package VladimirBot::Math;

use strict;
use Parse::Earley;
use Data::Dumper;
$Data::Dumper::Deparse = 1;
#$Data::Dumper::Maxdepth = 4;

# Here I push myself onto the module call stack
push @VladimirBot::vladimir_module, 'Math';

#$Parse::Earley::DEBUG = 1;
#$Data::Dumper::Maxdepth = 5;
$Data::Dumper::Indent = 1;

sub print_tree {
  my ($tree, $indent) = @_;
  if($tree->{tok}) {
    print 'terminal (' . $tree->{lhs} . '): ';
    print $tree->{tok};
  } elsif ($tree->{production}) {
    print "production: ";
    print $tree->{lhs};
  }
  print "\n";
  if($tree->{left} && $tree->{left}[0]->{left}) {
  #if($tree->{left}) {
    print $indent . 'left - ';
    print_tree($tree->{left}[0], $indent . '  ');
  }
  if($tree->{down}) {
    print $indent . 'down - ';
    print_tree($tree->{down}[0], $indent . '  ');
  }
}

sub parse {
  my $sentence = shift;
  my $grammar = <<'END';

input:
    expr
  | 'what' 'is' expr { $_[2] }
  | 'what' 'is' expr '?' { $_[2] }

expr:
    mul_expr '+' expr
  | mul_expr '-' expr
  | mul_expr

mul_expr:
    term '*' mul_expr
  | term '/' mul_expr
  | term

term:
    '(' expr ')'
  | /\d+(\.\d+)?/

#   | number
# 
# number:
#     ones
#   | tens ones
#   | tens
#   | ones 'hundred' 'and' tens ones
#   | ones 'hundred' 'and' tens
#   | Ones 'hundred' 'and' ones
# 
# ones:
#     'one' { '1' }
#   | 'two' { '2' }
#   | 'three' { '3' }
#   | 'four' { '4' }
#   | 'five' { '5' }
#   | 'six' { '6' }
#   | 'seven' { '6' }
#   | 'eight' { '6' }
#   | 'nine' { '6' }
#   | 'six' { '6' }
#   | 'six' { '6' }
#   | 'six' { '6' }
#   | 'six' { '6' }
#   | 'six' { '6' }
#   | 'six' { '6' }
#   | 'six' { '6' }
#   | 'six' { '6' }
#   | 'six' { '6' }
#   | 'six' { '6' }
#   | 'six' { '6' }

END


  #print "Trying to parse: $sentence\n";
  my $parser = new Parse::Earley;
  $parser->grammar($grammar);
  $parser->start('input');

  do {
    $parser->advance($sentence)
  } until(
      $parser->fails($sentence, 'input')
      or $parser->matches($sentence, 'input'));

  #print "Parse failed\n" if $parser->fails($sentence, 'input');

  if ($parser->matches($sentence, 'input'))
  {
    my $out;
    print "Parse succeeded\n";
    my $graph;
    ($graph) = $parser->matches($sentence, 'input');
    #my $action = $parser->{actions};
    #my $e = $parser->eval_production($action, $graph);
    my $e = $parser->eval_production($graph);
    #my $e = Parse::Earley::eval_production($action, $graph);
    $out = "result: $e = ";
    $out .= (eval $e);
   
   $out .= "\n";
    return $out;

    
    #print "here";
    #print "graph: " . Dumper(\$graph) . "\n";
    #print "Tree:\n";
    #print_tree($graph, '  ');
  }


  
  return 0;

}

1;