#
# Fluentd
#
#    Licensed under the Apache License, Version 2.0 (the "License");
#    you may not use this file except in compliance with the License.
#    You may obtain a copy of the License at
#
#        http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS,
#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#    See the License for the specific language governing permissions and
#    limitations under the License.
#

module Fluent
  class RoundRobinOutput < MultiOutput
    Plugin.register_output('roundrobin', self)

    def initialize
      super

      @outputs = []
      @weights = []
    end

    attr_reader :outputs, :weights
    attr_accessor :rand_seed

    def configure(conf)
      super

      conf.elements.select {|e|
        e.name == 'store'
      }.each {|e|
        type = e['@type'] || e['type']
        unless type
          raise ConfigError, "Missing 'type' parameter on <store> directive"
        end

        weight = e['weight']
        weight = weight ? weight.to_i : 1
        log.debug "adding store type=#{type.dump}, weight=#{weight}"

        output = Plugin.new_output(type)
        output.router = router
        output.configure(e)
        @outputs << output
        @weights << weight
      }
      @rr = -1  # starts from @output[0]
      @rand_seed = Random.new.seed
    end

    def start
      rebuild_weight_array

      @outputs.each {|o|
        o.start
      }
    end

    def shutdown
      @outputs.each {|o|
        o.shutdown
      }
    end

    def emit(tag, es, chain)
      next_output.emit(tag, es, chain)
    end

    private

    def next_output
      @rr = 0 if (@rr += 1) >= @weight_array.size
      @weight_array[@rr]
    end

    def rebuild_weight_array
      gcd = @weights.inject(0) {|r,w| r.gcd(w) }

      weight_array = []
      @outputs.zip(@weights).each {|output,weight|
        (weight / gcd).times {
          weight_array << output
        }
      }

      # don't randomize order if all weight is 1 (=default)
      if @weights.any? {|w| w > 1 }
        r = Random.new(@rand_seed)
        weight_array.sort_by! { r.rand }
      end

      @weight_array = weight_array
    end
  end
end
