require 'sidekiq'
require 'sidekiq/datadog/version'
require 'datadog/statsd'
require 'socket'

module Sidekiq
  module Middleware
    module Server
      class Datadog

        # Configure and install datadog instrumentation. Example:
        #
        #   Sidekiq.configure_server do |config|
        #     config.server_middleware do |chain|
        #       chain.add Sidekiq::Middleware::Server::Datadog
        #     end
        #   end
        #
        # Options:
        # * <tt>:hostname</tt>    - the hostname used for instrumentation, defaults to system hostname, respects +INSTRUMENTATION_HOSTNAME+ env variable
        # * <tt>:metric_name</tt> - the metric name (prefix) to use, defaults to "sidekiq.job"
        # * <tt>:tags</tt>        - array of custom tags, these can be plain strings or lambda blocks accepting a rack env instance
        # * <tt>:statsd_host</tt> - the statsD host, defaults to "localhost", respects +STATSD_HOST+ env variable
        # * <tt>:statsd_port</tt> - the statsD port, defaults to 8125, respects +STATSD_PORT+ env variable
        # * <tt>:statsd</tt>      - custom statsd instance
        def initialize(opts = {})
          hostname      = opts[:hostname] || ENV['INSTRUMENTATION_HOSTNAME'] || Socket.gethostname
          statsd_host   = opts[:statsd_host] || ENV['STATSD_HOST'] || "localhost"
          statsd_port   = (opts[:statsd_port] || ENV['STATSD_PORT'] || 8125).to_i

          @metric_name  = opts[:metric_name] || "sidekiq.job"
          @statsd       = opts[:statsd] || ::Datadog::Statsd.new(statsd_host, statsd_port)
          @tags         = opts[:tags] || []

          if @tags.none? {|t| t =~ /^host\:/ }
            @tags.push("host:#{hostname}")
          end

          env = Sidekiq.options[:environment] || ENV['RACK_ENV']
          if env && @tags.none? {|t| t =~ /^env\:/ }
            @tags.push("env:#{ENV['RACK_ENV']}")
          end
        end

        def call(worker, job, queue, *)
          start = Time.now
          begin
            yield
            record(worker, job, queue, start)
          rescue => e
            record(worker, job, queue, start, e)
            raise
          end
        end

        private

          def record(worker, job, queue, start, error = nil)
            ms   = ((Time.now - start) * 1000).round
            if job["enqueued_at"]
              queued_ms = ((start - Time.at(job["enqueued_at"])) * 1000).round
            end
            name = underscore(job['wrapped'] || worker.class.to_s)
            tags = @tags.map do |tag|
              case tag when String then tag when Proc then tag.call(worker, job, queue, error) end
            end

            tags.push "name:#{name}"
            tags.push "queue:#{queue}" if queue
            if error
              kind = underscore(error.class.name.sub(/Error$/, ''))
              tags.push "status:error", "error:#{kind}"
            else
              tags.push "status:ok"
            end
            tags.compact!

            @statsd.increment @metric_name, :tags => tags
            @statsd.timing "#{@metric_name}.time", ms, :tags => tags
            if queued_ms
              @statsd.timing "#{@metric_name}.queued_time", queued_ms, :tags => tags
            end
          end

          def underscore(word)
            word = word.to_s.gsub(/::/, '/')
            word.gsub!(/([A-Z\d]+)([A-Z][a-z])/,'\1_\2')
            word.gsub!(/([a-z\d])([A-Z])/,'\1_\2')
            word.tr!("-", "_")
            word.downcase
          end

      end
    end
  end
end