module Gitlab
  module Database
    BINARY_TYPE = if Gitlab::Database.postgresql?
                    # PostgreSQL defines its own class with slightly different
                    # behaviour from the default Binary type.
                    ActiveRecord::ConnectionAdapters::PostgreSQL::OID::Bytea
                  else
                    ActiveRecord::Type::Binary
                  end

    # Class for casting binary data to hexadecimal SHA1 hashes (and vice-versa).
    #
    # Using ShaAttribute allows you to store SHA1 values as binary while still
    # using them as if they were stored as string values. This gives you the
    # ease of use of string values, but without the storage overhead.
    class ShaAttribute < BINARY_TYPE
      PACK_FORMAT = 'H*'.freeze

      # Casts binary data to a SHA1 in hexadecimal.
      def type_cast_from_database(value)
        value = super

        value ? value.unpack(PACK_FORMAT)[0] : nil
      end

      # Casts a SHA1 in hexadecimal to the proper binary format.
      def type_cast_for_database(value)
        arg = value ? [value].pack(PACK_FORMAT) : nil

        super(arg)
      end
    end
  end
end