text: """
  The live module provides a mechanism of periodically checking which games are
  being actively played.
  
  It requires the third party library pytz to be
  installed, which makes sure game times are compared properly with respect
  to time zones. pytz can be downloaded from PyPI:
  http://pypi.python.org/pypi/pytz/
  
  It works by periodically downloading data from NFL.com for games that started
  before the current time. Once a game completes, the live module stops asking
  NFL.com for data for that game.
  
  If there are no games being actively played (i.e., it's been more than N hours
  since the last game started), then the live module sleeps for longer periods
  of time.
  
  Thus, the live module can switch between two different modes: active and
  inactive.
  
  In the active mode, the live module downloads data from NFL.com in
  short intervals. A transition to an inactive mode occurs when no more games
  are being played.
  
  In the inactive mode, the live module only checks if a game is playing (or
  about to play) every 15 minutes. If a game is playing or about to play, the
  live module switches to the active mode. Otherwise, it stays in the inactive
  mode.
  
  With this strategy, if the live module is working properly, you could
  theoretically keep it running for the entire season.
  
  (N.B. Half-time is ignored. Games are either being actively played or not.)
  
  Alpha status
  ============
  This module is emphatically in alpha status. I believe things will work OK for
  the regular season, but the postseason brings new challenges. Moreover, it
  will probably affect the API at least a little bit.
  """
  import datetime
  import time
  import xml.dom.minidom as xml
  
  try:
      import pytz
  except ImportError:
      pass
  
  import requests
  
  import nflgame
  import nflgame.game
  
  # [00:21] <rasher> burntsushi: Alright, the schedule changes on Wednesday 7:00
  # UTC during the regular season
  
  _MAX_GAME_TIME = 60 * 60 * 6
  """
  The assumed maximum time allowed for a game to complete. This is used to
  determine whether a particular game that isn't over is currently active.
  """
  
  _WEEK_INTERVAL = 60 * 60 * 12
  """
  How often to check what the current week is. By default, it is twice a day.
  """
  
  _CUR_SCHEDULE = "http://www.nfl.com/liveupdate/scorestrip/ss.xml"
  # """
  # Pinged infrequently to discover the current week number, year and week type.
  # The actual schedule of games is taken from the schedule module.
  # """
  #_CUR_SCHEDULE = "http://www.nfl.com/liveupdate/scorestrip/postseason/ss.xml"
  
  """
  The URL for the XML schedule of the post season. This is only used
  during the post season.
  
  TODO: How do we know if it's the post season?
  """
  
  _cur_week = None
  """The current week. It is updated infrequently automatically."""
  
  _cur_year = None
  """The current year. It is updated infrequently automatically."""
  
  _cur_season_phase = 'PRE'
  """The current phase of the season."""
  
  _regular = False
  """True when it's the regular season."""
  
  _last = None
  """
  A list of the last iteration of games. These are diffed with the current
  iteration of games.
  """
  
  _completed = []
  """
  A list of game eids that have been completed since the live module started
  checking for updated game stats.
  """
  
  
  def current_year_and_week():
      """
      Returns a tuple (year, week) where year is the current year of the season
      and week is the current week number of games being played.
      i.e., (2012, 3).
  
      N.B. This always downloads the schedule XML data.
      """
      _update_week_number()
      return _cur_year, _cur_week
  
  
  def current_games(year=None, week=None, kind='REG'):
      """
      Returns a list of game.Games of games that are currently playing.
      This fetches all current information from NFL.com.
  
      If either year or week is none, then the current year and week are
      fetched from the schedule on NFL.com. If they are *both* provided, then
      the schedule from NFL.com won't need to be downloaded, and thus saving
      time.
  
      So for example::
  
          year, week = nflgame.live.current_year_and_week()
          while True:
              games = nflgame.live.current_games(year, week)
              # Do something with games
              time.sleep(60)
  
      The kind parameter specifies whether to fetch preseason, regular season
      or postseason games. Valid values are PRE, REG and POST.
      """
      if year is None or week is None:
          year, week = current_year_and_week()
  
      guesses = []
      now = _now()
      games = _games_in_week(year, week, kind=kind)
      for info in games:
          gametime = _game_datetime(info)
          if gametime >= now:
              if (gametime - now).total_seconds() <= 60 * 15:
                  guesses.append(info['eid'])
          elif (now - gametime).total_seconds() <= _MAX_GAME_TIME:
              guesses.append(info['eid'])
  
      # Now we have a list of all games that are currently playing, are
      # about to start in less than 15 minutes or have already been playing
      # for _MAX_GAME_TIME (6 hours?). Now fetch data for each of them and
      # rule out games in the last two categories.
      current = []
      for guess in guesses:
          game = nflgame.game.Game(guess)
          if game is not None and game.playing():
              current.append(game)
      return current
  
  
  def run(callback, active_interval=15, inactive_interval=900, stop=None):
      """
      Starts checking for games that are currently playing.
  
      Every time there is an update, callback will be called with three
      lists: active, completed and diffs. The active list is a list of
      game.Game that are currently being played. The completed list is
      a list of game.Game that have just finished. The diffs list is a
      list of `nflgame.game.GameDiff` objects, which collects statistics
      that are new since the last time `callback` was called. A game will
      appear in the completed list only once, after which that game will
      not be in either the active or completed lists. No game can ever
      be in both the `active` and `completed` lists at the same time.
  
      It is possible that a game in the active list is not yet playing because
      it hasn't started yet. It ends up in the active list because the "pregame"
      has started on NFL.com's GameCenter web site, and sometimes game data is
      partially filled. When this is the case, the 'playing' method on
      a nflgame.game.Game will return False.
  
      When in the active mode (see live module description), active_interval
      specifies the number of seconds to wait between checking for updated game
      data. Please do not make this number too low to avoid angering NFL.com.
      If you anger them too much, it is possible that they could ban your IP
      address.
  
      Note that NFL.com's GameCenter page is updated every 15 seconds, so
      setting the active_interval much smaller than that is wasteful.
  
      When in the inactive mode (see live module description), inactive_interval
      specifies the number of seconds to wait between checking whether any games
      have started or are about to start.
  
      With the default parameters, run will never stop. However, you may set
      stop to a Python datetime.datetime value. After time passes the stopping
      point, run will quit. (Technically, it's possible that it won't quit until
      at most inactive_interval seconds after the stopping point is reached.)
      The stop value is compared against datetime.datetime.now().
      """
      active = False
      last_week_check = _update_week_number()
  
      # Before we start with the main loop, we make a first pass at what we
      # believe to be the active games. Of those, we check to see if any of
      # them are actually already over, and add them to _completed.
      for info in _active_games(inactive_interval):
          game = nflgame.game.Game(info['eid'])
  
          # If we couldn't get a game, that probably means the JSON feed
          # isn't available yet. (i.e., we're early.)
          if game is None:
              continue
  
          # Otherwise, if the game is over, add it to our list of completed
          # games and move on.
          if game.game_over():
              _completed.append(info['eid'])
  
      while True:
          if stop is not None and datetime.datetime.now() > stop:
              return
  
          if time.time() - last_week_check > _WEEK_INTERVAL:
              last_week_check = _update_week_number()
  
          games = _active_games(inactive_interval)
          if active:
              active = _run_active(callback, games)
              if not active:
                  continue
              time.sleep(active_interval)
          else:
              active = not _run_inactive(games)
              if active:
                  continue
              time.sleep(inactive_interval)
  
  
  def _run_active(callback, games):
      """
      The active mode traverses each of the active games and fetches info for
      each from NFL.com.
  
      Then each game (that has info available on NFL.com---that is, the game
      has started) is added to one of two lists: active and completed, which
      are passed as the first and second parameters to callback. A game is
      put in the active list if it's still being played, and into the completed
      list if it has finished. In the latter case, it is added to a global store
      of completed games and will never be passed to callback again.
      """
      global _last
  
      # There are no active games, so just quit and return False. Which means
      # we'll transition to inactive mode.
      if len(games) == 0:
          return False
  
      active, completed = [], []
      for info in games:
          game = nflgame.game.Game(info['eid'])
  
          # If no JSON was retrieved, then we're probably just a little early.
          # So just ignore it for now---but we'll keep trying!
          if game is None:
              continue
  
          # If the game is over, added it to completed and _completed.
          if game.game_over():
              completed.append(game)
              _completed.append(info['eid'])
          else:
              active.append(game)
  
      # Create a list of game diffs between the active + completed games and
      # whatever is in _last.
      diffs = []
      for game in active + completed:
          for last_game in _last or []:
              if game.eid != last_game.eid:
                  continue
              diffs.append(game - last_game)
  
      _last = active
      callback(active, completed, diffs)
      return True
  
  
  def _run_inactive(games):
      """
      The inactive mode simply checks if there are any active games. If there
      are, inactive mode needs to stop and transition to active mode---thus
      we return False. If there aren't any active games, then the inactive
      mode should continue, where we return True.
  
      That is, so long as there are no active games, we go back to sleep.
      """
      return len(games) == 0
  
  
  def _active_games(inactive_interval):
      """
      Returns a list of all active games. In this case, an active game is a game
      that will start within inactive_interval seconds, or has started within
      _MAX_GAME_TIME seconds in the past.
      """
      games = _games_in_week(_cur_year, _cur_week, _cur_season_phase)
      active = []
      for info in games:
          if not _game_is_active(info, inactive_interval):
              continue
          active.append(info)
      return active
  
  
  def _games_in_week(year, week, kind='REG'):
      """
      A list for the games matching the year/week/kind parameters.
  
      The kind parameter specifies whether to fetch preseason, regular season
      or postseason games. Valid values are PRE, REG and POST.
      """
      return nflgame._search_schedule(year, week, kind=kind)
  
  
  def _game_is_active(gameinfo, inactive_interval):
      """
      Returns true if the game is active. A game is considered active if the
      game start time is in the past and not in the completed list (which is
      a private module level variable that is populated automatically) or if the
      game start time is within inactive_interval seconds from starting.
      """
      gametime = _game_datetime(gameinfo)
      now = _now()
      if gametime >= now:
          return (gametime - now).total_seconds() <= inactive_interval
      return gameinfo['eid'] not in _completed
  
  
  def _game_datetime(info):
      hour, minute = info['time'].strip().split(':')
      d = datetime.datetime(int(info['eid'][:4]), info['month'], info['day'],
                            (int(hour) + 12) % 24, int(minute))
      return pytz.timezone('US/Eastern').localize(d).astimezone(pytz.utc)
  
  
  def _now():
      return datetime.datetime.now(pytz.utc)
  
  
  def _update_week_number():
      global _cur_week, _cur_year, _cur_season_phase
  
      dom = xml.parseString(requests.get(_CUR_SCHEDULE).text)
      gms = dom.getElementsByTagName('gms')[0]
      _cur_week = int(gms.getAttribute('w'))
      _cur_year = int(gms.getAttribute('y'))
  
      phase = gms.getAttribute('t').strip()
      if phase == 'P':
          _cur_season_phase = 'PRE'
      elif phase == 'POST' or phase == 'PRO':
          _cur_season_phase = 'POST'
          _cur_week -= 17
      else:
          _cur_season_phase = 'REG'
      return time.time()
  