Ability to Add Discounts and Taxes to Transactions

[risangbaskoro]

This PR should close #16.

The ability to assign discounts and taxes in Kasir object.

Discounts

To add a discount, call thediscount() method and pass the parameters to create a discount, This method will also automatically calculate the gross_amount.

The available parameters for discount are:

• amount: int required The amount of the discount, in fixed amount or percentage of the gross_amount.
• percentage: bool Determines if the amount is in percentage.
• name: string The name of the discount. This will be displayed in the Midtrans Merchant Account Portal.
• id: string The ID of the discount. This will be displayed in the Midtrans Merchant Account Portal.

Adding a Discount

$kasir = Kasir::make()
    ->itemDetails($items)
    ->discount(10, true, 'Voucher GoPay', 'voucher-gopay');

Note
The example above will assign an array of discount to the discounts property and will automatically calculate the gross_amount.

Adding Multiple Discounts

To add multiple discounts, chain the discount() method:

$kasir = Kasir::make()
    ->itemDetails($items)
    ->discount(10, true, 'Voucher GoPay', 'voucher-gopay')
    ->discount(2, true, 'Promo Pengguna Baru', 'new-user');

Note
The example above will create two discounts; first is a 10% discount, and second is a 2% discount calculated after the first discount is applied.

Warning
The gross_amount will be calculated in the order in which the discount is called.

You can also add multiple discounts by using discounts() method and passing an array of discounts with each discount parameters as the keys.

$kasir = Kasir::make()
    ->itemDetails($items)
    ->discounts([
        [
            'id' => 'voucher-gopay',
            'name' => 'Voucher GoPay',
            'amount' => 10,
            'percentage' => true,
        ], [
            'id' => 'new-user',
            'name' => 'Promo Pengguna Baru',
            'amount' => 2,
            'percentage' => true,
        ]
    ]);

or pass an anonymous function:

$kasir = Kasir::make()
    ->itemDetails($items)
    ->discounts(function() {
        return [
            [
                'id' => 'voucher-gopay',
                'name' => 'Voucher GoPay',
                'amount' => 10,
                'percentage' => true,
            ], [
                'id' => 'new-user',
                'name' => 'Promo Pengguna Baru',
                'amount' => 2,
                'percentage' => true,
            ]
        ];
    });

Taxes

Similar to adding discounts, adding taxes is done by calling tax() or taxes() method and passing the parameters:

$kasir = Kasir::make()
    ->itemDetails($items)
    ->tax(1000, false, 'Biaya Metode Pembayaran', 'snap-fee')
    ->tax(11, true, 'PPN 11%', 'ppn');

or using an array of taxes:

$kasir = Kasir::make()
    ->itemDetails($items)
    ->taxes([
        [
            'id' => 'snap-fee',
            'name' => 'Biaya Metode Pembayaran',
            'amount' => 1000,
            'percentage' => false,
        ], [
            'id' => 'ppn',
            'name' => 'PPN 11%',
            'amount' => 11,
            'percentage' => true,
        ],
    ]);

or using an anonymous function:

$kasir = Kasir::make()
    ->itemDetails($items)
    ->taxes(function () {
        return [
            [
                'id' => 'snap-fee',
                'name' => 'Biaya Metode Pembayaran',
                'amount' => 1000,
                'percentage' => false,
            ], [
                'id' => 'ppn',
                'name' => 'PPN 11%',
                'amount' => 11,
                'percentage' => true,
            ],
        ];
    });

Default Behavior

By default, the gross_amount will be calculated from the discounts first, then the taxes. This behavior is to avoid unrealistic tax charges.

Warning
There are currently no method for overriding this behavior.

[risangbaskoro]

Didn't use this #16 (comment) for recalculating taxes and discounts. Instead, recalculate taxes and discounts from gross_amount for each taxes and discounts added.