OFFLINE.Mall: Create custom virtual product files

Plugin.php

<?php namespace OFFLINE\MallGiftCards;

use Event;
use OFFLINE\Mall\Models\Category;
use OFFLINE\Mall\Models\Currency;
use OFFLINE\Mall\Models\Discount;
use OFFLINE\Mall\Models\Price;
use OFFLINE\Mall\Models\Product;
use OFFLINE\Mall\Models\ProductFileGrant;
use System\Classes\PluginBase;

class Plugin extends PluginBase
{
    public function boot()
    {
        /**
         * Listen for created download grants.
         * Create a discount code, generate a gift card PDF,
         * then attach it to the grant.
         */
        Event::listen('mall.product.file_grant.created', function (ProductFileGrant $grant, Product $product) {
            // Make sure the event is triggered by a product you care about. Validate this using the slug, the
            // assigned category or one of the other unique values (user_defined_id, gtin, mpn, etc).
            // In this example we check if the product belongs to a category that has the
            // "generate-gift-cards" code set as a custom code.
            $isGiftCardCategory = $product->categories->contains(function (Category $category) {
                return $category->code === 'generate-gift-cards';
            });
            // Exit here if this is not a product with a gift card category attached.
            if ( ! $isGiftCardCategory) {
                return;
            }

            // Create a new discount model.
            $discount = Discount::create([
                // Generate a descriptive name for the discount using the product's price information.
                'name'                 => sprintf('%s Gift Card', $product->price()->string),
                // Make sure it can only be used once.
                'max_number_of_usages' => 1,
                // Re-use the grant's expiry date.
                'expires'              => $grant->expires_at,
                // The discount is triggered by a code. The code will be created automatically on save.
                'trigger'              => 'code',
                // The discount is of a fixed amount. The amount will be defined below.
                'type'                 => 'fixed_amount',
            ]);

            // Set the amounts relation for each currency.
            Currency::getAll()->each(function (Currency $currency) use ($discount, $product) {
                $discount->amounts()->save(new Price([
                    'currency_id' => $currency->id,
                    'field'       => 'amounts',
                    // Re-use the price information form the product itself.
                    'price'       => $product->price($currency)->float,
                ]));
            });

            // Generate a gift card PDF (or image). We're creating a text file here for simplicity.
            $path = storage_path(sprintf('app/gift_card_%s.txt', $grant->id));
            file_put_contents($path, 'Your coupon code is: ' . $discount->code);

            // Attach the created file to the ProductFileGrant. This makes sure your custom file
            // will be downloaded and not the file that is attached to the $product itself.
            $grant->file = $path;
            // Set a custom display name for the grant.
            $grant->display_name = $discount->name;
            // Don't forget to save the changes!
            $grant->save();
        });
    }
}