# Invite Protocol (Frontend <-> Backend)

This document defines the invite/referral contract for authenticated web users.

Protocol verification status:

- Backend route source: `backend/src/v1/invite/router.py`
- Backend service source: `backend/src/v1/invite/service.py`
- Backend schema source: `backend/src/v1/invite/schemas.py`
- Web mapping source: `web/src/lib/api.ts`

## Compatibility strategy

- Additive evolution only.
- Existing response fields are stable and must remain backward-compatible.

## Route

### GET /api/v1/invite/me

Get the current user's invite overview.

**Authorization**: Requires authenticated session. User identity from JWT `sub`.

**Response (200)**:

```json
{
  "myCode": "ABC123",
  "binding": {
    "canBind": false,
    "boundInviteCode": "QWE789",
    "boundAt": "2026-05-21T10:30:00+00:00"
  },
  "summary": {
    "rewardPoints": 40,
    "invitedCount": 3,
    "rewardedCount": 2,
    "pendingCount": 1,
    "rewardedPoints": 80,
    "totalPotentialRewardPoints": 120
  },
  "items": [
    {
      "referralId": "5ed7c3f0-6d1c-4f3f-8b40-2cb537da53e6",
      "inviteCode": "ABC123",
      "boundAt": "2026-05-18T09:00:00+00:00",
      "firstCreemPaidAt": "2026-05-20T11:15:00+00:00",
      "rewardGranted": true,
      "rewardGrantedAt": "2026-05-20T11:15:02+00:00"
    }
  ]
}
```

Field rules:

- `myCode`: string, unique invite code assigned to the current user
- `binding.canBind`: boolean, whether the current user can still bind another user's invite code
- `binding.boundInviteCode`: string or `null`, bound inviter code snapshot
- `binding.boundAt`: ISO 8601 datetime or `null`
- `summary.rewardPoints`: integer `>= 0`, reward granted to inviter and invitee per qualified post-bind CREEM payment
- `summary.invitedCount`: integer `>= 0`
- `summary.rewardedCount`: integer `>= 0`
- `summary.pendingCount`: integer `>= 0`, computed as `invitedCount - rewardedCount`
- `summary.rewardedPoints`: integer `>= 0`, computed as `rewardedCount * rewardPoints`
- `summary.totalPotentialRewardPoints`: integer `>= 0`, computed as `invitedCount * rewardPoints`
- `items`: inviter-side referral list, newest first
- `items[].firstCreemPaidAt`: present only when the invitee has completed the qualifying CREEM payment after binding
- `items[].rewardGranted`: whether inviter-side invite reward has been credited
- `items[].rewardGrantedAt`: present only when `rewardGranted=true`

### POST /api/v1/invite/bind

Bind another user's invite code to the current account.

This endpoint is write-once:

- a user can bind at most once;
- binding cannot be removed;
- self-binding is forbidden;
- binding is allowed even if the current user already has completed CREEM payments.

**Authorization**: Requires authenticated session.

**Request**:

```json
{
  "code": "ABC123"
}
```

Field rules:

- `code`: string, exactly 6 uppercase alphanumeric invite characters after normalization

**Response (200)**:

Same shape as `GET /api/v1/invite/me` after the bind succeeds.

## Error contract linkage

- RFC7807 + extension `code`, optional `params`.
- Shared registry: `docs/protocols/common/http-error-codes.md`.
- Error codes for this feature:
  - `INVITE_CODE_NOT_FOUND` (404): Invite code not found for current user
  - `INVITE_BIND_CODE_NOT_FOUND` (404): Invite code to bind does not exist
  - `INVITE_ALREADY_BOUND` (409): Current user already bound an inviter
  - `INVITE_SELF_BIND_FORBIDDEN` (409): Current user attempted to bind their own code
  - `INVITE_CODE_NOT_BINDABLE` (409): Invite code is disabled, expired, or has no owner
  - `INVITE_CODE_INVALID` (422): Invite code format is invalid

## Data model linkage

- Invite codes are stored in `invite_codes` table.
- Referral bindings are stored in `invite_referrals`.
- See `docs/protocols/common/user-points-chat-data-protocol.md` for `profiles.referred_by`, `invite_referrals`, `redeem_code_batches`, and `redeem_codes`.