# Copyright (c) 2020 Contrast Security, Inc. See https://www.contrastsecurity.com/enduser-terms-0317a for more details.
# frozen_string_literal: true

cs__scoped_require 'digest'

module Contrast
  module Utils
    # We use this class to provide hashes for our Request and Finding objects
    # based upon our definitions of uniqueness.
    # While the uniqueness of the request object is something internal to the
    # Ruby agent, the uniqueness of the Finding hash is defined by a
    # specification shared across all agent teams. The spec can be found here:
    # https://bitbucket.org/contrastsecurity/assess-specifications/src/master/vulnerability/preflight.md
    class HashDigest < Digest::Class
      include Digest::Instance

      CONTENT_LENGTH_HEADER = 'Content-Length'
      CRYPTO_RULES = %w[
        crypto-bad-ciphers
        crypto-bad-mac
      ].cs__freeze
      CONFIG_PATH_KEY = 'path'
      CONFIG_SESSION_ID_KEY = 'sessionId'
      CLASS_SOURCE_KEY = 'source'
      CLASS_CONSTANT_NAME_KEY = 'name'
      CLASS_LINE_NO_KEY = 'lineNo'
      class << self
        def generate_request_hash request
          hash = new
          hash.update(request.request_method)
          hash.update(request.normalized_uri)
          request.parameters.each_key do |name|
            hash.update(name)
          end
          cl = request.normalized_request_headers[CONTENT_LENGTH_HEADER]
          hash.update(request.normalized_length_header(cl)) if cl
          hash.finish
        end

        def generate_event_hash finding, source
          return generate_dataflow_hash(finding) if finding.events.length.to_i > 1

          id = finding.rule_id
          return generate_crypto_hash(finding, source) if CRYPTO_RULES.include?(id)

          generate_trigger_hash(finding)
        end

        def generate_config_hash finding
          hash = new
          hash.update(finding.rule_id)
          path = finding.properties[CONFIG_PATH_KEY]
          hash.update(path)
          method = finding.properties[CONFIG_SESSION_ID_KEY]
          hash.update(method)
          hash.finish
        end

        def generate_class_scanning_hash finding
          hash = new
          hash.update(finding.rule_id)
          module_name = finding.properties[CLASS_SOURCE_KEY]
          hash.update(module_name)
          # We're not currently collecting this. 30/7/19 HM
          line_no = finding.properties[CLASS_LINE_NO_KEY]
          hash.update(line_no)
          field = finding.properties[CLASS_CONSTANT_NAME_KEY]
          hash.update(field)
          hash.finish
        end

        def generate_crypto_hash finding, algorithm
          hash = new
          hash.update(finding.rule_id)
          hash.update(algorithm)
          hash.update_on_request
          hash.finish
        end

        def generate_dataflow_hash finding
          hash = new
          hash.update(finding.rule_id)
          hash.update_on_sources(finding.events)
          hash.update_on_request
          hash.finish
        end

        def generate_response_hash finding
          hash = new
          hash.update(finding.rule_id)
          hash.update_on_request
          hash.finish
        end

        def generate_trigger_hash finding
          hash = new
          hash.update(finding.rule_id)
          hash.update_on_request
          hash.finish
        end
      end

      def update_on_request
        context = Contrast::Agent::REQUEST_TRACKER.current
        return unless context

        route = context.route
        request = context.request
        if route
          update(route.route)
          update(route.verb)
        elsif request
          update(request.normalized_uri)
          update(request.request_method)
        end
      end

      def update_on_sources events
        return unless events&.any?

        events.each do |event|
          event.event_sources.each do |source|
            update(source.type)
            update(source.name)
          end
        end
      end

      def initialize
        @crc32 = 0
      end

      def update str
        return unless str

        @crc32 = Zlib.crc32(str, @crc32)
      end

      def reset
        @crc32 = 0
      end

      def finish
        @crc32.to_s
      end
    end
  end
end