# 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' | 'telegram' | 'max';
  providerUserId: 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 — VK ID (build first)

```
GET  /api/identity/v1/vk/authorize     -> redirects into VK's OAuth 2.1/PKCE flow
POST /api/identity/v1/vk/callback      { code, codeVerifier } -> completes OAuth **backend-side**,
                                          links ExternalIdentity, returns session
```

Invariants:
- OAuth completion happens entirely backend-side; the VK client secret never reaches the frontend.
- A repeat login for the same `providerUserId` must resolve to the same `Customer`, never create a duplicate.
- If `providerUserId` is already linked to a *different* `Customer` than the one currently authenticated (or none), this is an identity conflict — route to controlled resolution, never silently overwrite the existing binding (plan §14.3).

## 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 login button + OAuth redirect flow on storefront (primary social login).
- 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).
