Melodia/archiver/models/song.py

from django.db import models
from Melodia import melodia_settings

from archive import Archive

import datetime
import os.path
"""
The Song model
Each instance of a Song represents a single music file.
This database model is used for storing the metadata information about a song,
and helps in doing sorting etc.
"""

_default_string = "_UNAVAILABLE_"
_default_date   = datetime.datetime.now
_default_int    = -1

_default_rating = 0
_default_rating_bad       = 1
_default_rating_ok        = 2
_default_rating_decent    = 3
_default_rating_good      = 4
_default_rating_excellent = 5
_default_rating_choices = (
		(_default_rating, 'Default'),
		(_default_rating_bad, 'Bad'),
		(_default_rating_ok, 'OK'),
		(_default_rating_decent, 'Decent'),
		(_default_rating_good, 'Good'),
		(_default_rating_excellent, 'Excellent'),
		)

class Song (models.Model):
	class Meta:
		app_label = 'archiver'
	
	"""
	This class defines the fields and functions related to controlling
	individual music files.
	Note that the Playlist model depends on this model's PK being an int.
	"""

	#Standard song metadata
	title        = models.CharField(max_length = 64, default = _default_string)
	artist       = models.CharField(max_length = 64, default = _default_string)
	album        = models.CharField(max_length = 64, default = _default_string)
	year         = models.IntegerField(default = _default_string)
	genre        = models.CharField(max_length = 64, default = _default_string)
	bpm          = models.IntegerField(default = _default_int)
	disc_number  = models.IntegerField(default = _default_int)
	disc_total   = models.IntegerField(default = _default_int)
	track_number = models.IntegerField(default = _default_int)
	track_total  = models.IntegerField(default = _default_int)
	comment      = models.CharField(default = _default_string, max_length=512)

	#File metadata
	bit_rate         = models.IntegerField(default = _default_int)
	duration         = models.FloatField(default = _default_int)
	add_date         = models.DateField(default = _default_date)
	echonest_song_id = models.CharField(max_length = 64, default = _default_string)
	url              = models.CharField(max_length = 255)
	file_hash        = melodia_settings.HASH_RESULT_DB_TYPE
	file_size        = models.IntegerField(default = _default_int)

	#Melodia metadata
	play_count = models.IntegerField(default = _default_int)
	skip_count = models.IntegerField(default = _default_int)
	rating     = models.IntegerField(default = _default_int, choices = _default_rating_choices)

	#Link back to the archive this comes from
	parent_archive = models.ForeignKey(Archive)

	#Set a static reference to the rating options
	RATING_DEFAULT   = _default_rating
	RATING_BAD       = _default_rating_bad
	RATING_OK        = _default_rating_ok
	RATING_DECENT    = _default_rating_decent
	RATING_GOOD      = _default_rating_good
	RATING_EXCELLENT = _default_rating_excellent

	def _get_full_url(self):
		"Combine this song's URL with the URL of its parent"
		return os.path.join(parent_archive.root_folder, self.url)

	def _file_not_changed(self):
		"Make sure the hash for this file is valid - return True if it has not changed."
		#Overload the hash function with whatever Melodia as a whole is using
		from Melodia.melodia_settings import HASH_FUNCTION as hash

		#Check if there's a hash entry - if there is, the song may not have changed,
		#and we can go ahead and return
		if self.file_hash != None:
			song_file = open(self._get_full_url, 'rb')
			current_file_hash = hash(song_file.read())

			if current_file_hash == self.file_hash:
				#The song data hasn't changed at all, we don't need to do anything
				return True

		return False

	def _grab_file_info(self):
		"Populate file-based metadata about this song."
		import os
		#Overload the hash function with whatever Melodia as a whole is using
		from Melodia.melodia_settings import HASH_FUNCTION as hash
		
		file_handle = open(self._get_full_url, 'rb')
		
		self.file_hash = hash(file_handle.read())
		self.file_size = os.stat(self._get_full_url).st_size

	def _grab_metadata_echonest(self):
		"Populate this song's metadata using EchoNest"
		pass

	def _grab_metadata_local(self):
		"Populate this song's metadata using what is locally available"
		#Use mutagen to get the song metadata
		import mutagen

		try:
			#Use mutagen to scan local metadata - don't update anything else (i.e. play_count)
			track             = mutagen.File(self._get_full_url)
			track_easy        = mutagen.File(self._get_full_url, easy=True)

			self.title        = track_easy['title'][0]  or _default_string
			self.artist       = track_easy['artist'][0] or _default_string
			self.album_artist = track_easy['albumartist'][0] or _default_string
			self.album        = track_easy['album'][0]  or _default_string
			self.year         = int(track_easy['date'][0][0:4]) or _default_int
			self.genre        = track_easy["genre"][0] or _default_string

			self.disc_number  = int(track_easy['discnumber'][0].split('/')[0]) or _default_int
			self.disc_total   = int(track_easy['discnumber'][0].split('/')[-1]) or _default_int
			self.track_number = int(track_easy['track_number'][0].split('/')[0]) or _default_int
			self.track_total  = int(track_easy['track_number'][0].split('/')[-1])  or _default_int
			self.comment      = track_easy['comment'][0] or _default_string

			self.bit_rate         = track.info.bitrate or _default_int
			self.duration         = track.info.length or _default_int

		except:
			#Couldn't grab the local data
			return False

	def populate_metadata(self, use_echonest = False):
		"Populate the metadata of this song (only if file hash has changed), and save the result."
		if self._file_not_changed():
			return

		#If we've gotten to here, we do actually need to fully update the metadata
		if use_echonest:
			self._grab_echonest()

		else:
			self._grab_metadata_local()
			
	def convert(self, output_location, output_format, progress_func = lambda x, y: None):
		"Convert a song to a new format."
		pass #Need to get pydub code in place