# encoding: utf-8
# author: Christoph Hartmann
# author: Dominik Richter

# Usage:
# describe host('example.com') do
#   it { should be_resolvable }
#   it { should be_reachable }
#   its(:ipaddress) { should include '93.184.216.34' }
# end
#
# To verify a hostname with protocol and port
# describe host('example.com', port: 53, proto: 'udp') do
#   it { should be_reachable }
# end
#
# We do not support the following serverspec syntax:
# describe host('example.com') do
#   it { should be_reachable.with( :port => 22 ) }
#   it { should be_reachable.with( :port => 22, :proto => 'tcp' ) }
#   it { should be_reachable.with( :port => 53, :proto => 'udp' ) }
#
#   it { should be_resolvable.by('hosts') }
#   it { should be_resolvable.by('dns') }
# end

class Host < Inspec.resource(1)
  name 'host'
  desc 'Use the host InSpec audit resource to test the name used to refer to a specific host and its availability, including the Internet protocols and ports over which that host name should be available.'
  example "
    describe host('example.com') do
      it { should be_reachable }
    end
  "

  def initialize(hostname, params = {})
    @hostname = hostname
    @port = params[:port]   || nil
    @proto = params[:proto] || nil

    @host_provider = nil
    if inspec.os.linux?
      @host_provider = LinuxHostProvider.new(inspec)
    elsif inspec.os.windows?
      @host_provider = WindowsHostProvider.new(inspec)
    else
      return skip_resource 'The `host` resource is not supported on your OS yet.'
    end
  end

  # if we get the IP adress, the host is resolvable
  def resolvable?(type = nil)
    warn "The `host` resource ignores #{type} parameters. Continue to resolve host." if !type.nil?
    resolve.nil? || resolve.empty? ? false : true
  end

  def reachable?(port = nil, proto = nil, timeout = nil)
    fail "Use `host` resource with host('#{@hostname}', port: #{port}, proto: '#{proto}') parameters." if !port.nil? || !proto.nil? || !timeout.nil?
    ping.nil? ? false : ping
  end

  # returns all A records of the IP adress, will return an array
  def ipaddress
    resolve.nil? || resolve.empty? ? nil : resolve
  end

  def to_s
    "Host #{@hostname}"
  end

  private

  def ping
    return @ping_cache if defined?(@ping_cache)
    @ping_cache = @host_provider.ping(@hostname, @port, @proto) if !@host_provider.nil?
  end

  def resolve
    return @ip_cache if defined?(@ip_cache)
    @ip_cache = @host_provider.resolve(@hostname) if !@host_provider.nil?
  end
end

class HostProvider
  attr_reader :inspec
  def initialize(inspec)
    @inspec = inspec
  end
end

class LinuxHostProvider < HostProvider
  # ping is difficult to achieve, since we are not sure
  def ping(hostname, _port = nil, _proto = nil)
    # fall back to ping, but we can only test ICMP packages with ping
    # therefore we have to skip the test, if we do not have everything on the node to run the test
    ping = inspec.command("ping -w 1 -c 1 #{hostname}")
    ping.exit_status.to_i != 0 ? false : true
  end

  def resolve(hostname)
    # TODO: we rely on getent hosts for now, but it prefers to return IPv6, only then IPv4
    cmd = inspec.command("getent hosts #{hostname}")
    return nil if cmd.exit_status.to_i != 0

    # extract ip adress
    resolve = /^\s*(?<ip>\S+)\s+(.*)\s*$/.match(cmd.stdout.chomp)
    [resolve[1]] if resolve
  end
end

# Windows
# TODO: UDP is not supported yey, we need a custom ps1 script to add udp support
# @see http://blogs.technet.com/b/josebda/archive/2015/04/18/windows-powershell-equivalents-for-common-networking-commands-ipconfig-ping-nslookup.aspx
# @see http://blogs.technet.com/b/heyscriptingguy/archive/2014/03/19/creating-a-port-scanner-with-windows-powershell.aspx
class WindowsHostProvider < HostProvider
  def ping(hostname, port = nil, proto = nil)
    # TODO: abort if we cannot run it via udp
    return nil if proto == 'udp'

    # ICMP: Test-NetConnection www.microsoft.com
    # TCP and port: Test-NetConnection -ComputerName www.microsoft.com -RemotePort 80
    request = "Test-NetConnection -ComputerName #{hostname}"
    request += " -RemotePort #{port}" unless port.nil?
    request += '| Select-Object -Property ComputerName, RemoteAddress, RemotePort, SourceAddress, PingSucceeded | ConvertTo-Json'
    p request
    request += '| Select-Object -Property ComputerName, PingSucceeded | ConvertTo-Json'
    cmd = inspec.command(request)

    begin
      ping = JSON.parse(cmd.stdout)
    rescue JSON::ParserError => _e
      return nil
    end

    ping['PingSucceeded']
  end

  def resolve(hostname)
    cmd = inspec.command("Resolve-DnsName –Type A #{hostname} | ConvertTo-Json")
    begin
      resolv = JSON.parse(cmd.stdout)
    rescue JSON::ParserError => _e
      return nil
    end

    resolv = [resolv] unless resolv.is_a?(Array)
    resolv.map { |entry| entry['IPAddress'] }
  end
end