Extending Taxation

Taxation is driver-based, allowing custom tax calculation logic to replace or extend the default system.

Overview

Taxation is complex and sometimes what Lunar offers out of the box is not sufficient. This is why taxation is driver-based, allowing custom logic to be added as needed.

By default, a SystemTaxDriver is used, which relies on Lunar’s internal models and database as outlined in the Taxation reference. To use a custom implementation, the driver can be changed in the config/lunar/taxes.php config file.

<?php

return [
    'driver' => 'system',
];

Writing a Custom Driver

A custom driver must implement the Lunar\Base\TaxDriver interface:

<?php

namespace App\Drivers;

use Lunar\Base\Addressable;
use Lunar\Base\Purchasable;
use Lunar\Base\TaxDriver;
use Lunar\Base\ValueObjects\Cart\TaxBreakdown;
use Lunar\Models\Contracts\CartLine;
use Lunar\Models\Contracts\Currency;

class TaxJar implements TaxDriver
{
    /**
     * Set the shipping address.
     */
    public function setShippingAddress(?Addressable $address = null): self
    {
        // ...
        return $this;
    }

    /**
     * Set the billing address.
     */
    public function setBillingAddress(?Addressable $address = null): self
    {
        // ...
        return $this;
    }

    /**
     * Set the currency.
     */
    public function setCurrency(Currency $currency): self
    {
        // ...
        return $this;
    }

    /**
     * Set the purchasable item.
     */
    public function setPurchasable(Purchasable $purchasable): self
    {
        // ...
        return $this;
    }

    /**
     * Set the cart line.
     */
    public function setCartLine(CartLine $cartLine): self
    {
        // ...
        return $this;
    }

    /**
     * Return the tax breakdown from a given sub total.
     *
     * @param  int  $subTotal
     */
    public function getBreakdown($subTotal): TaxBreakdown
    {
        // Build and return a TaxBreakdown instance...
    }
}

Once the driver is created, register it by extending the tax manager in a service provider:

public function boot()
{
    \Lunar\Facades\Taxes::extend('taxjar', function ($app) {
        return $app->make(TaxJar::class);
    });
}

Then set the driver in the config/lunar/taxes.php config:

<?php

return [
    'driver' => 'taxjar',
];