<?php

declare(strict_types=1);

namespace LIT\MCP\Integrations\Divi\BlockTree;

use stdClass;

defined('ABSPATH') || exit;

/**
 * Fingerprints of a node (E11) for lit/library-find-similar, the "similar section" warning (spec §5.5) and
 * lit/library-make-global. structure(): block names and nesting, column layout (flexType) and preset IDs – two
 * sections built alike with other texts share it. content(): every attribute but the admin label,
 * builderVersion and globalParent, children and every non-whitespace text part included – "the same section"
 * (ruling Q25: raw HTML between blocks and the inner HTML of core blocks are visible too). Whitespace between
 * blocks never counts; an opaque block counts with all its bytes (content) or by its effective type (structure).
 * Pure PHP.
 */
final class Fingerprint
{
    /** Top-level attributes that say nothing about what visitors see. */
    private const IGNORED = ['builderVersion', 'globalParent'];

    public static function structure(Block $block): string
    {
        return self::hash(self::shape($block));
    }

    public static function content(Block $block): string
    {
        return self::hash(self::body($block));
    }

    /**
     * The normalized bytes content() hashes (ruling Q25): block names, attributes with sorted keys (without admin
     * label, builderVersion, globalParent), every non-whitespace text part – raw HTML or shortcodes between blocks
     * and the inner HTML of core blocks – and opaque blocks with all their bytes. Two nodes with the same
     * canonical() look the same to visitors; lit/library-make-global compares these bytes, not only the hash.
     */
    public static function canonical(Block $block): string
    {
        return self::body($block);
    }

    private static function shape(Block $block): string
    {
        if ($block->isOpaque()) {
            return 'opaque:' . GlobalInstance::effectiveName($block);
        }

        $presets = NodeSummary::presetIds($block);
        sort($presets);
        $children = array_map(self::shape(...), $block->children());

        return $block->name() . '|' . (NodeSummary::columnWidth($block) ?? '') . '|' . implode(',', $presets)
            . '[' . implode(';', $children) . ']';
    }

    private static function body(Block $block): string
    {
        if ($block->isOpaque()) {
            return 'opaque:' . self::text(Serializer::block($block));
        }

        $attrs = $block->attrs();
        foreach (self::IGNORED as $key) {
            unset($attrs[$key]);
        }
        if (is_array($attrs['module']['meta'] ?? null)) {
            unset($attrs['module']['meta']['adminLabel']);
        }
        $parts = [];
        foreach ($block->isVoid() ? [] : $block->parts() as $part) {
            if ($part instanceof Block) {
                $parts[] = self::body($part);
            } elseif (trim($part) !== '') {
                $parts[] = 'text:' . Json::encode(self::text($part));
            }
        }

        return $block->name() . Json::encode(self::sorted($attrs)) . '[' . implode(';', $parts) . ']';
    }

    /** Text as visitors get it: line breaks unified, whitespace at both ends dropped. */
    private static function text(string $text): string
    {
        return trim(str_replace("\r\n", "\n", $text));
    }

    /** Object keys sorted at every depth, so the key order Divi or the plugin wrote does not count. */
    private static function sorted(mixed $value): mixed
    {
        if ($value instanceof stdClass) {
            $value = (array) $value;
        }
        if (! is_array($value)) {
            return $value;
        }
        if (! array_is_list($value)) {
            ksort($value);
        }

        return array_map(self::sorted(...), $value);
    }

    private static function hash(string $value): string
    {
        return substr(hash('sha256', $value), 0, 16);
    }
}