function custom_override_checkout_fields( $fields ) {
unset($fields['billing']['billing_address_2']);
unset($fields['billing']['billing_country']);
unset($fields['billing']['billing_postcode']);
unset($fields['billing']['billing_company']);
unset($fields['order']['order_comments']);
$fields['billing']['billing_address_1']['label'] = 'Adres';
$fields['billing']['billing_address_1']['placeholder'] = 'Mahalle, Sokak, Bina No, Daire vb.';
$fields['billing']['billing_address_1']['priority'] = '90';    
$fields['billing']['billing_first_name']['placeholder'] = 'Ad';
$fields['billing']['billing_first_name']['label'] = 'Ad';
$fields['billing']['billing_last_name']['placeholder'] = 'Soyad';
$fields['billing']['billing_last_name']['label'] = 'Soyad';
$fields['billing']['billing_city']['label'] = 'İlçe';
$fields['billing']['billing_city']['placeholder'] = 'İlçe';    
unset($fields['shipping']['shipping_address_2']);
unset($fields['shipping']['shipping_country']);
unset($fields['shipping']['shipping_postcode']);
unset($fields['shipping']['shipping_company']);
$fields['shipping']['shipping_address_1']['label'] = 'Adres';
$fields['shipping']['shipping_address_1']['priority'] = '90';    
$fields['shipping']['shipping_city']['label'] = 'İlçe';
$fields['shipping']['shipping_city']['placeholder'] = 'İlçe';
$fields['shipping']['shipping_address_1']['placeholder'] = 'Mahalle, Sokak, Bina No, Daire vb.';
$fields['shipping']['shipping_first_name']['placeholder'] = 'Ad';
$fields['shipping']['shipping_first_name']['label'] = 'Ad';
$fields['shipping']['shipping_last_name']['placeholder'] = 'Soyad';
$fields['shipping']['shipping_last_name']['label'] = 'Soyad';
return $fields;
}

add_filter('woocommerce_checkout_fields','custom_override_checkout_fields');

add_filter( 'woocommerce_enable_order_notes_field', '__return_false', 9999 );

//T.C. No, Vergi No ve Vergi Dairesi Alanlarını Oluştur
add_filter('woocommerce_checkout_fields', 'tc_vergi_icin_new_checkout_field');

function tc_vergi_icin_new_checkout_field($fields)
{
    $fields['billing']['checkbox_tckno'] = array(
        'type'      => 'checkbox',
        'priority'  => 5,
        'label'     => __('TC Kimlik No', 'woocommerce'),
        'class'     => array('form-row-left'),
        'clear'     => true
    );
    $fields['billing']['checkbox_trigger'] = array(
        'type'      => 'checkbox',
        'priority'  => 8,
        'label'     => __('Kurumsal Fatura', 'woocommerce'),
        'class'     => array('form-row-right'),
        'clear'     => true
    );

    $fields['billing']['billing_tc_kimlik_no'] = array(
        'label'     => __('Vergi / TC Kimlik No', 'woocommerce'),
        'placeholder'   => _x('Vergi No', 'placeholder', 'woocommerce'),
        'class'     => array('form-row form-row-last'),
        'required' => true,
        'priority' => 31,
        'clear'     => true
    );
    
    $fields['billing']['billing_vergi_dairesi'] = array(
        'label'     => __('Vergi Dairesi', 'woocommerce'),
        'placeholder'   => _x('Vergi Dairesi', 'placeholder', 'woocommerce'),
        'class'     => array('form-row form-row-first'),
        'required' => true,
        'priority' => 32,
        'clear'     => true
    );
    
    if (!isset($_POST['checkbox_trigger'])) {
    $fields['billing']['billing_tc_kimlik_no']['required'] = false;
        $fields['billing']['billing_vergi_dairesi']['required'] = false;
    } else {
        $fields['billing']['billing_tc_kimlik_no']['required'] = true;        
    $fields['billing']['billing_vergi_dairesi']['required'] = true;
    }
    if (!isset($_POST['checkbox_trigger'])) {
    $fields['billing']['billing_tc_kimlik_no']['default'] = '11111111111';
    } else {
    $fields['billing']['billing_tc_kimlik_no']['default'] = '11111111111';
    }
    
    return $fields;
}
// TC Doğrula Fonksiyonu
function isTcKimlik($tc)
{
    // Array içindeki denemeler tc kriterine uyduğu için hariç tuttuk.
    $exclude = array('11111111110', '22222222220', '33333333330', '44444444440', '55555555550', '66666666660', '7777777770', '88888888880', '99999999990'); //Bunlar aşağıdaki fonksiyonu yanıltan numaralar dilerseniz kaldırabilirsiniz satırı.
    if (in_array($tc, $exclude)) {
        return false;
    }
    if (strlen($tc) < 11) {
        return false;
    }
    if ($tc[0] == '0') {
        return false;
    }
    $plus = ($tc[0] + $tc[2] + $tc[4] + $tc[6] + $tc[8]) * 7;
    $minus = $plus - ($tc[1] + $tc[3] + $tc[5] + $tc[7]);
    $mod = $minus % 10;
    if ($mod != $tc[9]) {
        return false;
    }
    $all = 0;
    for ($i = 0; $i < 10; $i++) {
        $all += $tc[$i];
    }
    if ($all % 10 != $tc[10]) {
        return false;
    }

    return true;
}
// TC Kimlik Noyu Doğrula
add_action('woocommerce_checkout_process', 'tc_numara_dogrula');

function tc_numara_dogrula()
{
    $tcno = $_POST['shipping_tc'];
    if (!empty($tcno)) {
        if (!is_numeric($tcno) && !isset($_POST['checkbox_trigger'])) {
            wc_add_notice(__('T.C alanına lütfen sayısal bir değer girin yada siparişiniz 5.000,00 TL den küçük ise boş bırakın.'), 'error');
        } else if (!empty($tcno) && !isset($_POST['checkbox_trigger'])) {
            if (!isTcKimlik($tcno))
                wc_add_notice(__('Lütfen doğru bir TC kimlik no girin yada siparişiniz 5.000,00 TL den küçük ise boş bırakın.'), 'error');
        }
    }
}
// Vergi No Doğrulama Fonksiyonu
function validateTaxNo($taxNo)
{
    if (strlen($taxNo) == 10) {
        for ($i = 0; $i < 9; $i++) {
            $v[$i + 1] = ($taxNo[$i] + (9 - $i)) % 10;
            $vv[$i + 1] = ($v[$i + 1] * pow(2, (9 - $i))) % 9;
            $vv[$i + 1] = ($v[$i + 1] != 0 && $vv[$i + 1] == 0) ? 9 : $vv[$i + 1];
        }
        $sum = array_sum($vv);
        $sum = ($sum % 10 == 0) ? 0 : (10 - ($sum % 10));
        return ($sum == $taxNo[9]) ? true : false;
    }
    return false;
}
// Vergi Noyu Doğrula
add_action('woocommerce_checkout_process', 'vergi_no_dogrula');

function vergi_no_dogrula()
{
    $tc_kimlik_no = $_POST['billing_tc_kimlik_no'];
    if (isset($_POST['checkbox_trigger'])) {
        if (!validateTaxNo($tc_kimlik_no))
            wc_add_notice(__('Lütfen Doğru Bir Vergi No Girin.'), 'error');
        }
    }


//Adminin Sipariş Detayında Fatura Bilgilerinde TC No ve Vergi Dairesi Görebilmesi İçin
add_action('woocommerce_admin_order_data_after_billing_address', 'vergi_no_dairesi', 10, 1);

function vergi_no_dairesi($order)
{
    echo '<p><strong>' . __('Vergi / TC Kimlik No') . ':</strong> ' . $tc_kimlik_no = get_post_meta($order->get_id(), '_billing_tc_kimlik_no', true) . '</p>';
        echo '<p><strong>' . __('Vergi Dairesi') . ':</strong> ' . $vergi_dairesi = get_post_meta($order->get_id(), '_billing_vergi_dairesi', true) . '</p>';
}

//Koşullara göre alanları göstermek için gerekli javascript kodları

add_action('woocommerce_after_checkout_form', 'kosullu_alan_goster', 6);

function kosullu_alan_goster()
{

    ?>
    <script type="text/javascript">
    jQuery('#ship-to-different-address').hide()
    jQuery('.woocommerce-billing-fields > h3').html('Adres bilgileri');
        jQuery('#billing_tc_kimlik_no').hide();
        jQuery('#billing_vergi_dairesi').hide();
    jQuery('#billing_tc_kimlik_no_field  > label').hide();
        jQuery('#billing_vergi_dairesi_field  > label').hide();
        jQuery("#billing_tc_kimlik_no_field > label").append("<abbr class='required' title='gerekli'>*</abbr>");
        jQuery("#billing_vergi_dairesi_field > label").append("<abbr class='required' title='gerekli'>*</abbr>");
        
        jQuery('input#checkbox_trigger').change(function() {
            if (this.checked) {

        jQuery('.woocommerce-billing-fields > h3').html('Fatura bilgileri');
        jQuery("#checkbox_tckno").prop( "checked", false );
        jQuery('#billing_tc_kimlik_no').show();
                jQuery('#billing_vergi_dairesi').show();
                jQuery('#billing_last_name_field').hide();
                jQuery('#billing_tc_kimlik_no_field  > label').show();                
                jQuery('#billing_vergi_dairesi_field  > label').show();
                jQuery('#billing_tc_kimlik_no_field > label > span').remove();
                jQuery('#billing_vergi_dairesi_field > label > span').remove();
                jQuery('#billing_tc_kimlik_no_field').addClass('validate-required');
                jQuery('#billing_vergi_dairesi_field').addClass('validate-required');
        jQuery('#billing_first_name_field > label').html('Şirket Ünvanı&nbsp;<abbr class="required" title="gerekli">*</abbr>')
        jQuery('#billing_tc_kimlik_no').attr("value", "")
        jQuery('#billing_first_name').attr("placeholder", "Şirket Ünvanı")
        jQuery('#billing_first_name_field').attr("class", "form-row form-row-first validate-required fullwidth_custom")
        jQuery('#ship-to-different-address').show()
        jQuery('#billing_tc_kimlik_no').attr("placeholder", "Vergi No")
        jQuery('#billing_tc_kimlik_no_field').attr("class", "form-row form-row form-row-last ")
        jQuery('#billing_tc_kimlik_no_field > label').html('Vergi No&nbsp;<abbr class="required" title="gerekli">*</abbr>')

            } else {                
        jQuery('.woocommerce-billing-fields > h3').html('Adres bilgileri');
                jQuery('#billing_last_name_field').show();
                jQuery('#billing_vergi_dairesi').hide();
                jQuery('#billing_vergi_dairesi_field > label').hide();
                jQuery('#billing_vergi_dairesi').hide();
                jQuery('#billing_tc_kimlik_no').hide();
                jQuery('#billing_vergi_dairesi_field > label').hide();
                jQuery('#billing_tc_kimlik_no_field  > label').hide();
        jQuery('#billing_first_name_field > label').html('Ad&nbsp;<abbr class="required" title="gerekli">*</abbr>')
        jQuery('#billing_tc_kimlik_no').attr("value", "11111111111")
        jQuery('#billing_first_name').attr("placeholder", "Ad")
        jQuery('#billing_first_name_field').attr("class", "form-row form-row-first validate-required")
        jQuery('#billing_tc_kimlik_no_field > label').html('TC Kimlik No&nbsp;<abbr class="required" title="gerekli">*</abbr>')
        jQuery('#ship-to-different-address').hide()
            }

        });
    jQuery('input#checkbox_tckno').change(function() {
            if (this.checked) {
        jQuery( "#checkbox_trigger" ).prop( "checked", false );
                jQuery('#billing_tc_kimlik_no').show();
                jQuery('#billing_tc_kimlik_no_field  > label').show();
                jQuery('#billing_tc_kimlik_no_field > label > span').remove();
                jQuery('#billing_tc_kimlik_no_field').addClass('validate-required');
        jQuery('#billing_tc_kimlik_no').attr("value", "")
        jQuery('#billing_first_name').attr("placeholder", "Ad")
        jQuery('#billing_tc_kimlik_no').attr("placeholder", "TC Kimlik No")
        jQuery('#billing_tc_kimlik_no_field').attr("class", "form-row form-row form-row-last fullwidth_custom ")
                jQuery('#billing_last_name_field').show()
        jQuery('#billing_first_name_field > label').html('Ad&nbsp;<abbr class="required" title="gerekli">*</abbr>')
                jQuery('#billing_vergi_dairesi').hide();
                jQuery('#billing_vergi_dairesi_field > label').hide();
                jQuery('#billing_vergi_dairesi').hide();
                jQuery('#billing_vergi_dairesi_field > label').hide();
        jQuery('#billing_first_name_field').attr("class", "form-row form-row-first validate-required")
        jQuery('#billing_tc_kimlik_no_field > label').html('TC Kimlik No&nbsp;<abbr class="required" title="gerekli">*</abbr>')
        jQuery('#ship-to-different-address').hide()
        jQuery('.woocommerce-billing-fields > h3').html('Adres bilgileri');

            } else {
                jQuery('#billing_tc_kimlik_no').hide();
                jQuery('#billing_tc_kimlik_no_field  > label').hide();
        jQuery('#billing_tc_kimlik_no').attr("value", "11111111111")
        jQuery('#billing_first_name').attr("placeholder", "Ad")
        jQuery('#billing_tc_kimlik_no').attr("placeholder", "Vergi No")
        jQuery('#billing_tc_kimlik_no_field').attr("class", "form-row form-row form-row-last ")
        jQuery('#billing_first_name_field').attr("class", "form-row form-row-first validate-required")
                jQuery('#billing_last_name_field').show()
        jQuery('#billing_first_name_field > label').html('Ad&nbsp;<abbr class="required" title="gerekli">*</abbr>')
        jQuery('#billing_tc_kimlik_no_field > label').html('Vergi No&nbsp;<abbr class="required" title="gerekli">*</abbr>')
                
            }
        });
    </script>

<?php

}