# Copyright (c) 2021 Contrast Security, Inc. See https://www.contrastsecurity.com/enduser-terms-0317a for more details.
# frozen_string_literal: true

require 'contrast/agent/inventory/dependencies'
require 'contrast/components/interface'
require 'contrast/utils/object_share'
require 'set'

module Contrast
  module Agent
    module Inventory
      # Used to analyze class usage for reporting
      class DependencyUsageAnalysis
        include Singleton
        include Contrast::Components::Interface
        include Contrast::Agent::Inventory::Dependencies

        access_component :analysis, :config, :logging

        def initialize
          return unless enabled?

          @lock = Mutex.new
          @lock.synchronize { @gemdigest_cache = Hash.new { |hash, key| hash[key] = Set.new } }
        end

        # This method is invoked once, along with the rest of our catchup code to report libraries and their associated
        # files that have already been loaded pre-contrast.
        def catchup
          return unless enabled?

          loaded_specs.each do |_name, spec|
            # Get a digest of the Gem file itself.
            next unless (digest = Contrast::Utils::Sha256Builder.instance.build_from_spec(spec))

            loaded_files_from_gem = $LOADED_FEATURES.select { |f| f.start_with?(spec.full_gem_path) }

            new_files = loaded_files_from_gem.each_with_object(Set.new) do |file_path, set|
              set << adjust_path_for_reporting(file_path, spec)
              logger.trace('Recording loaded file for inventory analysis', line: file_path)
            end

            # Even if new_files is empty, still need to add digest key for library discovery.
            @lock.synchronize { @gemdigest_cache[digest].merge(new_files) }
          end
        end

        # This method is invoked once per TracePoint :end - to map a specific file being required to the gem to which
        # it belongs.
        #
        # @param path [String] the result of TracePoint#path from the :end event in which the Module was defined.
        def associate_file path
          return unless enabled?

          spec_lookup_path = adjust_path_for_spec_lookup(path)

          spec = Gem::Specification.find_by_path(spec_lookup_path)
          unless spec
            logger.debug('Unable to resolve gem spec for path', path: path)
            return
          end

          digest = Contrast::Utils::Sha256Builder.instance.build_from_spec(spec)
          unless digest
            logger.debug('Unable to resolve digest for gem spec', spec: spec.to_s)
            return
          end
          report_path = adjust_path_for_reporting(path, spec)
          @lock.synchronize { @gemdigest_cache[digest] << report_path }
        rescue StandardError => e
          logger.error('Unable to inventory file path', e, path: path)
        end

        # Populate the library_usages field of the Activity message using the data stored in the @gemdigest_cache.
        #
        # @param activity [Contrast::Api::Dtm::Activity] the message to which to append the usage data
        def generate_library_usage activity
          return unless enabled?
          return unless activity

          # Copy gemdigest_cache and clear it in sync.
          gem_spec_digest_to_files = @lock.synchronize do
            copy = @gemdigest_cache.dup
            @gemdigest_cache.clear
            copy
          end

          gem_spec_digest_to_files.each_pair do |digest, files|
            usage = Contrast::Api::Dtm::LibraryUsageUpdate.build(digest, files)
            activity.library_usages[usage.hash_code] = usage
          end
        rescue StandardError => e
          logger.error('Unable to generate library usage.', e)
        end

        private

        def adjust_path_for_spec_lookup path
          idx = path.index('/lib/')
          path = path[(idx + 4)..-1] if idx
          path
        end

        def adjust_path_for_reporting path, gem_spec
          path.delete_prefix(gem_spec.full_gem_path)
        end

        # We only use this if inventory and library analysis are enabled
        def enabled?
          @_enabled = INVENTORY.enabled? && INVENTORY.analyze_libraries? if @_enabled.nil?
          @_enabled
        end
      end
    end
  end
end