const formatDistanceLocale = {
  lessThanXSeconds: {
    standalone: {
      one: "manner wéi eng Sekonn",
      other: "manner wéi {{count}} Sekonnen",
    },
    withPreposition: {
      one: "manner wéi enger Sekonn",
      other: "manner wéi {{count}} Sekonnen",
    },
  },

  xSeconds: {
    standalone: {
      one: "eng Sekonn",
      other: "{{count}} Sekonnen",
    },
    withPreposition: {
      one: "enger Sekonn",
      other: "{{count}} Sekonnen",
    },
  },

  halfAMinute: {
    standalone: "eng hallef Minutt",
    withPreposition: "enger hallwer Minutt",
  },

  lessThanXMinutes: {
    standalone: {
      one: "manner wéi eng Minutt",
      other: "manner wéi {{count}} Minutten",
    },
    withPreposition: {
      one: "manner wéi enger Minutt",
      other: "manner wéi {{count}} Minutten",
    },
  },

  xMinutes: {
    standalone: {
      one: "eng Minutt",
      other: "{{count}} Minutten",
    },
    withPreposition: {
      one: "enger Minutt",
      other: "{{count}} Minutten",
    },
  },

  aboutXHours: {
    standalone: {
      one: "ongeféier eng Stonn",
      other: "ongeféier {{count}} Stonnen",
    },
    withPreposition: {
      one: "ongeféier enger Stonn",
      other: "ongeféier {{count}} Stonnen",
    },
  },

  xHours: {
    standalone: {
      one: "eng Stonn",
      other: "{{count}} Stonnen",
    },
    withPreposition: {
      one: "enger Stonn",
      other: "{{count}} Stonnen",
    },
  },

  xDays: {
    standalone: {
      one: "een Dag",
      other: "{{count}} Deeg",
    },
    withPreposition: {
      one: "engem Dag",
      other: "{{count}} Deeg",
    },
  },

  aboutXWeeks: {
    standalone: {
      one: "ongeféier eng Woch",
      other: "ongeféier {{count}} Wochen",
    },
    withPreposition: {
      one: "ongeféier enger Woche",
      other: "ongeféier {{count}} Wochen",
    },
  },

  xWeeks: {
    standalone: {
      one: "eng Woch",
      other: "{{count}} Wochen",
    },
    withPreposition: {
      one: "enger Woch",
      other: "{{count}} Wochen",
    },
  },

  aboutXMonths: {
    standalone: {
      one: "ongeféier ee Mount",
      other: "ongeféier {{count}} Méint",
    },
    withPreposition: {
      one: "ongeféier engem Mount",
      other: "ongeféier {{count}} Méint",
    },
  },

  xMonths: {
    standalone: {
      one: "ee Mount",
      other: "{{count}} Méint",
    },
    withPreposition: {
      one: "engem Mount",
      other: "{{count}} Méint",
    },
  },

  aboutXYears: {
    standalone: {
      one: "ongeféier ee Joer",
      other: "ongeféier {{count}} Joer",
    },
    withPreposition: {
      one: "ongeféier engem Joer",
      other: "ongeféier {{count}} Joer",
    },
  },

  xYears: {
    standalone: {
      one: "ee Joer",
      other: "{{count}} Joer",
    },
    withPreposition: {
      one: "engem Joer",
      other: "{{count}} Joer",
    },
  },

  overXYears: {
    standalone: {
      one: "méi wéi ee Joer",
      other: "méi wéi {{count}} Joer",
    },
    withPreposition: {
      one: "méi wéi engem Joer",
      other: "méi wéi {{count}} Joer",
    },
  },

  almostXYears: {
    standalone: {
      one: "bal ee Joer",
      other: "bal {{count}} Joer",
    },
    withPreposition: {
      one: "bal engem Joer",
      other: "bal {{count}} Joer",
    },
  },
};

const EXCEPTION_CONSONANTS = ["d", "h", "n", "t", "z"];
const VOWELS = ["a,", "e", "i", "o", "u"];
const DIGITS_SPOKEN_N_NEEDED = [0, 1, 2, 3, 8, 9];
const FIRST_TWO_DIGITS_SPOKEN_NO_N_NEEDED = [40, 50, 60, 70];

// Eifeler Regel
function isFinalNNeeded(nextWords) {
  const firstLetter = nextWords.charAt(0).toLowerCase();
  if (
    VOWELS.indexOf(firstLetter) != -1 ||
    EXCEPTION_CONSONANTS.indexOf(firstLetter) != -1
  ) {
    return true;
  }

  // Numbers would need to converted into words for checking.
  // Therefore, I have listed the digits that require a preceeding n with a few exceptions.
  const firstWord = nextWords.split(" ")[0];
  const number = parseInt(firstWord);
  if (
    !isNaN(number) &&
    DIGITS_SPOKEN_N_NEEDED.indexOf(number % 10) != -1 &&
    FIRST_TWO_DIGITS_SPOKEN_NO_N_NEEDED.indexOf(
      parseInt(firstWord.substring(0, 2)),
    ) == -1
  ) {
    return true;
  }

  // Omit other checks as they are not expected here.
  return false;
}

export const formatDistance = (token, count, options) => {
  let result;

  const tokenValue = formatDistanceLocale[token];

  const usageGroup = options?.addSuffix
    ? tokenValue.withPreposition
    : tokenValue.standalone;

  if (typeof usageGroup === "string") {
    result = usageGroup;
  } else if (count === 1) {
    result = usageGroup.one;
  } else {
    result = usageGroup.other.replace("{{count}}", String(count));
  }

  if (options?.addSuffix) {
    if (options.comparison && options.comparison > 0) {
      return "a" + (isFinalNNeeded(result) ? "n" : "") + " " + result;
    } else {
      return "viru" + (isFinalNNeeded(result) ? "n" : "") + " " + result;
    }
  }

  return result;
};