mandant-crm/backend/app/Modules/History/Requests/CreateHistoryEntryRequest.php

<?php

namespace App\Modules\History\Requests;

use App\Modules\History\Models\HistoryType;
use Illuminate\Contracts\Validation\Validator;
use Illuminate\Foundation\Http\FormRequest;

class CreateHistoryEntryRequest extends FormRequest
{
    public function authorize(): bool { return true; }

    public function rules(): array
    {
        return [
            'history_entry_type_id' => ['required', 'integer', 'exists:history_types,id'],
            'body' => ['required', 'string', 'max:65535'],
            // The picker emits a naive local datetime; presence is enforced
            // conditionally below based on the chosen type.
            'occurred_at' => ['nullable', 'date_format:Y-m-d\TH:i:s'],
        ];
    }

    public function withValidator(Validator $validator): void
    {
        $validator->after(function (Validator $validator) {
            $typeId = $this->input('history_entry_type_id');
            if (! $typeId) {
                return;
            }

            $type = HistoryType::find($typeId);
            if ($type && $type->requires_datetime && ! $this->filled('occurred_at')) {
                $validator->errors()->add(
                    'occurred_at',
                    'Für diesen Verlaufstyp sind Datum und Uhrzeit erforderlich.'
                );
            }
        });
    }
}