#!/usr/bin/env perl
# ***************************************************************************
#.MODULE:   sexagesimal.pl
#.PURPOSE:  Parser for a single sexagesimal number
#.AUTHOR:   A.Micol, ST-ECF
#.DATE:     A boring Saturday night.
#.DEFINITIONS:
#
# 1.- A (one) sexagesimal number is a sequence of up to 3 (minimum 1)
#     groups of numbers separated (followed) by an indefinite number of
#     whatever characters except 0-9 + -
#     Only one group, ***the last one***, can be a float.
#     If none of the groups is a float, the sequence must contain 3 groups.
#     Only one group, the first one, can have a sign (+-).
#     The second and third groups are base-60.
# 
# 2.- A pair of sexagesimal numbers is a sequence of two sexagesimal numbers.
#
# ***************************************************************************

my( @group, $rest, $is_float, $is_integer );
my( $sexagesimal )  = $ARGV[0];

print "Input string: [$sexagesimal]\n";

#
# Copy input into destroyable $trynum
#

my( $trynum ) = $sexagesimal;

#
# Try the three groups, but stop as soon as float is encountered.
#
foreach( $i=0; $i < 3; $i++)
{
   # Get first available numeric group in trynum

   ( $is_float, $float, $sep, $rest ) = &isFloat( $trynum );

   if ( $is_float )
   {
      &checkCompliance( $i, $float );
      $group[ $i ] = $float;
      last;
   }
   else
   {
      ( $is_integer, $integer, $sep, $rest ) = &isInteger( $trynum );
      if ( ! $is_integer ) {  &exception( $trynum ); }

      &checkCompliance( $i, $float );
      $group[ $i ] = $integer;
   }

   if ( $sep =~ /[+-]/ )
   {
      &exception( "Found sign in wrong position\n" );
   }
   
   $trynum = $rest;

   if ( $trynum eq "" ) { last; }
}

#
# Last group can be integer if and only if it is the third one!
#

if ( $#group + 1 < 3  && ! $is_float )
{
   &exception( "Found only two integer groups" );
}

#
# Final check:
# No remaining part of the input string can contains other digits!
#

if ( $sep =~ /.*\d.*/ ) { &exception( "Found extra digits ($sep)" ); }
if ( $rest =~ /.*\d.*/ ) { &exception( "Found extra digits ($rest)" ); }

#
# Success!
#

print "Found a ", $#group + 1, "-group sexagesimal number.\n";

#
# Return the sexagesimal number in a "canonical" format (e.g. 12:00:23.71).
#

$canonical = "";
foreach( $i=0; $i < $#group+1; $i++ )
{
   $canonical .= "$group[$i]:";
}
chop( $canonical );

print "Canonical form: [$canonical]\n";
#print "Successfully parsed sexagesimal\n";

#
# --- END OF MAIN ---
#

#
# The second or third group shall not be negative, nor .ge. 60.
sub checkCompliance
{
   my( $group_index, $number ) = @_;

   if ( $group_index > 0 && $number < 0.0 )
   {
      &exception( "Only first group can be negative" );
   }
   if ( $group_index > 0 && $number >= 60.0 )
   {
      &exception( "Only first group can be greater (or equal) than 60." );
   }
}

sub isInteger
{
   my( $num ) = $_[0];
   my( $is_integer ) = 0;
   my( $integer, $rest );

   if ( $num =~ /^([+-]){0,1}(\d+)(\D+)(.*)/  ||
        $num =~ /^(\d+)$/          )
   {
      $is_integer = 1;
      $sign      = $1;
      $integer   = $2;
      $separator = $3;
      $rest      = $4;
   }

   return( $is_integer, $sign.$integer, $separator, $rest );
}

sub isFloat
{
   my( $num ) = $_[0];
   my( $is_float ) = 0;
   my( $float, $rest );

   if ( $num =~ /^([+-]){0,1}(\d+\.\d*)(\D+.*)/  ||
        $num =~ /^([+-]){0,1}(\d+\.\d*)$/   )
   {
      $is_float  = 1;
      $sign      = $1;
      $float     = $2;
      $separator = $3;
      $rest      = $4;
   }

   return( $is_float, $sign.$float, $separator, $rest );
}

sub exception
{
   my( $msg ) = $_[0];

   print "*** ERROR $msg \n";
   exit(1);
}