#!/usr/bin/perl
##
## snapdiff -- Compare the contents of two CPAN.pm autobundle snapshot
##             files for differing versions
##
## Mike Fletcher <fletch+perl@phydeaux.org>
##
use strict;
use Pod::Parser;

{
  ## Define a Pod::Parser subclass that pulls version information out
  ## of the autobundle file
  package MyParser;

  our @ISA = qw( Pod::Parser );

  ## command -- note when we see `=head1 CONTENTS'
  sub command {
    my ($parser, $command, $paragraph, $line_num) = @_;

    if( $command eq 'head1' and $paragraph =~ /CONTENTS/ ) {
      $parser->{in_contents} = 1;
    } else {
      $parser->{in_contents} = undef;
    }
  }

  ## textblock -- Pull out module/version pairs if we're inside a
  ##              CONTENTS section
  sub textblock {
    my( $parser, $para, $line_num ) = @_;

    ## Ignore text if we haven't seen a `=head1 CONTENTS' command
    return unless $parser->{in_contents};

    $para =~ /(\S+)\s+(\S+)/;
    $parser->{results}->{$1} = $2;
  }
}

## back in package main main

## Check that we're given two filenames
die "usage: $0 snap1 snap2\n" unless @ARGV == 2;

my( $snap1, $snap2 ) = @ARGV;

## Create some hashes to hold the results for each file
my $results = {
           $snap1 => {},
           $snap2 => {},
          };

## To track mismatched versions that we've already seen
my %mismatch;

## Parse out the bundle contents from each file
foreach( $snap1, $snap2 ) {
  local( *IN );
  open( IN, $_ ) or die "Error opening $_: $!\n";

  ## Create new MyParser, passing it the hashref to store results into
  ## for the file in question
  my $p = MyParser->new( results => $results->{$_} );

  $p->parse_from_filehandle( \*IN );

  close( IN );
}

print "$snap1 vs $snap2\n";
cmp_hashes( $results->{$snap1}, $results->{$snap2}, \%mismatch );

print "\n\n$snap2 vs $snap1\n";
cmp_hashes( $results->{$snap2}, $results->{$snap1}, \%mismatch );

exit 0;

##
## cmp_hashes -- Compare contents of hash $ha to hash $hb.  $mismatch
##               contains keys we already know don't match
##
sub cmp_hashes {
  my( $ha, $hb, $mismatch ) = @_;

  foreach( sort keys %{ $ha } ) {
    ## format a nice, space justified version of name for printing
    my $name = sprintf "%-35s", $_;

    unless( exists $hb->{$_} ) {
      ## it exists in hash a but not b
      print "$name ver ", $ha->{$_}, " only here\n";
    } else {
      ## If they're not equal and we don't know about the mismatch
      ## already then gripe about it (and make note of the fact)
      if( $ha->{$_} ne $hb->{$_} and not $mismatch->{$_} ) {
    print "$name here ver ", $ha->{$_}, " there ver ", $hb->{$_}, "\n"
+;
    $mismatch->{$_}++;    # note that there was a mismatch
      }
    }
  }

}

__END__
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