#! /usr/bin/env python
#
# Copyright (c) 2010 Ryan Armstrong
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:

# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

import os, sys, random


class song:
	""" 
	Class to store song information. Can contain the EXTINF line
	and the file name (both assume the newline character is included). 
	Can then re-combine 
	"""
	def __init__(self, extinf, filename):
		self.extinf = extinf;
		self.filename = filename;

	def listing(self):
		""" Creates a M3U entry for this song """
		if len(self.extinf) > 0:
			return "{0}{1}".format(self.extinf, self.filename)
		else:
			return self.filename


def loadPlaylist(filename):
	""" Loads the specified playlist in M3U format into a dictionary of
	'Albums' (really directories), and songs. """
	
	playlistfile = open(filename, 'r')
	extinf = ""
	albumlist = dict()
	
	for line in playlistfile:
		
		if line.upper().startswith("#EXTM3U"):
			# Ignore header line
			pass
		
		elif line.upper().startswith("#EXTINF"):
			# Remember Extinf entries
			extinf = line
			
		elif len(line.strip()) > 0:
			# All other non-blank lines are songs
			filename = line
			(filedir, fileonly) = os.path.split(filename)
			
			thissong = song(extinf, filename)
			
			if filedir in albumlist:
				songlist = albumlist[filedir]
				songlist.append(thissong)
			else:
				songlist = [ thissong ]
				albumlist[filedir] = songlist
				
			extinf = ""
	
	return albumlist

def shuffleAndSave(filename, albumlist):
	""" Shuffles the specified dictionary of albums, then
	writes it to the specified file in M3U format """

	# Shuffle by album
	albums = list(albumlist.keys())
	random.seed()
	random.shuffle(albums)
	
	# Generate the output playlist
	playlistoutput = open(playlistoutputname, 'w')
	
	playlistoutput.write('#EXTM3U\n')

	for album in albums:
		for mysong in albumlist[album]:
			playlistoutput.write( mysong.listing() )

	playlistoutput.close()


# "Main" Program start:
if len(sys.argv) > 1:
	
	for playlistname in sys.argv[1:]:

		# Load the old playlist
		albumlist = loadPlaylist(playlistname)

		# Figure out our output name, then shuffle and write the new one
		(plbase, plext) = os.path.splitext(playlistname)
		playlistoutputname = "{0}_shuffled{1}".format(plbase, plext)
		shuffleAndSave(playlistoutputname, albumlist)

else:
	sys.stdout.write('Please specify an m3u playlist to shuffle.\n\n')
	sys.stdout.write('E.g.:  python ShufflePlaylistByAlbum.py bestmusic.m3u\n')