// ── Team notification fan-out (TEAMS.md Part 6, phase 6) ───────────────────
//
// One event in, up to two sinks out: a content-free push tickle and — for forum
// content only — an email. The expensive part of a notification is working out
// who should get it, and that is computed once here and handed to both.
//
// **Nothing in this file ever throws.** Every entry point is called from a path
// that has already done the real work: a forum reply is written and answered
// before this runs, and the roster sync's whole job is the roster. A notification
// is a courtesy, and a courtesy that can fail the transaction behind it is a
// defect. So every export catches, logs and returns.
//
// **Push and email do not carry the same thing, on purpose.** The tickle is
// `{ stream, ref }` and goes to ntfy, an untrusted relay reached by an unguessable
// topic; the app wakes and PULLS the real content over the authenticated,
// access-checked API. The email carries a title and an excerpt, because a mailbox
// is a destination the recipient chose rather than a relay (§6.4). The asymmetry
// is the security model, not an inconsistency to tidy up.
//
// **Phase 8 added a THIRD sink, and it is a second delivery rather than a second
// pipeline.** `utils/teamBridge.js` takes the same event, already computed, and
// hands it to a Discord channel the operator configured — which is why every
// entry point below calls it beside the tickle instead of anything re-deriving
// the event. Note that the bridge does NOT take the recipient set: its audience
// is whoever can read a channel, which is why enabling it for members-only
// content needs an operator acknowledgement (§7.2, teamIntegration.model.js).
//
// **Roster events are push-only, and forum events are the only ones that email.**
// §6.4's argument for the email sink is the web-only user who never learns that
// someone replied to their own thread. "Someone joined the guild" is not that: it
// arrives from a sweep that runs every fifteen minutes, it is already on the
// activity feed, and mailing it is how a notification feature earns a spam
// complaint. The streams exist for all four events; the SINKS differ, and this is
// the file that says so.

const pushDispatch = require('./pushDispatch')
const teamBridge = require('./teamBridge')
const teamNotify = require('../model/teams/teamNotify.model')
const forumSettings = require('../model/teams/teamForumSettings.model')
const mailer = require('./mailer')
const registries = require('../modules/registries')
const unsubscribeToken = require('./unsubscribeToken')
const brand = require('../config/brand')
const log = require('./logger')('team-notify')

const STREAMS = {
  MEMBER_JOINED: 'team.member.joined',
  LEADERSHIP_CHANGED: 'team.leadership.changed',
  FORUM_POST: 'team.forum.post',
  ANNOUNCEMENT: 'team.announcement',
}

// How much of a post body an email carries. Long enough to tell whether the
// thread is worth opening, short enough that the mail is not a copy of the forum.
const EXCERPT_CHARS = 200

const baseUrl = () => (process.env.APP_BASE_URL || 'http://localhost:5173').replace(/\/+$/, '')

/**
 * Where this Team's page lives, or null.
 *
 * Core does not own a Team page — the module that owns the vocabulary owns the
 * page (Part 3) — so the only way core can write a link to one is the optional
 * `pageUrlTemplate` the provider registers. A deployment whose module omits it
 * gets email that names the Team and cannot link to it, which is a worse email
 * and not a broken one.
 */
function teamPageUrl(team) {
  const provider = registries.registeredTeamProvider()
  const template = provider && provider.pageUrlTemplate
  if (!template || !team) return null
  const path = template
    .replace('{externalId}', encodeURIComponent(team.external_id ?? team.externalId ?? ''))
    .replace('{slug}', encodeURIComponent(team.slug ?? ''))
  return `${baseUrl()}${path}`
}

const threadUrl = (team, threadId) => {
  const page = teamPageUrl(team)
  // The forum navigates by SEARCH PARAM rather than by a route, because core has
  // no route on a page it does not own (TeamForumPanel.jsx). So a deep link to a
  // thread is the module's page plus `?thread=`, and it works under whatever path
  // the module chose.
  return page ? `${page}?thread=${Number(threadId)}` : null
}

// TWO urls from one token, and they are not interchangeable.
//
// `unsubscribeUrl` is the human one that goes in the mail body: the site's own
// page, which explains what is about to happen and POSTs once a person has read
// it. `unsubscribeApiUrl` is the machine one that goes in the `List-Unsubscribe`
// header, where RFC 8058 says a client may POST without showing anybody anything —
// so it has to be an endpoint, not a page. The API route answers GET on the same
// path with a redirect to the page, which covers the clients that render the
// header as an ordinary link.
const unsubscribeUrl = (userId, teamId) =>
  `${baseUrl()}/unsubscribe/${unsubscribeToken.sign(userId, teamId)}`

const unsubscribeApiUrl = (userId, teamId) =>
  `${baseUrl()}/api/v1/public/teams/unsubscribe/${unsubscribeToken.sign(userId, teamId)}`

const teamLabel = (team) => (team && (team.display_name_override || team.name)) || 'your team'

/** Markup out, whitespace collapsed, truncated. The email is plain text. */
function excerpt(html) {
  const text = String(html || '')
    .replace(/<[^>]*>/g, ' ')
    .replace(/&nbsp;/g, ' ')
    .replace(/&amp;/g, '&')
    .replace(/&lt;/g, '<')
    .replace(/&gt;/g, '>')
    .replace(/&quot;/g, '"')
    .replace(/\s+/g, ' ')
    .trim()
  return text.length > EXCERPT_CHARS ? `${text.slice(0, EXCERPT_CHARS - 1)}…` : text
}

/** The push half. Resolves recipients, honours mutes and subscriptions, never throws. */
async function tickle(streamId, team, { ref, exclude = [] } = {}) {
  const userIds = await teamNotify.recipientIds(team.id, { exclude })
  if (userIds.length === 0) return 0
  await pushDispatch.publishToUsers(streamId, { ref, userIds })
  return userIds.length
}

// ── Roster events (push only, see the header) ──────────────────────────────

// No `memberName` argument, and that is the point: a tickle is content-free, so
// there is nothing about WHO joined for this function to carry. The name is on
// the activity feed the app pulls after waking.
//
// `count` is phase 8's one addition and it is for the BRIDGE, not the tickle: a
// Discord channel has no app on the other end to pull anything, so the message
// has to say something, and "3 new members joined" is the most a caller that
// notifies once per sweep can honestly say. Optional, so the sync is the only
// caller that has to know it exists.
async function memberJoined(team, { count } = {}) {
  try {
    const sent = await tickle(STREAMS.MEMBER_JOINED, team, { ref: `team:${team.id}` })
    await teamBridge.deliver(STREAMS.MEMBER_JOINED, team, {
      body: teamBridge.memberJoinedBody(count),
      teamUrl: teamPageUrl(team),
      url: teamPageUrl(team),
    })
    return sent
  } catch (err) {
    log.warn('member-joined notification failed', { teamId: team && team.id, message: err.message })
    return 0
  }
}

async function leadershipChanged(team) {
  try {
    const sent = await tickle(STREAMS.LEADERSHIP_CHANGED, team, { ref: `team:${team.id}` })
    await teamBridge.deliver(STREAMS.LEADERSHIP_CHANGED, team, {
      body: 'Leadership has changed.',
      teamUrl: teamPageUrl(team),
      url: teamPageUrl(team),
    })
    return sent
  } catch (err) {
    log.warn('leadership notification failed', { teamId: team && team.id, message: err.message })
    return 0
  }
}

// ── Forum events (push + immediate email) ──────────────────────────────────

/**
 * A new thread or reply.
 *
 * `type` picks the stream: an announcement is its own stream so a user can take
 * the thing a leader wants everyone to read and mute the day-to-day chatter,
 * which is the split §6.2 drew and the reason there are four streams and not two.
 *
 * The author is excluded from both sinks. Not as a nicety — a forum that emails
 * you your own post is the first thing anyone turns off, and turning it off costs
 * the deployment every other notification too.
 */
async function forumPost({ team, threadId, threadTitle, type, authorUserId, authorName, bodyHtml }) {
  try {
    // Belt and braces with the routes, which already 404 when forums are off. The
    // digest worker has no route in front of it, so the check has to live here as
    // well as there — and a switch flipped between a write and its notification
    // must silence the notification.
    if (!(await forumSettings.forumsEnabled())) return { push: 0, emails: 0, bridged: false }

    const stream = type === 'announcement' ? STREAMS.ANNOUNCEMENT : STREAMS.FORUM_POST
    const exclude = authorUserId ? [authorUserId] : []
    const push = await tickle(stream, team, { ref: `team:${team.id}:thread:${threadId}`, exclude })
    const emails = await emailImmediate({ team, threadId, threadTitle, type, exclude, authorName, bodyHtml })
    // The bridge is NOT given `exclude`. Excluding the author is a property of a
    // per-recipient sink — nobody wants their own post mailed back to them — and a
    // channel has no per-recipient anything. Suppressing the message because the
    // author happens to be in the channel would deprive everyone else in it.
    const bridged = await teamBridge.deliver(stream, team, {
      title: threadTitle,
      body: teamBridge.excerpt(bodyHtml),
      url: threadUrl(team, threadId),
      teamUrl: teamPageUrl(team),
    })
    return { push, emails, bridged }
  } catch (err) {
    log.warn('forum notification failed', { teamId: team && team.id, message: err.message })
    return { push: 0, emails: 0, bridged: false }
  }
}

/**
 * The `immediate` email mode: one mail per event, to the people who asked for
 * exactly that.
 *
 * Skipped entirely when no email is configured — §6.4's "off unless configured"
 * — and checked BEFORE the recipient query so a deployment with no mail
 * transport configured pays nothing for the sink it does not have.
 */
async function emailImmediate({ team, threadId, threadTitle, type, exclude, authorName, bodyHtml }) {
  if (!(await mailer.isConfigured())) return 0
  const rows = await teamNotify.emailRecipients(team.id, { exclude })
  const recipients = rows.filter((r) => r.email_mode === 'immediate')
  if (recipients.length === 0) return 0

  const label = teamLabel(team)
  const kind = type === 'announcement' ? 'announcement' : 'post'
  const url = threadUrl(team, threadId)
  let sent = 0

  for (const r of recipients) {
    // Serial rather than Promise.all: this is an SMTP conversation per recipient
    // against a relay with its own rate limits, and a burst of them from a
    // busy thread is how a sending account gets throttled. The loop is also why the
    // send below is fire-and-report rather than fire-and-throw.
    // eslint-disable-next-line no-await-in-loop
    const res = await mailer.sendTeamNotification({
      to: r.email,
      subject: `[${brand.name}] ${label}: ${threadTitle}`,
      intro: `${authorName || 'Someone'} posted a new ${kind} in ${label}.`,
      items: [{ heading: threadTitle, excerpt: excerpt(bodyHtml), url }],
      teamUrl: teamPageUrl(team),
      unsubscribeUrl: unsubscribeUrl(r.user_id, team.id),
      unsubscribeApiUrl: unsubscribeApiUrl(r.user_id, team.id),
    })
    if (res && res.sent) sent += 1
  }
  return sent
}

module.exports = {
  STREAMS,
  memberJoined,
  leadershipChanged,
  forumPost,
  // Exported for the digest worker and for the tests, which is the whole reason
  // they are not inlined: a URL that only ever appears inside a mail body is a
  // URL nothing can assert on.
  teamPageUrl,
  threadUrl,
  unsubscribeUrl,
  unsubscribeApiUrl,
  excerpt,
  teamLabel,
}