#!/usr/bin/perl

#
# Intent:
#  re-usable routines ...
#
# Note:
#   This work has been done during my time at Doctor I·T
# 
# -- Copyright drit, 2021 --
#
package misc;
require Exporter;
@ISA = qw(Exporter);
# Subs we export by default.
@EXPORT = qw();
# Subs we will export if asked.
#@EXPORT_OK = qw(nickname);
@EXPORT_OK = grep { $_ !~ m/^_/ && defined &$_; } keys %{__PACKAGE__ . '::'};

use strict;

# The "use vars" and "$VERSION" statements seem to be required.
use vars qw/$dbug $VERSION/;
# ----------------------------------------------------
our $VERSION = sprintf "%d.%02d", q$Revision: 0.0 $ =~ /: (\d+)\.(\d+)/;
my ($State) = q$State: Exp $ =~ /: (\w+)/; our $dbug = ($State eq 'dbug')?1:0;
# ----------------------------------------------------
$VERSION = &version(__FILE__) unless ($VERSION ne '0.00');

# -----------------------------------------------------------------------
sub khash { # keyed hash
   use Crypt::Digest qw();
   my $alg = shift;
   my $data = join'',@_;
   my $msg = Crypt::Digest->new($alg) or die $!;
      $msg->add($data);
   my $hash = $msg->digest();
   return $hash;
}
# -----------------------------------------------------------------------
sub version {
  #y ($atime,$mtime,$ctime) = (lstat($_[0]))[8,9,10];
  my @times = sort { $a <=> $b } (lstat($_[0]))[9,10]; # ctime,mtime
  my $vtime = $times[-1]; # biggest time...
  my $version = &rev($vtime);

  if (wantarray) {
     my $shk = &get_shake(160,$_[0]);
     print "$_[0] : shk:$shk\n" if $dbug;
     my $pn = unpack('n',substr($shk,-4)); # 16-bit
     my $build = &word($pn);
     return ($version, $build);
  } else {
     return sprintf '%g',$version;
  }
}
# -----------------------------------------------------------------------
sub rev {
  my ($sec,$min,$hour,$mday,$mon,$yy,$wday,$yday) = (localtime($_[0]))[0..7];
  my $rweek=($yday+&fdow($_[0]))/7;
  my $rev_id = int($rweek) * 4;
  my $low_id = int(($wday+($hour/24)+$min/(24*60))*4/7);
  my $revision = ($rev_id + $low_id) / 100;
  return (wantarray) ? ($rev_id,$low_id) : $revision;
}
# -----------------------------------------------------------------------
sub fdow {
   my $tic = shift;
   use Time::Local qw(timelocal);
   ##     0    1     2    3    4     5     6     7
   #y ($sec,$min,$hour,$day,$mon,$year,$wday,$yday)
   my $year = (localtime($tic))[5]; my $yr4 = 1900 + $year ;
   my $first = timelocal(0,0,0,1,0,$yr4);
   our $fdow = (localtime($first))[6];
   #printf "1st: %s -> fdow: %s\n",&hdate($first),$fdow;
   return $fdow;
}
# -----------------------------------------------------------------------
sub get_shake { # use shake 256 because of ipfs' minimal length of 20Bytes
  use Crypt::Digest::SHAKE;
  my $len = shift;
  local *F; open F,$_[0] or do { warn qq{"$_[0]": $!}; return undef };
  #binmode F unless $_[0] =~ m/\.txt/;
  my $msg = Crypt::Digest::SHAKE->new(256);
  $msg->addfile(*F);
  my $digest = $msg->done(($len+7)/8);
  return $digest;
}
# -----------------------------------------------------------------------
sub word { # 20^4 * 6^3 words (25bit worth of data ...)
 use integer;
 my $n = $_[0];
 my $vo = [qw ( a e i o u y )]; # 6
 my $cs = [qw ( b c d f g h j k l m n p q r s t v w x z )]; # 20
 my $str = '';
 if (1 && $n < 26) {
 $str = chr(ord('a') +$n%26);
 } else {
 $n -= 6;
 while ($n >= 20) {
   my $c = $n % 20;
      $n /= 20;
      $str .= $cs->[$c];
   #print "cs: $n -> $c -> $str\n";
      $c = $n % 6;
      $n /= 6;
      $str .= $vo->[$c];
   #print "vo: $n -> $c -> $str\n";

 }
 if ($n > 0) {
   $str .= $cs->[$n];
 }
 return $str;
 }
}
# -----------------------------------------------------------------------
1; # $Source: /my/perl/modules/misc.pm $