blackjack.rb

require 'net/http'
require 'nokogiri'

#you need Nokogiri for this to work: gem install 'nokogiri'

#fetch html if not cached
html_cache_file = 'blackjack-chart.html'
if File.exist? html_cache_file
  html = File.read(html_cache_file)
else
  html = Net::HTTP.get(URI.parse('http://www.blackjack-chart.com/'))
  File.write(html_cache_file, html)
end

#extract strategy matrix from html
strategy_matrix = Nokogiri::HTML(html).
  css('table#tablepress-3 tr').
  drop(1).
  map{ |tr| 
    tr.css('td').
      map{ |td| td.text }
  }

#extract letter to description lookup from html
advice_legend = Nokogiri::HTML(html).
  css('table#tablepress-4 tr').
  map{ |tr| tr.css('td') }.
  map{ |td| [ td[0].text,td[1].text ] }.
  to_h

#extract lookup index for dealer's card from strategy matrix
dealer_hand_lookup = strategy_matrix.
  take(1).
  flatten.
  drop(1).
  each_with_index.
  map{ |elem,idx| [elem,idx + 1] }.
  to_h

#extract lookup index for player's hand from strategy matrix
player_hand_lookup = strategy_matrix.
  transpose.
  take(1).
  flatten.
  drop(1).
  each_with_index.
  map{ |elem,idx| [elem,idx + 1] }.
  to_h

#read input from console.  try to do some cleanup
puts "What do you have?"
player = gets.chomp.
  upcase.
  split(",").
  sort{|x,y| y <=> x }.
  join(",")
puts "What does the dealer have?"
dealer = gets.chomp.upcase

begin
  player_index = player_hand_lookup[player]
  dealer_index = dealer_hand_lookup[dealer]
  answer = strategy_matrix[player_index][dealer_index]
  readable_answer = advice_legend[answer]
  puts readable_answer
rescue TypeError => e
  puts "player hand valid inputs: #{player_hand_lookup.keys}"
  puts "dealer hand valid inputs: #{dealer_hand_lookup.keys}"
end