WP-LIT-MCP/src/Integrations/Divi/Design/PresetDiff.php

<?php

declare(strict_types=1);

namespace LIT\MCP\Integrations\Divi\Design;

defined('ABSPATH') || exit;

/**
 * What a preset change does (spec §4 step 4, "diff"): per preset added, changed (with the changed top-level keys),
 * removed, and per module/group a default that is set or cleared. Keys the plugin derives or Divi maintains
 * (updated, styleAttrs, renderAttrs, version) are no change of their own. Sorted by kind, scope, id, action.
 * Pure PHP.
 */
final class PresetDiff
{
    private const DERIVED = ['updated', 'styleAttrs', 'renderAttrs', 'version'];

    /**
     * @return list<array{kind: string, scope: string, id: string, name: string, action: string,
     *     fields?: list<string>}>
     */
    public static function between(PresetBook $before, PresetBook $after): array
    {
        $old = $before->data();
        $new = $after->data();
        $rows = [];
        foreach ([PresetScope::MODULE, PresetScope::GROUP] as $kind) {
            $names = array_unique(array_merge(array_keys($old[$kind] ?? []), array_keys($new[$kind] ?? [])));
            sort($names);
            foreach ($names as $name) {
                $was = $old[$kind][$name] ?? ['default' => '', 'items' => []];
                $is = $new[$kind][$name] ?? ['default' => '', 'items' => []];
                array_push($rows, ...self::items($kind, (string) $name, $was['items'], $is['items']));
                array_push($rows, ...self::defaults($kind, (string) $name, $was, $is));
            }
        }

        return $rows;
    }

    /**
     * @param array<string, array<string, mixed>> $was
     * @param array<string, array<string, mixed>> $is
     * @return list<array<string, mixed>>
     */
    private static function items(string $kind, string $scope, array $was, array $is): array
    {
        $ids = array_unique(array_merge(array_keys($was), array_keys($is)));
        sort($ids);
        $rows = [];
        foreach ($ids as $id) {
            $key = (string) $id;
            $before = $was[$key] ?? null;
            $after = $is[$key] ?? null;
            if ($before === null || $after === null) {
                $rows[] = self::row($kind, $scope, $key, $after ?? $before, $before === null ? 'added' : 'removed');
                continue;
            }
            $fields = self::changedFields($before, $after);
            if ($fields !== []) {
                $rows[] = self::row($kind, $scope, $key, $after, 'changed') + ['fields' => $fields];
            }
        }

        return $rows;
    }

    /**
     * @param array{default: string, items: array<string, array<string, mixed>>} $was
     * @param array{default: string, items: array<string, array<string, mixed>>} $is
     * @return list<array<string, mixed>>
     */
    private static function defaults(string $kind, string $scope, array $was, array $is): array
    {
        if ($was['default'] === $is['default']) {
            return [];
        }
        if ($is['default'] === '') {
            $gone = $was['items'][$was['default']] ?? null;

            return [self::row($kind, $scope, $was['default'], $gone, 'default_cleared')];
        }

        $item = $is['items'][$is['default']] ?? null;

        return [self::row($kind, $scope, $is['default'], $item, 'default_set')];
    }

    /**
     * @param array<string, mixed> $before
     * @param array<string, mixed> $after
     * @return list<string>
     */
    private static function changedFields(array $before, array $after): array
    {
        $keys = array_diff(array_unique(array_merge(array_keys($before), array_keys($after))), self::DERIVED);
        $fields = [];
        foreach ($keys as $key) {
            $was = $before[$key] ?? null;
            $is = $after[$key] ?? null;
            if ($was != $is) { // phpcs:ignore Universal.Operators.StrictComparisons
                $fields[] = (string) $key;
            }
        }
        sort($fields);

        return $fields;
    }

    /**
     * @param array<string, mixed>|null $item
     * @return array{kind: string, scope: string, id: string, name: string, action: string}
     */
    private static function row(string $kind, string $scope, string $id, ?array $item, string $action): array
    {
        return [
            'kind' => $kind,
            'scope' => $scope,
            'id' => $id,
            'name' => is_string($item['name'] ?? null) ? $item['name'] : $id,
            'action' => $action,
        ];
    }
}