begin
  require "splunk-sdk-ruby"
rescue LoadError
  raise LoadError,
        'Gem splunk-sdk-ruby is required for logging to Splunk. Please add the gem "splunk-sdk-ruby" to your Gemfile.'
end

# Splunk log appender.
#
# Use the official splunk gem to log messages to Splunk.
#
# Example
#   SemanticLogger.add_appender(
#     appender: :splunk,
#     username: 'username',
#     password: 'password',
#     host:     'localhost',
#     port:     8089,
#     scheme:   :https,
#     index:    'main'
#   )
module SemanticLogger
  module Appender
    class Splunk < SemanticLogger::Subscriber
      attr_reader :config, :index, :service, :service_index, :source_type

      # Write to Splunk.
      #
      # Parameters
      #   :username [String]
      #     User name to log into splunk with.
      #     Not required if :token has been supplied.
      #
      #   :password [String]
      #     Password to log into splunk with.
      #     Not required if :token has been supplied.
      #
      #   :token
      #     Supply a preauthenticated Splunk token instead of username and password.
      #     Not required if username and password are supplied.
      #
      #   :host [String]
      #      Splunk server host name.
      #      Default: 'localhost'
      #
      #   :port [Integer]
      #      The Splunk management port.
      #      Default: 8089
      #
      #   :scheme [Symbol]
      #     Either :https or :http
      #     Default: :https
      #
      #   :index [String]
      #      Splunk index to use.
      #      Default: 'main'
      #
      #   :namespace [Namespace]
      #      Application namespace instance.
      #
      #   :ssl_client_cert [OpenSSL::X509::Certificate]
      #     Client certificate.
      #
      #   :ssl_client_key [OpenSSL::PKey::RSA | OpenSSL::PKey::DSA]
      #     Client key.
      #
      #   source_type: [String]
      #     Optional: Source type to display in Splunk
      #
      #   application: [String]
      #     The :source forwarded to Splunk
      #     Default: SemanticLogger.application
      #
      #   host: [String]
      #     Name of this host to appear in log messages.
      #     Default: SemanticLogger.host
      #
      #   level: [:trace | :debug | :info | :warn | :error | :fatal]
      #     Override the log level for this appender.
      #     Default: SemanticLogger.default_level
      #
      #   formatter: [Object|Proc]
      #     An instance of a class that implements #call, or a Proc to be used to format
      #     the output from this appender
      #     Default: Use the built-in formatter (See: #call)
      #
      #   filter: [Regexp|Proc]
      #     RegExp: Only include log messages where the class name matches the supplied.
      #     regular expression. All other messages will be ignored.
      #     Proc: Only include log messages where the supplied Proc returns true
      #           The Proc must return true or false.
      def initialize(index: "main", source_type: nil, **args, &block)
        @index       = index
        @source_type = source_type

        super(**args, &block)
        reopen
      end

      # After forking an active process call #reopen to re-open
      # open the handles to resources
      def reopen
        # Connect to splunk. Connect is a synonym for creating a Service by hand and calling login.
        @service = ::Splunk.connect(config)

        # The index we are logging to
        @service_index = service.indexes[index]
      end

      # Log the message to Splunk
      def log(log)
        event = formatter.call(log, self)
        service_index.submit(event.delete(:message), event)
        true
      end

      # Returns [Hash] To send to Splunk.
      #
      # For splunk format requirements see:
      #   http://dev.splunk.com/view/event-collector/SP-CAAAE6P
      def call(log, logger)
        h = SemanticLogger::Formatters::Raw.new.call(log, logger)
        h.delete(:time)
        message = {
          source:  logger.application,
          host:    logger.host,
          time:    log.time.utc.to_f,
          message: h.delete(:message),
          event:   h
        }
        message[:environment] = logger.environment if logger.environment
        message[:sourcetype]  = source_type if source_type
        message
      end
    end
  end
end