class ActionDispatch::Http::ParameterFilter::CompiledFilter

def self.compile(filters)
  return lambda { |params| params.dup } if filters.empty?
  strings, regexps, blocks = [], [], []
  filters.each do |item|
    case item
    when Proc
      blocks << item
    when Regexp
      regexps << item
    else
      strings << item.to_s
    end
  end
  regexps << Regexp.new(strings.join('|'), true) unless strings.empty?
  new regexps, blocks
end

def call(original_params)
  filtered_params = {}
  original_params.each do |key, value|
    if regexps.any? { |r| key =~ r }
      value = FILTERED
    elsif value.is_a?(Hash)
      value = call(value)
    elsif value.is_a?(Array)
      value = value.map { |v| v.is_a?(Hash) ? call(v) : v }
    elsif blocks.any?
      key = key.dup if key.duplicable?
      value = value.dup if value.duplicable?
      blocks.each { |b| b.call(key, value) }
    end
    filtered_params[key] = value
  end
  filtered_params
end

def initialize(regexps, blocks)
  @regexps = regexps
  @blocks  = blocks
end