[WP][WooCommerce] Calculate sale price dynamically / programmatically based on taxonomy term custom field % (also works for Facebook Catalog feed)

wc_dynamic_saleprice.php

<?php

// The discount is set through a term meta 'sale_value' associated to the product, so that product regular or sales prices never need to changed manually
// The script also assumes the use of ACF, through get_field()

// BACKEND (Product list, FB feed)
function custom_dynamic_sale_price( $sale_price, $product ) {
    $id = $product->get_id();
    $tax = get_the_terms($id,'product_cat');
    $regular_price = wc_format_decimal( $product->get_price() );
    $discount_total = 0;
    foreach ($tax as $term){
        $disc_single = get_field('sale_value', $term->taxonomy . '_' . $term->term_id);
        $discount_total += $disc_single;
    }
    if(!is_null($discount_total) && $discount_total !== 0 && $discount_total !== '') {
        $new_price = wc_format_decimal($regular_price - ($regular_price / 100 * $discount_total));
        //update_post_meta( $id, 'fb_product_price', $new_price); // Only if using Facebook for WooCommerce plugin
        return $new_price;
    } elseif(is_null($discount_total) || $discount_total == 0 || $discount_total == '') {
        //update_post_meta( $id, 'fb_product_price', ''); // Only if using Facebook for WooCommerce plugin
        return '';
    } else {
        //update_post_meta( $id, 'fb_product_price', $sale_price); // Only if using Facebook for WooCommerce plugin
        return $sale_price;
    }
}
if(is_admin()) {
    add_filter( 'woocommerce_product_get_sale_price', 'custom_dynamic_sale_price', 10, 2 );
    add_filter( 'woocommerce_product_variation_get_sale_price', 'custom_dynamic_sale_price', 10, 2 );
}
function custom_dynamic_sale_price_html( $price_html, $product ) {
    if( $product->is_type('variable') ) return $price_html;
    if($product->get_sale_price() == '') return $price_html;
    $price_html = wc_format_sale_price( wc_get_price_to_display( $product, array( 'price' => $product->get_regular_price() ) ), wc_get_price_to_display(  $product, array( 'price' => $product->get_sale_price() ) ) ) . $product->get_price_suffix();
    return $price_html;
}
if(is_admin()) {
    add_filter( 'woocommerce_get_price_html', 'custom_dynamic_sale_price_html', 20, 2 );
}

// FRONTEND (Shop / Archive / Single)
function custom_change_product_price_display( $price ) {
    $id = get_the_ID();
    $tax = get_the_terms($id,'product_cat');
    $discount_total = 0;
    foreach ($tax as $term){
        $disc_single = get_field('sale_value', $term->taxonomy . '_' . $term->term_id);
        $discount_total += $disc_single;
    }
    if (!is_null($discount_total) && $discount_total !== 0){
        $symbol = get_woocommerce_currency_symbol();
        $new_price = preg_replace("/[^0-9,]/", "",$price);
        $price = '<del>'.$price.'</del> '.wc_format_decimal(($new_price - ($new_price / 100 * $discount_total))).$symbol;
    }
    return $price;
}
if(!is_admin()) {
    add_filter( 'woocommerce_get_price_html', 'custom_change_product_price_display', 999 );
}
add_filter( 'woocommerce_cart_item_price', 'custom_change_product_price_display', 999 );

// FRONTEND (Cart)
function prefix_add_discount_line( $cart ) {
    $items = $cart->get_cart();
    $disc_cart_total = 0;
    foreach ($items as $item){
        $item_id = $item['product_id'];
        $discount_total = 0;
        $tax = get_the_terms($item_id,'product_cat');
        foreach ($tax as $term){
            $disc_single = get_field('sale_value', $term->taxonomy . '_' . $term->term_id);
            $discount_total += $disc_single;
        }
        if ($discount_total !== 0){
            $current_price = $item['line_total'];
            $discount_price = $current_price / 100 * $discount_total;
            $disc_cart_total +=$discount_price;
        }
    }
    if ($disc_cart_total !== 0){
        $cart->add_fee( __( 'Sale', TEXT_DOMAIN ) , -$disc_cart_total );
    }
}
add_action( 'woocommerce_cart_calculate_fees', 'prefix_add_discount_line' );
?>