Automatically apply a coupon to a user's first order in WooCommerce

gistfile1.txt

add_action('woocommerce_before_cart', 'firstTimeShopper');
add_action('woocommerce_before_checkout_form', 'firstTimeShopper');

function firstTimeShopper() {
	global $woocommerce;
	$coupon_code = 'firstimeshopper'; // Change this to whatever your coupon code is
	
	if (is_user_logged_in()) {
		$current_user = wp_get_current_user();
		
		if (!$current_user)
			return;
			
		$hasOrderedBefore = get_user_meta($current_user->ID, 'paying_customer', true);
		if (!$hasOrderedBefore) {
			// If coupon has been already been added remove it.
			if ($woocommerce->cart->has_discount(sanitize_text_field($coupon_code)))
				if (!$woocommerce->cart->remove_coupons(sanitize_text_field($coupon_code)))
					$woocommerce->show_messages();
			
			// Add coupon
			if (!$woocommerce->cart->add_discount(sanitize_text_field($coupon_code))) {
				$woocommerce->show_messages();
			} else {
				$woocommerce->clear_messages();
				// Change this message to whatever you like
				$woocommerce->add_message("Hi there! <b>Because this is your first order we've applied a 10% discount.</b> No hidden catches, we just want to say thanks!");
				$woocommerce->show_messages();
			}
			
			// Recalculate totals.
			$woocommerce->cart->calculate_totals();
			
		} else {
			// Is not user's first time shopping
			if ($woocommerce->cart->has_discount(sanitize_text_field($coupon_code))) {
				if ($woocommerce->cart->remove_coupons(sanitize_text_field($coupon_code)))
					$woocommerce->show_messages();
				
				//Recalculate totals.
				$woocommerce->cart->calculate_totals();
			}
		}
	}
}