#!/usr/bin/perl -w
use strict;

my $config = do(shift || "fsm.config");

my $state = $config->{start_state};
my $input = "";

while (($state, $input) = compute($state, get_input())) {
    action($state, $input);
}

action($state, $input);

# --------------------------------------------------
# subs
# --------------------------------------------------

sub get_input {
    print "Your input (", join("|", @{$config->{input_alphabet}}), "): ";
    my $input = <>;
    chomp($input);
    return $input;
}

sub compute {
    my ($state, $input) = @_;
    return $config->{transition_function}->{$state}->{$input}, $input;
}

sub action {
    my ($state, $input) = @_;
    $config->{action_function}->{$state}->{$input}->()
        if $config->{action_function}->{$state}->{$input};
    die "REJECT\n" unless $state;
    die "ACCEPT\n" if accept_p($state);
}

sub accept_p {
    my ($state) = @_;
    return 1 if grep {$state eq $_} @{$config->{goal_states}};
    return 0;
}