# frozen_string_literal: true

require "snmp"

class Netdisco
  class SNMP
    class NetdiscoError < StandardError; end

    class NoResponse < NetdiscoError; end

    # 类对象初始化入口函数
    def initialize(host, community = CFG.snmp.community, timeout = CFG.snmp.timeout, retries = CFG.snmp.retries)
      @host = host
      @snmp = ::SNMP::Manager.new(Host: @host, Community: community, Timeout: timeout, Retries: retries, MibModules: [])
    end

    # Closes the SNMP connection
    # @return [void]
    def close
      @snmp.close
    end

    # 查询某个 oid 监控值
    # Gets one oid, return value
    # @param [String] oid to get
    # @return [SNMP::VarBind]
    def get(oid)
      mget([oid]).first
    end

    # 批量查询多个 oids 监控值
    # Get multiple oids, return array of values
    # @param [Array(String)] oids to get
    # @return [SNMP::VarBindList]
    def mget(oids)
      snmp :get, oids
    end

    # 遍历 root_oid 监控值
    # Bulkwalk everything below root oid
    # @param [String] root oid to start from
    # @return [Array(SNMP::VarBind)]
    def bulkwalk(root)
      # 初始化变量
      last, oid, results = false, root.dup, []
      # 将点分10进制字串转换为数组对象
      root = root.split(".").map { |chr| chr.to_i }
      # 遍历 root_oid
      until last
        vbs = snmp(:get_bulk, 0, CFG.snmp.bulkrows, oid).varbind_list
        vbs.each do |vb|
          oid = vb.oid
          # 解析到的 oid 不匹配 root 跳出循环
          (last = true; break) unless oid[0..root.size - 1] == root
          results << vb
        end
      end
      results
    end

    # 将遍历的 root 监控值转换为 VBHash 样式
    # bulkwalks oid and returns hash with oid as key
    # @param [String] oid root oid to walk
    # @yield [VBHash] hash containing oids found
    # @return [Hash] resulting hash
    def hashwalk(oid, &block)
      hash = VBHash.new
      bulkwalk(oid).each do |vb|
        # value, key = block.call(vb)
        # key       ||= vb.oid
        hash[vb.oid] = vb
      end
      hash
    end

    private
      def snmp(method, *args)
        @snmp.send method, *args
      rescue ::SNMP::RequestTimeout, Errno::EACCES => e
        msg = "host '#{@host}' raised '#{e.class}' with message '#{e.message}' for method '#{method}' with args '#{args}'"
        Log.warn msg
        raise NoResponse, msg
      end

      # Hash with some helper methods to easier work with VarBinds
      class VBHash < Hash
        alias :org_bracket :[]
        undef :[]

        # 精确查询
        # @param [Array(Strin, Array)] oid root oid under which you want all oids below it
        # @return [VBHash] oids which start with param oid
        def by_oid(*oid)
          oid      = arg_to_oid(*oid)
          hash     = select do |key, value|
            key[0..oid.size - 1] == oid
          end
          new_hash = VBHash.new
          new_hash.merge hash
        end

        # 模糊匹配
        # @param [Array(String, Array)] args partial match 3.4.6 would match to 1.2.3.4.6.7.8
        # @return [SNMP::VarBind, nil] matching element
        def by_partial(*args)
          oid = arg_to_oid(*args)
          # got = nil
          keys.each do |key|
            return self[key] if key.each_cons(oid.size).find { |e| e == oid }
            # if key.each_cons(oid.size).find { |e| e == oid }
            #   got = self[key]
            #   break
            # end
          end
          nil
        end

        # @param [Array[String, Array)] key which you want, multiple arguments compiled into single key
        # @return [SNMP::VarBind] matching element
        def [](*args)
          org_bracket arg_to_oid(*args)
        end

        private
          def arg_to_oid(*args)
            # FIXME && TODO
            key = []
            args.each do |arg|
              if Array === arg
                key += arg.map { |e| e.to_i }
              elsif Fixnum === arg
                key << arg
              else
                key += arg.split(".").map { |e| e.to_i }
              end
            end
            key
          end
      end
  end
end

module SNMP
  class VarBind
    # @return [String] VarBind value as IP address
    def as_ip
      SNMP::IpAddress.new(value).to_s
    end

    # @param [String] root oid which is removed from self.oid
    # @return [Array] oid remaining after specified root oid
    def oid_id(root)
      root = root.split(".").map { |e| e.to_i }
      oid[root.size..-1]
    end
  end
end