Bind a Customer via LINE Login

Let your members bind their own LINE account. You just hand LOMA a member ID (customerExternalId); LOMA returns a one-time LINE authorization link. After the member authorizes on LINE, LOMA automatically binds that member to their LINE account and 302-redirects back to a URL you specify.

Once bound, you can send messages (notifications / OTP) to that member.

Flow

1. Your backend calls POST /api/v1/merchant/binding/line-login with the member ID and a returnUrl.
2. LOMA returns a one-time bindingUrl (valid 10 minutes by default).
3. You redirect / open bindingUrl for the member. They tap “Allow” on the LINE page.
4. LINE calls LOMA back → LOMA fetches the member's LINE userId and stores the binding.
5. LOMA 302-redirects the member back to your returnUrl with the result.

1. Create a binding link

POST /api/v1/merchant/binding/line-login

Headers

Requires X-Api-Key and X-Api-Secret (see Authentication).

Body

Field	Type	Required	Description
customerExternalId	string	✅	Your member / customer ID
returnUrl	string	✅	Where LOMA redirects after binding completes

{
  "customerExternalId": "C10086",
  "returnUrl": "https://your-app.com/line/bound"
}

Success 200

{
  "code": "OK",
  "message": "Success",
  "requestId": "req_...",
  "data": {
    "bindingUrl": "https://access.line.me/oauth2/v2.1/authorize?response_type=code&client_id=...&state=...",
    "state": "9f2a...c1",
    "expiresAt": "2026-07-02T08:20:00Z"
  }
}

Field	Description
bindingUrl	One-time LINE authorization link — redirect the member here
state	One-time token (LOMA-internal; you don't need to handle it)
expiresAt	Link expiry (UTC); after this, create a new link

Common errors

code	HTTP	Description
LOGIN_NOT_CONFIGURED	400	Merchant has no LINE Login channel configured
VALIDATION_ERROR	400	customerExternalId or returnUrl missing

2. Redirect result

After the member finishes (or cancels), LOMA 302-redirects the browser to your returnUrl with these query params appended:

Success:

https://your-app.com/line/bound?binding=success&customerExternalId=C10086

Failed / cancelled:

https://your-app.com/line/bound?binding=failed&customerExternalId=C10086&reason=cancelled

Param	Description
binding	success / failed
customerExternalId	The member ID for this binding (echoed back)
reason	Only on failure: cancelled (user cancelled) / expired (link expired) / already_used (link consumed) / ALREADY_BOUND (member already bound to another LINE) / LINE_ALREADY_BOUND (LINE already bound to another member) / exchange_failed (LINE exchange failed)

⚠️ Redirect params are for UI hints only. Trust the server: after the redirect, re-confirm with Check binding status before proceeding.

3. Unbind a customer

Remove a member's current LINE binding. After unbinding, the member can go through the binding flow again (rebinding to a different LINE account also requires unbinding first).

DELETE /api/v1/merchant/customer/{customerExternalId}/line-binding

Headers

Requires X-Api-Key and X-Api-Secret (see Authentication).

Path params

Param	Description
customerExternalId	Your member / customer ID

Success 200

{
  "code": "OK",
  "message": "Success",
  "requestId": "req_...",
  "data": {
    "customerExternalId": "C10086",
    "unbound": true,
    "status": "UNBOUND"
  }
}

Field	Description
unbound	Whether an active binding was removed this call. true = unbound; false = the member had no active binding (nothing to do)
status	Always UNBOUND

Idempotent: calling it repeatedly for the same member never errors; when there's nothing to remove it returns unbound=false.

Example

curl -X DELETE https://loma-dev.acorners.com/api/v1/merchant/customer/C10086/line-binding \
  -H "X-Api-Key: lk_xxxx" -H "X-Api-Secret: xxxx"

Idempotency & constraints

• One member maps to exactly one LINE account, and vice versa.
• Re-binding the same member with the same LINE account is idempotent — returns success, no duplicate record.
• To rebind, call the unbind endpoint first, then run the binding flow again.

Example

curl -X POST https://loma-dev.acorners.com/api/v1/merchant/binding/line-login \
  -H "X-Api-Key: lk_xxxx" -H "X-Api-Secret: xxxx" \
  -H "Content-Type: application/json" \
  -d '{"customerExternalId":"C10086","returnUrl":"https://your-app.com/line/bound"}'