require 'auto_network'

require 'ipaddress'

module AutoNetwork
class Pool

  class PoolExhaustedError < StandardError; end

  # Provide a single instance of this class
  #
  # @return [AutoNetwork::Pool]
  def self.instance
    @myself ||= new
  end

  # @param addr [String] The network address range to use as the address pool.
  #   Defaults to `AutoNetwork.default_pool`
  def initialize(addr = AutoNetwork.default_pool)
    @addr    = addr
    @network = IPAddress.parse(addr)

    @range = @network.hosts
    # Drop the first IP address as it should be reserved for the host system
    @range.shift
  end

  # @return [String] The string representation of the next available address
  # @raise [PoolExhaustedError] There are no remaining addresses in the pool.
  def next
    if @range.empty?
      raise PoolExhaustedError, "No addresses remaining in network address pool #{addr.inspect}"
    end

    addr = @range.shift
    addr.address
  end
end
end