class ReportProcessor
  attr_accessor :name, :report

  def initialize(name, report)
    # TODO: validate report
    @name = name
    @report = report
    @redis = Redis.new(:host => $config.redis.host, :port => $config.redis.port, :db => 5)
  end

  def prefix
    "reports_#{@name}"
  end

  def last_collected_at=(time)
    @redis.set "#{prefix}_last_collected_at", time.xmlschema
  end

  def last_collected_at
    value = @redis.get "#{prefix}_last_collected_at"
    Time.parse value if value
  end

  def last_record_index=(int)
    @redis.set "#{prefix}_last_record_index", int
  end

  def last_record_index
    (@redis.get("#{prefix}_last_record_index") || '-1').to_i
  end

  # sets an in use flag on the rows till the passed block is completed
  def lock
    if @redis.getset("#{prefix}_lock", 'locked') != 'locked'
      begin
        yield
      rescue StandardError => e
        raise e
      ensure
        @redis.del "#{prefix}_lock"
      end

      true
    else
      false
    end
  end

  def lock!
    throw StandardError, 'Lock could not be aquired' unless lock{ yield }
  end

  def reset!
    @redis.keys("#{prefix}*").each { |key| @redis.del key }
  end

  def keys(with_value=false)
    @redis.smembers("#{prefix}_keys").each do |key|
      @redis.smembers("#{prefix}_dimensions").each do |dimension|
        @report[:metrics].keys.each do |metric|
          if with_value
            value = @redis.get("#{prefix}:#{key}:#{dimension}:#{metric}") || '0'
            yield key, dimension, metric, value.to_i
          else
            yield key, dimension, metric
          end
        end
      end
    end
  end

  def collect(data)
    throw ArgumentError, "data must be enumerable" unless data.respond_to? :each

    last = nil

    data.each do |row|
      last        = row
      key         = @report[:key].call(row)
      dimensions  = @report[:dimensions].call(row)

      @redis.sadd "#{prefix}_keys", key

      dimensions.each do |dimension|
        @redis.sadd "#{prefix}_dimensions", dimension

        @report[:metrics].each do |metric, proc|
          @redis.incrby "#{prefix}:#{key}:#{dimension}:#{metric}", proc.call(row)
        end
      end
    end

    if last
      self.last_record_index = @report[:index].call last
      self.last_collected_at = Time.now
    end
  end
end