member_eligible_for_tier_rule.rb

class MemberEligibleForTierRule
  attr_reader :member, :tier

  def initialize(member:, tier:)
    @member, @tier = member, tier
  end

  def satisfied?
    (flew_enough_miles? || flew_enough_segments?) && spent_enough_money?
  end

  private

  def flew_enough_miles?
    member.miles + qualifying_partner_miles >= tier.required_miles
  end

  def flew_enough_segments?
    member.segments >= tier.required_segments
  end

  def spent_enough_money?
    member.dollars >= tier.required_dollars
  end

  def qualifying_partner_miles
    [member.partner_miles, 10_000].min
  end
end