Allow CoinPay identity links across SMSHub accounts

package.json

@@ -25,7 +25,7 @@
   },
   "dependencies": {
     "@profullstack/affiliates": "^0.3.0",
-    "@profullstack/coinpay-onboard": "0.3.1",
+    "@profullstack/coinpay-onboard": "0.4.0",
     "@profullstack/footer": "latest",
     "@profullstack/profile": "0.1.6",
     "@profullstack/redeem-credits": "^0.2.0",

src/lib/coinpay/__tests__/signin.test.ts

@@ -39,7 +39,7 @@ function memoryStore(users: Record<string, string> = {}) {
       return identities.find((i) => i.user_id === userId) ?? null;
     },
     async link(row) {
-      if (identities.some((i) => i.coinpay_sub === row.coinpay_sub || i.user_id === row.user_id)) return 'conflict';
+      if (identities.some((i) => i.user_id === row.user_id)) return 'conflict';
       identities.push(row);
       return 'ok';
     },
@@ -87,7 +87,7 @@ describe('resolveCoinpayUser', () => {
     expect(first.ok && again.ok && again.userId === first.userId && again.action).toBe('login');
   });
 
-  it('connects only for a signed-in user, and a sub belongs to one account', async () => {
+  it('connects only for a signed-in user, and links one CoinPay identity to several accounts', async () => {
     const m = memoryStore({ alice: 'alice@example.com', bob: 'bob@example.com' });
     expect(await resolveCoinpayUser({ mode: 'connect', currentUserId: null, claims: claims('s1') }, m.store)).toMatchObject({
       ok: false,
@@ -99,9 +99,11 @@ describe('resolveCoinpayUser', () => {
       action: 'linked',
     });
     expect(await resolveCoinpayUser({ mode: 'connect', currentUserId: 'bob', claims: claims('s1') }, m.store)).toMatchObject({
-      ok: false,
-      code: 'linked_elsewhere',
+      ok: true,
+      userId: 'bob',
+      action: 'linked',
     });
+    expect(m.identities.filter((identity) => identity.coinpay_sub === 's1')).toHaveLength(2);
     expect(await resolveCoinpayUser({ mode: 'connect', currentUserId: 'alice', claims: claims('s2') }, m.store)).toMatchObject({
       ok: false,
       code: 'already_connected',

src/lib/coinpay/signin.ts

@@ -20,6 +20,7 @@
 // memory; supabaseCoinpayStore() is the real one (service role).
 import { createHash, randomBytes, timingSafeEqual } from 'node:crypto';
 import type { SupabaseClient } from '@supabase/supabase-js';
+import { resolveCoinPayAccountLink } from '@profullstack/coinpay-onboard/identity';
 
 export const CALLBACK_PATH = '/api/coinpay/callback';
 export const STATE_COOKIE = 'smshub_cp_state';
@@ -121,7 +122,7 @@ export async function takeCallback(
 
 export type Resolution =
   | { ok: true; userId: string; action: 'login' | 'created' | 'linked' }
-  | { ok: false; code: 'not_signed_in' | 'linked_elsewhere' | 'already_connected'; error: string };
+  | { ok: false; code: 'not_signed_in' | 'already_connected'; error: string };
 
 /**
  * Decide which smshub user a verified CoinPay sub belongs to. Never looks at the
@@ -139,11 +140,14 @@ export async function resolveCoinpayUser(
     if (!input.currentUserId) {
       return { ok: false, code: 'not_signed_in', error: 'Sign in to smshub first, then connect CoinPay from Settings.' };
     }
-    if (bound) {
-      if (bound.user_id === input.currentUserId) return { ok: true, userId: bound.user_id, action: 'linked' };
-      return { ok: false, code: 'linked_elsewhere', error: 'That CoinPay account is already connected to another smshub account.' };
-    }
-    if (await store.identityByUser(input.currentUserId)) {
+    const mine = await store.identityByUser(input.currentUserId);
+    const decision = resolveCoinPayAccountLink({
+      bindings: [bound, mine].filter((row): row is IdentityRow => row !== null).map((row) => ({ sub: row.coinpay_sub, userId: row.user_id })),
+      sub: claims.sub,
+      userId: input.currentUserId,
+    });
+    if (decision.kind === 'already_linked') return { ok: true, userId: input.currentUserId, action: 'linked' };
+    if (decision.kind === 'account_has_other_identity') {
       return {
         ok: false,
         code: 'already_connected',
@@ -157,9 +161,7 @@ export async function resolveCoinpayUser(
       coinpay_name: claims.name,
       created_via: 'connect',
     });
-    if (r === 'conflict') {
-      return { ok: false, code: 'linked_elsewhere', error: 'That CoinPay account was just connected elsewhere.' };
-    }
+    if (r === 'conflict') return { ok: false, code: 'already_connected', error: 'This smshub account already has a CoinPay identity connected.' };
     return { ok: true, userId: input.currentUserId, action: 'linked' };
   }
 
@@ -234,7 +236,7 @@ export function supabaseCoinpayStore(sb: SupabaseClient): CoinpayStore {
       return { verifier: row.verifier, nonce: row.nonce, mode: row.mode, next: row.next_path, linkUserId: row.link_user_id };
     },
     async identityBySub(sub) {
-      const r = await sb.from('coinpay_connections').select(cols).eq('coinpay_user_id', sub).maybeSingle();
+      const r = await sb.from('coinpay_connections').select(cols).eq('coinpay_user_id', sub).order('created_at', { ascending: true }).limit(1).maybeSingle();
       if (r.error) throw new Error(r.error.message);
       return toIdentity(r.data as Row | null);
     },

supabase/migrations/027_coinpay_multi_account.sql

@@ -0,0 +1,5 @@
+-- One CoinPay identity may connect to multiple smshub accounts. Each local
+-- user remains limited to one connection by coinpay_connections.user_id UNIQUE.
+drop index if exists public.coinpay_connections_coinpay_user_id_key;
+create index if not exists coinpay_connections_coinpay_user_id_idx
+  on public.coinpay_connections (coinpay_user_id);