Replace Woocommerce “add to cart” to be “Download” button [closed]

1. hook into the woocommerce hook is_purchasable

    add_filter("woocommerce_is_purchasable", function($product, $isPurchasable)
    {
        if(!$isPurchasable)
            return $isPurchasable;
   
        $productId = $product->get_id();
        $user = wp_get_current_user();
        if($user->exists() && $productId == 769)
        {
            $userId = $user->ID;
            $userEmail = $user->user_email;
   
            if(wc_customer_bought_product($userEmail, $userId, $productId))
            {
                //block the purchase so the user sees read more instead of add to cart
                $isPurchasable = false;
            }
        }
   
        return $isPurchasable;
    });
   

2. hook into the init field and and if the current page is that product id
   then we will need to display:none the add to cart button and instead add a download
   button. If you have access to a theme builder add a button on the single product and
   hide it in the beginning. That will make this process much easier.

    add_action("init", function()
    {
        global $product;
        if(is_product() && $product->get_id() == 769)
        {
            $className = "add_to_cart_button";
            $downloadLink = ""; // your link here
   
            printf(
                "<script>
                     let element = document.getElementByClassName(\"%s\");
                     element.style.display=\"none\";
   
                     let link = document.createElement(\"a\");
                     link.classList.add(\"button\");
                     link.setAttribute(\"href\", \"%s\");
                     link.textContent = \"download\";
   
                     let parent = element.parentElement;
                     parent.insertAdjacentElement(\"afterend\", link);
                 </script>",
                 $className,
                 $downloadLink
            );
        }
    });
   

ps: If you want the user to be logged in before adding the item to cart do the following

    add_filter("woocommerce_is_purchasable", function($product, $isPurchasable)
    {
        if(!$isPurchasable)
            return $isPurchasable;

        $productId = $product->get_id();
        $user = wp_get_current_user();

        //block the user from even adding it to cart before logging in
        if($productId == 769 && !$user->exists())
            return false;

        if($user->exists() && $productId == 769)
        {
            $userId = $user->ID;
            $userEmail = $user->user_email;

            if(wc_customer_bought_product($userEmail, $userId, $productId))
            {
                //block the purchase so the user sees read more instead of add to cart
                $isPurchasable = false;
            }
        }

        return $isPurchasable;
    });

ps2: I did not run this code myself just off the top of my head. Should be close enough though to run. will check if it runs on my system.

New Code: Just did a test run and it works

            add_filter("woocommerce_is_purchasable", function($isPurchasable, $product)
            {
                if(!$isPurchasable)
                    return $isPurchasable;

                $productId = $product->get_id();
                $user = wp_get_current_user();
                if($user->exists() && $productId == 796)
                {
                    $userId = $user->ID;
                    $userEmail = $user->user_email;

                    if(wc_customer_bought_product($userEmail, $userId, $productId))
                    {
                        //block the purchase so the user sees read more instead of add to cart
                        $isPurchasable = false;
                    }
                }

                return $isPurchasable;
            }, 10, 2);

            add_filter("woocommerce_is_purchasable", function($isPurchasable, $product)
            {
                if(!$isPurchasable)
                    return $isPurchasable;

                $productId = $product->get_id();
                $user = wp_get_current_user();

                //dont allow non existing users to buy
                if(!$user->exists() && $productId == 796)
                    $isPurchasable = false;

                return $isPurchasable;
            }, 10, 2);

            add_action("woocommerce_after_single_product", function()
            {
                global $post;
                $product = wc_get_product($post->ID);
                
                if(empty($product) || is_null($product))
                    return;

                if($product->get_id() != 796)
                    return;

                $user = wp_get_current_user();
                if(!$user->exists())
                    return;

                if(!wc_customer_bought_product($user->user_email, $user->ID, $product->get_id()))
                    return;

                $productId = $product->get_id();
                $downloadLink = "#"; // your link here

                echo sprintf(
                    "<script>
                        let element = document.getElementById(\"product-%d\");
                        let form = element.getElementsByTagName(\"form\")[0];
                        let addToCartButton = form.getElementsByTagName(\"button\")[0];

                        element = addToCartButton;
                        let classList = element.classList;

                        element.style.display=\"none\";

                        let link = document.createElement(\"a\");
                        link.classList = classList;
                        link.setAttribute(\"href\", \"%s\");
                        link.textContent = \"download\";

                        let parent = element.parentElement;
                        parent.insertAdjacentElement(\"afterend\", link);
                    </script>",
                    $productId,
                    $downloadLink
                );
            });