class Sinatra::Base

def safe_ignore(ignore)
  unsafe_ignore = []
  ignore = ignore.gsub(/%[\da-fA-F]{2}/) do |hex|
    unsafe_ignore << hex[1..2]
    ''
  end
  unsafe_patterns = unsafe_ignore.map do |unsafe|
    chars = unsafe.split(//).map do |char|
      if char =~ /[A-Z]/
        char <<= char.tr('A-Z', 'a-z')
      end
      char
    end
    "|(?:%[^#{chars[0]}].|%[#{chars[0]}][^#{chars[1]}])"
  end
  if unsafe_patterns.length > 0
    "((?:[^#{ignore}/?#%]#{unsafe_patterns.join()})+)"
  else
    "([^#{ignore}/?#]+)"
  end
end