class Psych::ScalarScanner

def initialize
  @string_cache = {}
end

def parse_time string
  date, time = *(string.split(/[ tT]/, 2))
  (yy, m, dd) = date.split('-').map { |x| x.to_i }
  md = time.match(/(\d+:\d+:\d+)(?:\.(\d*))?\s*(Z|[-+]\d+(:\d\d)?)?/)
  (hh, mm, ss) = md[1].split(':').map { |x| x.to_i }
  us = (md[2] ? Rational("0.#{md[2]}") : 0) * 1000000
  time = Time.utc(yy, m, dd, hh, mm, ss, us)
  return time if 'Z' == md[3]
  return Time.at(time.to_i, us) unless md[3]
  tz = md[3].match(/^([+\-]?\d{1,2})\:?(\d{1,2})?$/)[1..-1].compact.map { |digit| Integer(digit, 10) }
  offset = tz.first * 3600
  if offset < 0
    offset -= ((tz[1] || 0) * 60)
  else
    offset += ((tz[1] || 0) * 60)
  end
  Time.at((time - offset).to_i, us)
end

def tokenize string
  return nil if string.empty?
  return string if @string_cache.key?(string)
  case string
  when /^[A-Za-z~]/
    if string.length > 5
      @string_cache[string] = true
      return string
    end
    case string
    when /^[^ytonf~]/i
      @string_cache[string] = true
      string
    when '~', /^null$/i
      nil
    when /^(yes|true|on)$/i
      true
    when /^(no|false|off)$/i
      false
    else
      @string_cache[string] = true
      string
    end
  when TIME
    parse_time string
  when /^\d{4}-(?:1[012]|0\d|\d)-(?:[12]\d|3[01]|0\d|\d)$/
    require 'date'
    begin
      Date.strptime(string, '%Y-%m-%d')
    rescue ArgumentError
      string
    end
  when /^\.inf$/i
    1 / 0.0
  when /^-\.inf$/i
    -1 / 0.0
  when /^\.nan$/i
    0.0 / 0.0
  when /^:./
    if string =~ /^:(["'])(.*)\1/
      $2.sub(/^:/, '').to_sym
    else
      string.sub(/^:/, '').to_sym
    end
  when /^[-+]?[0-9][0-9_]*(:[0-5]?[0-9])+$/
    i = 0
    string.split(':').each_with_index do |n,e|
      i += (n.to_i * 60 ** (e - 2).abs)
    end
    i
  when /^[-+]?[0-9][0-9_]*(:[0-5]?[0-9])+\.[0-9_]*$/
    i = 0
    string.split(':').each_with_index do |n,e|
      i += (n.to_f * 60 ** (e - 2).abs)
    end
    i
  when FLOAT
    begin
      return Float(string.gsub(/[,_]/, ''))
    rescue ArgumentError
    end
    @string_cache[string] = true
    string
  else
    if string.count('.') < 2
      begin
        return Integer(string.gsub(/[,_]/, ''))
      rescue ArgumentError
      end
    end
    @string_cache[string] = true
    string
  end
end