class ActiveSupport::ParameterFilter::CompiledFilter

def self.compile(filters, mask:)
  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 << Regexp.escape(item.to_s)
    end
  end
  deep_regexps = regexps.extract! { |r| r.to_s.include?("\\.") }
  deep_strings = strings.extract! { |s| s.include?("\\.") }
  regexps << Regexp.new(strings.join("|"), true) unless strings.empty?
  deep_regexps << Regexp.new(deep_strings.join("|"), true) unless deep_strings.empty?
  new regexps, deep_regexps, blocks, mask: mask
end

def call(params, parents = [], original_params = params)
  filtered_params = params.class.new
  params.each do |key, value|
    filtered_params[key] = value_for_key(key, value, parents, original_params)
  end
  filtered_params
end

def initialize(regexps, deep_regexps, blocks, mask:)
  @regexps = regexps
  @deep_regexps = deep_regexps.any? ? deep_regexps : nil
  @blocks = blocks
  @mask = mask
end

def value_for_key(key, value, parents = [], original_params = nil)
  parents.push(key) if deep_regexps
  if regexps.any? { |r| r.match?(key) }
    value = @mask
  elsif deep_regexps && (joined = parents.join(".")) && deep_regexps.any? { |r| r.match?(joined) }
    value = @mask
  elsif value.is_a?(Hash)
    value = call(value, parents, original_params)
  elsif value.is_a?(Array)
    # If we don't pop the current parent it will be duplicated as we
    # process each array value.
    parents.pop if deep_regexps
    value = value.map { |v| value_for_key(key, v, parents, original_params) }
    # Restore the parent stack after processing the array.
    parents.push(key) if deep_regexps
  elsif blocks.any?
    key = key.dup if key.duplicable?
    value = value.dup if value.duplicable?
    blocks.each { |b| b.arity == 2 ? b.call(key, value) : b.call(key, value, original_params) }
  end
  parents.pop if deep_regexps
  value
end