# frozen_string_literal: true

# 加载项目依赖
require_relative "netdisco/config"
require_relative "netdisco/poll_map"
require_relative "netdisco/name_map"
require_relative "netdisco/peer"
require_relative "netdisco/method/xdp"
require_relative "netdisco/dns"
require_relative "netdisco/output"

class Netdisco
  class NetdiscoError < StandardError; end

  class MethodNotFound < NetdiscoError; end

  # 类对象方法属性
  attr_reader :hosts

  # 类对象初始化函数
  def initialize
    @methods = []
    @hosts   = {}
    @poll    = PollMap.new

    # 动态加载邻居发现协议
    CFG.use.each do |method|
      method = File.basename method.to_s
      file   = "netdisco/method/#{method.downcase}"
      require_relative file
      @methods << Netdisco.const_get(method)
    rescue NameError, LoadError
      raise MethodNotFound, "unable to find method '#{method}'"
    end
  end

  # @param [String] host host to start discover from
  # @return [Netdisco::Output]
  def discover(host)
    recurse host
    Output.new @hosts, @poll
  end

  # @param [String] host host to get list of peers from
  # @return [Array] list of peers seen connected to host
  def neighbors(host)
    peers = []
    # 不同协议可能发现相同的联结关系，处理完成后根据 ip 自动去重
    @methods.each do |method|
      peers << method.send(:peers, host)
    end
    peers.flatten.uniq { |peer| peer.ip }
  end

  # Given string of IP address, recurses through peers seen and populates @hosts hash
  # @param [String] host host to start recurse from
  # @return [void]
  def recurse(host)
    # 第一步获取设备的邻居关系，同时将邻居关系缓存下来
    @hosts[host] = peers = neighbors(host)
    # 第二步遍历邻居的邻居关系
    peers.each do |peer|
      # 自动跳过已发现设备IP
      next if @hosts.has_key? peer.ip
      next unless @poll.include? peer.ip
      # 发现邻居关系
      discover peer.ip
    end
  end
end