/*
 *
 */

#include "cumsum.h"

/*
 * Global configuration variables. These are set based on command-line
 * arguments, and read-only beyond that point.
 */
static bool ARG_FP_INPUT = false;
static bool ARG_UINT_INPUT = false;
static bool ARG_HELP = false;
static bool ARG_RUNNING_SUM = false;
static int64_t ARG_WINDOW_SIZE = 0;

/*
 * Circular buffer for windowed sums. I made this global for
 * convenience--it's a simple enough program that this'll work
 * fine. It could be refactored to have a more restricted scope.
 */
static Number *window_buffer = nullptr;
static size_t window_idx = 0;

static int parse_options(int argc, char *const *argv) {
  int arg_index = 0;
  int arg;
  bool error = false;

  while ((arg = getopt(argc, argv, "fhurw:")) != -1 && !error) {
    switch (arg) {
    case 'f':
      ARG_FP_INPUT = true;
      break;
    case 'u':
      ARG_UINT_INPUT = true;
      break;
    case 'h':
      ARG_HELP = true;
      break;
    case 'r':
      ARG_RUNNING_SUM = true;
      break;
    case 'w':
      ARG_WINDOW_SIZE = atol(optarg);
      if (ARG_WINDOW_SIZE <= 0) {
        fprintf(stderr, "Error: invalid window size: %lld. Must be > 0.\n",
                ARG_WINDOW_SIZE);
        error = true;
        break;
      }

      window_buffer = calloc(ARG_WINDOW_SIZE, sizeof(window_buffer[0]));
      if (!window_buffer) {
        fprintf(stderr, "Error: memory allocation failed\n");
        error = true;
      }
      break;
    case '?':
      if (isprint(optopt)) {
        fprintf(stderr, "Error: unknown option `-%c`.\n", optopt);
      } else {
        fprintf(stderr, "Error: unknown option character `\\x%x`.\n", optopt);
      }
      error = true;
      break;
    default:
      error = true;
      break;
    }
  }

  if (ARG_UINT_INPUT && ARG_FP_INPUT) {
    fprintf(stderr, "Error: the -u and -f flags are mutually exclusive.\n");
    error = true;
  }

  if (ARG_RUNNING_SUM && ARG_WINDOW_SIZE) {
    fprintf(stderr, "Error: the -w and -r flags are mutually exclusive.\n");
    error = true;
  }

  if (!error) {
    arg_index = optind;
  }

  return arg_index;
}

static void help() {
  fprintf(stderr, "Usage:\ncumsum [-f|-u] [-r|-w window_size] [filename]\n");
}

void print_sum(Number sum) {
  if (ARG_FP_INPUT) {
    fprintf(stdout, "%lf\n", sum.d);
  } else if (ARG_UINT_INPUT) {
    fprintf(stdout, "%lld\n", sum.u);
  } else {
    fprintf(stdout, "%lld\n", sum.i);
  }
}

static int get_next_number(FILE *file, Number *num) {
  /* read the next white-space seperated token */
  char buffer[512];

  int rc = fscanf(file, "%511s", buffer);
  if (rc == EOF) {
    return 0;
  } else if (rc != -1) {
    return -1;
  }

  errno = 0;
  char *endptr;
  if (ARG_FP_INPUT) {
    double val = strtod(buffer, &endptr);
    if (*endptr != 0 || endptr == buffer || errno == ERANGE) {
      fprintf(stderr, "Skipping invalid input token: %s\n", buffer);
      return -1;
    }
    num->d = val;
  } else if (ARG_UINT_INPUT) {
    uint64_t val = strtoull(buffer, &endptr, 10);
    if (*endptr != 0 || endptr == buffer || errno == ERANGE) {
      fprintf(stderr, "Skipping invalid input token: %s\n", buffer);
      return -1;
    }
    num->u = val;
  } else {
    int64_t val = strtoll(buffer, &endptr, 10);
    if (*endptr != 0 || endptr == buffer || errno == ERANGE) {
      fprintf(stderr, "Skipping invalid input token: %s\n", buffer);
      return -1;
    }
    num->i = val;
  }

  return 1;
}

void accumulate_number(Number *sum, Number num) {
  if (ARG_FP_INPUT) {
    sum->d += num.d;
  } else if (ARG_UINT_INPUT) {
    sum->u += num.u;
  } else {
    sum->i += num.i;
  }
}

void print_buffer_sum() {
  Number sum = {};
  for (size_t i = 0; i < ARG_WINDOW_SIZE; i++) {
    accumulate_number(&sum, window_buffer[i]);
  }
  print_sum(sum);
}

static int read_data(FILE *file, Number *sum) {
  Number rec = {};
  int rc;
  while ((rc = get_next_number(file, &rec))) {
    if (rc == -1) {
      continue;
    }

    if (ARG_WINDOW_SIZE > 1) {
      window_buffer[window_idx] = rec;
      window_idx = (window_idx + 1) % ARG_WINDOW_SIZE;
      print_buffer_sum();
    } else {
      accumulate_number(sum, rec);
      if (ARG_RUNNING_SUM) {
        print_sum(*sum);
      }
    }
  }

  return 1;
}

static int process_data(FILE *file) {
  int rc = 1;

  Number sum = {};
  rc = read_data(file, &sum);

  if (rc && !ARG_RUNNING_SUM) {
    print_sum(sum);
  }

process_data_end:
  return rc;
}

int main(int argc, char **argv) {
  int rc = EXIT_SUCCESS;
  int file_index = 0;
  if (!(file_index = parse_options(argc, argv))) {
    help();
    rc = EXIT_FAILURE;
    goto program_exit;
  }

  /* if the -h argument is supplied, print usage and exit successfully */
  if (ARG_HELP) {
    help();
    goto program_exit;
  }

  /* open the input file, if one is specified, otherwise default to stdin */
  FILE *input_file;
  if (file_index < argc && strcmp(argv[file_index], "-") != 0) {
    if (!(input_file = fopen(argv[file_index], "r"))) {
      fprintf(stderr, "Error: Unable to open input file %s\n",
              argv[file_index]);
      rc = EXIT_FAILURE;
      goto program_exit;
    }
  } else {
    input_file = stdin;
  }

  if (!process_data(input_file)) {
    rc = EXIT_FAILURE;
  }

close_file:
  if (input_file != stdin) {
    fclose(input_file);
  }

  free(window_buffer);
program_exit:
  exit(rc);
}