class ActionDispatch::Http::ParameterFilter

def compile_filter
  strings, regexps, blocks = [], [], []
  @filters.each do |item|
    case item
    when NilClass
    when Proc
      blocks << item
    when Regexp
      regexps << item
    else
      strings << item.to_s
    end
  end
  regexps << Regexp.new(strings.join('|'), true) unless strings.empty?
  [regexps, blocks]
end

def compiled_filter
  @compiled_filter ||= begin
    regexps, blocks = compile_filter
    lambda do |original_params|
      filtered_params = {}
      original_params.each do |key, value|
        if regexps.find { |r| key =~ r }
          value = '[FILTERED]'
        elsif value.is_a?(Hash)
          value = filter(value)
        elsif value.is_a?(Array)
          value = value.map { |v| v.is_a?(Hash) ? filter(v) : v }
        elsif blocks.present?
          key = key.dup
          value = value.dup if value.duplicable?
          blocks.each { |b| b.call(key, value) }
        end
        filtered_params[key] = value
      end
      filtered_params
    end
  end
end

def enabled?
  @filters.present?
end

def filter(params)
  if enabled?
    compiled_filter.call(params)
  else
    params.dup
  end
end

def initialize(filters)
  @filters = filters
end