Use salt instead of device id for email settings

src/app/mail/index.ts

@@ -4,9 +4,8 @@ import {Address, DELETE, makeEvent, makeHttpAuth, makeHttpAuthHeader} from "@wel
 import {Relays, User} from "@welshman/app"
 import {buildUrl} from "@lib/util"
 import {app, thunks} from "@app/core"
-import {device} from "@app/device"
 import {EMAIL_NOTIFICATION_SERVER, PUSH_BRIDGE} from "@app/env"
-import {userSettingsValues} from "@app/settings"
+import {ensureEmailSalt, userSettingsValues} from "@app/settings"
 import {emailNotificationState, syncRelaySubscriptions} from "@app/push/adapters/common"
 
 export class MailNotifications {
@@ -138,8 +137,11 @@ export class MailNotifications {
     )
   }
 
-  _getSubscriptionIdentifier = (relay: string, key: string) =>
+  _getSubscriptionIdentifier = async (relay: string, key: string) => {
-    String(hash(relay + key + device.get() + "email"))
+    const salt = await ensureEmailSalt()
+
+    return String(hash(relay + key + salt + "email"))
+  }
 
   _getPushUrl = async (url: string) => {
     for (const candidate of [url, PUSH_BRIDGE]) {
@@ -161,7 +163,7 @@ export class MailNotifications {
       return
     }
 
-    const identifier = this._getSubscriptionIdentifier(relay, key)
+    const identifier = await this._getSubscriptionIdentifier(relay, key)
 
     const thunk = thunks.get().publish({
       relays: [url],
@@ -188,7 +190,7 @@ export class MailNotifications {
     if (!url) return
 
     const $pubkey = User.require(app.get()).pubkey
-    const identifier = this._getSubscriptionIdentifier(relay, key)
+    const identifier = await this._getSubscriptionIdentifier(relay, key)
     const address = new Address(30390, $pubkey, identifier).toString()
     const event = makeEvent(DELETE, {tags: [["a", address]]})
     const error = await thunks

src/app/settings.ts

@@ -1,5 +1,5 @@
 import {derived, writable} from "svelte/store"
-import {append, remove, spec} from "@welshman/lib"
+import {append, call, randomId, remove, spec} from "@welshman/lib"
 import {APP_DATA} from "@welshman/util"
 import {withGetter} from "@welshman/store"
 import {AppData} from "@welshman/domain"
@@ -10,6 +10,8 @@ import {app, fromApp, usePlugin} from "@app/core"
 
 export const SETTINGS = "flotilla/settings"
 
+const emailSaltsByPubkey = new Map<string, Promise<string>>()
+
 export enum RelayAuthMode {
   Aggressive = "aggressive",
   Conservative = "conservative",
@@ -34,6 +36,7 @@ export type SettingsValues = {
   email: boolean
   emailAddress: string
   emailFrequency: string
+  emailSalt: string
 }
 
 export const defaultSettings: SettingsValues = {
@@ -49,6 +52,7 @@ export const defaultSettings: SettingsValues = {
   email: false,
   emailAddress: "",
   emailFrequency: "daily",
+  emailSalt: "",
 }
 
 export class Settings extends DerivedPlugin<AppDataReader> {
@@ -121,6 +125,31 @@ export const publishSettings = async (params: Partial<SettingsValues>) => {
   return command.publish()
 }
 
+// A per-account salt for building deterministic identifiers (e.g. kind 30390 email
+// subscription ids) that reproduce on any device of the user, stored with the settings.
+export const ensureEmailSalt = () => {
+  const $pubkey = User.require(app.get()).pubkey
+  const existing = emailSaltsByPubkey.get($pubkey)
+  if (existing) return existing
+
+  // Force-load from the network so a salt synced by another device wins over a fresh one,
+  // and memoize the in-flight promise so parallel syncs (one per space relay) share a salt.
+  const promise = call(async () => {
+    await settings.get().forceLoad($pubkey)
+    const salt = userSettingsValues.get().emailSalt
+    if (salt) return salt
+
+    const emailSalt = randomId()
+    await publishSettings({emailSalt})
+
+    return emailSalt
+  })
+
+  emailSaltsByPubkey.set($pubkey, promise)
+
+  return promise
+}
+
 export const addTrustedRelay = (url: string) =>
   publishSettings({trusted_relays: append(url, getSetting("trusted_relays"))})