#!/usr/bin/python
#
# Script to fix MP3 double zero offset Main Data Begin frame problem.
# This causes problems for iTunes 6.0.2 when they appear in the middle
# of an MP3 file.  However, as any file may be joined with other MP3
# files, this script will remove all occurrances of this problem.
#
# This script does not actually do the edits.  It creates the mpgedit
# command line that you must execute to fix the file being checked.
#
# Copyright (C) 2006 Adam Bernstein
#
import sys
import os

if __name__ == "__main__":
    try:
        fname = sys.argv[1]
    except IndexError:
        sys.exit("usage: %s mp3_name" % sys.argv[0])

    try:
        fp = open(fname, 'rb')
    except IOError:
        sys.exit("Unable to open mp3 file '%s'" % fname)
    fp.close()

    parts = fname.split('.')
    outfile = "%s_fixed.%s" %(parts[0], parts[1])
    count = 0
    prev_mdb = -1
    cur_mdb = -1
    prev_header = ''
    cur_header = ''
    edit_start = ''
    edit_end = ''
    first = 1
    err_found = 0
    edit = '\\\n -e'

    # Make sure mpgedit version is 0.72 or better
    #
    for line in os.popen("mpgedit -V"):
        if line.find(' version ') != -1: 
            parts = line.split()
            print parts[2]
            ver_parts = parts[2].split('.')
            if int(ver_parts[0]) == 0 and int(ver_parts[1]) < 72:
                sys.exit("fixmdb.py requires mpgedit 0.72 beta or better")
            
    # Can't use -I here, because it is off by 1 frame.  This is an mpgedit 
    # bug that needs fixing.
    #
    # cmd = "mpgedit -I -vvv %s" % fname
    cmd = "mpgedit -vvv %s" % fname
    try:
        for line in os.popen(cmd):
            if line.startswith('MPEG header t='):
                if not prev_header:
                    prev_header = line
                    cur_header = line
                else:
                    prev_header = cur_header
                    cur_header = line
                
            if line.startswith('MainDataBegin:'):
                if line[14:].startswith('  0'):
                    print "%5d: %s" % (count, line),
                    if cur_mdb == -1:
                        cur_mdb = count
                    else:
                        prev_mdb = cur_mdb
                        cur_mdb = count
                        # print "cur_mdb=%d prev_mdb=%d" %(cur_mdb, prev_mdb)
                        testval = prev_mdb + 1
                        if testval == count:
                            err_found = 1
                            # print "Found offending MDB value!"
                            # print prev_header
                            # print cur_header
    
                            prev_parts = prev_header.split('t=')
                            prev_tparts = prev_parts[1].split('s')
                            tprev = prev_tparts[0]
    
                            cur_parts = cur_header.split('t=')
                            cur_tparts = cur_parts[1].split('s')
                            tcur = cur_tparts[0]
                            if first:
                                first = 0
                                edit = edit + tprev + '-'
                            else:
                                edit = edit + tprev + ' \\\n -e' + tcur + '-' 
                            print ''
    
                count += 1
    except IOError:
        sys.exit("Unable to open mp3 file")

    # Print the edit command line.
    #
    if err_found:
        print("Copy/paste the following mpgedit command:\n")
        print "mpgedit -o %s %s %s" %(outfile, edit, fname)
    else:
        print("\nMP3 file '%s' is okay" % fname)