invoiceninja/app/Factory/CloneInvoiceToQuoteFactory.php

<?php
/**
 * Invoice Ninja (https://invoiceninja.com).
 *
 * @link https://github.com/invoiceninja/invoiceninja source repository
 *
 * @copyright Copyright (c) 2021. Invoice Ninja LLC (https://invoiceninja.com)
 *
 * @license https://www.elastic.co/licensing/elastic-license
 */

namespace App\Factory;

use App\Models\Invoice;
use App\Models\Quote;

class CloneInvoiceToQuoteFactory
{
    public static function create(Invoice $invoice, $user_id) : ?Quote
    {
        $quote = new Quote();
        $quote->discount = $invoice->discount;
        $quote->is_amount_discount = $invoice->is_amount_discount;
        $quote->po_number = $invoice->po_number;
        $quote->is_deleted = false;
        $quote->footer = $invoice->footer;
        $quote->public_notes = $invoice->public_notes;
        $quote->private_notes = $invoice->private_notes;
        $quote->terms = $invoice->terms;
        $quote->tax_name1 = $invoice->tax_name1;
        $quote->tax_rate1 = $invoice->tax_rate1;
        $quote->tax_name2 = $invoice->tax_name2;
        $quote->tax_rate2 = $invoice->tax_rate2;
        $quote->tax_rate3 = $invoice->tax_rate3;
        $quote->tax_rate3 = $invoice->tax_rate3;
        $quote->custom_value1 = $invoice->custom_value1;
        $quote->custom_value2 = $invoice->custom_value2;
        $quote->custom_value3 = $invoice->custom_value3;
        $quote->custom_value4 = $invoice->custom_value4;
        $quote->amount = $invoice->amount;
        //$quote->balance = $invoice->amount;
        $quote->partial = $invoice->partial;
        $quote->partial_due_date = $invoice->partial_due_date;
        $quote->last_viewed = $invoice->last_viewed;

        $quote->status_id = Quote::STATUS_DRAFT;
        $quote->number = '';
        $quote->date = null;
        $quote->due_date = null;
        $quote->partial_due_date = null;
        $quote->line_items = $invoice->line_items;

        return $quote;
    }
}