#!/usr/bin/perl -w

=head1 NAME find_changes.pl - Find patterns in text files and propose changes.

This script passes lines of text through a perl function with the aim of
reporting the occurence of patterns and proposing changes to be
done. L<patch> should be used to actually modify the original files.

=head1 SYNOPSIS

find_changes.pl [options] changes_def file(s).txt ... E<gt> changes_patch

Reads and executes the perl F<changes_def> file, which must contain the
definition of a function called C<change_line()>, and then reads the
F<file(s).txt> line by line.

For each line of each file, the function F<change_line()> is called with the
line as single argument, which can be modified inplace.

If any change is done to the line, it is reported by printing to stdout a
universal diff patch.

=head2 Modifying files

It is then recommended to inspect and edit the file F<changes_patch>,
removing lines that should not be changed. Once this is done, the changes
can be done in the original files by using C<patch -p0 < changes_patch>.

=head2 Commenting on lines

If a function C<comment_line()> is present, each line will be passed to it
and its output will be shown on standard error.

=head1 OPTIONS

=over 4

=item -p, --patch

Output a patch (default).

=item -d

Use another output format, adapted to some F<do_changes.pl> script.

=item -v, --verbose

Print some info on stderr during execution.

=item -h, --help

Print a help message and exit.

=head1 COPYRIGHT

This file is distributed under the terms of the GNU General Public Licence.

=head1 AUTHOR Etienne Grossmann E<lt>etienne@egdn.netE<gt>

=cut

###
sub help {system ("perldoc $0|cat")}

$patch = 1;
$verbose = 0;
				# Read options

while (@ARGV && ($ARGV[0] =~ /^\-/)) {
    if    ($ARGV[0] =~ /^\-(h|\-help)$/){ help(); exit 0;}
    elsif ($ARGV[0] =~ /^\-(v|\-verbose)$/){ $verbose = 1;}
    elsif ($ARGV[0] =~ /^\-(p|\-patch)$/) { 
	$patch = 1;
    } elsif ($ARGV[0] =~ /^\-(d)$/) { 
	$patch = 0;
    } else {
	die "Unknown option '$ARGV[0]'. Try '$0 --help'";
    }
    
    shift @ARGV;
}

die "No definition file specified" unless @ARGV;

$dfile = shift @ARGV;

				# Read and compile definition file
print STDERR "Definition file is $dfile\n" if $verbose;

if (!defined (do ($dfile))) {
    if ($!) {
	print STDERR "Can't find $dfile : '$!'\n";
	exit 1;
    } elsif ($@) {
	print STDERR "Can't compile $dfile : '$@'\n";
	exit 1;
    } else {
	print STDERR "Problem with $dfile : do returns undefined\n";
	exit 1;
    }
} 

if (!defined (&change_line)) {
    print STDERR "File '$dfile' does not define a function 'change_line()'\n";
    exit 1;
}

$has_comment = defined (&comment_line);

foreach my $f (@ARGV) {

    if (!$patch) {
	unless (open FF, "<$f") {
	    print "## Whoa!!! Can't open file '$f'. Skipping";
	    next;
	}
	print STDERR "Scanning file $f\n" if $verbose;
	
	
	local $lnum = 0;
	while (! eof (FF)) {
	    
	    my $line = <FF>;	# Read a line
	    my $olin = $line;
	    $lnum++;
	    
	    if ($has_comment) {
		if ($comment = &comment_line ($line)) {
		    $comment = "## $comment" if $comment !~ /^\s*\#/;
		    $comment .= "\n" if $comment !~ /\n$/;
		    print "$f:$.:$comment";
		}
	    }
	    
	    &change_line ($line);
	    if ($olin ne $line) {
		print "$f:$.:$olin";
	    }
	}
	close FF;
    } else {			# Do a patch. Using diff, what else?
	my $nf = "$f.new";
	my $i = 1;
	while (-e $nf) {	# Find a name for the temp file.
	    $nf = $f . ".new." . $i ;
	}
	unless (open FF, "<$f") {
	    print STDERR "## Whoa!!! Can't open file '$f'. Skipping\n";
	}
	unless (open GG, ">$nf") {
	    print STDERR "## Whoa!!! Can't open temp file '$nf'. Skipping\n";
	    next;
	}
	print STDERR "## Scanning file $f\n" if $verbose;

	while (! eof (FF)) {	# Create (temp) transformed file
	    
	    my $line = <FF>;	# Read a line
	    
	    &change_line ($line);
	    print GG $line;
	}
	close FF; close GG;
				# Call diff and modify slightly the output
	my $tmp = `diff -u $f $nf`;
	$tmp =~ s{^\+\+\+ $nf}{+++ $f}m;
	print $tmp;

	unlink($nf) or print STDERR "## Whoa!!! Can't remove temp file '$nf'\n";
    }
}