#!/usr/bin/perl -0777 -pi

# Update b4_copyright invocations or b4_copyright_years definitions to
# include the current year.

# Copyright (C) 2009-2015, 2018-2021 Free Software Foundation, Inc.

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

use strict;
use warnings;

my $margin = 72;

my $this_year = $ENV{UPDATE_COPYRIGHT_YEAR};
if (!$this_year || $this_year !~ m/^\d{4}$/)
  {
    my ($sec, $min, $hour, $mday, $month, $year) = localtime (time ());
    $this_year = $year + 1900;
  }
my $old_re = <<'EOF'
  (
    (?:^|\n)
    #BEFORE
    (?:
      b4_copyright\(\[[^][]*]
      | m4_(?:push|pop)def\(\[b4_copyright_years]
    )
    #AFTER
  )
  (?:
    ,\s*
    (
      \[\s* (?:\d{4}(?:,\s*|-))* (\d{4}) \s*]
    )
  )?
  \)
EOF
  ;

while (/($old_re)/gx)
  {
    my $start = pos() - length ($1);
    my $b4_copyright_line = $2;
    my $year_lines = $3;
    my $final_year = $4;
    $year_lines .= ')';

    # If there was a second argument, it contains years, so update them.
    if ($final_year)
      {
        $b4_copyright_line .= ',';
        if ($final_year != $this_year)
          {
            # Update the year.
            $year_lines =~ s/$final_year/$final_year, $this_year/;
          }

        # Normalize all whitespace.
        $year_lines =~ s/\s+/ /g;

        # Put spaces after commas.
        $year_lines =~ s/, ?/, /g;

        # Compress to intervals.
        $year_lines =~
          s/
            (\d{4})
            (?:
              (,\ |-)
              ((??{
                if    ($2 eq '-') { '\d{4}'; }
                elsif (!$3)       { $1 + 1;  }
                else              { $3 + 1;  }
              }))
            )+
          /$1-$3/gx;

        # Format within margin.
        my $year_lines_new;
        my $indent = index ($b4_copyright_line, '[');
        --$indent if ($b4_copyright_line =~ m/^\n/);
        while (length $year_lines)
          {
            my $text_margin = $margin - $indent;
            if (($year_lines =~ s/^(.{1,$text_margin})(?: |$)//)
                || ($year_lines =~ s/^([\S]+)(?: |$)//))
              {
                my $line = "\n" . (' 'x$indent) . $1;
                ++$indent if (!$year_lines_new);
                $year_lines_new .= $line;
              }
            else
              {
                # Should be unreachable, but we don't want an infinite
                # loop if it can be reached.
                die;
              }
          }

        # Replace the old invocation.  Should never die.
        die if (!s/$old_re\G/$b4_copyright_line$year_lines_new/x);

        # Prepare for the next search.
        pos () = $start + length ("$b4_copyright_line$year_lines_new");
      }
  }

while (/(\bb4_copyright\()/g)
  {
    my $start = pos () - length ($1);
    my $end = pos ();
    my $re = $old_re;
    pos () = $start;
    $re =~ s/\#BEFORE/\\G/;
    if (!/$re/x)
      {
        my $line = (substr ($_, 0, $start) =~ s/\n/\n/g) + 1;
        print STDERR
          "$ARGV:$line: warning: failed to update a b4_copyright\n";
      }
    pos () = $end;
  }

while (/(\[b4_copyright_years])/g)
  {
    my $start = pos () - length ($1);
    my $end = pos ();
    my $re = $old_re;
    $re =~ s/\#AFTER/\\G/;
    if (!/$re/x)
      {
        # The substr operation blows away pos (), so restoring pos ()
        # at the end is necessary.
        my $line = (substr ($_, 0, $start) =~ s/\n/\n/g) + 1;
        print STDERR
          "$ARGV:$line: warning: failed to update a"
          . " b4_copyright_years\n";
      }
    pos () = $end;
  }