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

module Contrast
  module Utils
    # Utilities for encoding and normalizing strings
    class StringUtils
      UTF8 = 'utf-8'
      HTTP_PREFIX = 'HTTP-'

      # Convenience method. We assume that we're working on Strings or tags
      # String representations of things. To that end, we'll to_s anything
      # that comes in before returning its length.
      #
      # But don't worry though, String.to_s just returns self. teehee
      def self.ret_length string
        string.nil? ? 0 : string.to_s.length
      end

      # Protobuf has a very strict typing. Nil is not a String and will throw
      # an exception if you try to set it. Use this to be safe.
      # Uses the object share to avoid creating several new strings per request
      def self.protobuf_safe_string string
        string.nil? ? Contrast::Utils::ObjectShare::EMPTY_STRING : string.to_s
      end

      # Truncate a string to 255 characters max length
      def self.truncate str, default = Contrast::Utils::ObjectShare::EMPTY_STRING
        return default if str.nil?

        str.to_s[0..255]
      end

      def self.force_utf8 str, logger = nil
        return Contrast::Utils::ObjectShare::EMPTY_STRING unless str

        str = str.to_s
        if str.encoding == Encoding::UTF_8
          str = str.encode(UTF8, invalid: :replace, undef: :replace) unless str.valid_encoding?
        else
          str = str.encode(UTF8, str.encoding, invalid: :replace, undef: :replace)
        end
        str.to_s
      rescue StandardError => e
        # We were unable to switch the String to a UTF-8 format.
        # Return non-nil so as not to throw an exception later when trying
        # to do regexp or other compares on the String
        logger&.debug "Unable to change '#{ str }' to valid UTF-8: #{ e.message }"

        Contrast::Utils::ObjectShare::EMPTY_STRING
      end

      # Given a string return a normalized version of that string.
      # Keys are memoized so that the normalization process doesn't need
      # to happen every time.
      def self.normalized_key str
        return nil unless str

        str = str.to_s
        @_normalized_keys ||= {}
        if @_normalized_keys.key?(str)
          @_normalized_keys[str]
        else
          up = str.upcase.strip
          up = up.gsub(/[_-]/, '-')
          up = up[5..-1] if up.start_with?(HTTP_PREFIX)
          @_normalized_keys[str] = up
        end
      end
    end
  end
end