# 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/policy/trigger_validation/trigger_validation'
require 'contrast/agent/excluder'
require 'contrast/components/logger'
require 'contrast/utils/object_share'
require 'contrast/utils/sha256_builder'
require 'contrast/utils/assess/trigger_method_utils'
require 'contrast/agent/assess/events/event_data'
require 'contrast/agent/reporting/reporting_events/preflight'
require 'contrast/agent/reporting/reporting_events/application_activity'
require 'contrast/agent/reporting/reporting_events/preflight_message'
require 'contrast/agent/reporting/reporting_events/route_discovery'
require 'contrast/agent/reporting/reporting_utilities/reporting_storage'
require 'contrast/agent/reporting/reporting_utilities/build_preflight'
require 'contrast/utils/assess/event_limit_utils'

module Contrast
  module Agent
    module Assess
      module Policy
        # A trigger method is one which can perform a dangerous action, as described by the
        # Contrast::Agent::Assess::Policy::TriggerNode class. Each such method will call to this module just after
        # invocation in order to determine if the call was done safely. In those cases where it was not, a Finding
        # report is issued to TeamServer.
        module TriggerMethod
          extend Contrast::Components::Logger::InstanceMethods
          extend Contrast::Utils::Assess::TriggerMethodUtils
          extend Contrast::Utils::Assess::EventLimitUtils

          # Rules that always exists outside of Request Context
          # @return [Array<String>]
          NON_REQUEST_RULES = [
            'hardcoded-password', # Contrast::Agent::Assess::Rule::Provider::HardcodedPassword.NAME,
            'hardcoded-key' # Contrast::Agent::Assess::Rule::Provider::HardcodedKey.NAME
          ].cs__freeze

          class << self
            # This is called from within our woven proc. It will be called as if it were inline in the Rack
            # application.
            #
            # @param trigger_node [Contrast::Agent::Assess::Policy::TriggerNode] the node that applies to the method
            #   being called
            # @param object [Object] the Object on which the method was invoked
            # @param ret [Object] the Return of the invoked method
            # @param args [Array<Object>] the Arguments with which the method was invoked
            def apply_trigger_rule trigger_node, object, ret, args
              return if trigger_node.nil?
              return if event_limit_for_rule?(trigger_node.rule_id)

              context = Contrast::Agent::REQUEST_TRACKER.current
              # return if there is no context and the flag is set to default => false
              # we need to have request if the flag is default
              # else proceed, if the flag is true we don't need to check for context we
              # go as currently.
              # When outside of a request, only track when the feature is enabled
              return unless context ||
                  Contrast::ASSESS.non_request_tracking? ||
                  NON_REQUEST_RULES.include?(trigger_node.rule_id)

              if trigger_node.sources&.any?
                trigger_node.sources.each do |marker|
                  source = determine_source(marker, object, ret, args)
                  apply_trigger(trigger_node, source, object, ret, *args)
                end
              else
                apply_trigger(trigger_node, nil, object, ret, *args)
              end
            end

            def apply_eval_trigger trigger_node, source, object, ret, *args
              apply_trigger(trigger_node, source, object, ret, *args)
            end

            # This converts the source of the finding, and the events leading up to it into a Finding
            #
            # @param trigger_node [Contrast::Agent::Assess::Policy::TriggerNode] the node to direct applying this
            #   trigger event
            # @param source [Object] the source of the Trigger Event
            # @param object [Object] the Object on which the method was invoked
            # @param ret [Object, nil] the Return of the invoked method, or nil if void method
            # @param args [Array<Object>] the Arguments with which the method was invoked
            # @return [Contrast::Agent::Reporting::Finding, nil] the finding to send to TeamServer if found
            def build_finding trigger_node, source, object, ret, *args
              content_type = Contrast::Agent::REQUEST_TRACKER.current&.response&.content_type
              if content_type.nil? && trigger_node.collectable?
                Contrast::Agent::FINDINGS.collect_finding(trigger_node, source, object, ret, *args)
                return
              end
              return unless Contrast::Agent::Assess::Policy::TriggerValidation.valid?(trigger_node, object, ret, args)

              request = find_request(source)
              return unless reportable?(request&.env)
              return if excluded_by_url_and_rule?(request, trigger_node.rule_id)

              finding = Contrast::Agent::Reporting::Finding.new(trigger_node.rule_id)
              finding.attach_data(trigger_node, source, object, ret, request, *args)
              return if excluded_by_input_and_rule?(request, finding, trigger_node.rule_id)

              finding.hash_code = Contrast::Utils::HashDigest.generate_event_hash(finding, source, request)
              finding
            rescue StandardError => e
              logger.error('Unable to build a finding', e, rule: trigger_node.rule_id, node_id: trigger_node.id)
              nil
            end

            # Given a finding, append it to an activity message and send it to the TeamServer for processing. If an
            # activity message does not exist, b/c we're invoked outside of a request context, build an activity and
            # immediately report it with the finding.
            #
            # @param finding [Contrast::Agent::Reporting::Finding] the Finding to report.
            def report_finding finding
              return unless finding

              preflight = Contrast::Agent::Reporting::BuildPreflight.generate(finding)
              return unless preflight

              preflight_data = preflight.messages[0].data
              return if Contrast::Agent::REQUEST_TRACKER.current&.reported_findings&.include?(preflight_data)

              Contrast::Agent::Reporting::ReportingStorage[preflight.messages[0].data] = finding
              if Contrast::Agent::REQUEST_TRACKER.current
                Contrast::Agent::REQUEST_TRACKER.current.reported_findings << preflight_data
              end
              Contrast::Agent.reporter&.send_event(preflight)
            end

            private

            def settings
              Contrast::Agent::FeatureState.instance
            end

            # Given the marker from the trigger_node (the pointer indicating the entity from which the taint
            # originated), return the entity on which this trigger needs to operate.
            #
            # In an effort to speed up this lookup, we've changed the marker for parameters to be implicit - if it is
            # not a return or an object, it must be a parameter, which we can reference by index.
            #
            # @param marker [String] the source marker that indicates which Object
            # @param object [Object] the Object on which the method was invoked
            # @param ret [Object] the Return of the invoked method
            # @param args [Array<Object>] the Arguments with which the method was invoked
            # @return [Object] the literal object that this Trigger Event verifies
            def determine_source marker, object, ret, args
              case marker
              when Contrast::Utils::ObjectShare::RETURN_KEY
                ret
              when Contrast::Utils::ObjectShare::OBJECT_KEY
                object
              else # 'P'
                if marker.is_a?(Integer)
                  args[marker]
                else
                  arg = nil
                  args.each do |search|
                    next unless search.is_a?(Hash)

                    arg = search[marker]
                    break if arg
                  end
                  arg
                end
              end
            end

            def build_events finding, event
              return unless event

              event.parent_events&.each do |parent_event|
                build_events(finding, parent_event)
              end
              # events could technically be nil, but we would have failed the rule check before getting here. not
              # worth the nil check
              finding.events << event.to_dtm_event
            end

            # Check if the finding should be excluded due to the assess exclusion rules.
            #
            # @param request [Contrast::Agent::Request] a wrapper around the Rack::Request for the current request
            # @param rule_id [String]
            # return [Boolean]
            def excluded_by_url_and_rule? request, rule_id
              Contrast::SETTINGS.excluder.assess_excluded_by_url_and_rule?(request, rule_id)
            end

            def excluded_by_input_and_rule? request, finding, rule_id
              Contrast::SETTINGS.excluder.assess_excluded_by_input_and_rule?(request, finding, rule_id)
            end
          end
        end
      end
    end
  end
end