A snippet of code for use with WooCommerce and Advanced Custom Fields to make a product discontinued or forthcoming.

product-lifecycle.php

<?php

function is_released($id) {
	$status = get_field('product_status', $id);

	// We consider null to be for sale, as this indicates an old product
	// where we haven't made a selection yet
	if (is_null($status) || $status === "forsale") {
		return True;
	} else if ($status === "forthcoming") {
		/* A product can also be released if it was forthcoming
		with an 'available from' date that has passed */
		$release_date = strtotime(get_field('available_from', $id));
		// Check that a release date was set, and that the date has passed.
		return $release_date && time() > $release_date;
	}
	return False;
}
function is_forthcoming($id) {
	$status = get_field('product_status', $id);
	if ($status === "forthcoming") {
		$release_date = strtotime(get_field('available_from', $id));
		// Either no release date was set, or the date has not passed.
		return !$release_date || time() < $release_date;
	}
	return False;
}
function is_discontinued($id) {
	$status = get_field('product_status', $id);
	return $status === "discontinued";
}

/* Prevent purchase of products that have not been released */
add_filter('woocommerce_is_purchasable', 'lifecycle_woocommerce_is_purchasable', 10, 2);
function lifecycle_woocommerce_is_purchasable($is_purchasable, $product) {
	return $is_purchasable && is_released($product->get_id());
}

add_filter('woocommerce_variation_is_purchasable', 'lifecycle_woocommerce_variation_is_purchasable', 10, 2);
function lifecycle_woocommerce_variation_is_purchasable($is_purchasable, $product) {
	return $is_purchasable && is_released($product->get_parent_id());
}

/* Remove the add to cart buttons... We add it back later when needed */
remove_action( 'woocommerce_single_product_summary', 'woocommerce_template_single_add_to_cart', 30 );

/* Replace the add to cart buttons with our custom text */
add_filter( 'woocommerce_single_product_summary', 'lifecycle_single_add_to_cart', 30 );
/* Helper functions to generate the discontinued replacement products list: */
function id_to_link($product_id){
    $product = wc_get_product( $product_id );
    return '<a href="'. get_permalink( $product_id ) .'">' . $product->get_title() . '</a>';
}
function lifecycle_single_add_to_cart() {
	global $product;
	$id = $product->get_id();
	$status = get_field('product_status', $id);

	if ( is_released($id) ) {
		/* Product is released, so use the default add to cart buttons */
		woocommerce_template_single_add_to_cart();
	} else if ( is_discontinued($id) ) {

		// Replaced with is an array containing the ids of replacement products
		$replaced_with = get_field('replaced_with', $id);
	    if($replaced_with) {

	        // Turn the array of id's of replacement products into an array of links
	        $titles_as_links = array_map(function ($product_id) {return id_to_link($product_id);}, $replaced_with);

	        // We want to join the array to follow the rules of sentences, like this:
	        // item 1, item 2, and item 3
	        // ... rather than just item 1, item 2, item 3, like regular implode would.
	        if ( count($titles_as_links) < 3 ) {
	        	$sentence = implode (" and ", $titles_as_links);
	        } else {
	        	$last = array_pop($titles_as_links);
	        	$sentence = implode(", ", $titles_as_links);
	        	$sentence .= ", and " . $last;
	        }

	        // Echo it
	        echo '<span class="discontinued">This product has been discontinued. It has been replaced by ' . $sentence . '.</span>';
	    } else {
	        echo '<span class="discontinued">This product has been discontinued.</span>';
	    }
	} else {
		// Product is forthcoming
		// Release date here depends on ACF return value for available_from being set
		// appropriately to display nicely.
		$release_date = get_field('available_from', $id);
		if ($release_date !== "") {
			echo '<span class="forthcoming">This product is forthcoming and will be available from ' . $release_date . '</span>';
		} else {
			echo '<span class="forthcoming">This product is forthcoming and will be available soon!</span>';
		}
	}
}

?>