0;



static CANUSB_SPEED canusb_int_to_speed(int speed)
{
  switch (speed) {
  case 1000000:
    return CANUSB_SPEED_1000000;
  case 800000:
    return CANUSB_SPEED_800000;
  case 500000:
    return CANUSB_SPEED_500000;
  case 400000:
    return CANUSB_SPEED_400000;
  case 250000:
    return CANUSB_SPEED_250000;
  case 200000:
    return CANUSB_SPEED_200000;
  case 125000:
    return CANUSB_SPEED_125000;
  case 100000:
    return CANUSB_SPEED_100000;
  case 50000:
    return CANUSB_SPEED_50000;
  case 20000:
    return CANUSB_SPEED_20000;
  case 10000:
    return CANUSB_SPEED_10000;
  case 5000:
    return CANUSB_SPEED_5000;
  default:
    return 0;
  }
}



static int generate_checksum(const unsigned char *data, int data_len)
{
  int i, checksum;

  checksum = 0;
  for (i = 0; i < data_len; i++) {
    checksum += data[i];
  }

  return checksum & 0xff;
}



static int frame_is_complete(const unsigned char *frame, int frame_len)
{
  if (frame_len > 0) {
    if (frame[0] != 0xaa) {
      /* Need to sync on 0xaa at start of frames, so just skip. */
      return 1;
    }
  }

  if (frame_len < 2) {
    return 0;
  }

  if (frame[1] == 0x55) { /* Command frame... */
    if (frame_len >= 20) { /* ...always 20 bytes. */
      return 1;
    } else {
      return 0;
    }
  } else if ((frame[1] >> 4) == 0xc) { /* Data frame... */
    if (frame_len >= (frame[1] & 0xf) + 5) { /* ...payload and 5 bytes. */
      return 1;
    } else {
      return 0;
    }
  }

  /* Unhandled frame type. */
  return 1;
}



static int frame_send(int tty_fd, const unsigned char *frame, int frame_len)
{
  int result, i;

  if (print_traffic) {
    printf(">>> ");
    for (i = 0; i < frame_len; i++) {
      printf("%02x ", frame[i]);
    }
    if (print_traffic > 1) {
      printf("    '");
      for (i = 4; i < frame_len - 1; i++) {
        printf("%c", isalnum(frame[i]) ? frame[i] : '.');
      }
      printf("'");
    }
    printf("\n");
  }

  result = write(tty_fd, frame, frame_len);
  if (result == -1) {
    fprintf(stderr, "write() failed: %s\n", strerror(errno));
    return -1;
  }

  return frame_len;
}



static int frame_recv(int tty_fd, unsigned char *frame, int frame_len_max)
{
  int result, frame_len, checksum;
  unsigned char byte;

  if (print_traffic)
    fprintf(stderr, "<<< ");

  frame_len = 0;
  while (program_running) {
    result = read(tty_fd, &byte, 1);
    if (result == -1) {
      if (errno != EAGAIN && errno != EWOULDBLOCK) {
        fprintf(stderr, "read() failed: %s\n", strerror(errno));
        return -1;
      }

    } else if (result > 0) {
      if (print_traffic)
        fprintf(stderr, "%02x ", byte);

      if (frame_len == frame_len_max) {
        fprintf(stderr, "frame_recv() failed: Overflow\n");
        return -1;
      }

      frame[frame_len++] = byte;

      if (frame_is_complete(frame, frame_len)) {
        break;
      }
    }

    usleep(10);
  }

  if (print_traffic)
    fprintf(stderr, "\n");

  /* Compare checksum for command frames only. */
  if ((frame_len == 20) && (frame[0] == 0xaa) && (frame[1] == 0x55)) {
    checksum = generate_checksum(&frame[2], 17);
    if (checksum != frame[frame_len - 1]) {
      fprintf(stderr, "frame_recv() failed: Checksum incorrect\n");
      return -1;
    }
  }

  return frame_len;
}



static int command_settings(int tty_fd, CANUSB_SPEED speed, CANUSB_MODE mode, CANUSB_FRAME frame)
{
  int cmd_frame_len;
  unsigned char cmd_frame[20];

  cmd_frame_len = 0;
  cmd_frame[cmd_frame_len++] = 0xaa;
  cmd_frame[cmd_frame_len++] = 0x55;
  cmd_frame[cmd_frame_len++] = 0x12;
  cmd_frame[cmd_frame_len++] = speed;
  cmd_frame[cmd_frame_len++] = frame;
  cmd_frame[cmd_frame_len++] = 0; /* Filter ID not handled. */
  cmd_frame[cmd_frame_len++] = 0; /* Filter ID not handled. */
  cmd_frame[cmd_frame_len++] = 0; /* Filter ID not handled. */
  cmd_frame[cmd_frame_len++] = 0; /* Filter ID not handled. */
  cmd_frame[cmd_frame_len++] = 0; /* Mask ID not handled. */
  cmd_frame[cmd_frame_len++] = 0; /* Mask ID not handled. */
  cmd_frame[cmd_frame_len++] = 0; /* Mask ID not handled. */
  cmd_frame[cmd_frame_len++] = 0; /* Mask ID not handled. */
  cmd_frame[cmd_frame_len++] = mode;
  cmd_frame[cmd_frame_len++] = 0x01;
  cmd_frame[cmd_frame_len++] = 0;
  cmd_frame[cmd_frame_len++] = 0;
  cmd_frame[cmd_frame_len++] = 0;
  cmd_frame[cmd_frame_len++] = 0;
  cmd_frame[cmd_frame_len++] = generate_checksum(&cmd_frame[2], 17);

  if (frame_send(tty_fd, cmd_frame, cmd_frame_len) < 0) {
    return -1;
  }

  return 0;
}



static int send_data_frame(int tty_fd, CANUSB_FRAME frame, unsigned char id_lsb, unsigned char id_msb, unsigned char data[], int data_length_code)
{
#define MAX_FRAME_SIZE 13
  int data_frame_len = 0;
  unsigned char data_frame[MAX_FRAME_SIZE] = {0x00};

  if (data_length_code < 0 || data_length_code > 8)
  {
    fprintf(stderr, "Data length code (DLC) must be between 0 and 8!\n");
    return -1;
  }

  /* Byte 0: Packet Start */
  data_frame[data_frame_len++] = 0xaa;

  /* Byte 1: CAN Bus Data Frame Information */
  data_frame[data_frame_len] = 0x00;
  data_frame[data_frame_len] |= 0xC0; /* Bit 7 Always 1, Bit 6 Always 1 */
  if (frame == CANUSB_FRAME_STANDARD)
    data_frame[data_frame_len] &= 0xDF; /* STD frame */
  else /* CANUSB_FRAME_EXTENDED */
    data_frame[data_frame_len] |= 0x20; /* EXT frame */
  data_frame[data_frame_len] &= 0xEF; /* 0=Data */
  data_frame[data_frame_len] |= data_length_code; /* DLC=data_len */
  data_frame_len++;

  /* Byte 2 to 3: ID */
  data_frame[data_frame_len++] = id_lsb; /* lsb */
  data_frame[data_frame_len++] = id_msb; /* msb */

  /* Byte 4 to (4+data_len): Data */
  for (int i = 0; i < data_length_code; i++)
    data_frame[data_frame_len++] = data[i];

  /* Last byte: End of frame */
  data_frame[data_frame_len++] = 0x55;

  if (frame_send(tty_fd, data_frame, data_frame_len) < 0)
  {
    fprintf(stderr, "Unable to send frame!\n");
    return -1;
  }

  return 0;
}



static int hex_value(int c)
{
  if (c >= 0x30 && c <= 0x39) /* '0' - '9' */
    return c - 0x30;
  else if (c >= 0x41 && c <= 0x46) /* 'A' - 'F' */
    return (c - 0x41) + 10;
  else if (c >= 0x61 && c <= 0x66) /* 'a' - 'f' */
    return (c - 0x61) + 10;
  else
    return -1;
}



static int convert_from_hex(const char *hex_string, unsigned char *bin_string, int bin_string_len)
{
  int n1, n2, high;

  high = -1;
  n1 = n2 = 0;
  while (hex_string[n1] != '\0') {
    if (hex_value(hex_string[n1]) >= 0) {
      if (high == -1) {
        high = hex_string[n1];
      } else {
        bin_string[n2] = hex_value(high) * 16 + hex_value(hex_string[n1]);
        n2++;
        if (n2 >= bin_string_len) {
          printf("hex string truncated to %d bytes\n", n2);
          break;
        }
        high = -1;
      }
    }
    n1++;
  }

  return n2;
}



static int inject_data_frame(int tty_fd, const char *hex_id, const char *hex_data)
{
  int data_len;
  unsigned char binary_data[8];
  unsigned char binary_id_lsb = 0, binary_id_msb = 0;
  struct timespec gap_ts;
  struct timeval now;
  int error = 0;

  gap_ts.tv_sec = inject_sleep_gap / 1000;
  gap_ts.tv_nsec = (long)(((long long)(inject_sleep_gap * 1000000)) % 1000000000LL);

  /* Set seed value for pseudo random numbers. */
  gettimeofday(&now, NULL);
  srandom(now.tv_usec);

  data_len = convert_from_hex(hex_data, binary_data, sizeof(binary_data));
  if (data_len == 0) {
    fprintf(stderr, "Unable to convert data from hex to binary!\n");
    return -1;
  }

  switch (strlen(hex_id)) {
  case 1:
    binary_id_lsb = hex_value(hex_id[0]);
    break;

  case 2:
    binary_id_lsb = (hex_value(hex_id[0]) * 16) + hex_value(hex_id[1]);
    break;

  case 3:
    binary_id_msb = hex_value(hex_id[0]);
    binary_id_lsb = (hex_value(hex_id[1]) * 16) + hex_value(hex_id[2]);
    break;

  default:
    fprintf(stderr, "Unable to convert ID from hex to binary!\n");
    return -1;
  }

  while (program_running && ! error) {
    if (gap_ts.tv_sec || gap_ts.tv_nsec)
      nanosleep(&gap_ts, NULL);

    if (terminate_after && (--terminate_after == 0))
      program_running = 0;

    if (inject_payload_mode == CANUSB_INJECT_PAYLOAD_MODE_RANDOM) {
      int i;
      for (i = 0; i < data_len; i++)
        binary_data[i] = random();
    } else if (inject_payload_mode == CANUSB_INJECT_PAYLOAD_MODE_INCREMENTAL) {
      int i;
      for (i = 0; i < data_len; i++)
        binary_data[i]++;
    }

    error = send_data_frame(tty_fd, CANUSB_FRAME_STANDARD, binary_id_lsb, binary_id_msb, binary_data, data_len);
  }

  return error;
}



static void dump_data_frames(int tty_fd)
{
  int i, frame_len;
  unsigned char frame[32];
  struct timespec ts;

  while (program_running) {
    frame_len = frame_recv(tty_fd, frame, sizeof(frame));

    if (! program_running)
      break;

    clock_gettime(CLOCK_MONOTONIC, &ts);
    printf("%lu.%06lu ", ts.tv_sec, ts.tv_nsec / 1000);

    if (frame_len == -1) {
      printf("Frame recieve error!\n");

    } else {

      if ((frame_len >= 6) &&
          (frame[0] == 0xaa) &&
          ((frame[1] >> 4) == 0xc)) {
        printf("Frame ID: %02x%02x, Data: ", frame[3], frame[2]);
        for (i = frame_len - 2; i > 3; i--) {
          printf("%02x ", frame[i]);
        }
        printf("\n");

      } else {
        printf("Unknown: ");
        for (i = 0; i <= frame_len; i++) {
          printf("%02x ", frame[i]);
        }
        printf("\n");
      }
    }

    if (terminate_after && (--terminate_after == 0))
      program_running = 0;
  }
}



static int adapter_init(const char *tty_device, int baudrate)
{
  int tty_fd, result;
  struct termios2 tio;

  tty_fd = open(tty_device, O_RDWR | O_NOCTTY | O_NONBLOCK);
  if (tty_fd == -1) {
    fprintf(stderr, "open(%s) failed: %s\n", tty_device, strerror(errno));
    return -1;
  }

  result = ioctl(tty_fd, TCGETS2, &tio);
  if (result == -1) {
    fprintf(stderr, "ioctl() failed: %s\n", strerror(errno));
    close(tty_fd);
    return -1;
  }

  tio.c_cflag &= ~CBAUD;
  tio.c_cflag = BOTHER | CS8 | CSTOPB;
  tio.c_iflag = IGNPAR;
  tio.c_oflag = 0;
  tio.c_lflag = 0;
  tio.c_ispeed = baudrate;
  tio.c_ospeed = baudrate;

  result = ioctl(tty_fd, TCSETS2, &tio);
  if (result == -1) {
    fprintf(stderr, "ioctl() failed: %s\n", strerror(errno));
    close(tty_fd);
    return -1;
  }

  return tty_fd;
}



static void display_help(const char *progname)
{
  fprintf(stderr, "Usage: %s <options>\n", progname);
  fprintf(stderr, "Options:\n"
     "  -h          Display this help and exit.\n"
     "  -t          Print TTY/serial traffic debugging info on stderr.\n"
     "  -d DEVICE   Use TTY DEVICE.\n"
     "  -s SPEED    Set CAN SPEED in bps.\n"
     "  -b BAUDRATE Set TTY/serial BAUDRATE (default: %d).\n"
     "  -i ID       Inject using ID (specified as hex string).\n"
     "  -j DATA     CAN DATA to inject (specified as hex string).\n"
     "  -n COUNT    Terminate after COUNT frames (default: infinite).\n"
     "  -g MS       Inject sleep gap in MS milliseconds (default: %d ms).\n"
     "  -m MODE     Inject payload MODE (%d = random, %d = incremental, %d = fixed).\n"
     "\n",
     CANUSB_TTY_BAUD_RATE_DEFAULT,
     CANUSB_INJECT_SLEEP_GAP_DEFAULT,
     CANUSB_INJECT_PAYLOAD_MODE_RANDOM,
     CANUSB_INJECT_PAYLOAD_MODE_INCREMENTAL,
     CANUSB_INJECT_PAYLOAD_MODE_FIXED);
}



static void sigterm(int signo)
{
  program_running = 0;
}



int main(int argc, char *argv[])
{
  int c, tty_fd;
  char *tty_device = NULL, *inject_data = NULL, *inject_id = NULL;
  CANUSB_SPEED speed = 0;
  int baudrate = CANUSB_TTY_BAUD_RATE_DEFAULT;

  while ((c = getopt(argc, argv, "htd:s:b:i:j:n:g:m:")) != -1) {
    switch (c) {
    case 'h':
      display_help(argv[0]);
      return EXIT_SUCCESS;

    case 't':
      print_traffic++;
      break;

    case 'd':
      tty_device = optarg;
      break;

    case 's':
      speed = canusb_int_to_speed(atoi(optarg));
      break;

    case 'b':
      baudrate = atoi(optarg);
      break;

    case 'i':
      inject_id = optarg;
      break;

    case 'j':
      inject_data = optarg;
      break;

    case 'n':
      terminate_after = atoi(optarg);
      break;

    case 'g':
      inject_sleep_gap = strtof(optarg, NULL);
      break;

    case 'm':
      inject_payload_mode = atoi(optarg);
      break;

    case '?':
    default:
      display_help(argv[0]);
      return EXIT_FAILURE;
    }
  }

  signal(SIGTERM, sigterm);
  signal(SIGHUP, sigterm);
  signal(SIGINT, sigterm);

  if (tty_device == NULL) {
    fprintf(stderr, "Please specify a TTY!\n");
    display_help(argv[0]);
    return EXIT_FAILURE;
  }

  if (speed == 0) {
    fprintf(stderr, "Please specify a valid speed!\n");
    display_help(argv[0]);
    return EXIT_FAILURE;
  }

  tty_fd = adapter_init(tty_device, baudrate);
  if (tty_fd == -1) {
    return EXIT_FAILURE;
  }

  command_settings(tty_fd, speed, CANUSB_MODE_NORMAL, CANUSB_FRAME_STANDARD);

  if (inject_data == NULL) {
    /* Dumping mode (default). */
    dump_data_frames(tty_fd);
  } else {
    /* Inject mode. */
    if (inject_id == NULL) {
      fprintf(stderr, "Please specify a ID for injection!\n");
      display_help(argv[0]);
      return EXIT_FAILURE;
    }
    if (inject_data_frame(tty_fd, inject_id, inject_data) == -1) {
      return EXIT_FAILURE;
    } else {
      return EXIT_SUCCESS;
    }
  }

  return EXIT_SUCCESS;
}