#!/usr/bin/perl -w

# Copyright (C) 2015 Brian Masney <masneyb onstation org>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
# 
# This library 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
# Lesser General Public License for more details.
# 
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA


# This script is useful when scanning a large number of images.
# Name your files like: yyyy-name, yyyMM-name or yyyMMdd-name.
# Pass the filenames through this script and it will add an
# Exif DateTime tag to all of your photos.

while (<>) {
  chop;

  my $num = `exiv2 -pa $_ | grep Exif.Image.DateTime | wc -l`;
  next if $num != 0;

  my ($datestr) = /(^\d+)/;

  my $year;
  my $month;
  my $day;
  if (length($datestr) == 4) {
    $year = $datestr;
    $month = 7;
    $day = 1;
  }
  elsif (length($datestr) == 6) {
    ($year, $month) = $datestr =~ /^(\d{4})(\d{2})/;
    $day = 1;
  }
  elsif (length($datestr) == 8) {
    ($year, $month, $day) = $datestr =~ /^(\d{4})(\d{2})(\d{2})/;
  }
  else {
    print STDERR "Invalid date string $datestr\n";
    exit 1;
  }
  printf("exiv2 -M\"set Exif.Image.DateTime Ascii %04d:%02d:%02d 00:00:00\" \"$_\"\n", $year, $month, $day);
}