# encoding: utf-8
require "logstash/outputs/base"
require "logstash/namespace"
require "open3"

# The nagios_nsca output is used for sending passive check results to Nagios
# through the NSCA protocol.
#
# This is useful if your Nagios server is not the same as the source host from
# where you want to send logs or alerts. If you only have one server, this
# output is probably overkill # for you, take a look at the 'nagios' output
# instead.
#
# Here is a sample config using the nagios_nsca output:
#     output {
#       nagios_nsca {
#         # specify the hostname or ip of your nagios server
#         host => "nagios.example.com"
#
#         # specify the port to connect to
#         port => 5667
#       }
#     }

class LogStash::Outputs::NagiosNsca < LogStash::Outputs::Base

  config_name "nagios_nsca"
  milestone 1

  # The status to send to nagios. Should be 0 = OK, 1 = WARNING, 2 = CRITICAL, 3 = UNKNOWN
  config :nagios_status, :validate => :string, :required => true

  # The nagios host or IP to send logs to. It should have a NSCA daemon running.
  config :host, :validate => :string, :default => "localhost"

  # The port where the NSCA daemon on the nagios host listens.
  config :port, :validate => :number, :default => 5667

  # The path to the 'send_nsca' binary on the local host.
  config :send_nsca_bin, :validate => :path, :default => "/usr/sbin/send_nsca"

  # The path to the send_nsca config file on the local host.
  # Leave blank if you don't want to provide a config file.
  config :send_nsca_config, :validate => :path

  # The nagios 'host' you want to submit a passive check result to. This
  # parameter accepts interpolation, e.g. you can use @source_host or other
  # logstash internal variables.
  config :nagios_host, :validate => :string, :default => "%{host}"

  # The nagios 'service' you want to submit a passive check result to. This
  # parameter accepts interpolation, e.g. you can use @source_host or other
  # logstash internal variables.
  config :nagios_service, :validate => :string, :default => "LOGSTASH"

  # The format to use when writing events to nagios. This value
  # supports any string and can include %{name} and other dynamic
  # strings.
  config :message_format, :validate => :string, :default => "%{@timestamp} %{host}: %{message}"

  public
  def register
    #nothing for now
  end

  public
  def receive(event)
    # exit if type or tags don't match
    return unless output?(event)

    # catch logstash shutdown
    if event == LogStash::SHUTDOWN
      finished
      return
    end

    # skip if 'send_nsca' binary doesn't exist
    if !File.exists?(@send_nsca_bin)
      @logger.warn("Skipping nagios_nsca output; send_nsca_bin file is missing",
                   "send_nsca_bin" => @send_nsca_bin, "missed_event" => event)
      return
    end

    # interpolate params
    nagios_host = event.sprintf(@nagios_host)
    nagios_service = event.sprintf(@nagios_service)

    # escape basic things in the log message
    # TODO: find a way to escape the message correctly
    msg = event.sprintf(@message_format)
    msg.gsub!("\n", "<br/>")
    msg.gsub!("'", "&#146;")

    status = event.sprintf(@nagios_status)
    if status.to_i.to_s != status # Check it round-trips to int correctly
      msg = "status '#{status}' is not numeric"
      status = 2
    else
      status = status.to_i
      if status > 3 || status < 0
         msg "status must be > 0 and <= 3, not #{status}"
         status = 2
      end
    end

    # build the command
    # syntax: echo '<server>!<nagios_service>!<status>!<text>'  | \
    #           /usr/sbin/send_nsca -H <nagios_host> -d '!' -c <nsca_config>"

    cmd = [@send_nsca_bin, "-H", @host, "-p", @port, "-d", "~"]
    cmd = cmd + ["-c", @send_nsca_config]  if @send_nsca_config
    message = "#{nagios_host}~#{nagios_service}~#{status}~#{msg}"

    @logger.debug("Running send_nsca command", :nagios_nsca_command => cmd.join(" "), :message => message)

    begin
      Open3.popen3(*cmd) do |i, o, e|
        i.puts(message)
        i.close
      end
    rescue => e
      @logger.warn(
        "Skipping nagios_nsca output; error calling send_nsca",
        :error => $!,
        :nagios_nsca_command => cmd.join(" "),
        :message => message,
        :missed_event => event
      )
      @logger.debug("Backtrace", :backtrace => e.backtrace)
    end
  end # def receive
end # class LogStash::Outputs::NagiosNsca