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<?php
/**
* AI chat summarizer class file.
*
* @since 4.13.0
*
* @package LearnDash\Core
*/
namespace LearnDash\Core\Modules\AI;
use LearnDash\Core\App;
use LearnDash\Core\Services\ChatGPT;
use LearnDash\Core\Utilities\Cast;
/**
* Chat_Summarizer class.
*
* TODO: add wpunit tests for all methods and integration tests for the functionalities with the summarization stuff.
*
* @since 4.13.0
*/
class ChatGPT_Summarizer {
/**
* Default last preserved messages count.
*
* Last preserved messages count to be kept unsummarized to provide more context to AI provider.
*
* @since 4.13.0
*
* @var int
*/
private const LAST_PRESERVED_MESSAGES_COUNT = 10;
/**
* Maximum context characters count threshold allowed before chat messages are summarized.
*
* We use 1:1 ratio of tokens to characters and 50% of AI model max context length tokens to be very safe in
* any language such as Russian, Japanese, Arabic, etc.
* Currently, we don't have a reliable package to count tokens in PHP, so we use characters instead.
* For example, GPT-3 has a max context length of 4096 tokens, so we set the max characters to 2048.
*
* @since 4.13.0
*
* @var int
*/
private int $max_context_characters;
/**
* Chat messages.
*
* @since 4.13.0
*
* @var Chat_Message[]
*/
private array $messages;
/**
* Constructor.
*
* @since 4.13.0
*
* @param Chat_Message[] $messages Chat messages.
*/
public function __construct( array $messages ) {
$this->messages = $messages;
$this->max_context_characters = $this->get_max_context_characters();
}
/**
* Summarizes chat messages.
*
* The summarization logic is as follows:
*
* We keep the first system message + the last user message which has the latest question + the last 10
* unsummarized messages (5 pairs of user and assistant messages). We summarize the rest of the messages and
* return the summary to include it in the next request. We keep the last 10 unsummarized messages to provide
* more context to AI provider.
*
* In the end we will get 1 first system message + 1 messages summary + 10 last unsummarized messages + 1
* last user message in that particular order.
*
* @since 4.13.0
*
* @return string Summarized chat messages.
*/
public function summarize_messages(): string {
$messages_to_summarize = array_slice( $this->messages, 1, $this->get_last_preserved_messages_count() * -1 );
$summary = $this->generate_summary( $messages_to_summarize );
/**
* Filters the summary of the previous conversation.
*
* @since 4.13.0
*
* @param string $content Summary content of the previous conversation to be passed to AI provider including the message prefix to describe what it is.
* @param string $summary Raw summary of the previous conversation.
* @param Chat_Message[] $messages Original chat messages.
*
* @return string Summary content of the previous conversation.
*/
return apply_filters(
'learndash_module_ai_chatgpt_summarizer_messages_summary_content',
sprintf(
// translators: %s: Summary of the previous conversation.
__( 'Here is the summary of the previous conversation: %s', 'learndash' ),
$summary
),
$summary,
$this->messages
);
}
/**
* Checks if messages need summarization.
*
* @since 4.13.0
*
* @return bool
*/
public function messages_need_summarization(): bool {
// Skip summarization if the messages count is less than or equal to the last preserved messages count.
if ( count( $this->messages ) <= $this->get_last_preserved_messages_count() ) {
return false;
}
$total_chars = 0;
foreach ( $this->messages as $message ) {
$total_chars += mb_strlen( $message->content );
if ( $total_chars > $this->max_context_characters ) {
return true;
}
}
return false;
}
/**
* Gets preserved messages.
*
* The preserved messages are the last messages to be kept unsummarized to provide more context to AI provider.
*
* @since 4.13.0
*
* @return Chat_Message[]
*/
public function get_preserved_messages(): array {
return array_slice( $this->messages, $this->get_last_preserved_messages_count() * -1 );
}
/**
* Generates summary of provided chat messages.
*
* @since 4.13.0
*
* @param Chat_Message[] $messages Messages to summarize.
*
* @return string ChatGPT chat messages summary.
*/
private function generate_summary( array $messages ): string {
$messages_string = wp_json_encode( $messages );
if ( $messages_string === false ) {
return '';
}
/**
* Filters the command to generate summary of chat messages.
*
* @since 4.13.0
*
* @param string $command Command to generate summary of chat messages.
* @param Chat_Message[] $messages Original messages.
*
* @return string Command to generate summary of chat messages.
*/
$command = apply_filters(
'learndash_module_ai_chatgpt_summarizer_command_generate_summary',
sprintf(
// translators: %1$d: Maximum characters count, %2$s: Messages in JSON format.
__( 'Summarize these chat messages which are in JSON format to be maximum below %1$d characters and return it as string: %2$s', 'learndash' ),
$this->max_context_characters,
$messages_string
),
$messages
);
/**
* ChatGPT service instance.
*
* @var ChatGPT $chatgpt ChatGPT service instance.
*/
$chatgpt = App::make( ChatGPT::class );
return $chatgpt->send_command( $command );
}
/**
* Returns the last preserved messages count.
*
* @since 4.13.0
*
* @return int
*/
private function get_last_preserved_messages_count(): int {
/**
* Filters the kept last messages count to be used in summarization.
*
* The kept last messages count is the number of last messages to be kept unsummarized to provide more
* context to AI provider.
*
* @since 4.13.0
*
* @param int $last_preserved_messages_count Last preserved messages count.
*
* @return int Last preserved messages count.
*/
return apply_filters(
'learndash_module_ai_chatgpt_summarizer_last_preserved_messages_count',
self::LAST_PRESERVED_MESSAGES_COUNT
);
}
/**
* Returns the maximum context characters count threshold allowed before chat messages are summarized.
*
* @since 4.13.0
*
* @return int
*/
private function get_max_context_characters(): int {
/**
* Filters the maximum context characters count threshold allowed before chat messages are summarized.
*
* We use 1:1 ratio of tokens to characters and 50% of AI model max context length tokens to be very safe
* in any language such as Russian, Japanese, Arabic, etc.
* Currently, we don't have a reliable package to count tokens in PHP, so we use characters instead.
* For example, GPT-3 has a max context length of 4096 tokens, so we set the max characters to 2048.
*
* @since 4.13.0
*
* @param int $max_context_characters Maximum context characters count threshold allowed before chat messages are summarized.
*
* @return int Maximum context characters count threshold allowed before chat messages are summarized.
*/
return apply_filters(
'learndash_module_ai_chatgpt_summarizer_max_context_characters',
Cast::to_int(
ceil( ChatGPT::get_model_max_context_window_tokens() / 2 )
)
);
}
}