"""
A pure-python library to assist sending data to AudioScrobbler (the Last.fm
backend)
"""
import urllib, urllib2, logging
from time import mktime
from datetime import datetime, timedelta
from hashlib import md5
from xl.nls import gettext as _

logger = logging.getLogger(__name__)

SESSION_ID = None
POST_URL   = None
NOW_URL    = None
HARD_FAILS = 0
LAST_HS    = None   # Last handshake time
HS_DELAY   = 0      # wait this many seconds until next handshake
SUBMIT_CACHE = []
MAX_CACHE  = 5      # keep only this many songs in the cache
MAX_SUBMIT = 10     # submit at most this many tracks at one time
PROTOCOL_VERSION = '1.2'
__LOGIN      = {}     # data required to login

class BackendError(Exception):
   "Raised if the AS backend does something funny"
   pass
class AuthError(Exception):
   "Raised on authencitation errors"
   pass
class PostError(Exception):
   "Raised if something goes wrong when posting data to AS"
   pass
class SessionError(Exception):
   "Raised when problems with the session exist"
   pass
class ProtocolError(Exception):
   "Raised on general Protocol errors"
   pass

def login(user, password, hashpw=False, client=('exa', '0.3.0'),
   post_url=None):
   """Authencitate with AS (The Handshake)

   @param user:     The username
   @param password: md5-hash of the user-password
   @param hashpw:   If True, then the md5-hash of the password is performed
                    internally. If set to False (the default), then the module
                    assumes the passed value is already a valid md5-hash of the
                    password.
   @param client:   Client information (see http://www.audioscrobbler.net/development/protocol/ for more info)
   @type  client:   Tuple: (client-id, client-version)"""
   global LAST_HS, SESSION_ID, POST_URL, NOW_URL, HARD_FAILS, HS_DELAY, \
          PROTOCOL_VERSION, __LOGIN

   __LOGIN['u'] = user
   __LOGIN['c'] = client

   if LAST_HS is not None:
      next_allowed_hs = LAST_HS + timedelta(seconds=HS_DELAY)
      if datetime.now() < next_allowed_hs:
         delta = next_allowed_hs - datetime.now()
         raise ProtocolError("""Please wait another %d seconds until next handshake
(login) attempt.""" % delta.seconds)

   LAST_HS = datetime.now()

   tstamp = int(mktime(datetime.now().timetuple()))
   url    = post_url or POST_URL

   if hashpw is True:
      __LOGIN['p'] = md5(password).hexdigest()
   else:
      __LOGIN['p'] = password

   token  = md5( "%s%d" % (__LOGIN['p'], int(tstamp))).hexdigest()
   values = {
         'hs': 'true',
         'p' : PROTOCOL_VERSION,
         'c': client[0],
         'v': client[1],
         'u': user,
         't': tstamp,
         'a': token
         }
   data = urllib.urlencode(values)
   req = urllib2.Request("%s?%s" % (url, data) )
   response = urllib2.urlopen(req)
   result = response.read()
   lines = result.split('\n')

   if lines[0] == 'BADAUTH':
      raise AuthError('Bad username/password')

   elif lines[0] == 'BANNED':
      raise Exception('''This client-version was banned by Audioscrobbler. Please
contact the author of this module!''')

   elif lines[0] == 'BADTIME':
      raise ValueError('''Your system time is out of sync with Audioscrobbler.
Consider using an NTP-client to keep you system time in sync.''')

   elif lines[0].startswith('FAILED'):
      handle_hard_error()
      raise BackendError("Authencitation with AS failed. Reason: %s" %
            lines[0])

   elif lines[0] == 'OK':
      # wooooooohooooooo. We made it!
      SESSION_ID = lines[1]
      NOW_URL    = lines[2]
      POST_URL   = lines[3]
      HARD_FAILS = 0
      logger.info("Logged in successfully to AudioScrobbler (%s)" % url)

   else:
      # some hard error
      handle_hard_error()

def handle_hard_error():
   "Handles hard errors."
   global SESSION_ID, HARD_FAILS, HS_DELAY

   if HS_DELAY == 0:
      HS_DELAY = 60
   elif HS_DELAY < 120*60:
      HS_DELAY *= 2
   if HS_DELAY > 120*60:
      HS_DELAY = 120*60

   HARD_FAILS += 1
   if HARD_FAILS == 3:
      SESSION_ID = None

def now_playing( artist, track, album="", length="", trackno="", mbid="",
    inner_call=False ):
    """Tells audioscrobbler what is currently running in your player. This won't
    affect the user-profile on last.fm. To do submissions, use the "submit"
    method

    @param artist:  The artist name
    @param track:   The track name
    @param album:   The album name
    @param length:  The song length in seconds
    @param trackno: The track number
    @param mbid:    The MusicBrainz Track ID
    @return: True on success, False on failure"""

    global SESSION_ID, NOW_URL

    if SESSION_ID is None:
        raise AuthError("Please 'login()' first. (No session available)")

    if POST_URL is None:
        raise PostError("Unable to post data. Post URL was empty!")

    if length != "" and type(length) != type(1):
        raise TypeError("length should be of type int")

    if trackno != "" and type(trackno) != type(1):
        raise TypeError("trackno should be of type int")

    # Quote from AS Protocol 1.1, Submitting Songs:
    #     Note that all the post variables noted here MUST be
    #     supplied for each entry, even if they are blank.
    track = track or ''
    artist = artist or ''
    album = album or ''

    values = {'s': SESSION_ID,
              'a': unicode(artist).encode('utf-8'),
              't': unicode(track).encode('utf-8'),
              'b': unicode(album).encode('utf-8'),
              'l': length,
              'n': trackno,
              'm': mbid }

    data = urllib.urlencode(values)

    req = urllib2.Request(NOW_URL, data)
    response = urllib2.urlopen(req)
    result = response.read()

    if result.strip() == "OK":
        logger.info("Submitted \"Now Playing\" successfully to AudioScrobbler")
        return True
    elif result.strip() == "BADSESSION" :
        if inner_call is False:
            login(__LOGIN['u'], __LOGIN['p'], client=__LOGIN['c'])
            now_playing(artist, track, album, length, trackno, mbid, inner_call=True)
        else:
             raise SessionError('Invalid session')
    else:
        logger.warning("Error submitting \"Now Playing\"")

    return False

def submit(artist, track, time=0, source='P', rating="", length="", album="",
      trackno="", mbid="", autoflush=False):
    """Append a song to the submission cache. Use 'flush()' to send the cache to
    AS. You can also set "autoflush" to True.

    From the Audioscrobbler protocol docs:
    ---------------------------------------------------------------------------

    The client should monitor the user's interaction with the music playing
    service to whatever extent the service allows. In order to qualify for
    submission all of the following criteria must be met:

    1. The track must be submitted once it has finished playing. Whether it has
      finished playing naturally or has been manually stopped by the user is
      irrelevant.
    2. The track must have been played for a duration of at least 240 seconds or
      half the track's total length, whichever comes first. Skipping or pausing
      the track is irrelevant as long as the appropriate amount has been played.
    3. The total playback time for the track must be more than 30 seconds. Do
      not submit tracks shorter than this.
    4. Unless the client has been specially configured, it should not attempt to
      interpret filename information to obtain metadata instead of tags (ID3,
      etc).

    @param artist: Artist name
    @param track:  Track name
    @param time:   Time the track *started* playing in the UTC timezone (see
                  datetime.utcnow()).

                  Example: int(time.mktime(datetime.utcnow()))
    @param source: Source of the track. One of:
                  'P': Chosen by the user
                  'R': Non-personalised broadcast (e.g. Shoutcast, BBC Radio 1)
                  'E': Personalised recommendation except Last.fm (e.g.
                       Pandora, Launchcast)
                  'L': Last.fm (any mode). In this case, the 5-digit Last.fm
                       recommendation key must be appended to this source ID to
                       prove the validity of the submission (for example,
                       "L1b48a").
                  'U': Source unknown
    @param rating: The rating of the song. One of:
                  'L': Love (on any mode if the user has manually loved the
                       track)
                  'B': Ban (only if source=L)
                  'S': Skip (only if source=L)
                  '':  Not applicable
    @param length: The song length in seconds
    @param album:  The album name
    @param trackno:The track number
    @param mbid:   MusicBrainz Track ID
    @param autoflush: Automatically flush the cache to AS?
    @return:       True on success, False if something went wrong
    """
    if None in (artist, track):
        raise Exception

    if not artist.strip() or not track.strip():
        raise Exception

    global SUBMIT_CACHE, MAX_CACHE

    source = source.upper()
    rating = rating.upper()

    if source == 'L' and (rating == 'B' or rating == 'S'):
        raise ProtocolError("""You can only use rating 'B' or 'S' on source 'L'.
    See the docs!""")

    if source == 'P' and length == '':
        raise ProtocolError("""Song length must be specified when using 'P' as
    source!""")

    if type(time) != type(1):
        raise ValueError("""The time parameter must be of type int (unix
    timestamp). Instead it was %s""" % time)

    album = album or ''

    SUBMIT_CACHE.append(
         { 'a': unicode(artist).encode('utf-8'),
           't': unicode(track).encode('utf-8'),
           'i': time,
           'o': source,
           'r': rating,
           'l': length,
           'b': unicode(album).encode('utf-8'),
           'n': trackno,
           'm': mbid
            }
         )

    if autoflush or len(SUBMIT_CACHE) >= MAX_CACHE:
        return flush()
    else:
        return True

def flush(inner_call=False):
   """Sends the cached songs to AS.

   @param inner_call: Internally used variable. Don't touch!"""
   global SUBMIT_CACHE, __LOGIN, MAX_SUBMIT

   if POST_URL is None:
      raise ProtocolError('''Cannot submit without having a valid post-URL. Did
you login?''')

   values = {}

   for i, item in enumerate(SUBMIT_CACHE[:MAX_SUBMIT]):
      for key in item:
         values[key + "[%d]" % i] = item[key]

   values['s'] = SESSION_ID

   data = urllib.urlencode(values)
   req = urllib2.Request(POST_URL, data)
   response = urllib2.urlopen(req)
   result = response.read()
   lines = result.split('\n')

   if lines[0] == "OK":
      SUBMIT_CACHE = SUBMIT_CACHE[MAX_SUBMIT:]
      logger.info("AudioScrobbler OK: %s" % data)
      return True
   elif lines[0] == "BADSESSION" :
      if inner_call is False:
         login(__LOGIN['u'], __LOGIN['p'], client=__LOGIN['c'])
         flush(inner_call=True)
      else:
         raise Warning("Infinite loop prevented")
   elif lines[0].startswith('FAILED'):
      handle_hard_error()
      raise BackendError("Submission to AS failed. Reason: %s" %
            lines[0])
   else:
      # some hard error
      handle_hard_error()
      return False

if __name__ == "__main__":
   login( 'user', 'password' )
   submit(
         'De/Vision',
         'Scars',
         1192374052,
         source='P',
         length=3*60+44
         )
   submit(
         'Spineshank',
         'Beginning of the End',
         1192374052+(5*60),
         source='P',
         length=3*60+32
         )
   submit(
         'Dry Cell',
         'Body Crumbles',
         1192374052+(10*60),
         source='P',
         length=3*60+3
         )
   print flush()

