#!/usr/bin/perl
use strict;
use warnings;

use constant MinChapter       => 1;
use constant MaxChapter       => 4;

$| = 1;

use File::Basename;
use Inline::Files -backup;

my $MyName = (fileparse($0, '\..*'))[0];
my $Chapter;

sub PickARandomChapter
{
   my $Chapter;

   #
   # Get an Initial Random Chapter
   #
   $Chapter = int(rand(MaxChapter)) + MinChapter;

   #
   # Read in Previously Viewed Chapters
   #
   my $fh;
   my %PreviousChapters;
   while(<PREVIOUSCHAPTERS>)
      {
      chomp();
      print(__LINE__ . ":\[$_\]\n");
      if($_ ne '')
         {
         $PreviousChapters{$_} = 0;
         }
      }

   my $TriedChapters = 0;
   while($TriedChapters < MaxChapter)
      {
      if(exists($PreviousChapters{$Chapter}))
         {
         $TriedChapters++;
         $Chapter++;

         if($Chapter > MaxChapter)
            {
            $Chapter = MinChapter;
            }
         }
      else
         {
         $PreviousChapters{$Chapter} = 1;
         print PREVIOUSCHAPTERS "$Chapter\n";
         return($Chapter);
         }
      }

   #
   # All Chapters have been read
   # Start Over
   #
   seek(PREVIOUSCHAPTERS, 0, 0);
   print PREVIOUSCHAPTERS "$Chapter\n";

   return($Chapter);
}

if($ARGV[0])
   {
   if(lc($ARGV[0]) eq 'next')
      {
      $Chapter = <LASTCHAPTER>;
      print("\$Chapter\[$Chapter\]\n");
      $Chapter >= MaxChapter ? $Chapter = MinChapter : $Chapter++;
      print("\$Chapter\[$Chapter\]\n");
      seek LASTCHAPTER, 0, 0;
      print LASTCHAPTER $Chapter . "\n";
      close LASTCHAPTER;
      }
   elsif(($ARGV[0] =~ /\d+/) and $ARGV[0] > 0 and $ARGV[0] < 82)
      {
      $Chapter = $ARGV[0];
      }
   else
      {
      print STDERR << "USAGE";
Usage: $MyName [ChapterNumber] [Next]

$MyName               - Prints a Random Chapter from the Tao Te Ching
$MyName ChapterNumber - Prints ChapterNumber Chapter from the Tao Te C
+hing
$MyName Next          - Prints the Next Chapter from the Tao Te Ching 
+Starting at Chapter 1
USAGE
      exit(1);
      }
   }
else
   {
   $Chapter = PickARandomChapter();
   }

print("\$Chapter\[$Chapter\]\n");
__LASTCHAPTER__
1

__PREVIOUSCHAPTERS__
1
3

__CHAPTERS__
1
foo
foo bar
foo bar baz
2
foo
foo bar
3
foo
foo bar baz
4
foo
foo bar
foo bar baz
foo
foo bar
foo bar baz
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