Make subscription upsert idempotent via PUT

Switch the subscribe endpoint from POST to an idempotent PUT so clients can
always upsert without a stateful lookup first.

- Add GET /subscription/email?pubkey= lookup so clients can avoid re-POSTing.
- insertSubscription no longer clears confirmed_at unless the email address
  changes; a frequency change keeps the existing confirmation.
- registerSubscription only sends a confirmation email when the subscription
  is new, unconfirmed, or the email address changed.
- Update integration test and README for the PUT endpoint.

README.md

@@ -5,7 +5,7 @@ A Nostr email notification server. Receives events pushed from relays via NIP-9a
 ## Architecture
 
 ```
-Flotilla ──HTTP──▶ Mailship (POST /subscription/email)
+Flotilla ──HTTP──▶ Mailship (PUT /subscription/email)
   │                   NIP-98 auth
   │                   returns {key, callback}
   │
@@ -43,8 +43,10 @@ Flotilla ──HTTP──▶ Mailship (POST /subscription/email)
 
 ## API
 
-### POST /subscription/email
+### PUT /subscription/email
-Register for email digests.
+Idempotently register or update an email subscription. Re-sends the confirmation
+email only when the subscription is new or the email address changed; a frequency
+change keeps the existing confirmation.
 
 ```
 Body: { email, frequency, pubkey }
@@ -52,6 +54,14 @@ Auth: NIP-98 (planned)
 Response: { key, callback }
 ```
 
+### GET /subscription/email?pubkey=...
+Look up an existing subscription, so clients can avoid re-registering (and
+re-confirming) when settings haven't changed. Returns 404 if none exists.
+
+```
+Response: { key, callback, email, frequency, confirmed }
+```
+
 ### DELETE /subscription/:key
 Unsubscribe.
 

src/actions.ts

@@ -23,8 +23,12 @@ export const registerSubscription = instrument(
     const sub = await db.insertSubscription(pubkey, email, frequency)
     const callback = `${process.env.BASE_URL}/notify/${sub.id}`
 
-    // Send confirmation email
+    // Only send a confirmation when the subscription is new, unconfirmed, or
-    await mailer.sendConfirm(sub)
+    // its email address changed. An already-confirmed, unchanged subscription
+    // (or one where only the frequency changed) skips it.
+    if (!sub.confirmed_at) {
+      await mailer.sendConfirm(sub)
+    }
 
     return { key: sub.key, callback }
   },

src/database.ts

@@ -101,7 +101,26 @@ export const insertSubscription = instrument(
     const existing = await getSubscriptionByPubkey(pubkey)
 
     if (existing) {
-      // Update existing
+      // If nothing changed, keep confirmation and don't re-validate
+      if (existing.email === email && existing.frequency === frequency) {
+        return assertResult(parseSubscription(existing))
+      }
+
+      // Update existing. Only a change of email address invalidates the
+      // existing confirmation (the new address must be verified); changing
+      // the frequency keeps it confirmed.
+      if (existing.email === email) {
+        return assertResult(
+          parseSubscription(
+            await get(
+              `UPDATE subscriptions SET frequency = ?, unsubscribed_at = NULL
+               WHERE pubkey = ? RETURNING *`,
+              [frequency, pubkey],
+            ),
+          ),
+        )
+      }
+
       return assertResult(
         parseSubscription(
           await get(
@@ -113,7 +132,6 @@ export const insertSubscription = instrument(
       )
     }
 
-    // Create new
     return assertResult(
       parseSubscription(
         await get(

src/server.ts

@@ -20,7 +20,7 @@ const corsOrigin = process.env.CORS_ORIGIN ?? '*'
 
 server.use((req: Request, res: Response, next: NextFunction) => {
   res.setHeader('Access-Control-Allow-Origin', corsOrigin)
-  res.setHeader('Access-Control-Allow-Methods', 'GET,POST,DELETE,OPTIONS')
+  res.setHeader('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,OPTIONS')
   res.setHeader('Access-Control-Allow-Headers', 'Content-Type,Authorization')
   res.setHeader('Access-Control-Max-Age', '86400')
 
@@ -57,7 +57,7 @@ server.use(
 
 type Handler = (req: Request, res: Response) => Promise<any>
 
-const addRoute = (method: 'get' | 'post' | 'delete', path: string, handler: Handler) => {
+const addRoute = (method: 'get' | 'post' | 'put' | 'delete', path: string, handler: Handler) => {
   server[method](
     path,
     instrument(path, async (req: Request, res: Response, next: NextFunction) => {
@@ -89,8 +89,34 @@ addRoute('get', '/', async (req: Request, res: Response) => {
   })
 })
 
-// Subscribe to email digests
+// Look up an existing email subscription for a pubkey, so clients can avoid
-addRoute('post', '/subscription/email', async (req: Request, res: Response) => {
+// re-registering (and re-confirming) when settings haven't changed.
+addRoute('get', '/subscription/email', async (req: Request, res: Response) => {
+  const { pubkey } = req.query
+
+  if (!pubkey || typeof pubkey !== 'string') {
+    return res.status(400).json({ error: 'pubkey is required' })
+  }
+
+  const sub = await getSubscriptionByPubkey(pubkey)
+
+  if (!sub) {
+    return res.status(404).json({ error: 'Subscription not found' })
+  }
+
+  const callback = `${process.env.BASE_URL}/notify/${sub.id}`
+
+  res.json({
+    key: sub.key,
+    callback,
+    email: sub.email,
+    frequency: sub.frequency,
+    confirmed: Boolean(sub.confirmed_at),
+  })
+})
+
+// Subscribe to email digests (idempotent PUT upsert)
+addRoute('put', '/subscription/email', async (req: Request, res: Response) => {
   const { email, frequency, pubkey } = req.body
 
   if (!email || !email.includes('@')) {
@@ -202,7 +228,11 @@ addRoute('get', '/confirm', async (req: Request, res: Response) => {
   if (typeof req.query.token !== 'string') {
     return res.send(
       await render('pages/confirm-error.html', {
-        message: 'No confirmation token was provided.',
+        message: 'No confirmation token was provided. Please check the link in your email and try again.',
+        brandName: BRAND_NAME,
+        brandAccent: BRAND_ACCENT,
+        brandLogo: BRAND_LOGO,
+        settingsUrl: `${EVENT_VIEWER_URL.replace(/\/$/, '')}/settings/alerts`,
       })
     )
   }
@@ -220,7 +250,13 @@ addRoute('get', '/confirm', async (req: Request, res: Response) => {
     const isActionError = error instanceof ActionError
     const message = isActionError ? String(error) : 'Oops, something went wrong on our end!'
 
-    res.send(await render('pages/confirm-error.html', { message }))
+    res.send(await render('pages/confirm-error.html', {
+      message,
+      brandName: BRAND_NAME,
+      brandAccent: BRAND_ACCENT,
+      brandLogo: BRAND_LOGO,
+      settingsUrl: `${EVENT_VIEWER_URL.replace(/\/$/, '')}/settings/alerts`,
+    }))
 
     if (!isActionError) {
       throw error

test/integration.sh

@@ -117,7 +117,7 @@ check_field "Root endpoint returns Mailship" "$HEALTH" "name" "Mailship"
 # Test 2: Register subscription
 echo ""
 echo "2. Register subscription"
-REG=$(curl -s "$BASE_URL/subscription/email" -X POST -H "Content-Type: application/json" \
+REG=$(curl -s "$BASE_URL/subscription/email" -X PUT -H "Content-Type: application/json" \
   -d '{"email":"test@example.com","frequency":"daily","pubkey":"abc123"}')
 
 KEY=$(echo "$REG" | python3 -c "import sys,json; print(json.load(sys.stdin).get('key',''))" 2>/dev/null)