<?php
defined('ABSPATH') || exit();

final class APEARI_Context
{
    public const VERSION = 2;
    public const TTL = 2 * HOUR_IN_SECONDS;

    public static function nodes(array $blocks): array
    {
        return array_values(
            array_filter(
                $blocks,
                static fn($block) => $block['blockName'] || '' !== trim($block['innerHTML']),
            ),
        );
    }

    public static function find(string $content, array $path)
    {
        if (!$path || count($path) > 30) {
            return self::invalid();
        }
        $nodes = self::nodes(parse_blocks($content));
        $ancestors = [];
        foreach ($path as $index) {
            if (!is_int($index) || $index < 0 || !isset($nodes[$index])) {
                return self::invalid();
            }
            $block = $nodes[$index];
            $ancestors[] = $block;
            $siblings = $nodes;
            $nodes = self::nodes($block['innerBlocks']);
        }
        return ['block' => $block, 'ancestors' => $ancestors, 'siblings' => $siblings];
    }

    private static function invalid(): WP_Error
    {
        return new WP_Error('apeari_target', __('Zaznacz aktualny blok w podglądzie.', 'apeari'), [
            'status' => 422,
        ]);
    }

    public static function snapshot(string $session_id, string $ref)
    {
        if (!preg_match('/^[a-f0-9]{48}$/', $session_id)) {
            return new WP_Error('apeari_session', __('Sesja edytora wygasła.', 'apeari'), ['status' => 410]);
        }
        $session = APEARI_Workspace::load($session_id);
        if (
            is_wp_error($session) ||
            $session['user'] !== get_current_user_id() ||
            $session['theme'] !== get_stylesheet()
        ) {
            return new WP_Error('apeari_session', __('Sesja edytora wygasła. Odśwież edytor.', 'apeari'), [
                'status' => 410,
            ]);
        }
        $document = APEARI_Workspace::page($session, $ref);
        if (is_wp_error($document)) {
            return $document;
        }
        $content = $document['content'];
        if (!empty($session['drafts'][$ref])) {
            if ($session['drafts'][$ref]['baseHash'] !== $document['hash']) {
                return self::stale();
            }
            $content = $session['drafts'][$ref]['content'];
        }
        return ['document' => $document, 'content' => $content, 'version' => hash('sha256', $content)];
    }

    public static function stale(): WP_Error
    {
        return new WP_Error(
            'apeari_stale_target',
            __(
                'Źródło zaznaczonego elementu zmieniło się. Wczytaj podgląd i zaznacz element ponownie.',
                'apeari',
            ),
            ['status' => 409],
        );
    }

    private static function brief(array $block): array
    {
        return [
            'blockName' => $block['blockName'] ?: 'core/freeform',
            'text' => mb_substr(wp_strip_all_tags($block['innerHTML']), 0, 400),
        ];
    }

    public static function create(array $input)
    {
        $session_id = is_string($input['sessionId'] ?? null) ? $input['sessionId'] : '';
        $ref = is_string($input['documentRef'] ?? null) ? $input['documentRef'] : '';
        $snapshot = self::snapshot($session_id, $ref);
        if (is_wp_error($snapshot)) {
            return $snapshot;
        }
        if (($input['documentVersion'] ?? '') !== $snapshot['version']) {
            return self::stale();
        }
        $path = $input['blockPath'] ?? null;
        if (!is_array($path)) {
            return self::invalid();
        }
        $found = self::find($snapshot['content'], $path);
        if (is_wp_error($found)) {
            return $found;
        }
        $block = $found['block'];
        if (!in_array($block['blockName'], APEARI_Plans::BLOCKS, true)) {
            return self::invalid();
        }
        foreach ($found['ancestors'] as $ancestor) {
            if (
                !empty($ancestor['attrs']['templateLock']) ||
                !empty($ancestor['attrs']['lock']['edit']) ||
                !empty($ancestor['attrs']['metadata']['bindings'])
            ) {
                return self::invalid();
            }
        }
        $placement = $input['placement'] ?? 'edit';
        if (!in_array($placement, ['edit', 'before', 'after', 'inside'], true)) {
            return self::invalid();
        }
        if ('inside' === $placement && !in_array($block['blockName'], APEARI_Plans::CONTAINERS, true)) {
            return new WP_Error(
                'apeari_container',
                __(
                    'Wstawianie wewnątrz wymaga zaznaczenia grupy, kolumny albo innego kontenera Gutenberga.',
                    'apeari',
                ),
                ['status' => 422],
            );
        }
        $dom = $input['element'] ?? [];
        if (!is_array($dom) || strlen(wp_json_encode($dom)) > 6000) {
            return self::invalid();
        }
        $element = [];
        foreach (['tag', 'classes', 'path', 'text'] as $field) {
            if (isset($dom[$field]) && is_string($dom[$field])) {
                $element[$field] = sanitize_text_field(mb_substr($dom[$field], 0, 1200));
            }
        }
        $source = serialize_block($block);
        $target = [
            'documentRef' => $ref,
            'documentVersion' => $snapshot['version'],
            'baseHash' => $snapshot['document']['hash'],
            'blockPath' => $path,
            'blockHash' => hash('sha256', $source),
            'placement' => $placement,
        ];
        $scope =
            self::VERSION .
            '|' .
            get_current_blog_id() .
            '|' .
            get_current_user_id() .
            '|' .
            get_stylesheet() .
            '|' .
            $session_id;
        $id = hash('sha256', $scope . '|' . wp_json_encode($target) . '|' . wp_json_encode($element));
        $cached = get_transient('apeari_context_' . $id);
        APEARI_Privacy::track('apeari_context_' . $id);
        if (is_array($cached)) {
            return ['contextId' => $id, 'cacheHit' => true, 'target' => $target];
        }
        $index = end($path);
        $context = [
            'schemaVersion' => self::VERSION,
            'target' => $target,
            'blockName' => $block['blockName'],
            'attributes' => $block['attrs'],
            'source' => mb_substr($source, 0, 16000),
            'sourceTruncated' => mb_strlen($source) > 16000,
            'element' => $element,
            'ancestors' => array_map([self::class, 'brief'], array_slice($found['ancestors'], 0, -1)),
            'allowedStyles' => APEARI_Providers::allowed_styles($block['blockName']),
            'previous' => $index > 0 ? self::brief($found['siblings'][$index - 1]) : null,
            'next' => isset($found['siblings'][$index + 1])
                ? self::brief($found['siblings'][$index + 1])
                : null,
        ];
        if (strlen(wp_json_encode($context)) > 60000) {
            return new WP_Error('apeari_context_size', __('Zaznacz mniejszy fragment strony.', 'apeari'), [
                'status' => 413,
            ]);
        }
        set_transient(
            'apeari_context_' . $id,
            [
                'user' => get_current_user_id(),
                'theme' => get_stylesheet(),
                'sessionId' => $session_id,
                'context' => $context,
            ],
            self::TTL,
        );
        return ['contextId' => $id, 'cacheHit' => false, 'target' => $target];
    }

    public static function resolve(string $id)
    {
        if (!preg_match('/^[a-f0-9]{64}$/', $id)) {
            return self::invalid();
        }
        $cached = get_transient('apeari_context_' . $id);
        if (
            !is_array($cached) ||
            $cached['user'] !== get_current_user_id() ||
            $cached['theme'] !== get_stylesheet()
        ) {
            return new WP_Error(
                'apeari_context_expired',
                __('Kontekst AI wygasł. Zaznacz element ponownie.', 'apeari'),
                [
                    'status' => 410,
                ],
            );
        }
        $target = $cached['context']['target'];
        $snapshot = self::snapshot($cached['sessionId'], $target['documentRef']);
        if (is_wp_error($snapshot)) {
            return $snapshot;
        }
        if (
            $snapshot['version'] !== $target['documentVersion'] ||
            $snapshot['document']['hash'] !== $target['baseHash']
        ) {
            return self::stale();
        }
        return $cached['context'];
    }
}