<?php

declare(strict_types=1);

namespace App\Agent;

use App\Config\AgentRunnerConfig;

/**
 * Extracts generic reference anchors used to resolve follow-up questions.
 *
 * The extractor is deliberately domain-neutral: product model anchors and
 * measurement value anchors are configured through AgentRunnerConfig. Current
 * water-analysis patterns remain supported by configuration, but the calling
 * code no longer needs Testomat- or hardness-specific concepts.
 */
final readonly class ReferenceAnchorExtractor
{
    public function __construct(
        private AgentRunnerConfig $config,
    ) {
    }

    /**
     * Extract stable reference anchors from the latest assistant answer.
     *
     * These anchors are only used to resolve follow-up references such as
     * "der Wert" or "welcher Indikator". They are not factual evidence for
     * the final answer. To avoid propagating wrong earlier answers, only the
     * first explicit product-model reference and the first explicit measurement
     * value are kept. Indicator names, reagent codes, prices, URLs and product
     * numbers are intentionally ignored here.
     *
     * @return string[]
     */
    public function extractLatestAssistantReferenceAnchors(string $history): array
    {
        $turn = $this->extractLatestHistoryTurn($history);

        if ($turn === '') {
            return [];
        }

        $answer = preg_replace($this->config->getFollowUpHistoryQuestionStripPattern(), '', $turn, 1) ?? '';
        $answer = trim($answer);

        if ($answer === '') {
            return [];
        }

        $anchors = [];

        $model = $this->extractFirstProductModelAnchor($answer);
        if ($model !== '') {
            $anchors[] = $model;
        }

        $measurementValue = $this->extractFirstMeasurementValueAnchor($answer);
        if ($measurementValue !== '') {
            $anchors[] = $measurementValue;
        }

        return array_values(array_unique($anchors));
    }

    public function extractFirstProductModelAnchor(string $text): string
    {
        if (preg_match($this->config->getFollowUpReferenceAnchorProductModelPattern(), $text, $matches) !== 1) {
            return '';
        }

        $value = $this->sanitizeAnchor((string) ($matches[0] ?? ''));
        $value = preg_replace('/\s+/u', ' ', $value) ?? $value;

        return trim(str_replace('®', '', $value));
    }

    public function extractFirstMeasurementValueAnchor(string $text): string
    {
        if (preg_match($this->config->getFollowUpReferenceAnchorMeasurementValuePattern(), $text, $matches) !== 1) {
            return '';
        }

        $value = preg_replace('/\s+/u', ' ', (string) ($matches[0] ?? '')) ?? '';

        return trim($value);
    }

    private function extractLatestHistoryTurn(string $history): string
    {
        $history = trim($history);

        if ($history === '') {
            return '';
        }

        $parts = preg_split($this->config->getFollowUpHistoryTurnSplitPattern(), $history);

        if ($parts === false || $parts === []) {
            return '';
        }

        $turns = array_values(array_filter(
            array_map(static fn(string $part): string => trim($part), $parts),
            static fn(string $part): bool => $part !== ''
        ));

        if ($turns === []) {
            return '';
        }

        return (string) end($turns);
    }

    private function sanitizeAnchor(string $value): string
    {
        $value = trim((string) preg_replace('/\s+/u', ' ', $value));

        if ($value === '') {
            return '';
        }

        if (mb_strlen($value, 'UTF-8') <= 500) {
            return $value;
        }

        return rtrim(mb_substr($value, 0, 497, 'UTF-8')) . '...';
    }
}