#!/usr/bin/perl

# Конечный автомат для телеграм-бота
# Ю. Жиловец, 20.08.2024

use Modern::Perl;
use utf8;
use Mojo::Base -strict, -signatures, -async_await;

package fsa;

sub new($class, $rules, $state, $notes={})
{
  $notes->{_state} = $state;
  bless {rules=>$rules, notes=>$notes}, $class;
}

sub state($self, $new_state=undef)
{
  if (defined($new_state))
  {
    die "Unknown state '$new_state" unless exists $self->{rules}->{$new_state};
    $self->note(_state => $new_state);
  }

  $self->{notes}->{_state};
}

sub note($self, $key, $val=undef)
{
  if (defined $val)
  {
    $self->{notes}->{$key} = $val;
  }

  $self->{notes}->{$key};
}

sub notes($self)
{
  $self->{notes};
}

sub delete_note($self, $key)
{
  delete $self->{notes}->{$key};
}

async sub switch
{
  my ($self, $line, @rest) = @_;
  my $state = $self->{notes}->{_state};
  
  my $rule = $self->{rules}->{$state};
  die "fsa::switch: no rule for '$state'" unless $rule;
  
  my $new_state = $rule->($self, $line, @rest);
  $new_state = await $new_state if ref $new_state && $new_state->can("then");
  die "fsa::switch: unknown new state '$state'" unless exists $self->{rules}->{$new_state};

  $self->note("_state", $new_state);
  $new_state;
}

1;