# Copyright (c) 2022 Contrast Security, Inc. See https://www.contrastsecurity.com/enduser-terms-0317a for more details.
# frozen_string_literal: true

require 'contrast/agent/assess/rule/response/base_rule'
require 'contrast/utils/string_utils'

module Contrast
  module Agent
    module Assess
      module Rule
        module Response
          # These rules check the content of the HTTP Response to determine if the body contains a form which
          # incorrectly sets the action attribute.
          class ParametersPollution < BaseRule
            def rule_id
              'parameter-pollution'
            end

            protected

            # Rules discern which responses they can/should analyze.
            #
            # @param response [Contrast::Agent::Response] the response of the application
            def analyze_response? response
              super && body?(response)
            end

            # Determine if the Response violates the Rule or not. If it does, return the evidence that proves it so.
            #
            # @param response [Contrast::Agent::Response] the response of the application
            # @return [Hash, nil] the evidence required to prove the violation of the rule
            def violated? response
              body = response.body
              forms = forms(body)
              forms.each do |form|
                # Because TeamServer will reject any subsequent form on the same page due to deduplication, we can
                # skip out on the first violation.
                return form if action?(form[HTML_PROP])
              end
              nil
            end

            def accepted_values
              [/action="[^"]/i, /action='[^']/i, /action=[^\\'"]/i, /action=[^\s<>'"]/i].cs__freeze
            end

            def action? form
              return true unless /action=/i.match?(form)

              accepted_values.each do |off_value|
                return false if form.match?(off_value)
              end
              true
            end
          end
        end
      end
    end
  end
end