#!/usr/bin/perl -w

# m3udo: a script to iterate on all files in an m3u playlist.  There's
# no need to retype this whole fingerbusting thing every time, and
# getting even a thing as simple as this right takes a lot of error
# checking.
#
# The home of this code on the web is http://gonze.com/m3udo/latest
# Contact: Lucas Gonze <lucas@gonze.com>

# Changelog:
#
# May 17, 2003:
# * fix blank item test
# * escape shell metacharacters
#
# May 15, 2003:
# * Fix error message when invoked with no arguments
#
# April 24, 2003:
# * added -r flag for recursion
# * handle multiple m3u files on command line
# * swap position of cmd and m3us
# * added support for multiple M3Us
# * started changelog

use strict;
use FileHandle;

check_usage();

my $cmd;
my $recurse = 0;

while( $#ARGV > -1 ){

  my $arg = shift();

  # -r flag means to recurse into any .m3u files
  if( $arg eq "-r" ){
    $recurse = 1;
    next;
  }

  # the first un-flagged argument is the command string
  if( !$cmd ){
    $cmd = $arg;
    next;
  }

  # remaining arguments are input files.  the special filename "-",
  # meaning stdin, is handled automatically by perl.
  do_m3u($arg,$recurse,$cmd);

}

sub escape_shell_metacharacters {
   my( $str ) = @_;

   @_ = $str;

   # this list of dangerous characters is far from exhaustive, but
   # ultimately the responsibility has to rest on the user to inspect
   # filenames before passing them to this script.
   s/([;<>\*\|`&\$!#\(\)\[\]\{\}:'"!# ])/\\$1/g;

   return $_;
}

# iterate over an m3u file
sub do_m3u {
  my ($m3u, $recurse, $cmd) = @_;

  my $fh = new FileHandle;
  if(! $fh->open("< $m3u")) {
      print STDERR "Unable to open $m3u\n";
      return;
  }
  
  while (<$fh>) {

    # trim leading and trailing whitespace
    s/(^\s*)(.*)(\s*$)/$2/g;

    # trim trailing carriage return caused by windows-unix conversion
    s/(.*)(\r$)/$1/g;

    # skip comments
    if ( /^\#/ ) {
      next;
    }

    # skip blanks
    if ( ! length($_) ){
      next;
    }

    chomp();

    my $item = escape_shell_metacharacters($_);

    # if item is a .m3u file, process it recursively
    if( $recurse && /^.*\.m3u$/ ){
	print "$item:\n";
	do_m3u($item,$recurse,$cmd);
	next;
    }
    
    $_ = $cmd;
    if ( /(.*)(\{\})(.*)/ ) {

      # if {} exists in the command, replace it with the file name
      s/\{\}/$item/g;
      system($_);
      next;
    } 

    # append line to command and run it
    system("$cmd $item");
  }
	   
  $fh->close;

}

sub check_usage {

	if( !defined(@ARGV) || (
		     $#ARGV < 1 &&
		     $ARGV[0] ne "-h" &&
		     $ARGV[0] ne "--help" &&
		     $ARGV[0] ne "-help")
	    ){
	    
	    print <<EOF;

Usage: m3udo [switches] [command] [file(s)]

Do "m3udo -h" to get a detailed help message.

EOF

return;
}

  if ( $ARGV[0] ne "-h" &&
       $ARGV[0] ne "--help" &&
       $ARGV[0] ne "-help") {
    return;
  }

  print <<EOF;

m3udo allows you to apply a command to each line in a text file.

Usage: 
   m3udo [switches] [command] [file(s)]

Switches:
   -r: Recursive.  If any item in an m3u file is an m3u file, open and
       process it recursively.  

Command:
   The default behavior is to run the command once for each line in
   the m3u file.  By default each line is appended to the command, so
   the result will be a string of commands like:

      command first-line
      command second-line
      ...

   If the command contains "{}", "{}" will be replaced in the command
   by .  This allows you to insert the line somewhere other
   than at the end.

File(s):
   Any arguments after the command are assumed to be files in the m3u
   format, meaning files containing lists of files.

   A file named "-" is interpreted to mean standard input.

   A line in an m3u file beginning with "#" is considered a comment.

   A line in an m3u file ending with ".m3u" is assumed to be an m3u
   file.  If m3udo was invoked with the "-r" flag, the line is
   processed recursively.

   DOS-fuxored line breaks are cleaned at runtime.

Examples:
   m3udo ls my.m3u
	    will run the ls command on each item in my.m3u.
   m3udo wget my.m3u 
	    will fetch items that are HTTP urls.
   m3udo "mv {} newdir/" my.m3u 
	    will move items to a new directory.
   m3udo "wget {}; basename {} >> cache.m3u" my.m3u 
	    will fetch items that are HTTP urls and create a new
	    playlist with local copies.
   m3udo ls *.m3u
	    will run the ls command on each item in all m3u files.
   cat my.m3u | m3udo ls -
	    will run the ls command on each item in my.m3u.
   m3udo -r ls my.m3u
	    will run the ls command on each item in my.m3u, and on
	    each item in any m3u files contained in my.m3u, ad
	    recursivitum.

EOF
  exit 0;

}