flotilla/src/app/mail/index.ts

import {hash, maybe, throttle} from "@welshman/lib"
import type {Filter} from "@welshman/util"
import {Address, DELETE, makeEvent, makeHttpAuth, makeHttpAuthHeader} from "@welshman/util"
import {Relays, User} from "@welshman/app"
import {buildUrl} from "@lib/util"
import {app, thunks} from "@app/core"
import {EMAIL_NOTIFICATION_SERVER, PUSH_BRIDGE} from "@app/env"
import {ensureEmailSalt, userSettingsValues} from "@app/settings"
import {emailNotificationState, syncRelaySubscriptions} from "@app/push/adapters/common"

export class MailNotifications {
  _controller = maybe<AbortController>()

  async register(email: string, frequency: string) {
    const $user = User.require(app.get())
    const $signer = $user.signer

    if (!$signer) {
      emailNotificationState.set({error: "No signer available. Check your browser extension."})
      throw new Error("No signer available")
    }

    if (!EMAIL_NOTIFICATION_SERVER) {
      emailNotificationState.set({error: "Email notification server is not configured."})
      throw new Error("Email notification server not configured")
    }

    let authEvent
    try {
      authEvent = await $signer.sign(await makeHttpAuth(EMAIL_NOTIFICATION_SERVER, "PUT"))
    } catch (e) {
      emailNotificationState.set({error: "Failed to create authentication. Check your signer."})
      throw new Error("Failed to sign NIP-98 auth", {cause: e})
    }

    const authHeader = makeHttpAuthHeader(authEvent)

    let res
    try {
      res = await fetch(buildUrl(EMAIL_NOTIFICATION_SERVER, "subscription", "email"), {
        method: "PUT",
        body: JSON.stringify({email, frequency, pubkey: $user.pubkey}),
        headers: {Authorization: authHeader, "Content-Type": "application/json"},
      })
    } catch (e) {
      emailNotificationState.set({error: `Could not reach email server. Check your connection.`})
      throw new Error("Network error", {cause: e})
    }

    if (!res.ok) {
      const text = await res.text().catch(() => "unknown error")
      emailNotificationState.set({error: `Registration failed: ${text}`})
      throw new Error(`Registration failed: ${text}`)
    }

    const {key, callback} = await res.json()
    emailNotificationState.set({key, callback, email, frequency, error: undefined})
  }

  async unregister() {
    const {key} = emailNotificationState.get()
    if (!key) return

    const $signer = app.get().user?.signer
    if (!$signer) return

    try {
      const authEvent = await $signer.sign(await makeHttpAuth(EMAIL_NOTIFICATION_SERVER, "DELETE"))
      const authHeader = makeHttpAuthHeader(authEvent)

      await fetch(buildUrl(EMAIL_NOTIFICATION_SERVER, "subscription", key), {
        method: "DELETE",
        headers: {Authorization: authHeader},
      })
    } catch {
      // Best effort
    }

    emailNotificationState.set({})
  }

  async enable() {
    if (this._controller) return

    const {email, frequency} = emailNotificationState.get()

    if (!EMAIL_NOTIFICATION_SERVER) {
      console.warn("Email notification server not configured")
      return
    }

    this._controller = new AbortController()

    // Register if we don't have a subscription yet
    if (!emailNotificationState.get().callback && email && frequency) {
      await this.register(email, frequency)
    }

    // Sync kind 30390 subscriptions using the same filters as push
    syncRelaySubscriptions(
      this._controller.signal,
      async (url: string, key: string, filters: Filter[], ignore: Filter[]) => {
        const {callback} = emailNotificationState.get()
        if (!callback) return

        if (filters.length > 0) {
          await this._syncRelay(url, key, filters, ignore)
        } else {
          await this._unsyncRelay(url, key)
        }
      },
    )
  }

  async disable() {
    this._controller?.abort()
    this._controller = undefined

    await this.unregister()
  }

  sync() {
    return userSettingsValues.subscribe(
      throttle(500, async ({email, emailAddress, emailFrequency}) => {
        if (email && emailAddress) {
          try {
            await this.register(emailAddress, emailFrequency)
          } catch {
            return
          }

          await this.enable()
        } else {
          await this.disable()
        }
      }),
    )
  }

  _getSubscriptionIdentifier = async (relay: string, key: string) => {
    const salt = await ensureEmailSalt()

    return String(hash(relay + key + salt + "email"))
  }

  _getPushUrl = async (url: string) => {
    for (const candidate of [url, PUSH_BRIDGE]) {
      const relay = await app.get().use(Relays).load(candidate)

      if (relay?.hasNip("9a")) {
        return candidate
      }
    }
  }

  _syncRelay = async (relay: string, key: string, filters: Filter[], ignore: Filter[] = []) => {
    const {callback} = emailNotificationState.get()
    if (!callback) return

    const url = await this._getPushUrl(relay)
    if (!url) {
      console.warn(`Failed to subscribe ${relay} to email notifications: unsupported`)
      return
    }

    const identifier = await this._getSubscriptionIdentifier(relay, key)

    const thunk = thunks.get().publish({
      relays: [url],
      event: makeEvent(30390, {
        tags: [
          ["d", identifier],
          ["relay", relay],
          ["callback", callback],
          ["include_event", "true"],
          ...ignore.map(f => ["ignore", JSON.stringify(f)]),
          ...filters.map(f => ["filter", JSON.stringify(f)]),
        ],
      }),
    })

    const error = await thunk.waitForError()
    if (error) {
      console.warn(`Failed to subscribe ${relay} to email notifications:`, error)
    }
  }

  _unsyncRelay = async (relay: string, key: string) => {
    const url = await this._getPushUrl(relay)
    if (!url) return

    const $pubkey = User.require(app.get()).pubkey
    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
      .get()
      .publish({relays: [url], event})
      .waitForError()

    if (error) {
      console.warn(`Failed to unsubscribe ${relay} from email notifications:`, error)
    }
  }
}

export const Mail = new MailNotifications()