1. Open your theme directory and run:

yarn add @vue-storefront/checkout-com

If you are Developing Core of Alokai Next you might need to add @vue-storefront/checkout-com to useRawSource attribute in one of buildModules:

['@vue-storefront/nuxt', {
    coreDevelopment: true,
    useRawSource: {
        dev: [
          '@vue-storefront/commercetools',
          '@vue-storefront/core',
          '@vue-storefront/checkout-com'
        ],
        prod: [
          '@vue-storefront/commercetools',
          '@vue-storefront/core',
          '@vue-storefront/checkout-com'
        ]
    }
}],

2. Open your nuxt.config.js
3. At the bottom of modules add:

['@vue-storefront/checkout-com/nuxt', {
    channels: {
        en: {
            publicKey: 'pk_test_your-public-key',
            secretKey: 'sk_test_your-secret-key',
            ctApiUrl: 'https://your-commerctools-instance.com'
        }
    },
    defaultChannel: 'en'
}],

defaultChannel is the channel which will be chosen by default. Value should be keyname from channels channels allows us to define many variants of attributes. Developer is able to change them just by calling setChannel publicKey and secretKey comes from Checkout COM ctApiUrl is base URL to the CT CKO API - do not put slash at the end!

1. Import useCko:

import { useCko } from '@vue-storefront/checkout-com';

2. useCko returns:

interface {
    availableMethods: { name: string, [key: string]: any },
    error: Error | null,
    selectedPaymentMethod: CkoPaymentType,
    storedPaymentInstruments: PaymentInstrument[],
    submitDisabled: ComputedRef<boolean>,
    storedContextId: ComputedRef<string>,
    loadAvailableMethods: (cartId: string, email?: string): { id, apms },
    initForm: (): void,
    submitCardForm: (): void,
    makePayment: ({ cartId, email, contextDataId, success_url, failure_url, secure3d, cvv, reference }): Promise<Response | void>,
    setPaymentInstrument: (token: string): void,
    setSavePaymentInstrument: (newSavePaymentInstrument: boolean): void,
    loadSavePaymentInstrument: (): boolean,
    removePaymentInstrument: (customerId: string, paymentInstrument: string): Promise<void>,
    loadStoredPaymentInstruments: (customerId: string): Promise<void>
}

In this step you need:

const { cart } = useCart();
const { setBillingDetails } = useCheckout();
const { isAuthenticated, user } = useUser();
const {
    initForm,
    loadAvailableMethods,
    availableMethods,
    submitDisabled,
    storedPaymentInstruments,
    loadStoredPaymentInstruments,
    submitKlarnaForm,
    error
} = useCko();

3. setBillingDetails to save billing address. So you will be able to fetch availableMethods which base on your billing address (server-side)
4. Run loadStoredPaymentInstruments for logged in user to load stored payment instruments. They will be loaded to storedPaymentInstruments array of PaymentInstruments. Caution: This interface is being used for storing credit cards currently. It might have different shape for stored different payment methods in the future. Interface:

interface PaymentInstrument {
    id: string;
    type: string;
    expiry_month: number;
    expiry_year: number;
    scheme: string;
    last4: string;
    fingerprint: string;
    bin: string;
    card_type: string;
    card_category: string;
    issuer: string;
    issuer_country: string;
    product_id: string;
    product_type: string;
    avs_check: string;
    cvv_check: string;
    payouts: string;
    fast_funds: string;
    payment_instrument_id: string;
}

Example of usage:

if (isAuthenticated.value && cart.value && cart.value.customerId) {
    await loadStoredPaymentInstruments(cart.value.customerId);
}

4. Run loadAvailableMethods - first argument is cartId (access it via cart.value.id) - second for authenticated customer is an email (access it via user.value.email) - third for products, you can modify order products items. Then it will return interface { id, apms: Array<any> } and set apms inside availableMethods. E.g:

onMounted(async () => {
    await loadAvailableMethods(cart.value.id, user.value && user.value.email);
})

// You can modify products in order only on creation of context which init on call loadAvailableMethods (example: edit order for Klarna);
onMounted(async () => {
    const products = [
        {
            id: "dbe4f68c",
            name: "Product name",
            quantity: 2,
            price: 799,
            tax_amount: 220,
            type: "digital", // type?: "discount" | "gift_card"  | "physical" | "sales_tax" | "digital" | "shipping_fee" | "store_credit" | "surcharge";
            metadata: {
                tax_rate: 1600,
                reference: "ref",
                image_url: "",
                product_url: ""
            }
        }
    ];
    await loadAvailableMethods(cart.value.id, user.value && user.value.email, products);
})

5. Execute initForm. It mounts different payment handlers depends on arguments (check details below). If you are calling it after load component - use onMounted to make sure DOM Element where it should be mounted already exists.

• Card's Frames will be mounted in DOM element with class card-frame.
• PayPal & Sofort does not need any SDK, we just redirect to their's website like in 3DS redirection process for credit cards. So if you are interested only in this payment method you could omit this step.
• Klarna by default will be mounted in container with id klarna_container

interface PaymentMethods {
  card?: boolean;
  klarna?: boolean;
}

interface PaymentMethodsConfig {
  card?: Omit<Configuration, 'publicKey'>;
  klarna?: any;
}

const initForm = (initMethods: PaymentMethods = null, config: PaymentMethodsConfig = {}): void

initMethods - if it is null - method will try to mount handler for each supported payment method

• if it is {} - nothing will be mounted
• in object, you can specify which method you want to mount, e.g: { card: true } but it will still check whether it is supported or not

config allows to specify configuration for some payment handler, e.g. for card Frames we could use:

{
    card: {
        localization: 'es-ES'
    }
}

This configuration will have bigger priority than one from nuxt.config.js. The thing is you cannot overwrite is publicKey there. Signature for Frames looks like that:

(params?: Omit<Configuration, 'publicKey'>): void

Unfortunately, Checkout.com is not sharing any component for Saved Cards. After using loadStoredPaymentInstruments you can access an array of them via storedPaymentInstruments. Show them to user in a way you want. To choose certain Stored Instrument call setPaymentInstrument(item.id) where item is single element of storePaymentInstruments array.

setPaymentInstrument will set transaction token in your sessionStorage for a moment to make it work even after the refresh. Then it will set selectedPaymentMethod to CkoPaymentType.SAVED_CARD.

6. When submitDisabled changes to false - it means provided Card's data is proper and you could allow your user go forward. Card's token will be stored in sessionStorage for a moment.

7. Call submitCardForm function on card form submit (only for Credit Card method - not necessary for Stored Payment Method). It requires mounted Frames instance as it uses Frames.submitCard() under the hood. If you are using Klarna please call submitKlarnaForm (it returns promise) to authorize payment.

8. Then you need to make Payment error - contains error message from the response if you do not use 3ds or we have some server related issues. If the user just removed stored token from sessionStorage it will have There is no payment token inside. makePayment - it proceeds with the payment and removes card token afterward. Returns Promise if succeed, or Promise if failed.

9. You should call makePayment at first (remember to check if everything went ok):

// If it is guest
const payment = await makePayment({ cartId: cart.value.id });
// If it is guest & you require cvv
const payment = await makePayment({ cartId: cart.value.id, cvv: 1234 });
// If it is customer
const payment = await makePayment({ cartId: cart.value.id, email: user.value && user.value.email });
// If it is customer & require cvv
const payment = await makePayment({ cartId: cart.value.id, email: user.value && user.value.email, cvv: 100 });
// If you've already loaded available payment methods with same useCko composable instance
const payment = await makePayment();

if (error.value) {
    console.error(error.value.message);
    return;
}

10. If there is any error, you can access it via error.value. Otherwise, it will be nullish

11. If no errors, place an order:

const order = await placeOrder();

12. payment.data.redirect_url contains 3DS Auth redirect url for Credit Card if it requires it and it always contain redirect url for the PayPal and Sofort. You have to support it:

if (payment.data.redirect_url) {
    window.location.href = payment.data.redirect_url;
    return;
}

13. After 3DS Auth/PayPal Auth/Sofort Auth, user will be redirected to one of these urls. They are being created inside makePayment method:

success_url: `${window.location.origin}/cko/payment-success`,
failure_url: `${window.location.origin}/cko/payment-error`

You can override them while calling makePayment with success_url and failure_url attributes. E.g:

await makePayment({
    // ...
    success_url: 'https://example.com/success',
    failure_url: 'https://example.com/failure',
})

Would redirect after process to the:

success_url: 'https://example.com/success',
failure_url: 'https://example.com/failure'

14. You should make sure that after user leaves checkout - payment token is being removed from sessionStorage. For that purpose, useCko exports removeTransactionToken method. Call it when user exits Checkout's view! E.g:

// Checkout.vue
import { useCko } from '@vue-storefront/checkout-com';
import { onUnmounted } from '@vue/composition-api';
// ...
export default {
    // ...
    setup() {
        const { removeTransactionToken } = useCko();
        onUnmounted(removeTransactionToken);
    }
}

It is important to set proper CKO's Payment Method in useCko instance so it will be able to figure out proper payload to send in makePayment. To do that:

import { useCko, CkoPaymentType } from '@vue-storefront/checkout-com'

// ...

const {
    initForm,
    loadAvailableMethods,
    submitCardForm,
    makePayment,
    setPaymentInstrument,
    setSavePaymentInstrument,
    loadSavePaymentInstrument,
    selectedPaymentMethod, // Here
    loadStoredPaymentInstruments,
    removePaymentInstrument,
    storedPaymentInstruments,
    submitDisabled,
    error
} = useCko();

Currently, these are available payment methods:

enum CkoPaymentType {
    NOT_SELECTED = 0,
    CREDIT_CARD = 1,
    SAVED_CARD,
    KLARNA,
    PAYPAL,
    SOFORT
}

By default, selectedPaymentMethod equals CkoPaymentType.NOT_SELECTED. If user uses stored payment call setSavePaymentInstrument and it will set selectedPaymentMethod.value = CkoPaymentType.SAVED_CARD

setPaymentInstrument(item.id);

If user uses credit card use:

selectedPaymentMethod.value = CkoPaymentType.CREDIT_CARD

useCko composable shares loadSavePaymentInstrument method and setSavePaymentInstrument method for that purpose. It is being stored in the localStorage. E.g:

const {
      initForm,
      loadAvailableMethods,
      submitCardForm,
      makePayment,
      setPaymentInstrument,
      setSavePaymentInstrument, // Save
      loadSavePaymentInstrument, // Load
      selectedPaymentMethod,
      loadStoredPaymentInstruments,
      removePaymentInstrument,
      storedPaymentInstruments,
      submitDisabled,
      error
    } = useCko();
const savePaymentInstrument = ref(loadSavePaymentInstrument());

<SfCheckbox
    @change="setSavePaymentInstrument(savePaymentInstrument)"
    v-model="savePaymentInstrument"
    label="Save payment instrument"
    name="savePaymentInstrument"
    class="form__element"
/>

Checkout.com supports many payment methods, only a few have own SDKs - Credit Card & Klarna. By default, module fetches SDK only for Credit Card (Frames). You can customize it with module's config paymentMethods attribute. E.g:

['@vue-storefront/checkout-com/nuxt', {
    // ...
    paymentMethods: {
        cc: true,
        klarna: true
    }
}]

In nuxt.config.js module's config you can use each attribute from this page, e.g:

['@vue-storefront/checkout-com/nuxt', {
    // ...
    card: {
        localization: 'KO-KR',
        style: {
            'card-number': {
                color: 'red'
            },
            base: {
                color: '#72757e',
                fontSize: '19px',
                minWidth: '60px'
            },
            invalid: {
                color: 'red'
            },
            placeholder: {
                base: {
                    color: 'cyan',
                    fontSize: '50px'
                }
            }
        }
    }
}]

localization attribute must be a string or fulfill CustomLocalization interface:

interface CustomLocalization {
  cardNumberPlaceholder: string;
  expiryMonthPlaceholder: string;
  expiryYearPlaceholder: string;
  cvvPlaceholder: string;
}

In nuxt.config.js and initForm method call you can configure Klarna component. E.g:

['@vue-storefront/checkout-com/nuxt', {
    // ...
    klarna: {
        containerSelector: '#my-klarna-div',
        beforeLoad ({ apm, options, data }) {
            return {
                options,
                data
            }
        }
    }
}]

Also you can modify merchant_reference1 and customer phone on call initForm. For example:

const {
    initForm,
    availableMethods
} = useCko();

onMounted(async () => {
    // Firstly we have to create context by calling loadAvailableMethods
    await loadAvailableMethods(cart.value.id, user.value && user.value.email);

    initForm({ klarna: true },
      {
        klarna: {
          beforeLoad({ options, data }) {
            data.merchant_reference1 = cart.value?.custom?.merchant_reference; // order reference
            data.billing_address.phone = billingDetails.value.phone; // phone number of customer
            return { options, data };
          }
        }
      }
    );
})

beforeLoad - hook that allows you to modify options and data (first and second argument) used to call Klarna.Payments.load

At first, you have to save billing address in your backend to do that. You can do it just after setBillingDetails call from Creadit card component step. Then you can easily use loadAvailableMethods method. It requires reference as the first argument - which is cartId. E.g:

// Somewhere inside Vue3's setup method
const { cart } = useCart();
const { user } = useUser();
const { loadAvailableMethods, availableMethods } = useCko();
const { setBillingDetails } = useCheckout();

const handleFormSubmit = async () => {
    await setBillingDetails(billingDetails.value, { save: true });
    // If it is Guest
    const response = await loadAvailableMethods(cart.value.id);
    // If it is Customer
    const response = await loadAvailableMethods(cart.value.id, user.value.email);
    console.log('Server respond with ', response)
    console.log('Array of available payment methods ', availableMethods)
};

Response might look like:

{
    "id": "cid_XXX",
    "apms": [
        {
            "name": "paypal",
            "schema": "https://somewebsite.com/apms/paypal.json",
            "show": true
        }
    ]
}

availableMethods might look like:

[
    {
        "name": "card"
    },
    {
        "name": "klarna",
        "some_key": "123"
    },
    {
        "name": "paypal",
        "some_key": "456"
    }
]

useCko composable shares removePaymentInstrument method for that purpose. Keep in mind you use storedPaymentMethods[i].id for payment but storedPaymentMethods[i].payment_instrument for removing it from the vault. Use it like:

const {
    removePaymentInstrument,
    // ...
} = useCko();
const { isAuthenticated } = useUser();
const { cart } = useCart();

const removeMinePaymentInstrument = async (paymentInstrument: string): Promise<void> => {
    if (isAuthenticated.value && cart.value && cart.value.customerId) {
        await removePaymentInstrument(cart.value.customerId, paymentInstrument);
    }
}

All you have to do is just import setChannel method and call it:

import { setChannel } from '@vue-storefront/checkout-com';

setChannel('it');

Where it is name of channel to set. It should be present inside config's channels.

To send CVV for saved payment instrument just add cvv attribute to object provided inside makePayment, e.g:

// If it is guest & you require cvv
const payment = await makePayment({ cartId: cart.value.id, cvv: 1234 });
// If it is customer & require cvv
const payment = await makePayment({ cartId: cart.value.id, email: user.value && user.value.email, cvv: 100 });

You might wonder how you could learn whether you have to provide CVV for saved card or not. For that, I shared isCvvRequired computed boolean in useCko. It's value bases on loadAvailableMethods response. So you have to call this method before. If you didn't provide cvv to makePayment and it requires it - then it will throw an error.

There are banks (especially in US) which do not support any version of 3DS standard. You can instruct the makePayment method to attempt non-3DS payment in case customer's card is not enrolled for 3DS using attempt_n3d parameter. Visit checkout.com docs for more details. Please note: if you downgrade the payment to non-3DS, the liability shift advantage of 3DS2 will not apply, meaning you will not be protected against potentially fraudulent payments or chargebacks.

const payment = await makePayment({ cartId: cart.value.id, cvv: 1234, attempt_n3d: true });