# encoding: utf-8
require "logstash/outputs/base"
require "logstash/namespace"
require "socket"
require "timeout"
require "rexml/document"

# The OpenNMS output is used to send an event (xml document) to an OpenNMS
# server.  The event `@timestamp` will automatically be associated with the
# OpenNMS item data.
#
# NOTE: This plugin will log a warning if a necessary field is missing. It 
# will not attempt to resend if OpenNMS is down, but will log an error message.

class LogStash::Outputs::OpenNMS < LogStash::Outputs::Base
  config_name "opennms"
  concurrency :single

  # The IP or resolvable hostname where the OpenNMS server is running
  config :opennms_server_hosts, :validate => :hash, :default => {"localhost" => 5817}
  
  # The number of seconds to wait before giving up on a connection to the OpenNMS
  # server. This number should be very small, otherwise delays in delivery of
  # other outputs could result.
  config :opennms_server_timeout, :validate => :number, :default => 1

  # The field name which holds the OpenNMS time zone. This can be a sub-field of
  # the @metadata field.
  config :opennms_event_timezone, :validate => :string, :required => true

  # The field name which holds the OpenNMS ... This can be a sub-field of
  # the @metadata field.
  config :opennms_event_service, :validate => :string

  # The field name which holds the OpenNMS ... This can be a sub-field of
  # the @metadata field.
  config :opennms_event_nodeid, :validate => :number
  
  # The field name which holds the OpenNMS ... This can be a sub-field of
  # the @metadata field.
  config :opennms_event_interface, :validate => :string
  
  # The field name which holds the OpenNMS ... This can be a sub-field of
  # the @metadata field.
  config :opennms_event_uei, :validate => :string, :default => "uei.opennms.org/elastic/logstash/generic/state/1"
  
  # The field name which holds the OpenNMS ... This can be a sub-field of
  # the @metadata field.
  config :opennms_event_origin, :validate => :string, :default => "None"
  
  # The field name which holds the OpenNMS ... This can be a sub-field of
  # the @metadata field.
  config :opennms_event_severity, :validate => :string, :required => true, :default => "Warning"
  
    # The field name which holds the OpenNMS ... This can be a sub-field of
  # the @metadata field.
  config :opennms_event_source, :validate => :string, :default => "logstash"
  
  # The field name which holds the OpenNMS ... This can be a sub-field of
  # the @metadata field.
  config :opennms_event_description, :validate => :string, :default => "None"
  
  # The field name which holds the OpenNMS ... This can be a sub-field of
  # the @metadata field.
  config :opennms_event_logmsg, :validate => :string, :default => "None"
  
  # This directive cannot be used in conjunction with the single-value directives
  # `opennms_key` and `opennms_value`.
  config :opennms_event_parms, :validate => :hash
  
  # The field name which holds the OpenNMS ... This can be a sub-field of
  # the @metadata field.
  config :opennms_event_parms_order, :validate => :array

  public
  def register
    if !@opennms_key.nil? && !@multi_value.nil?
      @logger.warn("Cannot use multi_value in conjunction with opennms_key/opennms_value.  Ignoring opennms_key.")
    end
    
    if @opennms_event_parms.nil?
      @opennms_event_parms = { 'a' => '1', 'b' => '2', 'c' => '3' }
    end

    # We're only going to use @multi_value in the end, so let's build it from
    # @opennms_key and @opennms_value if it is empty (single value configuration).
    if @multi_value.nil?
      @multi_value = [ @opennms_key, @opennms_value ]
    end
    if @multi_value.length % 2 == 1
      raise LogStash::ConfigurationError, I18n.t("logstash.agent.configuration.invalid_plugin_register",
        :plugin => "output", :type => "opennms",
        :error => "Invalid opennms configuration #{@multi_value}. multi_value requires an even number of elements as ['opennms_key1', 'opennms_value1', 'opennms_key2', 'opennms_value2']")
    end
  end # def register

  public
  def field_check(event, fieldname)
    if !event.get(fieldname)
      @logger.warn("Field referenced by #{fieldname} is missing")
      false
    else
      true
    end
  end # def field_check

  public
  def kv_check(event, key_field, value_field)
    errors = 0
    for field in [key_field, value_field]
      errors += 1 unless field_check(event, field)
    end
    errors < 1 ? true : false
  end # def kv_check

  public
  def validate_fields(event)
    found = []
    (0..@multi_value.length-1).step(2) do |idx|
      @logger.warn("---> " + @multi_value[idx].to_s)
      if kv_check(event, @multi_value[idx], @multi_value[idx+1])
        found << @multi_value[idx]
        found << @multi_value[idx+1]
      end
    end
    found
  end # def validate_fields
  
  public
  def validate_props(event,props,found)
    props.each do |props_key,props_value|
      if props_value.is_a?(::Hash)
         found[props_key] = validate_props(event,props_value,{})
      elsif props_value.is_a?(::Array)
         found[props_key]=props_value
	    else
	     if !event.get(props_value)
         @logger.warn("Field referenced by #{props_value} is missing")
         found[props_key] = props_value.empty? ? "n/a" : props_value
       else
         found[props_key]=event.get(props_value)
       end
      end
    end
    found
  end # def validate_props
  
  # Build XML event document
  public
  def format_request(message)
    event_doc  = "<log>"
    event_doc += "<events>"
    event_doc += "<event>"
    event_doc += "<uei>" + message['uei'] + "</uei>"
    event_doc += "<source>" + message['source'] + "</source>"
    event_doc += "<nodeid>" + message['nodeid'] + "</nodeid>" if !message['nodeid'].empty?
    event_doc += "<time>" + Time.now.strftime("%A, %d %B %Y %H:%M:%S o'clock GMT") + "</time>"
    event_doc += "<host>" + message['origin'] + "</host>"
    event_doc += "<interface>" + message['interface'] + "</interface>" if !message['interface'].empty?
    event_doc += "<service>" + message ['service'] + "</service>" if !message['service'].empty?
    event_doc += "<parms>"
    #message['parms'].each do |parm_name, parm_value|
    message['parms_order'].each do |parm_name|
       parm_value = message['parms'][parm_name]
       next if parm_name == 'severity'
       event_doc += "<parm>"
       event_doc += "<parmName><![CDATA[" + parm_name + "]]></parmName>"
       event_doc += "<value type=\"string\" encoding=\"text\"><![CDATA[" + parm_value + "]]></value>"
       event_doc += "</parm>"
    end
    event_doc += "</parms>"
    #event_doc += "<descr>"    + message['description'] + "</descr>" if !message['description'].empty?
    event_doc += "<logmsg>"   + message['logmsg'] + "</logmsg>" if !message['logmsg'].empty?
    event_doc += "<severity>" + message['severity'] + "</severity>"
    event_doc += "</event>"
    event_doc += "</events>"
    event_doc += "</log>"
    xml_event = REXML::Document.new(event_doc)
  end # def format_request

  def tcp_send(message)
    begin
      @opennms_server_hosts.each do |server,port|
        TCPSocket.open(server,port) do |sock|
           xml_event = format_request(message).to_s
           logger.debug("XML Event: " + xml_event)
           sock.print xml_event
        end
      end
    rescue Errno::ECONNREFUSED, Errno::EHOSTUNREACH, Errno::ECONNRESET
      @logger.error("Connection error.  Unable to connect to OpenNMS server",
         :server => @opennms_server_hosts,
      )
      false
    end
  end # def tcp_send

  def send_to_opennms(event)
    begin
      Timeout::timeout(@opennms_server_timeout) do
        tcp_send(event)
      end
    rescue Timeout::Error
      @logger.warn("Connection attempt to OpenNMS server timed out.",
        :server => @opennms_server_host,
        :port => @opennms_server_port.to_s,
        :timeout => @opennms_server_timeout.to_s
      )
      false
    end
  end # def send_to_opennms

  public
  def receive(event)
    #parms = validate_props(event,@opennms_event_parms)
    
    message_map = { 'host'        => @opennms_server_host.to_s,
                    'port'        => @opennms_server_port.to_s,
                    'timezone'    => @opennms_event_timezone.to_s,
                    'service'     => @opennms_event_service.to_s,
                    'nodeid'      => @opennms_event_nodeid.to_s,
                    'interface'   => @opennms_event_interface.to_s,
                    'uei'         => @opennms_event_uei.to_s,
                    'origin'      => @opennms_event_origin.to_s,
                    'severity'    => @opennms_event_severity.to_s,
                    'source'      => @opennms_event_source.to_s,
                    'description' => @opennms_event_description.to_s,
                    'logmsg'      => @opennms_event_logmsg.to_s,
                    'parms'       => @opennms_event_parms,
                    'parms_order' => @opennms_event_parms_order
    }
    
    message = validate_props(event,message_map,{})
                 
    #message['parms'].each do |k,v| 
    #   @logger.debug("Hash: " + k + " => " + v) 
    #end

    #return unless field_check(event, @opennms_host)

    send_to_opennms(message)
    
  end # def receive

end # class LogStash::Outputs::OpenNMS