#include "length.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static double parse(char const* value, double res_mm) {
  char* suffix;
  double num = strtod(value, &suffix);
  if (suffix == value) {
    fprintf(stderr, "illegal value: %s\n", value);
    exit(2);
  }

  double add = 0;
  if (*suffix == '+') {
    add = num;
    num = strtod(suffix + 1, &suffix);
  }

  if (*suffix == '/') {
    double denom = strtod(suffix + 1, &suffix);
    if (denom <= 0.0) {
      fprintf(stderr, "illegal fraction: %s\n", value);
      exit(2);
    }
    num /= denom;
  }

  num += add;

  if (!strcmp(suffix, "") || !strcmp(suffix, "px")) {
    return num;
  } else if (!strcmp(suffix, "um")) {
    return num / 1000 / res_mm;
  } else if (!strcmp(suffix, "mm")) {
    return num / res_mm;
  } else if (!strcmp(suffix, "cm")) {
    return num * 10 / res_mm;
  } else if (!strcmp(suffix, "m")) {
    return num * 1000 / res_mm;
  } else if (!strcmp(suffix, "mil") || !strcmp(suffix, "thou")) {
    return num / 1000 * 2.54 * 10 / res_mm;
  } else if (!strcmp(suffix, "in") || !strcmp(suffix, "\"")) {
    return num * 2.54 * 10 / res_mm;
  } else if (!strcmp(suffix, "ft") || !strcmp(suffix, "'")) {
    return num * 12 * 2.54 * 10 / res_mm;
  } else {
    fprintf(stderr, "illegal suffix: %s\n", suffix);
    exit(2);
  }
}

int parse_length(char const* value) {
  double res_mm = 0.025;
  char const* res = getenv("RESOLUTION");
  if (res != NULL && *res != '\0') {
    res_mm = parse(res, 1.0);
    if (res_mm <= 0) {
      fprintf(stderr, "illegal $RESOLUTION: %s\n", res);
      exit(2);
    }
  }
  return (int) (parse(value, res_mm) + 0.5);
}