module Kthxbye

  # This class is our main job runner. It also handles the instantiation and
  # the meat of the job queuing and retreival. 
  class Job
    include Helper
    extend Helper

    attr_accessor :id, :queue, :data, :worker
    attr_reader :failed_attempts

    # Adds a job to the queue from a given job id
    # and queue. useful for switching a job to another queue or adding a defined
    # job to multiple queues.
    def self.add_to_queue(id, queue)
      redis.rpush( "queue:#{queue}", id )
    end

    # The bulk of the job queuing method. Takes a string representing a queue
    # name, a job class, and arguments to pass to the perform method of the 
    # job class. Returns a unique id for the job based on a redis "uniq_id" key
    # (int) which is a simple incremented value. Queues the job in the given 
    # queue and the job in the data-store hash.
    def self.create(queue, klass, *args)
      raise "Need a queue to store job in" if queue.to_s.empty?
      raise "No class to reference job type by" if klass.nil?

      redis.incr :uniq_id
      id = redis.get :uniq_id

      Job.add_to_queue( id, queue )
      Kthxbye.register_queue( queue )
     
      # mark job as inactive currently. will mark active when job is getting run
      redis.sadd("jobs:inactive", id)
      redis.hset( "data-store:#{queue}", id, encode( {:klass => klass.to_s, :payload => args} ) )
      log "Created job in queue #{queue} with an unique key of #{id}"

      return id.to_i
    end

    # Returns a job object for a given job id off of a given queue.
    def self.find(id, queue)
      data = decode( redis.hget( "data-store:#{queue}", id ) )
      data ? Job.new(id, queue, data) : nil
    end
    
    # Removes all existence of this job and its data
    # Returns the last known status of the job
    def self.destroy(id, queue)
      ret = Job.find(id, queue).status

      # remove the element from the active queue
      redis.lrem("queue:#{queue}", 0, id) 
      # be sure we also remove it from the inactive queue
      redis.srem("queue:#{queue}:inactive", id)
      # remove the job's data as well
      redis.hdel("data-store:#{queue}", id) 
      redis.hdel("result-store:#{queue}", id)
      redis.hdel( :faulure, id )
      
      return ret
    end

    # Instantiates a job from a job id, a queue, and the job data.
    # Most often used in the ::find method and for the worker to recreate
    # the job for running.
    def initialize(id, queue, data)
      @id = id.to_i
      @queue = queue
      @data = data
      @failed_attempts =  Failure.fails_for_job(@id) # local tracking only, for rerun purposes
    end

    # Simply requeues the job to be rerun.
    def rerun
      Job.add_to_queue( @id, @queue )
    end

    # Returns the job's status. Will be one of 4 things.
    #   1) :succeeded - the job ran and has a result
    #   2) :failed - the job failed and reported an error
    #   3) :active - job is being run.
    #   4) :inactive - job is waiting to be run.
    def status
      if result
        :succeeded
      elsif Failure.find(@id)
        :failed
      elsif active?
        :active
      else
        :inactive
      end
    end

    # Returns the job's result once it has been run.
    def result
      decode( redis.hget("result-store:#{@queue}", @id) )
    end

    # Simply removes this job from the active queue and places it
    # on the inactive list. Does not remove job payload from storage. It just
    # removes its id from the actively run job queue.
    def dequeue
      redis.lrem("queue:#{@queue}", 0, @id) 
      inactive
    end
  
    # Does all the heavy lifting of performing the job and storing the results.
    # It will get the jobs class, payload and then run the job, storing the
    # result in the result's store once complete. Also responsible for reporting
    # errors and storing the job in the failure listing if an exception occurs.
    # Will also publish a message on the job.failed channel (Redis PUBSUB) with
    # the id of the failed job
    def perform
      begin
        @klass = Object.const_get(@data['klass'])
        @payload = @data['payload']
        #set job active, getting ready to run
        self.active

        result = @klass.send(:perform, *@payload)
        redis.hset( "result-store:#{@queue}", @id, encode( result ) )
        return result
      rescue Object => ex
        @failed_attempts += 1
        log "Error occured: #{ex.message}. Try: #{@failed_attempts}/#{Kthxbye::Config.options[:attempts]}"
        redis.publish("job.failed", @id)
        return Kthxbye::Failure.create( self, ex ) if @failed_attempts >= Kthxbye::Config.options[:attempts]
        perform
      end
    end

    # Removes the job from the inactive queue.
    def active
      redis.srem("jobs:inactive", @id)
    end

    def active?
      !redis.sismember("jobs:inactive", @id)
    end

    # Places the job on the active queue
    def inactive
      redis.sadd("jobs:inactive", @id)
    end

    def ==(obj) #:nodoc:
      return false if obj.nil?
      @data == obj.data &&
        @id == obj.id &&
        @queue == obj.queue
    end

  end
end