Rename WooCommerce “Coupon” terminology to “Discount”

if ( class_exists( 'WooCommerce' ) ) {

    add_filter( 'gettext', 'rd_wc_generic_coupon_replacement', 20, 3 );

    add_filter( 'ngettext', 'rd_wc_generic_coupon_replacement_plural', 20, 5 );

    // Also replace wording directly in notices (covers cases where text bypasses gettext later)

    add_filter( 'woocommerce_add_notice', 'rd_wc_generic_coupon_replacement_in_notice', 20, 1 );

    add_filter( 'woocommerce_add_success', 'rd_wc_generic_coupon_replacement_in_notice', 20, 1 );

    add_filter( 'woocommerce_add_error', 'rd_wc_generic_coupon_replacement_in_notice', 20, 1 );

    function rd_wc_apply_coupon_discount_replacements( $text ) {

        if ( ! is_string( $text ) || $text === '' ) {

            return $text;

        }

        // Phrase-level fixes first (prevents "discount discounts" headings and preserves case)

        $phrase_replace = array(

            // "coupon discount(s)" variants

            'COUPON DISCOUNT'     => 'DISCOUNT',

            'Coupon discount'     => 'Discount',

            'coupon discount'     => 'discount',

            'COUPON DISCOUNTS'    => 'DISCOUNTS',

            'Coupon discounts'    => 'Discounts',

            'coupon discounts'    => 'discounts',

            // "discount coupon(s)" variants – preserve case

            'DISCOUNT COUPONS'    => 'DISCOUNTS',

            'Discount Coupons'    => 'Discounts',

            'Discount coupons'    => 'Discounts',

            'discount coupons'    => 'discounts',

            // If something has already been partially replaced

            'DISCOUNT DISCOUNTS'  => 'DISCOUNTS',

            'Discount discounts'  => 'Discounts',

            'discount discounts'  => 'discounts',

        );

        $text = str_replace(

            array_keys( $phrase_replace ),

            array_values( $phrase_replace ),

            $text

        );

        $search_replace = array(

            // Theme-specific checkout wording

            'Have A Promotional Code'  => 'Got a Discount Code?',

            'have a promotional code'  => 'Got a Discount Code?',

            'HAVE A PROMOTIONAL CODE'  => 'Got a Discount Code?',

            // Composite phrases

            'COUPON CODE'        => 'DISCOUNT CODE',

            'Coupon Code'        => 'Discount Code',

            'Coupon code'        => 'Discount code',

            'coupon code'        => 'discount code',

            'PROMOTIONAL CODE'   => 'DISCOUNT CODE',

            'Promotional Code'   => 'Discount Code',

            'Promotional code'   => 'Discount code',

            'promotional code'   => 'discount code',

            // Plural

            'COUPONS'            => 'DISCOUNTS',

            'Coupons'            => 'Discounts',

            'coupons'            => 'discounts',

            // Singular

            'COUPON'             => 'DISCOUNT',

            'Coupon'             => 'Discount',

            'coupon'             => 'discount',

        );

        $text = str_replace(

            array_keys( $search_replace ),

            array_values( $search_replace ),

            $text

        );

        // Final cleanup for any duplicates introduced elsewhere (case-preserving)

        $text = preg_replace( '/\b(Discounts)\s+\1\b/', '$1', $text );

        $text = preg_replace( '/\b(discounts)\s+\1\b/', '$1', $text );

        $text = preg_replace( '/\b(DISCOUNTS)\s+\1\b/', '$1', $text );

        $text = preg_replace( '/\b(Discount)\s+\1\b/', '$1', $text );

        $text = preg_replace( '/\b(discount)\s+\1\b/', '$1', $text );

        $text = preg_replace( '/\b(DISCOUNT)\s+\1\b/', '$1', $text );

        return $text;

    }

    function rd_wc_generic_coupon_replacement( $translated, $original, $domain ) {

        if ( is_admin() ) {

            return $translated;

        }

        return rd_wc_apply_coupon_discount_replacements( $translated );

    }

    function rd_wc_generic_coupon_replacement_plural( $translated, $single, $plural, $number, $domain ) {

        if ( is_admin() ) {

            return $translated;

        }

        return rd_wc_apply_coupon_discount_replacements( $translated );

    }

    function rd_wc_generic_coupon_replacement_in_notice( $message ) {

        if ( is_admin() ) {

            return $message;

        }

        return rd_wc_apply_coupon_discount_replacements( $message );

    }

}