# Phase 8 Backend Contract — Customer Identity, VK ID, MAX/Telegram Messaging

Companion to [PRODUCT-PLAN-v3.1-DELIVERY-PLAN.md](../PRODUCT-PLAN-v3.1-DELIVERY-PLAN.md) Phase 8 (Sprints 8.1–8.5). Covers plan §2.9, §3.4, and all of §14 (the v3.1-only addition).

**Status: ready to build. Sprint order fixed by Sprint 0.1 decision: VK ID first, then everything else** ("do all after vk"). Sequence below follows that: identity core → VK ID → email/phone OTP → MAX/Telegram → Notification Orchestrator.

---

## 1. Entities

```ts
interface Customer {
  id: string;
  marketplaceId: string;      // or global identity strategy, tenant-configurable
  name?: string;
  email?: string;
  phone?: string;
  status: 'active' | 'suspended';
  createdAt: string;
}

interface ExternalIdentity {
  customerId: string;
  provider: 'vk_id' | 'yandex_id' | 'telegram' | 'max';   // yandex_id added 2026-08-21, FH-4.5
  providerUserId: string;
  email?: string;          // VK frequently returns none - never require it
  phone?: string;
  displayName?: string;
  verifiedAt: string;
  metadata: Record<string, unknown>;
  lastUsedAt: string;
}

interface ContactMethod {
  customerId: string;
  type: 'email' | 'phone';
  value: string;
  verifiedAt?: string;
}

interface ContactChannel {
  customerId: string;
  provider: 'telegram' | 'vk' | 'max';
  chatId: string;
  verified: boolean;
  notificationsEnabled: boolean;
  deliveryEnabled: boolean;
}

interface MessagingConsent {
  customerId: string;
  channel: string;
  purpose: 'marketing' | 'order_service_messages';
  grantedAt?: string;
  revokedAt?: string;
}
```

Telegram is demoted from sole identity to one `ExternalIdentity` provider among several — it must remain fully functional, just no longer the only path.

## 2. Sprint 8.2 — Social identity: VK ID first, Yandex ID second

Rewritten 2026-08-21 (FH-4.1–FH-4.5). Previously this section specified a VK-only pair of endpoints where the callback took `{ code, codeVerifier }` from the browser. Two changes: the surface is provider-agnostic, and the PKCE verifier stops travelling through the client.

### 2.1 Surface

```
GET  /api/identity/v1/{provider}/authorize?returnTo=   -> { url }  (or 302)
GET  /api/identity/v1/{provider}/callback?code=&state=[&device_id=]
POST /api/identity/v1/{provider}/unlink                (authenticated)
GET  /api/identity/v1/me/identities                    (authenticated) -> ExternalIdentity[]
```

`{provider}` is `vk` or `yandex` today; `telegram` and `max` join it when §4 migrates them onto `ExternalIdentity`. One controller, one strategy object per provider. The frontend gateway is a single interface (`src/app/core/identity/services/social-identity-gateway.interface.ts`) — providers differ only in a path segment, because everything that actually differs between them is backend-side.

### 2.2 The backend owns state and the code verifier

`/authorize` generates `state` and `code_verifier`, stores `{ state, codeVerifier, marketplaceId, returnTo, expiresAt }` server-side or in a signed `HttpOnly` cookie, TTL 10 minutes, **single use — deleted on first presentation**. It returns (or redirects to) the provider URL carrying `code_challenge` (S256) and `state`.

`/callback` validates `state`, exchanges the code using the stored verifier, fetches the profile, resolves or links the `ExternalIdentity`, issues the customer session cookie ([Track S §2.1](TRACK-S-SECURITY-RBAC-CONTRACT.md)), and redirects to `returnTo`.

- The client never sees a client secret, an access token, or a code verifier. We are a confidential client; a browser-held verifier buys nothing and adds a place to steal it from.
- An unknown, expired, or replayed `state` is a generic error. Do not distinguish the cases to the caller.
- `returnTo` is validated against the tenant's own verified origin. It is an open redirect otherwise.

### 2.3 Identity resolution

- A repeat login for the same `providerUserId` resolves to the same `Customer`, never a duplicate.
- `UNIQUE (provider, providerUserId)`. If a provider account is already bound to a *different* `Customer`, that is an identity conflict — route to controlled resolution, never silently rebind (plan §14.3). The unique index is what enforces this; a service-layer check is not sufficient.
- Whether one VK account across two of our storefronts is one `Customer` or two is a **product decision that must be made before implementation** (FH-0.1). `Customer.marketplaceId` currently implies two, and two is the safer default for data protection.
- Email is optional on `Customer`. Yandex returns one in most cases; VK frequently does not.

### 2.4 Per-tenant OAuth applications

Client id and secret are per marketplace, stored with the [Track S §4.2](TRACK-S-SECURITY-RBAC-CONTRACT.md) envelope: `{ clientId, clientSecret, scopes[], redirectUri }`. Never returned by any endpoint.

**The redirect_uri problem, which must be solved before any code is written.** Both providers validate `redirect_uri` against an exact registered list. We cannot register one per tenant domain and we cannot let tenants supply their own. Resolution: one **central identity host** as the sole registered callback, the origin tenant carried inside the signed `state`, then a 302 back to the tenant domain with a short-lived signed one-time handoff token that the tenant API exchanges for its session cookie. This is a one-way door — retrofitting it after the first provider is live is expensive.

### 2.5 Provider notes

Confirm exact parameter and scope names against live provider documentation before implementing; both providers have revised their flows recently.

**VK ID** — OAuth 2.1, PKCE mandatory (S256).

```
authorize  GET  https://id.vk.com/authorize
                client_id, redirect_uri, response_type=code,
                code_challenge, code_challenge_method=S256, state, scope
token      POST https://id.vk.com/oauth2/auth
                grant_type=authorization_code, code, code_verifier,
                device_id, client_id, redirect_uri
profile    POST https://id.vk.com/oauth2/user_info
logout          https://id.vk.com/oauth2/logout      (call on unlink)
```

**The callback returns `device_id` alongside `code`, and the token exchange fails without it.** This is the single most common VK ID integration bug; it is in this contract so it is not rediscovered at debugging time.

**Yandex ID** — OAuth 2.0, PKCE supported; use it.

```
authorize  GET  https://oauth.yandex.ru/authorize
                response_type=code, client_id, redirect_uri, state,
                code_challenge, code_challenge_method=S256
token      POST https://oauth.yandex.ru/token
                grant_type=authorization_code, code, code_verifier
                HTTP Basic: client_id:client_secret
profile    GET  https://login.yandex.ru/info?format=json
                Authorization: OAuth <access_token>
                -> id, login, default_email, default_phone, psuid
```

Yandex is a second strategy object against the same surface, not a second integration. Build it after VK works.

## 3. Sprint 8.3 — Email/phone OTP (after VK ID)

Implements the already-approved [email/phone login spec](../superpowers/specs/2026-08-15-email-phone-login-design.md). Per v3.1 §14, position this as **recovery/fallback** when a messenger channel is unavailable — not the primary login path. No new contract beyond that spec; this section exists only to fix its place in the build order relative to VK ID.

## 4. Sprint 8.4 — MAX + Telegram bot channels

```ts
interface BotConversationBinding {
  customerId: string;
  marketplaceId: string;
  provider: 'telegram' | 'max';
  chatId: string;
  state: string;              // see §5 state machine
  orderId?: string;
  lastMessageAt: string;
}
```

MAX linking flow (bot-assisted, one-time code):
```
POST /api/identity/v1/max/link-code       -> { code, expiresAt }  (TTL, single-use, bound to marketplace + browser session)
```
User opens the MAX bot, sends the code; a confirmed bot update on the backend calls:
```
POST /api/providers/v1/max/bot-webhook    -- idempotent; a repeated update must not create a duplicate binding
```
which links the pending `Customer` session to the MAX `chatId`.

All three providers' incoming bot updates (VK, MAX, Telegram) normalize into one shape:

```ts
interface MessagingEvent {
  provider: 'telegram' | 'vk' | 'max';
  chatId: string;
  orderId?: string;
  text?: string;
  receivedAt: string;
}
```

Provider bot tokens/secrets never reach the frontend, ever — only the backend calls each provider's Bot API.

## 5. Sprint 8.5 — Notification Orchestrator + Delivery Conversation State Machine

On `order.paid` (Phase 2 event bus), the orchestrator picks the customer's chosen channel (captured at checkout, see [Phase 6](PHASE-6-CART-CHECKOUT-CONTRACT.md) and `OrderContactSnapshot` in [Phase 2](PHASE-2-ORDERS-NOTIFICATIONS-CONTRACT.md)) and drives:

```
not_started -> awaiting_customer -> details_received -> manager_assigned/auto_confirmed -> shipment_planned -> completed
```

```ts
interface DeliveryDetailsSnapshot {
  orderId: string;
  city?: string;
  address?: string;
  recipientName?: string;
  phone?: string;
  timeWindow?: string;
  comment?: string;
  receivedAt: string;
}
```

Hard rules:
- **The bot never changes financial statuses.** It can only write `DeliveryDetailsSnapshot` fields via a dedicated Delivery Service — no bot code path touches `Order.paymentStatus`/`orderStatus`.
- The backoffice `Notification` (Phase 2 §6) fires unconditionally on `order.paid`, independent of whether the customer's messenger channel is reachable.
- If the chosen channel is unavailable, log a `DeliveryAttempt` error (Phase 2 §6) and fall back per tenant-configured policy (e.g. email/SMS) — never block the order itself.
- Follow-up messages are rate-limited per tenant policy; after the configured attempt limit, hand off to a human manager instead of continuing to message.

```
POST /api/providers/v1/{provider}/bot-webhook   -- generic entrypoint for all three providers
GET  /api/admin/v2/orders/{orderId}/conversation -- message history + current state, for manager handoff
POST /api/admin/v2/orders/{orderId}/conversation/handoff
```

## 6. What the frontend will start doing once this ships

- VK ID and Yandex ID login buttons on the storefront. The client half already exists and is provider-agnostic: `SocialLoginButtonComponent` behind `SOCIAL_IDENTITY_GATEWAY`, with a real HTTP gateway waiting on §2.1's endpoints. Adding Yandex once VK works is a `provider` input, not new code.
- Account linking screen (`GET /me/identities`, link/unlink), including the identity-conflict resolution path from §2.3.
- MAX/Telegram linking UI (one-time code flow).
- Checkout channel-choice step ("where should we send confirmation?") — VK / MAX / Telegram / email/SMS fallback.
- Manager-facing conversation view (message history, current delivery state, accept handoff).