P1 of Puzzlenode

puzzlenode_p1.rb

#!/usr/bin/ruby
require 'rubygems'
require 'hpricot'
require 'yaml'
require 'csv'
require 'bigdecimal'

$Conversion = Hash.new
$Transactions = Hash.new
$One = BigDecimal.new('1')

def read_rates(file)
  xml = File.read(file)
  doc, rates = Hpricot::XML(xml), []

  (doc/:rate).each do |p|
     from = (p/:from).inner_text
     to =  (p/:to).inner_text
     conv = (p/:conversion).inner_text
     $Conversion[to] ||= Hash[ to, $One ]
     $Conversion[from] ||= Hash[ from, $One ]
     $Conversion[to][from] = BigDecimal.new(conv)
     $Conversion[from][to] = $One / $Conversion[to][from]
  end
  
  build_full_conversion_table
end

# Build conversion table using BFS
def build_full_conversion_table()
  from = "USD"
  queue = $Conversion[from].keys - [from]
  seen = []
  until queue.empty?
    curr = queue.shift
    seen << curr
    $Conversion[curr].keys.each do |k|
      unless $Conversion[from][k]
        $Conversion[from][k] = $Conversion[from][curr] * $Conversion[curr][k]
        queue << k
      end
    end
  end
  
  $Conversion
end

def convert(amount, from, to = "USD")
  c = amount * $Conversion[to][from]
  return roundIt(c)
end

def roundIt(c)
  c.round(2, BigDecimal::ROUND_HALF_EVEN)
end

def read_transactions(file)
  CSV.foreach(file) do |r|
    store, sku, amount = r
    next if store == 'store' # skip header
    amount, currency = amount.split(" ")
    $Transactions[sku] ||= BigDecimal.new('0')
    $Transactions[sku] += convert(BigDecimal.new(amount), currency)
  end
end

def assert_eq(a, b)
  raise "Assert failed! #{a} != #{b}" unless a == b
end

read_rates("RATES.xml")
read_transactions("TRANS.csv")

puts  ($Transactions["DM1182"]).to_s('F')