// ── The forum: access + announcements (5a), discussion + moderation (5b) ───
//
// TEAMS.md §5.1's split is BY LAYER, not by feature: 5a shipped the whole access
// model and a single announcements stream per Team; 5b (phase 5) opens discussion
// threads, replies, editing and post-level moderation. The schema for all of it
// landed together, so this phase added no ALTER — every column it needed
// (`type`, `locked`, `edited_at`, `edited_by`, the post table's `status`, the
// ledger's `target_type='post'`) was already there waiting.
//
// **Every function here takes an already-resolved access decision.** Nothing in
// this file reads `team_members` or `team_forum_grants`; the caller asks
// teamAccess.forumAccess() once and hands the answer down. That is §5.4's "never
// by checking membership directly, which is how paths 1 and 3 would drift back
// together", made structural.
//
// **The read path is where the image policy is applied**, once, in `renderPost`.
// Not in the controller and never in the client: the client is TOLD the mode so it
// can draw the right composer, and is never the thing that decides whether an
// image appears (§5.5.6).

const forumDb = require('./teamForum.db')
const forumSettings = require('./teamForumSettings.model')
const { cleanForumBody, renderForumBody } = require('../../utils/forumHtml')

// Announcements are leader-authored and take no replies; discussion threads are
// member-authored and do. Both have been in the enum since 5a — what phase 5
// changed is that both are now CREATABLE, and by different people.
//
// **The authority split lives in the controller, not here.** This list says what
// kinds of thread exist; who may make one is a question about the caller, which
// this file deliberately never asks (see the header on access decisions).
const CREATABLE_TYPES = ['announcement', 'discussion']

// Kept as an export because it names a real fact — the one type 5a could create —
// and because removing a name from a module's surface to save a line is how a
// consumer outside this repo breaks. It is not used to decide anything.
const CREATABLE_TYPES_5A = ['announcement']

// Which thread types accept replies. An announcement's `locked` stays false even
// though nothing may reply to it: replies are refused because the TYPE takes none,
// not because the thread was closed, and conflating the two would make "unlock"
// look like it would open replies on an announcement.
const REPLYABLE_TYPES = ['discussion']

const DELETED_AUTHOR = '[deleted account]'

/**
 * Moderation actions, and what each one does to the row.
 *
 * A table rather than a switch because the ledger and the effect have to stay in
 * step: every entry here writes one row of `team_forum_moderation` naming the
 * authority that was exercised, and an action with an effect but no ledger entry
 * would be a moderation nobody can audit.
 */
const THREAD_ACTIONS = {
  pin: { pinned: true },
  unpin: { pinned: false },
  lock: { locked: true },
  unlock: { locked: false },
  hide: { status: 'hidden' },
  unhide: { status: 'visible' },
  delete: { status: 'deleted' },
  restore: { status: 'visible' },
}

// Post-level moderation. A strict subset of THREAD_ACTIONS: `pin` and `lock`
// describe a thread's place in a list and its openness to replies, neither of
// which a post has. Naming them here as "not applicable" rather than as "unknown"
// is what lets `moderatePost` tell a caller which mistake they made.
const POST_ACTIONS = {
  hide: { status: 'hidden' },
  unhide: { status: 'visible' },
  delete: { status: 'deleted' },
  restore: { status: 'visible' },
}

function publicThread(row) {
  return {
    id: row.id,
    type: row.type,
    title: row.title,
    author: row.created_username || DELETED_AUTHOR,
    authorDeleted: row.created_by == null,
    createdAt: row.created_at,
    lastPostAt: row.last_post_at,
    postCount: row.post_count,
    pinned: Boolean(row.pinned),
    locked: Boolean(row.locked),
    status: row.status,
  }
}

/**
 * May this viewer edit this post, and until when?
 *
 * **Computed on the server and handed to the client, never the other way round** —
 * the same rule §5.5.3 applies to the image policy, for the same reason. A client
 * that decided this would be deciding it against its own clock, and a clock is the
 * one input a time-bounded permission must not take from the party it bounds.
 *
 * Staff get `editableUntil: null`, which reads as "no deadline" rather than as "no
 * permission" — `canEdit` is the permission and this is only its expiry. An author
 * past their window keeps a past `editableUntil`, so the UI can say *why* the
 * control is gone instead of silently dropping it.
 */
function editability(row, { userId = null, isStaff = false, windowMinutes = 0, now = Date.now() } = {}) {
  // A hidden or deleted post is not editable by anybody, staff included. Restoring
  // it is a moderation action with a ledger row; quietly rewriting it while it is
  // out of sight is the same act with no record.
  if (row.status !== 'visible') return { canEdit: false, editableUntil: null }
  if (isStaff) return { canEdit: true, editableUntil: null }
  if (!userId || row.author_user_id == null || row.author_user_id !== userId) {
    return { canEdit: false, editableUntil: null }
  }
  const until = new Date(row.created_at).getTime() + windowMinutes * 60_000
  return { canEdit: until > now, editableUntil: new Date(until).toISOString() }
}

/**
 * One post, rendered for one image policy and one viewer.
 *
 * `body` is what the reader gets and `mode` decides whether it carries images.
 * The STORED html is never modified — flipping the policy changes this function's
 * output and nothing on disk, which is the property §5.5.3 exists to give and the
 * one acceptance criterion 3 measures.
 *
 * `viewer` is optional so that every 5a caller keeps working unchanged; omitting
 * it yields `canEdit: false`, which is the right answer for a caller that has not
 * said who is reading.
 */
function renderPost(row, mode, viewer) {
  return {
    id: row.id,
    author: row.author_username || DELETED_AUTHOR,
    authorDeleted: row.author_user_id == null,
    body: renderForumBody(row.body_html, mode),
    createdAt: row.created_at,
    editedAt: row.edited_at,
    status: row.status,
    mine: Boolean(viewer?.userId) && row.author_user_id === viewer.userId,
    ...editability(row, viewer),
  }
}

/**
 * The thread list for one viewer.
 *
 * `canModerate` widens what is returned, not just what is offered: a hidden
 * thread is visible to the people who can unhide it and to nobody else, so the
 * same call answers both audiences without a second endpoint that could disagree
 * with this one.
 */
async function listThreads(teamId, { canModerate = false, limit = 50, offset = 0 } = {}) {
  const rows = await forumDb.threadsByTeam(teamId, { includeHidden: canModerate, limit, offset })
  return rows.map(publicThread)
}

/**
 * One thread with its posts, rendered under the current image policy and for one
 * viewer.
 *
 * `viewer` carries who is reading and what the edit window is, so every post comes
 * back already knowing whether this caller may edit it. The alternative — shipping
 * the window to the client and letting it compare timestamps — is the thing
 * `editability` exists not to do.
 */
async function getThread(teamId, threadId, { canModerate = false, viewer } = {}) {
  const thread = await forumDb.threadById(threadId)
  // The team check is here rather than in the SQL so a thread id from another
  // Team reads as "not found" and not as "found, but not yours" — a forum is a
  // private room and the existence of a thread in it is itself private.
  if (!thread || thread.team_id !== teamId) return null
  if (thread.status === 'deleted' && !canModerate) return null
  if (thread.status === 'hidden' && !canModerate) return null

  const mode = await forumSettings.imageMode()
  const posts = await forumDb.postsByThread(threadId, { includeHidden: canModerate })
  return {
    ...publicThread(thread),
    // A reply control is offered when the TYPE takes replies and the thread is
    // open. Both halves are reported separately (`type`, `locked`) so the UI can
    // say which one is why, but the decision itself is made here — a client that
    // recomputed it would be a second place for the rule to live.
    canReply: REPLYABLE_TYPES.includes(thread.type) && !thread.locked && thread.status === 'visible',
    posts: posts.map((p) => renderPost(p, mode, viewer)),
  }
}

/**
 * Open a thread: the thread and its first post, in one call.
 *
 * An announcement is a degenerate thread rather than its own thing (§5.1), which
 * is why phase 5 added no migration — a discussion thread is the same two writes
 * with a different `type`. The FIRST post is an ordinary post and is moderated,
 * edited and reported like any other; nothing here marks it as special, because a
 * thread whose opening post could not be moderated would be a hole shaped exactly
 * like the one moderation exists to close.
 */
async function createThread({ team, actor, type, title, body }) {
  if (!CREATABLE_TYPES.includes(type)) {
    return { ok: false, status: 400, error: 'Unknown thread type' }
  }
  const cleaned = cleanForumBody(body)
  if (!cleaned || !cleaned.replace(/<[^>]*>/g, '').trim()) {
    return { ok: false, status: 400, error: 'A post needs a body' }
  }
  const threadId = await forumDb.insertThread({
    teamId: team.id,
    type,
    title,
    createdBy: actor.id,
    createdUsername: actor.username,
  })
  const postId = await forumDb.insertPost({
    threadId,
    authorUserId: actor.id,
    authorUsername: actor.username,
    bodyHtml: cleaned,
  })
  // `notify` is what the CONTROLLER needs to fan a notification out, and it is a
  // separate key rather than more fields on the result because the controller
  // spreads the result straight into the response body — a notification's excerpt
  // is not part of the API's answer to "did my post save".
  //
  // The notification itself is fired from the controller and not from here, on
  // this file's own rule (see the header): everything in it takes an
  // already-resolved access decision and reads no membership table. The fan-out
  // reads both, so importing it here would make the forum model transitively
  // depend on exactly what it exists not to touch.
  return { ok: true, threadId, postId, notify: { threadId, title, type, bodyHtml: cleaned } }
}

/**
 * Reply to a discussion thread.
 *
 * Three refusals, and the status codes are chosen to be distinguishable rather
 * than uniform. A thread that is not there, or is hidden from this caller, is 404
 * for the §5.5.1 reason. An announcement is 400 — the request is malformed for
 * this thread, and no amount of retrying fixes it. A locked thread is **409**: the
 * request is fine and the resource's state is what refuses, which is exactly the
 * distinction a client needs to tell "you cannot" from "not right now".
 *
 * **Locked refuses staff too.** They hold `unlock`, so nothing is lost — and what
 * is gained is that `locked` means the same thing to every reader. A moderator's
 * reply appearing in a thread nobody else may answer is the last word by fiat;
 * unlock, post, relock is the same outcome with three ledger rows saying so.
 */
async function createPost({ team, threadId, actor, body }) {
  const thread = await forumDb.threadById(threadId)
  if (!thread || thread.team_id !== team.id || thread.status !== 'visible') {
    return { ok: false, status: 404, error: 'Thread not found' }
  }
  if (!REPLYABLE_TYPES.includes(thread.type)) {
    return { ok: false, status: 400, error: 'Announcements do not take replies' }
  }
  if (thread.locked) {
    return { ok: false, status: 409, error: 'This thread is locked' }
  }
  const cleaned = cleanForumBody(body)
  if (!cleaned || !cleaned.replace(/<[^>]*>/g, '').trim()) {
    return { ok: false, status: 400, error: 'A reply needs a body' }
  }
  const postId = await forumDb.insertPost({
    threadId,
    authorUserId: actor.id,
    authorUsername: actor.username,
    bodyHtml: cleaned,
  })
  // The thread's OWN title and type, not the reply's — a reply has neither, and
  // what a recipient needs to know is which conversation moved. `type` is always
  // 'discussion' here (an announcement takes no replies) and is carried anyway so
  // the controller has one shape to hand the fan-out from both routes.
  return { ok: true, threadId, postId, notify: { threadId, title: thread.title, type: thread.type, bodyHtml: cleaned } }
}

/**
 * Edit a post: the author inside the window, staff at any time (§5.4).
 *
 * The window is re-derived HERE from `created_at` and never trusted from the
 * request, which is also why `editability` runs on the read path — the read tells
 * the client whether to draw the control, and this decides whether the edit
 * happens. Two evaluations of one rule, deliberately: the read one is advice and
 * this one is enforcement.
 *
 * A staffer editing someone else's post is reported back as `staffEdit` so the
 * controller can write the §5.3 accountability row. A staffer editing their OWN
 * post is an ordinary edit and is not: the trail records interventions, and
 * everything a staffer ever typed is not an intervention.
 */
async function editPost({ team, postId, actor, isStaff = false, windowMinutes = 0, body }) {
  const post = await forumDb.postById(postId)
  if (!post) return { ok: false, status: 404, error: 'Post not found' }

  const thread = await forumDb.threadById(post.thread_id)
  if (!thread || thread.team_id !== team.id) return { ok: false, status: 404, error: 'Post not found' }
  if (post.status !== 'visible' || thread.status !== 'visible') {
    return { ok: false, status: 404, error: 'Post not found' }
  }

  const isAuthor = post.author_user_id != null && post.author_user_id === actor.id
  if (!isAuthor && !isStaff) {
    return { ok: false, status: 403, error: 'You may only edit your own posts' }
  }
  if (!isStaff) {
    if (thread.locked) return { ok: false, status: 409, error: 'This thread is locked' }
    const { canEdit } = editability(post, { userId: actor.id, windowMinutes })
    if (!canEdit) {
      return {
        ok: false,
        status: 403,
        error: windowMinutes > 0
          ? `The ${windowMinutes}-minute edit window for this post has closed`
          : 'Posts cannot be edited on this site',
      }
    }
  }

  const cleaned = cleanForumBody(body)
  if (!cleaned || !cleaned.replace(/<[^>]*>/g, '').trim()) {
    return { ok: false, status: 400, error: 'A post needs a body' }
  }
  await forumDb.updatePostBody(postId, cleaned, actor.id)
  return { ok: true, postId, threadId: post.thread_id, staffEdit: isStaff && !isAuthor }
}

/**
 * Apply a moderation action to a thread, and record WHICH authority did it.
 *
 * `actorRole` is 'leader' or 'staff' — the column that makes a leader's ordinary
 * housekeeping distinguishable from a staff intervention after the fact (§5.3).
 * The caller resolves it; this function records it and never infers it, because
 * an actor who is both would otherwise be recorded as whichever the code checked
 * first.
 */
async function moderateThread({ team, threadId, action, actor, actorRole, reason }) {
  const effect = THREAD_ACTIONS[action]
  if (!effect) return { ok: false, status: 400, error: 'Unknown moderation action' }

  const thread = await forumDb.threadById(threadId)
  if (!thread || thread.team_id !== team.id) return { ok: false, status: 404, error: 'Thread not found' }

  await forumDb.setThreadFlags(threadId, effect)
  await forumDb.insertModeration({
    teamId: team.id,
    targetType: 'thread',
    targetId: threadId,
    action,
    actorUserId: actor.id,
    actorUsername: actor.username,
    actorRole,
    reason,
  })
  return { ok: true, action, threadId }
}

/**
 * Apply a moderation action to a POST, and record which authority did it.
 *
 * The same ledger as `moderateThread`, with `target_type='post'` — one table, two
 * target kinds, because "show me everything that was moderated in this Team" is
 * the question the admin view asks and two tables would make it a union.
 *
 * `pin` and `unpin`, `lock` and `unlock` are refused with a message that names the
 * mistake rather than a bare "unknown action": they are real actions applied to
 * the wrong kind of object, and a caller who sent one has a bug worth telling
 * them about precisely.
 *
 * **The opening post of a thread is moderatable like any other.** Hiding it leaves
 * a thread with a title and its replies and no body, which looks odd and is
 * correct — an abusive opener does not have to take a good discussion with it, and
 * a moderator who wants the whole thing gone has `hide` on the thread.
 */
async function moderatePost({ team, postId, action, actor, actorRole, reason }) {
  const effect = POST_ACTIONS[action]
  if (!effect) {
    return {
      ok: false,
      status: 400,
      error: THREAD_ACTIONS[action]
        ? `"${action}" applies to a thread, not to a post`
        : 'Unknown moderation action',
    }
  }

  const post = await forumDb.postById(postId)
  if (!post) return { ok: false, status: 404, error: 'Post not found' }
  const thread = await forumDb.threadById(post.thread_id)
  if (!thread || thread.team_id !== team.id) return { ok: false, status: 404, error: 'Post not found' }

  await forumDb.setPostStatus(postId, effect.status)
  // The counters are recomputed rather than nudged, because these four actions
  // form cycles (hide → unhide → hide) that a delta gets wrong the first time one
  // is retried.
  await forumDb.recountThread(post.thread_id)

  // Images follow their post. Soft on the way out and reversible on the way back
  // in, so `delete` → `restore` inside the retention window returns the post
  // whole; past it, the sweep has taken the bytes and nothing can.
  if (action === 'delete') await forumDb.softDeleteUploadsForPost(postId, actor.id)
  if (action === 'restore') await forumDb.restoreUploadsForPost(postId)

  await forumDb.insertModeration({
    teamId: team.id,
    targetType: 'post',
    targetId: postId,
    action,
    actorUserId: actor.id,
    actorUsername: actor.username,
    actorRole,
    reason,
  })
  return { ok: true, action, postId, threadId: post.thread_id }
}

/** The ledger for the admin Team page. Staff-only by its route, not by this function. */
async function moderationLedger(teamId, opts) {
  return forumDb.moderationForTeam(teamId, opts)
}

module.exports = {
  CREATABLE_TYPES,
  CREATABLE_TYPES_5A,
  REPLYABLE_TYPES,
  THREAD_ACTIONS,
  POST_ACTIONS,
  listThreads,
  getThread,
  createThread,
  createPost,
  editPost,
  moderateThread,
  moderatePost,
  moderationLedger,
  publicThread,
  renderPost,
  editability,
}