<?php

declare(strict_types=1);

if (!defined('ABSPATH')) {
    exit;
}

/** Local-only extraction of heading + immediately following static answer blocks. */
final class TheDotDevAgenticBridge_Block_Answer_Extractor
{
    public const VERSION = '1.0.0';
    public const MAX_CANDIDATES = 100;
    public const MAX_TEXT_CHARS = 280;
    private const STATIC_CONTAINERS = ['core/group', 'core/columns', 'core/column', 'core/cover', 'core/media-text'];
    private const ANSWER_BLOCKS = ['core/paragraph', 'core/list', 'core/table'];

    /** @return array{source: string, status: string, candidates: list<array<string, mixed>>, limitation: string} */
    public static function extract_post(WP_Post $post): array
    {
        if (!TheDotDevAgenticBridge_Content_Policy::is_eligible_post($post) || !function_exists('parse_blocks')) {
            return self::empty('not_applicable', 'Only eligible public content is inspected with WordPress block APIs.');
        }
        $blocks = parse_blocks($post->post_content);
        if (!is_array($blocks)) {
            return self::empty('unknown', 'WordPress block parsing did not return a valid block tree.');
        }
        return self::extract_blocks($post, $blocks);
    }

    /** @param list<array<string, mixed>> $blocks @return array{source: string, status: string, candidates: list<array<string, mixed>>, limitation: string} */
    public static function extract_blocks(WP_Post $post, array $blocks): array
    {
        if (!TheDotDevAgenticBridge_Content_Policy::is_eligible_post($post)) {
            return self::empty('not_applicable', 'Only eligible public content is inspected.');
        }
        $candidates = [];
        self::inspect_siblings($blocks, '', $post, $candidates);
        return [
            'source' => 'local_block_structure',
            'status' => $candidates === [] ? 'not_applicable' : 'local_candidate',
            'candidates' => $candidates,
            'limitation' => 'Static block structure only; this does not judge answer quality or predict AI citation.',
        ];
    }

    /** @param list<array<string, mixed>> $blocks @param list<array<string, mixed>> $out */
    private static function inspect_siblings(array $blocks, string $prefix, WP_Post $post, array &$out): void
    {
        foreach ($blocks as $index => $block) {
            if (count($out) >= self::MAX_CANDIDATES || !is_array($block)) {
                return;
            }
            $path = $prefix === '' ? (string) $index : $prefix . '.' . $index;
            $name = (string) ($block['blockName'] ?? '');
            if ($name === 'core/heading') {
                $answer = $blocks[$index + 1] ?? null;
                if (is_array($answer) && in_array((string) ($answer['blockName'] ?? ''), self::ANSWER_BLOCKS, true)) {
                    $heading = self::text((string) ($block['innerHTML'] ?? ''));
                    $answer_text = self::text((string) ($answer['innerHTML'] ?? ''));
                    if ($heading !== '' && $answer_text !== '') {
                        $out[] = [
                            'postId' => (int) $post->ID,
                            'url' => esc_url_raw(get_permalink($post)),
                            'heading' => $heading,
                            'headingLevel' => max(1, min(6, (int) (($block['attrs']['level'] ?? 2)))),
                            'answerText' => $answer_text,
                            'answerType' => (string) $answer['blockName'],
                            'headingPath' => $path,
                            'answerPath' => $prefix === '' ? (string) ($index + 1) : $prefix . '.' . ($index + 1),
                            'status' => 'local_candidate',
                        ];
                    }
                }
            }
            if (in_array($name, self::STATIC_CONTAINERS, true) && is_array($block['innerBlocks'] ?? null)) {
                self::inspect_siblings($block['innerBlocks'], $path, $post, $out);
            }
        }
    }

    private static function text(string $html): string
    {
        $text = sanitize_text_field(wp_strip_all_tags($html));
        return function_exists('mb_substr') ? mb_substr($text, 0, self::MAX_TEXT_CHARS) : substr($text, 0, self::MAX_TEXT_CHARS);
    }

    /** @return array{source: string, status: string, candidates: list<array<string, mixed>>, limitation: string} */
    private static function empty(string $status, string $limitation): array
    {
        return ['source' => 'local_block_structure', 'status' => $status, 'candidates' => [], 'limitation' => $limitation];
    }
}