An OpenAI chatbot in Perl and Corinna

Chat.pm

# See also: https://curtispoe.org/articles/an-openai-chatbot-in-perl.html
use v5.40.0;
use experimental qw( class );

class OpenAI::Chat;

use OpenAPI::Client::OpenAI;
use Data::Printer;
use Carp qw( croak );
use utf8::all;

# these parameters are optional
field $model          :param = 'gpt-3.5-turbo-0125';
field $temperature    :param = .1;
field $context_size   :param = 16384; # roughly

# For this example, you must pass a system message. However,
# for production code, you probably want a default one.
field $system_message :param :reader; # no default for this one

# we use $history to track the full history of the conversation, including
# token usage. The LLM is stateless. I cannot remember your conversation,
# so we send the full conversation to the LLM each time.
field $history = [];
field $openai  = OpenAPI::Client::OpenAI->new;

method _get_messages ($message) {
    my @messages = map { $_->{messages}->@* } $history->@*;
    if ($system_message) {
        # we always add the system message to the front so that the LLM can
        # understand how it's supposed to behave.
        unshift @messages, { role => 'system', content => $system_message };
    }
    push @messages, $self->_format_user_message($message);
    return \@messages;
}

method _format_user_message ($message) {
    return { role => 'user', content => $message };
}

method _total_tokens () {
    my $total_tokens = 0;
    for my $entry ( $history->@* ) {
        $total_tokens += $entry->{usage}{total_tokens};
    }
    return $total_tokens;
}

method _trim_messages_to_context_size () {
    while ( $self->_total_tokens > $context_size ) {
        # remove the oldest messages first
        shift $history->@*;
    }
}

method prompt ($prompt) {
    my $response = $openai->createChatCompletion(
        {
            body => {
                model       => $model,
                messages    => $self->_get_messages($prompt),
                temperature => $temperature,
            }
        }
    );
    if ( $response->res->is_success ) {
        my $result;
        try {
            my $message = $response->res->json->{choices}[0]{message};
            my $usage   = $response->res->json->{usage};
            push $history->@* => {
                # track the messages *and* the token usage so we can
                # keep track of our context size
                messages => [
                    $self->_format_user_message($prompt),    # prompt
                    $message,                                # response
                ],
                usage => $usage,
            };
            $result = $message->{content};
            $self ->_trim_messages_to_context_size;
        }
        catch ($e) {
            croak("Error decoding JSON: $e");
        }
        return $result;
    }
    else {
        my $error = $response->res;
        croak( $error->to_string );
    }
}

method _data_printer {
    my $details = {
        model          => $model,
        system_message => $system_message,
        temperature    => $temperature,
        context_size   => $context_size,
        history        => $history,
    };
    return np $details;
}