class Chronic::Numerizer

def self.numerize(string)
  string = string.dup
  # preprocess
  string.gsub!(/ +|([^\d])-([^\d])/, '\1 \2') # will mutilate hyphenated-words but shouldn't matter for date extraction
  string.gsub!(/a half/, 'haAlf') # take the 'a' out so it doesn't turn into a 1, save the half for the end
  # easy/direct replacements
  DIRECT_NUMS.each do |dn|
    string.gsub!(/#{dn[0]}/i, '<num>' + dn[1])
  end
  ORDINALS.each do |on|
    string.gsub!(/#{on[0]}/i, '<num>' + on[1] + on[0][-2, 2])
  end
  # ten, twenty, etc.
  TEN_PREFIXES.each do |tp|
    string.gsub!(/(?:#{tp[0]}) *<num>(\d(?=[^\d]|$))*/i) { '<num>' + (tp[1] + $1.to_i).to_s }
  end
  TEN_PREFIXES.each do |tp|
    string.gsub!(/#{tp[0]}/i) { '<num>' + tp[1].to_s }
  end
  # hundreds, thousands, millions, etc.
  BIG_PREFIXES.each do |bp|
    string.gsub!(/(?:<num>)?(\d*) *#{bp[0]}/i) { '<num>' + (bp[1] * $1.to_i).to_s}
    andition(string)
  end
  # fractional addition
  # I'm not combining this with the previous block as using float addition complicates the strings
  # (with extraneous .0's and such )
  string.gsub!(/(\d+)(?: | and |-)*haAlf/i) { ($1.to_f + 0.5).to_s }
  string.gsub(/<num>/, '')
end

def andition(string)
  sc = StringScanner.new(string)
  while sc.scan_until(/<num>(\d+)( | and )<num>(\d+)(?=[^\w]|$)/i)
    if sc[2] =~ /and/ || sc[1].size > sc[3].size
      string[(sc.pos - sc.matched_size)..(sc.pos-1)] = '<num>' + (sc[1].to_i + sc[3].to_i).to_s
      sc.reset
    end
  end
end