Functions required for the incentive program

functions.php

<?php
/**
 * Will extract the Variation ID if available otherwise it will get the Product ID
 * @param $product Product
 * @param bool $check_variations Whether or not to check for variation IDs
 * @return mixed
 */
function get_id_from_product( $product, $check_variations = true ) {
    // Are we taking variations into account?
    if( $check_variations ) {
        // Ternary Operator
        // http://php.net/manual/en/language.operators.comparison.php
        return ( isset( $product['variation_id'] )
            && ! empty( $product['variation_id'])
            && $product['variation_id'] != 0 )
            ? $product['variation_id']
            : $product['product_id'];
    } else {
        // No variations, just need the product IDs
        return $product['product_id'];
    }
}

/**
 * Checks the existence of a specific product in the cart
 * @param $product_required The Product ID required to be in the cart
 * @return bool
 */
function qualifies_basedon_specific_product( $product_required ) {
    /*
     * We only want to run this on the cart or checkout page
     */
    if( is_cart() || is_checkout () ) {
        foreach( WC()->cart->cart_contents as $key => $product_in_cart ) {
            if( $product_required == get_id_from_product( $product_in_cart ) ) {
                return true;
            }
        }
        // Return false in case anything fails
        return false;
    }
}

/**
 * Checks the cart for the weight required to qualify for the incentive
 * @param $weight_required Weight Required
 * @return bool
 */
function qualifies_basedon_weight( $weight_required ) {

    /*
     * We only want to run this on the cart or checkout page
     */
    if( is_cart() || is_checkout () ) {
        if( $weight_required >= WC()->cart->cart_contents_weight ) {
            return true;
        }
    }
    // Return false in case anything fails
    return false;
}

/**
 * Checks the cart for the Total excluding taxes
 * @param $total_required
 * @return bool
 */
function qualifies_basedon_cart_total( $total_required ) {
    /*
     * We only want to run this on the cart or checkout page
     */
    if( is_cart() || is_checkout () ) {
        if( WC()->cart->subtotal_ex_tax >= $total_required ) {
            return true;
        }
    }
    // Return false in case anything fails
    return false;
}

/**
 * Checks the cart to verify whether or not a product from a Category is in the cart
 * @param $category Accepts the Product Category Name, ID, Slug or array of them
 * @return bool
 */
function qualifies_basedon_product_category( $category ) {
    foreach( WC()->cart->cart_contents as $key => $product_in_cart ) {
        if( has_term( $category, 'product_cat', get_id_from_product( $product_in_cart, false ) ) ) {
            return true;
        }
    }
    // Return false in case anything fails
    return false;
}

/**
 * Adds a specific product to the cart
 * @param $product_id Product to be added to the cart
 */
function add_incentive_to_cart( $product_id ) {
    // Check the cart for this product
    $cart_id = WC()->cart->generate_cart_id( $product_id );
    $prod_in_cart = WC()->cart->find_product_in_cart( $cart_id );
    // Add the product only if it's not in the cart already
    if( ! $prod_in_cart ) {
        WC()->cart->add_to_cart( $product_id );
    }
}

/**
 * Removes a specific product from the cart
 * @param $product_id Product ID to be removed from the cart
 */
function remove_incentive_from_cart( $product_id ) {
     $prod_unique_id = WC()->cart->generate_cart_id( $product_id );
    // Remove it from the cart by un-setting it
    unset( WC()->cart->cart_contents[$prod_unique_id] );
}