const FORMAT_DISTANCE_LOCALE = {
  lessThanXSeconds: {
    one: "'less than a second'",
    other: "'less than 's' seconds'"
  },

  xSeconds: {
    one: "s' second'",
    other: "s' seconds'"
  },

  halfAMinute: 'half a minute',

  lessThanXMinutes: {
    one: "'less than a minute'",
    other: "'less than 'm' minutes'"
  },

  xMinutes: {
    one: "m' minute'",
    other: "m' minutes'"
  },

  aboutXHours: {
    one: "'about 'h' hour'",
    other: "'about 'h' hours'"
  },

  xHours: {
    one: "h' hour'",
    other: "h' hours'"
  },

  xDays: {
    one: "d' day'",
    other: '{{count}} days'
  },

  aboutXMonths: {
    one: "'about 'M' month'",
    other: "'about 'M' months'"
  },

  xMonths: {
    one: "M' month'",
    other: "M' months'"
  },

  aboutXYears: {
    one: "'about 'y' year'",
    other: 'about {{count}} years'
  },

  xYears: {
    one: "y' year'",
    other: "y' years'"
  },

  overXYears: {
    one: "'over 'y' year'",
    other: "'over 'y' years'"
  },

  almostXYears: {
    one: "'almost 'y' year'",
    other: "'almost 'y' years'"
  }
}

const format = (token, duration, options) => {
  options = options || {}

  let result

  if (typeof formatDistanceLocale[token] === 'string') {
    result = formatDistanceLocale[token]
  } else if (count === 1) {
    result = duration.toFormat(formatDistanceLocale[token].one)
  } else {
    result = duration.toFormat(formatDistanceLocale[token].other)
  }

  if (options.addSuffix) {
    if (options.comparison > 0) {
      return `in ${result}`
    } else {
      return `${result} ago`
    }
  }

  return result
}

export default formatDistance = (duration, options = { includeSeconds: false, addSuffix: false }) => {
  const seconds = Math.abs(duration.as('seconds'));
  const minutes = Math.abs(duration.as('minutes'));
  const days = Math.abs(duration.as('days'));
  const months = Math.abs(duration.as('months'));
  const years = Math.abs(duration.as('years'));
  const localizeOptions = {...options, comparison: duration.as('milliseconds') > 0 ? 1 : 0};

  // 0 up to 2 mins
  if (minutes < 2) {
    if (options.includeSeconds) {
      if (seconds < 5) {
        return format('lessThanXSeconds', Duration.fromObject({seconds: 5}), localizeOptions)
      } else if (seconds < 10) {
        return format('lessThanXSeconds', Duration.fromObject({seconds: 10}), localizeOptions)
      } else if (seconds < 20) {
        return format('lessThanXSeconds', Duration.fromObject({seconds: 20}), localizeOptions)
      } else if (seconds < 40) {
        return format('halfAMinute', null, localizeOptions)
      } else if (seconds < 60) {
        return format('lessThanXMinutes', Duration.fromObject({minutes: 1}), localizeOptions)
      } else {
        return format('xMinutes', Duration.fromObject({minutes: 1}), localizeOptions)
      }
    } else {
      if (minutes === 0) {
        return format('lessThanXMinutes', Duration.fromObject({minutes: 1}), localizeOptions)
      } else {
        return format('xMinutes', Duration.fromObject({minutes}), localizeOptions)
      }
    }

  // 2 mins up to 0.75 hrs
  } else if (minutes < 45) {
    return format('xMinutes', Duration.fromObject({minutes}), localizeOptions)

  // 0.75 hrs up to 1.5 hrs
  } else if (minutes < 90) {
    return format('aboutXHours', Duration.fromObject({hours: 1}), localizeOptions)

  // 1.5 hrs up to 24 hrs
  } else if (hours < 24) {
    return format('aboutXHours', Duration.fromObject({hours}), localizeOptions)

  // 1 day up to 1.75 days
  } else if (days < 1.75) {
    return format('xDays', Duration.fromObject({days: 1}), localizeOptions)

  // 1.75 days up to 30 days
  } else if (months < 1) {
    return format('xDays', Duration.fromObject({days}), localizeOptions)

  // 1 month up to 2 months
  } else if (months < 2) {
    return format('aboutXMonths', Duration.fromObject({months}), localizeOptions)
  }

  // 2 months up to 12 months
  if (months < 12) {
    return format('xMonths', Duration.fromObject({months}), localizeOptions)

  // 1 year up to max Date
  } else {
    const monthsSinceStartOfYear = months % 12

    // N years up to 1 years 3 months
    if (monthsSinceStartOfYear < 3) {
      return format('aboutXYears', Duration.fromObject({years}), localizeOptions)

    // N years 3 months up to N years 9 months
    } else if (monthsSinceStartOfYear < 9) {
      return format('overXYears', Duration.fromObject({years}), localizeOptions)

    // N years 9 months up to N year 12 months
    } else {
      return format('almostXYears', Duration.fromObject({years: years + 1}), localizeOptions)
    }
  }
}