mem_spons_mr.rb

def mr
  # total_sponsor_amount = sum{|d| d.amount * dollars_per_locale_currency_unit(d.locale)}

  reduce = {
    usd_per_could_sponsor: ->(d){d.usd / d.could_count},
    usd_per_did_sponsor:   ->(d){d.usd / d.did_count},
  }
  map = {
    usd: where(->(d){d.type == :did_member_sponsor}, sum{|d| d.amount * dollars_per_locale_currency_unit(d.locale)}),
    could_count: count{|d| d.type == :could_member_sponsor},
    did_count:   count{|d| d.type ==   :did_member_sponsor}
  }
  # :usd_per_did_sponsor,   {sum{|d| d.amount * dollars_per_locale_currency_unit(d.locale)} / count{|d| d.type ==   :did_member_sponsor}}
end