#!/usr/bin/env perl
# This program is part of Aspersa (http://code.google.com/p/aspersa/)

=pod

=head1 NAME

rel - Make each number in a line of text relative to the previous matching line.

=head1 SYNOPSIS

Given a file with some lines of text that follow a repeated pattern, including
numbers,

  rel /path/to/file.txt

For example, if the text is this:

  Mutex spin waits 0, rounds 99584819933, OS waits 437663963
  RW-shared spins 834337527, OS waits 20258150; RW-excl spins 1769749834
  Mutex spin waits 0, rounds 99591465498, OS waits 437698122
  RW-shared spins 834352175, OS waits 20259032; RW-excl spins 1769762980

The output will be

  Mutex spin waits 0, rounds 99584819933, OS waits 437663963
  RW-shared spins 834337527, OS waits 20258150; RW-excl spins 1769749834
  Mutex spin waits 0, rounds 6645565, OS waits 34159
  RW-shared spins 14648, OS waits 882; RW-excl spins 13146

=head1 AUTHOR

Baron Schwartz

=cut

use strict;
use warnings FATAL => 'all';
use English qw(-no_match_vars);

use constant MKDEBUG => $ENV{MKDEBUG};

my $file = shift @ARGV || '-';
my $fh;
if ( $file eq '-' ) {
   $fh = *STDIN;
}
else {
   open $fh, "<", $file or die "Cannot open $file: $OS_ERROR";
}

my @line_patterns;
my %last_match;
my %printf_for;

while ( my $line = <$fh> ) {
   MKDEBUG && print "read: $line\n";
   my $matched = 0;
   foreach my $pat ( @line_patterns ) {
      MKDEBUG && print "trying to match: $pat\n";
      if ( my @vals = $line =~ m/$pat/ ) {
         MKDEBUG && print "matches\n";
         $matched = 1;
         my @last_vals = @{ $last_match{$pat} };
         my @offset_vals;
         for my $i ( 0..$#vals ) {
            $offset_vals[$i] = $vals[$i] - $last_vals[$i];
         }
         $last_match{$pat} = \@vals;
         printf $printf_for{$pat}, @offset_vals;
         last;
      }
   }
   if ( !$matched ) {
      my $new_pat = $line;
      $new_pat    =~ s/\d+/(\\d+)/g;
      my @vals    = $line =~ m/$new_pat/;
      MKDEBUG && print "new pattern: $new_pat: @vals\n";
      push @line_patterns, $new_pat;
      (my $printf_pat = $line ) =~ s/\d+/%d/g;
      $printf_for{$new_pat} = $printf_pat;
      $last_match{$new_pat} = \@vals;
      print $line;
   }
}


close $fh or warn "Cannot close $file: $OS_ERROR";
exit;