// ---------------------------------------------------------------------------
// inbox/inboxModel.ts — WAVE 32 · T20 (owner item 16, ruling R7, contract C3):
// the Inbox module's PURE half. React-free and fetch-free, so `verify_alerts.py`
// compiles it and RUNS it under node.
//
// Owner, item 16: *"Alerts becomes an Inbox that looks like email."* An email
// client is three decisions, and every one of them is a function here rather
// than markup, because markup a gate cannot reach is markup no control can
// mutate:
//
//   1. ORDER — unread ABOVE read, newest first inside each. Not a sort key on
//      one axis: a reader opens an inbox to find what they have not seen, and
//      an unread item that has aged below a read one is functionally lost.
//   2. THE HEADER — `subject` (what this is about) sits above `label` (what
//      happened). They were ONE field until C3, which is precisely why the old
//      pane could only render a sentence with no sender.
//   3. WHETHER IT OPENS AT ALL — `target` is ABSENT when the server cannot
//      resolve a destination, and that absence must reach the eye as a row that
//      does not pretend to be clickable.
//
// ⛔ THERE IS NO CLIENT-SIDE `target` DERIVATION HERE, DELIBERATELY. The server
// derives it (`routes_alerts.notification_view`) and this module only reads what
// arrived. A fallback that re-derived the same answer from `topic`/`alertId`
// would be a SECOND normaliser for one question — the exact defect this wave's
// item 6 is about in `routes_connectors` vs `routes_keychain`, and the reason
// every tenant currently sees another tenant's Odoo connection. One question,
// one answer, on the side that owns the vocabulary.
// ---------------------------------------------------------------------------

import {
  NOTIF_KIND_AUTOMATION,
  NOTIF_KIND_SHARE,
  TARGET_MODULE_AUTOMATION,
  TARGET_MODULE_DATABASE,
} from "../alerts/alertsModel";
import type { Notification, NotificationTarget } from "../alerts/alertsModel";

const str = (v: unknown): string => (typeof v === "string" ? v : "");

/** One block of the list. `unread` renders first and always, even when empty — an
 *  inbox that hides its own "Unread" heading at zero makes "I have read everything"
 *  and "this failed to load" look identical. */
export interface InboxSections {
  unread: Notification[];
  read: Notification[];
}

/**
 * The mail order: unread above read, newest first within each.
 *
 * ⛔ TWO SECTIONS, NOT ONE SORT, and the difference is visible the moment an inbox has both. A
 * single comparator that puts `read` before `at` produces the same sequence but no SEAM — so a
 * reader scrolling past the last unread item cannot tell they have crossed it, which is the one
 * thing the ordering exists to tell them.
 *
 * ⚠ STABLE within a timestamp: `_queue` mints several notifications with an IDENTICAL `at`
 * (one write, N entrants), so a comparator returning non-zero for equal stamps would reshuffle
 * them on every render.
 */
export function inboxSections(items: Notification[],
                              held: ReadonlySet<string> = EMPTY_HELD): InboxSections {
  const byAt = (a: Notification, b: Notification) =>
    a.at < b.at ? 1 : a.at > b.at ? -1 : 0;
  // ⭐⭐ W33-T28 — `held` IS WHY THE ROW YOU CLICKED STAYS WHERE YOU CLICKED IT.
  //
  // ⛔ THE DEFECT, found by a `verifier` and worth stating in full because it is the first thing
  // a reader meets: selecting a row marks it read IN THE SAME CLICK (that is deliberate — see
  // `InboxPage.select`), which moved it out of `unread`, into `read`, under a different heading,
  // and decremented "Unread (3)". **The list re-sectioned itself while the cursor was still on
  // the row.** No mail client does that; every one of them leaves a message where it is until
  // the next load. The bug is not the marking, it is that the SECTIONING is a live function of
  // the same flag.
  //
  // ⚠ SO THE FIX IS A HOLD, NOT A DELAY. `held` is the ids read during THIS visit; they render
  // in place, styled as read, and settle into "Earlier" on the next load. The unread COUNT is
  // untouched (it is the server's number and the badge's — see `parseInbox`'s note), so the badge
  // still clears immediately, which is the half the reader wanted.
  const isUnread = (n: Notification) => !n.read || held.has(n.id);
  return {
    unread: items.filter(isUnread).sort(byAt),
    read: items.filter((n) => !isUnread(n)).sort(byAt),
  };
}

/** A stable empty identity, so the default argument does not mint a Set per call and defeat
 *  `useMemo` at the one call site that has one. */
const EMPTY_HELD: ReadonlySet<string> = new Set<string>();

/**
 * The header line.
 *
 * ⚠ IT FALLS BACK RATHER THAN RENDERING BLANK. A notification queued before C3 existed carries no
 * `subject`, and a mail list whose header row is empty reads as a corrupt item — the reader
 * cannot tell it apart from one whose subject really is missing. `alertLabel` is what the server
 * derives `subject` FROM, so the fallback lands on the same words rather than on a placeholder.
 */
export function subjectOf(n: Notification): string {
  return (
    str(n.subject).trim() ||
    str(n.alertLabel).trim() ||
    str(n.label).trim() ||
    "Notification"
  );
}

/**
 * The preview line — what actually happened.
 *
 * ⚠ EMPTY WHEN IT WOULD MERELY REPEAT THE SUBJECT. On a notification with no `subject` the
 * fallback above already used `label`, and printing it twice makes a two-line row that says one
 * thing — the shape that reads as a rendering bug rather than as an item.
 */
export function previewOf(n: Notification): string {
  const label = str(n.label).trim();
  return label && label !== subjectOf(n) ? label : "";
}

/** The kind, in the reader's words. Unknown kinds fall to the alert wording rather than to a raw
 *  server token — a row is never allowed to print a vocabulary word at somebody. */
export function kindLabel(kind: string | undefined): string {
  if (kind === NOTIF_KIND_AUTOMATION) return "Automation";
  if (kind === NOTIF_KIND_SHARE) return "Shared with you";
  return "Alert";
}

/**
 * ⭐⭐ W33-T28 — WHO IT IS FROM, which this list did not have.
 *
 * ⛔ `kindLabel` WAS STANDING IN THE SENDER'S PLACE and that is the defect, not the styling: a
 * `verifier` reading the finished wave-32 Inbox found the row's first meta token was always
 * "Alert" / "Automation" / "Shared with you" — a CATEGORY where mail puts a who. The two are
 * different questions and they now have different functions; `kindLabel` keeps its own job.
 *
 * ⚠ THE FALLBACK IS BY KIND, NOT A BLANK. A notification queued before the server learned to
 * send `sender` still has to render a From column, and an empty one reads as a broken inbox
 * rather than as an old row — so it degrades to the honest machine name for its kind.
 */
export function senderOf(n: Notification): string {
  const sent = String(n.sender || "").trim();
  if (sent) return sent;
  if (n.kind === NOTIF_KIND_AUTOMATION) return "Automation";
  if (n.kind === NOTIF_KIND_SHARE) return "A teammate";
  return "Alerts";
}

/**
 * Where this item opens, or `null`.
 *
 * ⛔ `null` IS A RENDERED STATE, NOT A SWALLOWED ONE. An alert outlives the view it was made from
 * and a database can be un-shared out from under a notification; when that happens the server
 * sends no `target` and the Inbox must show a row that is visibly not a link. The failure this
 * replaces is the old pane's: it rendered every row as a button and told the reader *"That
 * alert's table is no longer available to this account"* only AFTER they clicked.
 */
export function targetOf(n: Notification): NotificationTarget | null {
  return n.target ?? null;
}

/** Can this row be opened? The one predicate the row's markup and its click handler share, so
 *  they cannot disagree about whether a row is a link. */
export function canOpen(n: Notification): boolean {
  return targetOf(n) !== null;
}

/**
 * Why a row cannot be opened, for the reader.
 *
 * ⚠ SAID ON THE ROW, NOT ON THE CLICK. The sentence is the same one the pane used to raise as a
 * toast; moving it onto the row is the whole difference between "this is unavailable" and "you
 * pressed a button and were told off".
 */
export const UNOPENABLE_NOTE = "The thing this is about is no longer available to this account.";

/**
 * ⭐ C3's dispatch, as data rather than as a branch in the frame.
 *
 * The FRAME owns routing (it holds the router and the module surfaces); this module owns the
 * question *"which surface, and what does it need?"*. Returning a discriminated answer means A's
 * `onOpenTarget` is a switch over two literals it can exhaust, instead of a second copy of the
 * `topic`→route table that `routeForTopic` already owns.
 *
 * ⚠ AN UNKNOWN MODULE ANSWERS `null` AND THE FRAME MUST SAY SO. It must not silently do nothing:
 * an unknown module means this client is older than the server that sent it, and a reader who
 * clicks and sees no change concludes the Inbox is broken rather than that their tab is stale.
 */
export type TargetRoute =
  | { surface: "database"; key: string; viewId?: string }
  | { surface: "automation"; autoId: string; tab: string };

/**
 * ⭐⭐ WAVE 32 · T29 (owner item 19) — WHY OPENING A TARGET NEEDS MORE THAN ONE EMIT.
 *
 * `CustomerGrid`'s `VIEW_OPEN_EVENT` listener drops anything it cannot yet resolve:
 *
 *     if (!detail || detail.topic !== scope) return;
 *     if (!views.some((v) => v.id === detail.viewId)) return;
 *
 * Both guards are RIGHT — an alert outlives the view it watches, and one grid must not react to
 * another's event. But together they mean a single emit fired the instant the hash changes is
 * **silently discarded**: the destination grid has not fetched its views yet, and there is no ack
 * channel to wait on. The click appears to work, the table opens, and the view is simply not
 * selected — this repo's most-repeated failure shape, on the feature whose whole purpose is
 * "clicking an Inbox item opens the thing it is about".
 *
 * ⭐ FOUND BY LANE E, NOT BY ME, and re-verified here against `CustomerGrid.tsx` before being
 * built on: `VIEW_OPEN_EVENT` had a listener and NO emitter anywhere in the tree until this wave,
 * so wave 20's click-through had never actually been exercised.
 *
 * ⚠ RE-EMITTING IS FREE. `selectView` early-returns once the view is already active, and the
 * listener drops a duplicate that arrives after selection, so a late tick costs nothing. The
 * ladder is coarse on purpose — a tight interval would fire a dozen times inside one render.
 */
export const OPEN_RETRY_MS = [0, 250, 700, 1500, 2600] as const;

/**
 * Fire `emit` on the {@link OPEN_RETRY_MS} ladder, stopping early when it reports success.
 *
 * Returns a CANCEL function: a reader who clicks a second notification while the first is still
 * retrying would otherwise have two ladders racing, and the older one would yank them back.
 *
 * ⚠ `emit` returning `true` means "this landed" and ends the ladder. It is allowed to return
 * nothing — `VIEW_OPEN_EVENT` has no ack, so the honest answer there is `undefined` and the
 * ladder simply runs out. The signature admits both rather than pretending a confirmation exists.
 */
export function retryEmit(
  emit: () => boolean | void,
  schedule: (fn: () => void, ms: number) => number = setTimeout as never
): () => void {
  const timers: number[] = [];
  let done = false;
  for (const ms of OPEN_RETRY_MS) {
    timers.push(
      schedule(() => {
        if (done) return;
        if (emit() === true) done = true;
      }, ms)
    );
  }
  return () => {
    done = true;
    for (const t of timers) clearTimeout(t as never);
  };
}

export function routeForTarget(t: NotificationTarget | null): TargetRoute | null {
  if (!t) return null;
  if (t.module === TARGET_MODULE_AUTOMATION)
    return { surface: "automation", autoId: t.id, tab: str(t.tab).trim() || "runs" };
  if (t.module === TARGET_MODULE_DATABASE) {
    const viewId = str(t.tab).trim();
    return { surface: "database", key: t.id, ...(viewId ? { viewId } : {}) };
  }
  return null;
}