class Inspec::Resources::Routingtable

def fetch_routing_information
  # check if netstat is available on the system
  utility = find_netstat_or_error
  # the command to fetch the routing information
  fetch_route_cmd = "#{utility} -rn"
  # execute the above netstat command
  cmd = inspec.command(fetch_route_cmd)
  # raise error if the exit status is not zero;
  raise Inspec::Exceptions::ResourceFailed, "Executing netstat failed: #{cmd.stderr}" if cmd.exit_status.to_i != 0
  # Todo:
  # Improve logic to fetch destination, gateway & interface efficiently.
  # The below logic assumes the following:
  # 1. destination, gateway & interface header is present as Destination, Gateway & (Iface or Netif or Interface) respectively.
  #    (Netif on BSD, Darwin,Iface on linux & Interface on Windows)
  # 2. there is no blank data for any columns or the blank data are present after the interface column.
  # cmd.stdout is the standard out of netstat -rn; split on new line to get the rows
  raw_route_info = cmd.stdout.split("\n")
  # since raw_route_info contains some row before the header (i.e. Destination Gateway ...); remove those rows
  raw_route_info.shift until raw_route_info[0] =~ /Destination/i
  # split each rows based on space to get the individual columns
  # raw_route_info is now array of arrays with the routing information
  raw_route_info.map! { |info| info.strip.split }
  # these variables will store the indices where destination, gateway and interface are present
  destination_index, gateway_index, interface_index = -1, -1, -1
  # The headers in windows are as:
  # Network Destination        Netmask          Gateway       Interface  Metric
  # Splitting on space makes "Network Destination" to be two separate values as "Network" & "Destination"
  # Remove "Network" value to apply the logic of finding index
  raw_route_info[0].shift if inspec.os.windows?
  # find the indices of destination, gateway and interface;
  # because the position of gateway & interface varies with operating system
  raw_route_info[0].each_with_index do |header, index|
    if header =~ /Destination/i
      destination_index = index
    elsif header =~ /Gateway/i
      gateway_index = index
    elsif header =~ /Iface|Netif|Interface/i
      interface_index = index
    end
  end
  # remove the initial header consisting of Destination, Gateway, Mask, ... since this is of no use
  raw_route_info.shift
  # check the indices are assigned with some index and not -1
  if destination_index != -1 && gateway_index != -1 && interface_index != -1
    # iterate through the route_info; and find destination, gateway and interface from each row
    raw_route_info.each do |info|
      # if value exists at the destination_index, gateway_index, and interface_index; store the value in @routing_info
      if !info[destination_index].nil? && !info[gateway_index].nil? && !info[interface_index].nil?
        # if the destination_key is already present, append the gateway & interface; else create new array and add them
        if @routing_info.key?(info[destination_index])
          @routing_info[info[destination_index]] << [info[gateway_index], info[interface_index]]
        else
          @routing_info[info[destination_index]] = [[info[gateway_index], info[interface_index]]]
        end
      end
    end
  end
end

def find_netstat_or_error
  %w{/usr/sbin/netstat /sbin/netstat /usr/bin/netstat /bin/netstat netstat}.each do |cmd|
    return cmd if inspec.command(cmd).exist?
  end
  raise Inspec::Exceptions::ResourceFailed, "Could not find `netstat` utility to view routing table information"
end

def has_entry?(input_route)
  # check if the destination, gateway, interface exists as part of the routing_info
  if input_route.key?(:destination) && input_route.key?(:gateway) && input_route.key?(:interface)
    # check if there is key with destination's value in hash;
    # if yes, check if destination and gateway is present else return false
    @routing_info.key?(input_route[:destination]) ? @routing_info[input_route[:destination]].include?([input_route[:gateway], input_route[:interface]]) : false
  else
    raise Inspec::Exceptions::ResourceSkipped, "One or more missing key, have_entry? matcher expects a hash with 3 keys: destination, gateway and interface"
  end
end

def initialize
  skip_resource "The `routing_table` resource is not yet available on your OS." unless inspec.os.unix? || inspec.os.windows?
  # fetch the routing information and store it in @routing_info (could be hash, tbd)
  @routing_info = {}
  fetch_routing_information
end

def to_s
  "routing_table"
end