DEFAULT_TASK_MAX_DURATION = 36000
module OpenTox

  # Class for handling asynchronous tasks
  class Task

    attr_accessor :pid, :observer_pid

    def metadata
      super true # always update metadata
    end

    def self.run(description, creator=nil, subjectid=SUBJECTID)

      task = Task.new nil, subjectid
      task[RDF::OT.created_at] = DateTime.now
      task[RDF::OT.hasStatus] = "Running"
      task[RDF::DC.description] = description.to_s
      task[RDF::DC.creator] = creator.to_s
      task.put
      pid = fork do
        begin
          task.completed yield
        rescue
          if $!.respond_to? :to_ntriples
            RestClientWrapper.put(File.join(task.uri,'Error'),{:errorReport => $!.to_ntriples},{:content_type => 'text/plain', :subjectid => task.subjectid}) 
          else
            cut_index = $!.backtrace.find_index{|line| line.match /gems\/sinatra/}
            cut_index = -1 unless cut_index
            @rdf = RDF::Graph.new
            subject = RDF::Node.new
            @rdf << [subject, RDF.type, RDF::OT.ErrorReport]
            @rdf << [subject, RDF::OT.message, $!.message]
            @rdf << [subject, RDF::OT.errorCode, $!.class.to_s]
            @rdf << [subject, RDF::OT.errorCause, $!.backtrace[0..cut_index].join("\n")]
            prefixes = {:rdf => "http://www.w3.org/1999/02/22-rdf-syntax-ns#", :ot => RDF::OT.to_s}
            turtle = RDF::Turtle::Writer.for(:turtle).buffer(:prefixes => prefixes)  do |writer|
              @rdf.each{|statement| writer << statement}
            end
            $logger.error turtle
            nt = RDF::Writer.for(:ntriples).buffer do |writer|
              @rdf.each{|statement| writer << statement}
            end
            RestClientWrapper.put(File.join(task.uri,'Error'),{:errorReport => nt},{:content_type => 'text/plain', :subjectid => task.subjectid}) 
          end
          task.kill
        end
      end
      Process.detach(pid)
      task.pid = pid

      # watch if task has been cancelled 
      observer_pid = fork do
        task.wait
        begin
          Process.kill(9,task.pid) if task.cancelled?
        rescue
          $logger.warn "Could not kill process of task #{task.uri}, pid: #{task.pid}"
        end
      end
      Process.detach(observer_pid)
      task.observer_pid = observer_pid
      task

    end

    def kill
      Process.kill(9,@pid)
      Process.kill(9,@observer_pid)
    rescue # no need to raise an exception if processes are not running
    end

    def description
      self.[](RDF::DC.description)
    end

    def creator
      self.[](RDF::DC.creator)
    end
    
    def cancel
      kill
      self.[]=(RDF::OT.hasStatus, "Cancelled")
      self.[]=(RDF::OT.finished_at, DateTime.now)
      put
    end

    def completed(uri)
      self.[]=(RDF::OT.resultURI, uri)
      self.[]=(RDF::OT.hasStatus, "Completed")
      self.[]=(RDF::OT.finished_at, DateTime.now)
      put
    end

    # waits for a task, unless time exceeds or state is no longer running
    def wait
      start_time = Time.new
      due_to_time = start_time + DEFAULT_TASK_MAX_DURATION
      dur = 0.2
      while running? 
        sleep dur
        dur = [[(Time.new - start_time)/20.0,0.3].max,300.0].min
        request_timeout_error "max wait time exceeded ("+DEFAULT_TASK_MAX_DURATION.to_s+"sec), task: '"+@uri.to_s+"'" if (Time.new > due_to_time)
      end
    end

  end

  def code
    RestClientWrapper.head(@uri,{},:subjectid => @subjectid).code.to_i
  end

  # get only header for status requests
  def running?
    code == 202 
  end

  def cancelled?
    code == 503
  end

  def completed?
    code == 200
  end

  def error?
    code >= 400 and code != 503
  end

  [:hasStatus, :resultURI, :created_at, :finished_at].each do |method|
    define_method method do
      response = self.[](RDF::OT[method])
      response = self.[](RDF::OT1[method]) unless response  # API 1.1 compatibility
      response
    end
  end

  # Check status of a task
  # @return [String] Status
  def status
    self[RDF::OT.hasStatus]
  end

  def error_report
    get
    report = {}
    query = RDF::Query.new({
      :report => {
        RDF.type  => RDF::OT.ErrorReport,
        :property => :value,
      }
    })
    query.execute(@rdf).each do |solution|
      report[solution.property] = solution.value.to_s
    end
    report
  end

  #TODO: subtasks (only for progress)
  class SubTask
    
    def initialize(task, min, max)
      #TODO add subtask code
    end

    def self.create(task, min, max)
      if task
        SubTask.new(task, min, max)
      else
        nil
      end
    end
    
    def waiting_for(task_uri)
      #TODO add subtask code
    end
    
    def progress(pct)
      #TODO add subtask code
    end
    
    def running?()
      #TODO add subtask code
    end
  end

end