Merchant-Presented Mode (C scan B) NEW

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Accept in-store payments from WeChat Pay users through your point-of-sale system (POS) using the WeChat Pay Merchant-Presented Mode (C scan B) payment method.

This guide walks you through the payment flow and details on how to implement.

How to enable

  • Supported Countries: Thailand
  • Minimum API version: 2017-11-02

To enable Merchant-Presented Mode (C scan B), send an email requesting this feature to support@opn.ooo. You will need to review and accept new terms and conditions.

Payment flow

Customers paying via Merchant-Presented Mode (C scan B) go through an offline payment flow. This means that once the charge is created, it can only be authorized offline. In this case, the customer must scan the generated QR code with the WeChat Pay app on their phone to complete the flow.

After the customer selects Merchant-Presented Mode (C scan B) as their preferred payment method, your POS device should generate the QR code.

payment flow

❶ The customer opens an WeChat Pay on their mobile phone. Then, the customer scans QR code displayed in the merchant POS. ❷ The customer reviews payment information. ❸ The customer confirms payment in the application. ❹ The payment successful page is displayed after the payment is made.

Implementation

To create a charge using Merchant-Presented Mode (C scan B), make the following API requests.

  1. Create a new payment source (type: wechat_pay_mpm) using Omise.js or one of the mobile SDKs (iOS and Android)
  2. Create a new charge using the identifier of the source created in Step 1.
  3. After receiving the charge completion webhook event, retrieve the charge to verify its status (optional, but recommended).

Use your public key to create the Merchant-Presented Mode (C scan B) source on the client (a customer's browser or mobile phone). Use your secret key to create the Merchant-Presented Mode (C scan B) charge on the server.

If both the creation and charge of a source must happen server-side, you can create and charge the source in a single API request using your secret key.

Creating a source

When the customer confirms that they wish to pay with this payment method, create a new source specifying the amount, currency, and type.

Parameter Type Description
amount integer (required) Amount in subunits of source currency
currency string (required) THB
type string (required) Payment source type wechat_pay_mpm

The following examples demonstrate the creation of a new Merchant-Presented Mode (C scan B) source for ฿1500. Replace the omise_public_key and $OMISE_PUBLIC_KEY variables with the test public key found on your dashboard.

Using Omise.js, the type parameter is supplied as the first argument to the createSource method.

Omise.setPublicKey(omise_public_key);

Omise.createSource('wechat_pay_mpm', {
  "amount": 150000,
  "currency": "THB"
}, function(statusCode, response) {
  console.log(response)
});

For testing, you can create the same request using curl.

curl https://api.omise.co/sources \
  -u $OMISE_PUBLIC_KEY: \
  -d "amount=150000" \
  -d "currency=THB" \
  -d "type=wechat_pay_mpm"

{
  "object": "source",
  "id": "src_test_5y4zok6u6476rb67vqa",
  "livemode": false,
  "location": "/sources/src_test_5y4zok6u6476rb67vqa",
  "amount": 150000,
  "barcode": null,
  "bank": null,
  "created_at": "2023-12-18T10:18:41Z",
  "currency": "THB",
  "email": null,
  "flow": "offline",
  "installment_term": null,
  "ip": null,
  "absorption_type": null,
  "name": null,
  "mobile_number": null,
  "phone_number": null,
  "platform_type": null,
  "scannable_code": null,
  "billing": null,
  "shipping": null,
  "items": [],
  "references": null,
  "provider_references": null,
  "store_id": null,
  "store_name": null,
  "terminal_id": null,
  "type": "wechat_pay_mpm",
  "zero_interest_installments": null,
  "charge_status": "unknown",
  "receipt_amount": null,
  "discounts": []
}

The id attribute is the source identifier (begins with src).

Creating a charge

Create a charge specifying the parameters source, amount, and currency.

  • source specifies the source identifier.
  • amount and currency must match amount and currency of the source.

The following example demonstrates how to create a new charge using curl. Replace $OMISE_SECRET_KEY with your test secret key found on your dashboard. Replace $SOURCE_ID with the id of the source.

curl https://api.omise.co/charges \
  -u $OMISE_SECRET_KEY: \
  -d "amount=150000" \
  -d "currency=THB" \
  -d "source=$SOURCE_ID"

{
  "object": "charge",
  "id": "chrg_test_5y4zoka3l2te3r3m4d9",
  "location": "/charges/chrg_test_5y4zoka3l2te3r3m4d9",
  "amount": 150000,
  "acquirer_reference_number": null,
  "net": 147352,
  "fee": 2475,
  "fee_vat": 173,
  "interest": 0,
  "interest_vat": 0,
  "funding_amount": 150000,
  "refunded_amount": 0,
  "transaction_fees": {
    "fee_flat": "0.0",
    "fee_rate": "1.65",
    "vat_rate": "7.0"
  },
  "platform_fee": {
    "fixed": null,
    "amount": null,
    "percentage": null
  },
  "currency": "THB",
  "funding_currency": "THB",
  "ip": null,
  "refunds": {
    "object": "list",
    "data": [],
    "limit": 20,
    "offset": 0,
    "total": 0,
    "location": "/charges/chrg_test_5y4zoka3l2te3r3m4d9/refunds",
    "order": "chronological",
    "from": "1970-01-01T00:00:00Z",
    "to": "2023-12-18T10:18:41Z"
  },
  "link": null,
  "description": null,
  "metadata": {},
  "card": null,
  "source": {
    "object": "source",
    "id": "src_test_5y4zojx3u5rip7hc24q",
    "livemode": false,
    "location": "/sources/src_test_5y4zojx3u5rip7hc24q",
    "amount": 150000,
    "barcode": null,
    "bank": null,
    "created_at": "2023-12-18T10:18:39Z",
    "currency": "THB",
    "email": null,
    "flow": "offline",
    "installment_term": null,
    "ip": null,
    "absorption_type": null,
    "name": null,
    "mobile_number": null,
    "phone_number": null,
    "platform_type": null,
    "scannable_code": {
      "object": "barcode",
      "type": "qr",
      "image": {
        "object": "document",
        "livemode": false,
        "id": "docu_test_5y4zokbr211johx2ct6",
        "deleted": false,
        "filename": "qrcode.png",
        "location": "/charges/chrg_test_5y4zoka3l2te3r3m4d9/documents/docu_test_5y4zokbr211johx2ct6",
        "kind": "qr",
        "download_uri": "https://api.omise.co/charges/chrg_test_5y4zoka3l2te3r3m4d9/documents/docu_test_5y4zokbr211johx2ct6/downloads/95DE796635C528E6",
        "created_at": "2023-12-18T10:18:41Z"
      }
    },
    "billing": null,
    "shipping": null,
    "items": [],
    "references": null,
    "provider_references": null,
    "store_id": null,
    "store_name": null,
    "terminal_id": null,
    "type": "wechat_pay_mpm",
    "zero_interest_installments": null,
    "charge_status": "pending",
    "receipt_amount": null,
    "discounts": []
  },
  "schedule": null,
  "customer": null,
  "dispute": null,
  "transaction": null,
  "failure_code": null,
  "failure_message": null,
  "status": "pending",
  "authorize_uri": null,
  "return_uri": null,
  "created_at": "2023-12-18T10:18:41Z",
  "paid_at": null,
  "expires_at": "2023-12-19T10:18:41Z",
  "expired_at": null,
  "reversed_at": null,
  "zero_interest_installments": false,
  "branch": null,
  "terminal": null,
  "device": null,
  "authorized": false,
  "capturable": false,
  "capture": true,
  "disputable": false,
  "livemode": false,
  "refundable": false,
  "partially_refundable": false,
  "reversed": false,
  "reversible": false,
  "voided": false,
  "paid": false,
  "expired": false
}

Creating a source and charge

Alternatively, you can create and charge a source in a single API request.

curl https://api.omise.co/charges \
  -u $OMISE_SECRET_KEY: \
  -d "amount=150000" \
  -d "currency=THB" \
  -d "source[type]=wechat_pay_mpm"

Setting the charge to expire

By default, the charge expires 2 hours after creation.

You can assign different expiration periods to each charge by entering a timestamp between 1 minute and 2 hours from the current time in the expires_at field of the Charge API. If the timestamp is entered correctly, the charge will expire at the designated time instead of the default period.

After the charge is created, you can also manually call our Expire API to expire a pending charge.

curl https://api.omise.co/charges \
  -u $OMISE_SECRET_KEY: \
  -d "amount=150000" \
  -d "currency=THB" \
  -d "source[type]=wechat_pay_mpm" \
  -d "expires_at=2021-09-01T00:00:00Z"

curl https://api.omise.co/charges/$CHARGE_ID/expire \
  -X POST \
  -u $OMISE_SECRET_KEY:

Completing the charge

At this point, you have created a new charge with its status set to pending. Other possible values for charge status are successful, failed, and expired.

The following sections detail how to authorize a charge, receive its completion webhook event, and update its status.

sequenceDiagram participant customer participant omise.js participant merchant participant api.omise.co participant offline provider customer->>omise.js: Send payment details for purchase omise.js->>api.omise.co: Request source using payment details api.omise.co-->>omise.js: Return source omise.js->>merchant: Merchant gets returned source merchant->>api.omise.co: Request charge using source and purchase details api.omise.co-xmerchant: Send "charge.create" webhook api.omise.co-->>merchant: Return charge customer->>offline provider: Provide payment or charge authorization at offline provider offline provider-->>api.omise.co: Return result of payment or charge authorization api.omise.co-xmerchant: Send "charge.complete" webhook merchant-xcustomer: Send charge result (e.g. via email)

Authorizing the charge

Present the customer with QR code generated at charge creation. To authorize the charge, the customer scans the QR code using their phone.

You can simulate the authorization phase in test mode. Go to the specific charge on the dashboard, click on Actions and manually mark the charge as Successful or Failed.

Find the QR code nested within the charge object as follows:

charge:
  source:
    scannable_code:
      image:
        download_uri: QR code image to present to the customer

{
  "object": "barcode",
  "type": "qr",
  "image": {
    "object": "document",
    "livemode": false,
    "id": "docu_test_5y4zok13tct2lpnhze4",
    "deleted": false,
    "filename": "qrcode.png",
    "location": "/charges/chrg_test_5y4zojzk7oupjwkdh6a/documents/docu_test_5y4zok13tct2lpnhze4",
    "kind": "qr",
    "download_uri": "https://api.omise.co/charges/chrg_test_5y4zojzk7oupjwkdh6a/documents/docu_test_5y4zok13tct2lpnhze4/downloads/ADBEBFF26C4565EC",
    "created_at": "2023-12-18T10:18:40Z"
  }
}

Receiving the charge completion event

The best way to be notified about the completion of a charge is using webhook events.

Set up a location on the merchant server to receive webhook events, and add this location as a webhook endpoint on the dashboard.

Checking the charge status

After receiving this event, retrieve the charge using its id and confirm that its status matches the status of the charge contained in the event.

If the value of status is successful, you got paid.

If the value of status is failed, check the failure_code and failure_message in the charge object for an explanation.

Possible failure codes are as follows.

Failure Code Description
payment_expired Payment expired.
payment_rejected Payment rejected by issuer.
invalid_account Valid account for payment method not found.
insufficient_fund Insufficient funds in the account or the payment method has reached its limit.
failed_processing General payment processing failure.

Refunds

Merchant-Presented Mode (C scan B) charges can be partially or fully refunded within 90 days of the transaction date.

Limits

  • Minimum: 2000 (THB 20.00)
  • Maximum: 15000000 (THB 150,000.00)

How to check the public key and secret key

For information on how to obtain and check the public and secret keys, please refer to this document.

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