#!/usr/local/bin/perl
#
#
# This is pangram.pl
#
# This script searches for 'pangrammatic windows', i.e.
# minimal length strings of characters containing all 26 letters.
#
# The input text should be only contain A-Za-z, i.e., no punctuation, no spaces.
#
# author: Matthew M. Conroy
# 
# www.madandmoonly.com/doctormatt
#
# 
#

print("Input file name: ");
chop($infilename=<STDIN>);
print"\n";

print("Starting position: ");
chop($start=<STDIN>);
print"\n";

open(IN,$infilename) || die "Cannot open $infilename for input!";

open(STD,<stdout>);
while (<IN>) {   ### read a line from the input file to $_
   $search = $_; ### set $search to be the single line of the file
}

# initialize $record
$record = 1000 ;


print "hup...\n";

%alphabet =
   ('a',0,'b',0,'c',0,'d',0,'e',0,'f',0,'g',0,'h',0,'i',0,'j',0,'k',
      0,'l',0,'m',0,'n',0,'o',0,'p',0,'q',0,'r',0,'s',0,'t',0,'u',0,'v',0,
      'w',0,'x',0,'y',0,'z',0);
$j=0;
#$record=length($search);
for($position=$start; $position<length($search); ++$position) {
   if ((($position+1)%10000)==0) {
      print "--- ",$position+1,"  record is $record \n";
   }
   if ($alphabet{lc(substr($search,$position-1,1))}<2) {
      $j=$position;
      $lettersLeft = 26;
      %alphabet = 
         ('a',0,'b',0,'c',0,'d',0,'e',0,'f',0,'g',0,'h',0,'i',0,'j',0,'k',
         0,'l',0,'m',0,'n',0,'o',0,'p',0,'q',0,'r',0,'s',0,'t',0,'u',0,'v',0,
         'w',0,'x',0,'y',0,'z',0);
      while ( ($j<length($search)) && ($lettersLeft>0)) {   
         $letter = lc(substr($search,$j,1));
         if ($alphabet{$letter}==0) {
            --$lettersLeft;
         }
         ++$alphabet{$letter};
         ++$j;
      }
   }
   else {
      --$alphabet{lc(substr($search,$position-1,1))};
   }
   if (($j<length($search)) && (($j-$position)<$record)) {
      $record = $j-$position;
      $recordPosition = $position;
      print $position,"...",$record," ",substr($search,$j-1,1),"\n";
   }
}

### print out the record pangrammatic window
print "\nRecord is $record at $recordPosition.\n\n";
for($i=$recordPosition-50; $i<$recordPosition+$record+50; ++$i) {
   if ($i==$recordPosition) {
      print "*";
   }
   print substr($search,$i,1);
   if ((($i-$recordPosition+1)%50)==0) {
      print"\n";
   }
   if ($i==($recordPosition+$record-1)) {
      print "*";
   }
}
print"\n\n";

print "length of file: ",length($search),"\n\n";
print "Done.\n";
close(IN);
close(STD);