extension.php

<?php

declare(strict_types=1);

final class LlmClassificationExtension extends Minz_Extension {
	private const DEFAULT_MODEL = 'gpt-4o-mini';
	private const DEFAULT_TIMEOUT = 30;
	private const DEFAULT_MAX_CONTENT_LENGTH = 4000;
	private const DEFAULT_MAX_TOKENS = 512;
	private const DEFAULT_MAX_RETRIES = 2;
	private const RETRYABLE_HTTP_STATUSES = [429, 500, 502, 503, 504];
	private const PROMPT_FILENAME = 'prompt.md';
	private const ATTRIBUTE_PROMPT_HASH = 'prompt_hash';

	public string $user_prompt = '';

	/**
	 * @throws FreshRSS_Context_Exception
	 */
	#[\Override]
	public function init(): void {
		if (!FreshRSS_Context::hasSystemConf()) {
			throw new FreshRSS_Context_Exception('System configuration not initialised!');
		}
		$this->registerTranslates();
		$this->registerHook(Minz_HookType::EntryBeforeInsert, $this->classifyEntry(...));

		if ($this->getUserConfigurationString('api_url') === null) {
			$this->setUserConfigurationValue('api_url', '');
		}
		if ($this->getUserConfigurationString('api_key') === null) {
			$this->setUserConfigurationValue('api_key', '');
		}
		if ($this->getUserConfigurationString('model') === null) {
			$this->setUserConfigurationValue('model', self::DEFAULT_MODEL);
		}
		if ($this->getUserConfigurationInt('max_content_length') === null) {
			$this->setUserConfigurationValue('max_content_length', self::DEFAULT_MAX_CONTENT_LENGTH);
		}
		if ($this->getUserConfigurationInt('timeout') === null) {
			$this->setUserConfigurationValue('timeout', self::DEFAULT_TIMEOUT);
		}
		if ($this->getUserConfigurationBool('enable_tags') === null) {
			$this->setUserConfigurationValue('enable_tags', false);
		}
		if ($this->getUserConfigurationString('tag_prefix') === null) {
			$this->setUserConfigurationValue('tag_prefix', '');
		}
		if ($this->getUserConfigurationString('allowed_tags') === null) {
			$this->setUserConfigurationValue('allowed_tags', '');
		}
		if ($this->getUserConfigurationInt('max_tokens') === null) {
			$this->setUserConfigurationValue('max_tokens', self::DEFAULT_MAX_TOKENS);
		}
		if ($this->getUserConfigurationInt('max_retries') === null) {
			$this->setUserConfigurationValue('max_retries', self::DEFAULT_MAX_RETRIES);
		}
		if ($this->getUserConfigurationString('search_filter') === null) {
			$this->setUserConfigurationValue('search_filter', '');
		}
		if ($this->getUserConfigurationBool('allow_thinking') === null) {
			$this->setUserConfigurationValue('allow_thinking', true);
		}
	}

	#[\Override]
	public function handleConfigureAction(): void {
		$this->registerTranslates();

		if (Minz_Request::isPost()) {
			$apiUrl = trim(Minz_Request::paramString('api_url', plaintext: true));
			$apiUrl = preg_replace('#/chat/completions/?$#i', '', $apiUrl) ?? $apiUrl;
			$this->setUserConfigurationValue('api_url', $apiUrl);
			$this->setUserConfigurationValue('api_key', trim(Minz_Request::paramString('api_key', plaintext: true)));
			$this->setUserConfigurationValue('model', trim(Minz_Request::paramString('model', plaintext: true)));
			$userPrompt = trim(Minz_Request::paramString('user_prompt', plaintext: true))
				?: _t('ext.llm_classification.default_prompt');
			$this->saveFile(self::PROMPT_FILENAME, $userPrompt);
			$this->setUserConfigurationValue('max_content_length', Minz_Request::paramInt('max_content_length'));
			$this->setUserConfigurationValue('timeout', Minz_Request::paramInt('timeout') ?: self::DEFAULT_TIMEOUT);
			$this->setUserConfigurationValue('max_tokens', Minz_Request::paramInt('max_tokens'));
			$this->setUserConfigurationValue('max_retries', max(0, min(5, Minz_Request::paramInt('max_retries'))));
			$this->setUserConfigurationValue('enable_tags', Minz_Request::paramBoolean('enable_tags'));
			$this->setUserConfigurationValue('tag_prefix', trim(Minz_Request::paramString('tag_prefix', plaintext: true)));
			$this->setUserConfigurationValue('allowed_tags', trim(Minz_Request::paramString('allowed_tags', plaintext: true)));
			$this->setUserConfigurationValue('search_filter', trim(Minz_Request::paramString('search_filter', plaintext: true)));
			$this->setUserConfigurationValue('allow_thinking', Minz_Request::paramBoolean('allow_thinking'));
		}

		$this->user_prompt = '';
		if ($this->hasFile(self::PROMPT_FILENAME)) {
			$this->user_prompt = $this->getFile(self::PROMPT_FILENAME) ?? '';
		}
	}

	/**
	 * Build the system prompt that constrains the LLM to return a specific JSON structure.
	 */
	public function getSystemPrompt(): string {
		$prompt = <<<'PROMPT'
			You are a classification assistant.
			Your response MUST be valid JSON with exactly this structure: `{"tags": ["tag1", "tag2"]}`
			Rules:
			- "tags" is an array of short classification labels (UTF-8). It can be empty. Each label can only be used once.
			- Do NOT include any text outside the JSON object.

			PROMPT;

		$allowedTags = $this->getUserConfigurationString('allowed_tags') ?? '';
		if ($allowedTags !== '') {
			$tagList = array_filter(array_map('trim', explode("\n", $allowedTags)), static fn(string $tag) => $tag !== '');
			if ($tagList !== []) {
				$prompt .= '- You MUST only use tags from this list: ' . implode(', ', $tagList) . "\n";
			}
		}

		return $prompt;
	}

	/**
	 * Build the user prompt by replacing placeholders with entry values.
	 */
	private function buildUserPrompt(FreshRSS_Entry $entry): string {
		$template = $this->getFile(self::PROMPT_FILENAME) ?? '';
		if ($template === '') {
			return '';
		}

		$content = strip_tags($entry->content());
		$maxLength = $this->getUserConfigurationInt('max_content_length') ?? self::DEFAULT_MAX_CONTENT_LENGTH;
		if ($maxLength > 0 && mb_strlen($content) > $maxLength) {
			$content = mb_substr($content, 0, $maxLength) . '…';
		}

		$feed = $entry->feed();

		$replacements = [
			'{title}' => $entry->title(),
			'{content}' => $content,
			'{author}' => $entry->authors(true),
			'{url}' => $entry->link(),
			'{feed_url}' => $feed !== null ? $feed->url() : '',
			'{feed_name}' => $feed !== null ? $feed->name() : '',
			'{date}' => $entry->date(),
			'{tags}' => $entry->tags(true),
		];

		return strtr($template, $replacements);
	}

	/**
	 * Check whether the entry matches the configured search filter.
	 * Returns true if no filter is configured or the entry matches at least one filter line.
	 * @throws Minz_BadRequestException
	 */
	private function entryMatchesSearchFilter(FreshRSS_Entry $entry): bool {
		$filterStr = $this->getUserConfigurationString('search_filter') ?? '';
		if ($filterStr === '') {
			return true;
		}
		$lines = array_filter(array_map('trim', explode("\n", $filterStr)), static fn(string $line) => $line !== '');
		foreach ($lines as $line) {
			$booleanSearch = new FreshRSS_BooleanSearch($line);
			if ($entry->matches($booleanSearch)) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Build the response_format payload for the API request.
	 * Uses json_schema for strict structured output.
	 * When allowed_tags is configured, the schema constrains tag values via an enum.
	 * @return array<string,mixed>
	 */
	private function buildResponseFormat(): array {
		$allowedTagsStr = $this->getUserConfigurationString('allowed_tags') ?? '';
		$allowedTags = $allowedTagsStr !== ''
			? array_values(array_filter(array_map('trim', explode("\n", $allowedTagsStr)), static fn(string $tag) => $tag !== ''))
			: [];

		if ($allowedTags === []) {
			return ['type' => 'json_object'];
		}

		return [
			'type' => 'json_schema',
			'json_schema' => [
				'name' => 'classification',
				'strict' => true,
				'schema' => [
					'type' => 'object',
					'properties' => [
						'tags' => [
							'type' => 'array',
							'uniqueItems' => true,
							'maxItems' => count($allowedTags),
							'items' => ['type' => 'string', 'enum' => $allowedTags],
						],
					],
					'required' => ['tags'],
					'additionalProperties' => false,
				],
			],
		];
	}

	/**
	 * Determine whether an HTTP failure is transient and worth retrying.
	 * @param array{fail:bool,status:int,error:string} $response
	 */
	private static function isRetryableFailure(array $response): bool {
		if (!($response['fail'] ?? false)) {
			return false;
		}
		if (($response['status'] ?? 0) === 0 && ($response['error'] ?? '') !== '') {
			return true;
		}
		return in_array($response['status'] ?? 0, self::RETRYABLE_HTTP_STATUSES, true);
	}

	/**
	 * Call the LLM API and return the parsed classification result.
	 * @return array{tags:array<string>}|null
	 * @throws Minz_PermissionDeniedException
	 */
	private function callLlm(string $systemPrompt, string $userPrompt): ?array {
		$apiUrl = trim($this->getUserConfigurationString('api_url') ?? '');
		$apiKey = trim($this->getUserConfigurationString('api_key') ?? '');
		$model = trim($this->getUserConfigurationString('model') ?? '') ?: self::DEFAULT_MODEL;
		$timeout = $this->getUserConfigurationInt('timeout') ?? self::DEFAULT_TIMEOUT;

		if ($apiUrl === '') {
			return null;
		}

		$url = rtrim($apiUrl, '/') . '/chat/completions';

		$body = [
			'model' => $model,
			'messages' => [
				['role' => 'system', 'content' => $systemPrompt],
				['role' => 'user', 'content' => $userPrompt],
			],
			'response_format' => $this->buildResponseFormat(),
		];

		$maxTokens = $this->getUserConfigurationInt('max_tokens') ?? self::DEFAULT_MAX_TOKENS;
		if ($maxTokens > 0) {
			$body['max_completion_tokens'] = $maxTokens;
		}

		$allowThinking = $this->getUserConfigurationBool('allow_thinking') ?? true;
		if (!$allowThinking) {
			$body['chat_template_kwargs'] = [
				'enable_thinking' => false,
			];
		}

		$requestBody = json_encode($body, JSON_INVALID_UTF8_SUBSTITUTE | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);

		if ($requestBody === false) {
			Minz_Log::warning('LlmClassification: Failed to encode request body');
			return null;
		}

		$headers = [
			'Content-Type: application/json',
			'Accept: application/json',
		];
		if ($apiKey !== '') {
			$headers[] = 'Authorization: Bearer ' . $apiKey;
		}

		$cachePath = CACHE_PATH . '/llm_classification_' . sha1($apiUrl . $apiKey . $model . $requestBody) . '.json';

		$maxRetries = $this->getUserConfigurationInt('max_retries') ?? self::DEFAULT_MAX_RETRIES;
		$response = null;
		$httpStatus = 0;

		for ($attempt = 0; $attempt <= $maxRetries; $attempt++) {
			$response = FreshRSS_http_Util::httpGet($url, $cachePath, type: 'json', curl_options: [
				CURLOPT_POST => true,
				CURLOPT_POSTFIELDS => $requestBody,
				CURLOPT_HTTPHEADER => $headers,
				CURLOPT_CONNECTTIMEOUT => 5,
				CURLOPT_TIMEOUT => $timeout,
			]);

			$httpStatus = $response['status'] ?? null;
			$httpStatus = is_numeric($httpStatus) ? (int)$httpStatus : 0;

			if (!($response['fail'] ?? false) && ($response['body'] ?? '') !== '') {
				break;	// Success
			}

			if ($attempt < $maxRetries && self::isRetryableFailure($response)) {
				$delay = (int)pow(2, $attempt);	// Exponential backoff: 1s, 2s, 4s...
				Minz_Log::warning('LlmClassification: API call failed (HTTP ' . $httpStatus
					. (($response['error'] ?? '') !== '' ? '; ' . ($response['error'] ?? '') : '')
					. '), retry ' . ($attempt + 1) . '/' . $maxRetries . ' after ' . $delay . 's');
				sleep($delay);
				@unlink($cachePath);
				continue;
			}

			Minz_Log::warning('LlmClassification: API call failed for ' . $url
				. ' (HTTP ' . $httpStatus
				. (($response['error'] ?? '') !== '' ? '; ' . ($response['error'] ?? '') : '')
				. '), not retrying');
			return null;
		}

		if ($response === null || ($response['fail'] ?? false) || !is_string($response['body'] ?? null) || ($response['body'] ?? '') === '') {
			Minz_Log::warning('LlmClassification: API call failed after ' .
				(1 + $maxRetries) . ' attempt(s) for ' . $url . ' (HTTP ' . $httpStatus . ')');
			return null;
		}

		$responseData = json_decode($response['body'], true);
		if (!is_array($responseData)) {
			Minz_Log::warning('LlmClassification: Invalid JSON response from API! (HTTP ' . $httpStatus . ')');
			return null;
		}

		$choices = $responseData['choices'] ?? null;
		$choice = is_array($choices) && is_array($choices[0] ?? null) ? $choices[0] : null;
		$content = is_array($choice) && is_array($choice['message'] ?? null) ? ($choice['message']['content'] ?? null) : null;
		if (!is_string($content)) {
			Minz_Log::warning('LlmClassification: Missing `choices[0].message.content` in API response! (HTTP ' . $httpStatus . ')');
			return null;
		}

		$finishReason = is_array($choice) ? ($choice['finish_reason'] ?? 'stop') : null;
		if ($finishReason !== 'stop') {
			$finishReason = is_scalar($finishReason) ? (string)$finishReason : '?';
			Minz_Log::warning('LlmClassification: API terminated prematurely with finish_reason “' . $finishReason . '”! (HTTP ' . $httpStatus . ')');
		}

		$classification = json_decode($content, true);
		if (is_array($classification) && is_array($classification['tags'] ?? null)) {
			return [
				'tags' => array_filter($classification['tags'], static fn($tag) => is_string($tag) && $tag !== ''),
			];
		}

		Minz_Log::warning('LlmClassification: LLM returned invalid JSON structure! `' . ($response['body'] ?? '') . '` (HTTP ' . $httpStatus . ')');
		return null;
	}

	/**
	 * Apply classification results to an entry.
	 * @param array<string,mixed> $classification
	 */
	private function applyClassification(FreshRSS_Entry $entry, array $classification, bool $removeOldTags): FreshRSS_Entry {
		if (is_array($classification['tags'] ?? null)) {
			$prefix = $this->getUserConfigurationString('tag_prefix') ?? '';
			$allowedTagsStr = $this->getUserConfigurationString('allowed_tags') ?? '';
			$allowedTags = $allowedTagsStr !== ''
				? array_filter(array_map('trim', explode("\n", $allowedTagsStr)), static fn(string $tag) => $tag !== '')
				: [];

			$existingTags = $entry->tags();

			if ($removeOldTags && $prefix !== '') {
				$existingTags = array_values(array_filter(
					$existingTags,
					static fn(string $tag) => !str_starts_with($tag, $prefix)
				));
			}

			$newTags = [];
			foreach ($classification['tags'] as $tag) {
				if (!is_string($tag)) {
					continue;
				}
				$tag = trim($tag);
				if ($tag === '') {
					continue;
				}
				if (!empty($allowedTags) && !in_array($tag, $allowedTags, true)) {
					continue;
				}
				$newTags[] = htmlspecialchars($prefix . $tag, ENT_COMPAT, 'UTF-8');
			}

			$entry->_tags(array_values(array_unique(array_merge($existingTags, $newTags))));
		}

		return $entry;
	}

	/**
	 * Look up the currently stored entry for an entry being updated.
	 * @throws Minz_PermissionDeniedException
	 */
	private function loadExistingEntry(FreshRSS_Entry $incomingEntry): ?FreshRSS_Entry {
		$feedId = $incomingEntry->feedId();
		$guid = $incomingEntry->guid();
		if ($feedId === 0 || $guid === '') {
			return null;
		}
		try {
			$entryDAO = FreshRSS_Factory::createEntryDao();
			return $entryDAO->searchByGuid($feedId, $guid);
		} catch (Minz_ConfigurationNamespaceException | Minz_PDOConnectionException $e) {
			Minz_Log::warning('LlmClassification: Failed to load existing entry for re-classification: ' . $e->getMessage());
			return null;
		}
	}

	/**
	 * Hook for EntryBeforeInsert: classify a new entry.
	 * @throws Minz_BadRequestException
	 * @throws Minz_PermissionDeniedException
	 */
	public function classifyEntry(FreshRSS_Entry $entry): FreshRSS_Entry {
		$enableTags = $this->getUserConfigurationBool('enable_tags') ?? false;
		$apiUrl = $this->getUserConfigurationString('api_url') ?? '';
		if (!$enableTags || $apiUrl === '' || !$this->hasFile(self::PROMPT_FILENAME)) {
			return $entry;
		}

		if (!$this->entryMatchesSearchFilter($entry)) {
			return $entry;
		}

		$systemPrompt = $this->getSystemPrompt();
		$userPrompt = $this->buildUserPrompt($entry);
		$incomingPromptHash = sha1($systemPrompt . $userPrompt);
		$classification = null;

		if ($entry->isUpdated()) {
			$existingEntry = $this->loadExistingEntry($entry);

			// Compare prompt hashes for any meaningful change since the last classification
			$existingPromptHash = $existingEntry?->attributeArray($this->getEntrypoint())[self::ATTRIBUTE_PROMPT_HASH] ?? null;
			if ($existingPromptHash === $incomingPromptHash) {
				// Re-use existing tags matching the prefix
				$prefix = $this->getUserConfigurationString('tag_prefix') ?? '';
				$existingTags = $existingEntry->tags();
				if ($prefix !== '') {
					$existingTags = array_values(array_filter(
						$existingTags,
						static fn(string $tag) => str_starts_with($tag, $prefix)
					));
					// Strip the prefix from tags before re-adding them (will be re-applied in applyClassification)
					$prefixLength = strlen($prefix);
					$existingTags = array_map(static fn(string $tag) => substr($tag, $prefixLength), $existingTags);
				}
				$classification = [
					'tags' => $existingTags,
				];
			}
		}

		// re-attach the namespaced classification attribute so it survives the upcoming `updateEntry` write
		$entry->_attribute($this->getEntrypoint(), [
			self::ATTRIBUTE_PROMPT_HASH => $incomingPromptHash,
		]);
		if ($classification === null) {
			if ($userPrompt === '') {
				return $entry;
			}
			$classification = $this->callLlm($systemPrompt, $userPrompt) ?? [];
		}

		return $this->applyClassification($entry, $classification, removeOldTags: true);
	}
}