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

require 'contrast/utils/os'
require 'digest'
require 'socket'

module Contrast
  module Utils
    # Tools for supporting the Telemetry feature
    module Telemetry
      # Gets info about the instrumented application required to build unique identifiers,
      # used in the agent's Telemetry.
      module Identifier
        MAC_REGEX = /^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})$/.cs__freeze
        LINUX_OS_REG = /hwaddr=.*?(([A-F0-9]{2}:){5}[A-F0-9]{2})/im.cs__freeze
        MAC_OS_PRIMARY = 'en0'.cs__freeze
        LINUX_PRIMARY = 'enp'.cs__freeze

        # Sinatra and Grape both use similar approach to identify the app_name.
        # Rails has a different way of doing it, but to unify this we'll use this one.
        # If app_name is changed/renamed during production it would still get the
        # new folder's name.
        #
        # @ return [String] name of the application from the current working directory
        def self.app_name
          @_app_name ||= File.basename(Dir.pwd)
        end

        # Returns the MAC address of the primary network interface, depending on the used OS.
        # If the primary is unknown it finds the first available network interface and gets it's
        # MAC address instead.
        #
        # @return [String, nil] MAC address of the primary network interface or
        # the first available one, or nil if nothing found
        def self.mac
          primary = Contrast::Utils::OS.mac? ? MAC_OS_PRIMARY : LINUX_PRIMARY
          @_mac = find_mac(primary) || find_mac
        end

        def self.application_id
          @_application_id ||= begin
            id = nil
            mac = Contrast::Utils::Telemetry::Identifier.mac
            app_name = Contrast::Utils::Telemetry::Identifier.app_name
            id = mac + app_name if mac && app_name
            Digest::SHA2.new(256).hexdigest(id || "_#{ SecureRandom.uuid }")
          end
        end

        def self.instance_id
          @_instance_id ||= Digest::SHA2.new(256).hexdigest(Contrast::Utils::Telemetry::Identifier.mac ||
                                                              "_#{ SecureRandom.uuid }")
        end

        class << self
          private

          # Finds the primary MAC address of all listed network adapters.
          # If primary is not set or unknown, use the first MAC address found
          # from the listed adapters.
          #
          # @param primary [nil, String] optional param if set look only for primary
          # network adapter's name
          # @return [String, nil] MAC address of the first listed network adapter or
          # nil if not found
          def find_mac primary = nil
            result = nil
            idx = 0
            return if interfaces.empty?

            while idx < interfaces.length
              addr = interfaces[idx].addr
              name = interfaces[idx].name # rubocop:disable Security/Module/Name
              idx += 1
              next if primary && !name.include?(primary)

              # retrieving MAC address from primary network interface or first available
              mac = retrieve_mac addr
              next unless mac

              result = mac if mac && (mac.match? MAC_REGEX)
              break if result
            end
            result
          end

          # Retrieves MAC address for primary or any network interface.
          # This is OS dependent search.
          #
          # @param addr [String] address info
          # example: #<Addrinfo: LINK[en0 aa:bb:cc:00:11:22]>
          # @return mac [nil, String] MAC address of primary network interface,
          # any network interface, or nil if no interface is found.
          def retrieve_mac addr
            # Mac OS allow us to use getnameinfo(sockaddr [, flags]) => [hostname, servicename]
            #
            # returned address:
            # <Socket::Ifaddr en0 UP,BROADCAST,RUNNING,NOTRAILERS,SIMPLEX,MULTICAST LINK[en0 aa:bb:cc:00:11:22]>
            return addr.getnameinfo[0] if Contrast::Utils::OS.mac?

            # In Linux using Socket::addr#getnameinfo results in ai_family not supported exception.
            # In this case we are relying on match filtering of addresses.
            #
            # returned address:
            # #<Socket::Ifaddr eth0 UP,BROADCAST,RUNNING,MULTICAST,0x10000
            # PACKET[protocol=0 eth0 hatype=1 HOST hwaddr=aa:bb:cc:00:11:22]>
            return Regexp.last_match(1) if addr.inspect =~ LINUX_OS_REG

            nil
          end

          # Returns array of network interfaces.
          # This is OS dependent search.
          #
          # @return interfaces [Array] Returns an array of interface addresses.
          # Socket::Ifaddr - represents a result of getifaddrs().
          def interfaces
            @_interfaces ||= []

            return @_interfaces unless @_interfaces.empty?

            arr = Socket.getifaddrs
            idx = 0
            check_family = 0
            while idx < arr.length
              # We need only network adapters MACs. Checking for pfamily of every socket address:
              # 18 for Mac OS and 17 for Linux.
              # family should be an address family such as: :INET, :INET6, :UNIX, etc.
              check_family = 18 if Contrast::Utils::OS.mac?
              check_family = 17 if Contrast::Utils::OS.linux?
              if arr[idx].addr.pfamily != check_family
                idx += 1
                next
              end
              @_interfaces << arr[idx]
              idx += 1
            end
            @_interfaces
          end
        end
      end
    end
  end
end