package ANTLR::Runtime::DFA;

use Params::Validate qw( :types );
use Error qw( try finally );

use Moose;

has 'eot' => (
    is  => 'rw',
    isa => 'ArrayRef[Int]',
);

has 'eof' => (
    is  => 'rw',
    isa => 'ArrayRef[Int]',
);

has 'min' => (
    is  => 'rw',
    isa => 'ArrayRef[Str]',
);

has 'max' => (
    is  => 'rw',
    isa => 'ArrayRef[Str]',
);

has 'accept' => (
    is  => 'rw',
    isa => 'ArrayRef[Int]',
);

has 'special' => (
    is  => 'rw',
    isa => 'ArrayRef[Int]',
);

has 'transition' => (
    is  => 'rw',
    isa => 'ArrayRef[ArrayRef[Int]]',
);

has 'decision_number' => (
    is  => 'rw',
    isa => 'Int',
);


# Which recognizer encloses this DFA?  Needed to check backtracking
has 'recognizer' => (
    is  => 'rw',
    isa => 'ANTLR::Runtime::BaseRecognizer',
);


sub get_description {
    return "n/a";
}

# From the input stream, predict what alternative will succeed
# using this DFA (representing the covering regular approximation
# to the underlying CFL).  Return an alternative number 1..n.  Throw
# an exception upon error.
sub predict {
    my ($self, $input) = @_;

    my $mark = $input->mark();  # remember where decision started in input
    my $s = 0; # we always start at s0

    try {
        while (1) {
            my $special_state = $self->special->[$s];
            if ($special_state >= 0) {
                $s = $self->special_state_transition($special_state, $input);
                if ($s == -1) {
                    $self->no_viable_alt($s, $input);
                    return 0;
                }
                $input->consume();
                next;
            }

            if ($self->accept->[$s] >= 1) {
                return $self->accept->[$s];
            }

	    # look for a normal char transition
            my $c = $input->LA(1);  # -1 == \uFFFF, all tokens fit in 65000 space

            if ($c >= $self->min->[$s] && $c <= $self->max->[$s]) {
                my $next_s = $self->transition->[$s][$c - $self->min->[$s]];  # move to next state

                if ($next_s < 0) {
                    # was in range but not a normal transition
                    # must check EOT, which is like the else clause.
                    # eot[s]>=0 indicates that an EOT edge goes to another
                    # state.
                    if ($self->eot->[$s] >= 0) {  # EOT Transition to accept state?
                        $s = $self->eot->[$s];
                        $input->consume();
                        # TODO: I had this as return accept[eot[s]]
                        # which assumed here that the EOT edge always
                        #went to an accept...faster to do this, but
                        # what about predicated edges coming from EOT
                        # target?
                        next;
                    }

                    $self->no_viable_alt($s, $input);
                    return 0;
                }

                $s = $next_s;
                $input->consume();
                next;
            }

	    if ($self->eot->[$s] >= 0) {  # EOT Transition?
		$s = $self->eot->[$s];
		$input->consume();
		next;
	    }

	    if ($c == ANTLR::Runtime::Token->EOF && $self->eof->[$s] >= 0) {  # EOF Transition to accept state?
		return $self->accept->[$self->eof->[$s]];
	    }

	    # not in range and not EOF/EOT, must be invalid symbol
	    $self->no_viable_alt($s, $input);
	    return 0;
        }
    }
    finally {
	$input->rewind();
    };
}

sub no_viable_alt {
    my ($self, $s, $input) = @_;

    if ($self->recognizer->state->backtracking > 0) {
	$self->recognizer->state->failed = 1;
	return;
    }
    my $nvae = ANTLR::Runtime::NoViableAltException({
	grammar_decision_description => $self->get_description(),
	decision_number => $self->decision_number,
	state_number => $self->state_number,
	input => $input
    });
    $self->error($nvae);
    $nvae->throw();
}

# A hook for debugging interface
sub error {
    my ($self, $nvae) = @_;
}

sub special_state_transition {
    my ($self, $s, $input) = @_;

    return -1;
}

# Given a String that has a run-length-encoding of some unsigned shorts
# like "\1\2\3\9", convert to short[] {2,9,9,9}.  We do this to avoid
# static short[] which generates so much init code that the class won't
# compile. :(
sub unpack_encoded_string {
    my ($self, $encoded_string) = @_;

    my $data = [];
    while ($encoded_string =~ /(.)(.)/gxms) {
        my ($n, $v) = ($1, $2);

        push @$data, $v x $n;
    }

    return $data;
}

sub unpack_encoded_string_to_unsigned_chars {
    my ($self, $encoded_string) = @_;
   
    return $self->unpack_encoded_string($encoded_string);
}

no Moose;
__PACKAGE__->meta->make_immutable();
1;
__END__