/**
 * storeRegistry — resolves (account, scope) → document NURI.
 *
 * Stopgap / polyfill-era. Emulates the target infrastructure — where each
 * user owns their own public/protected/private stores — on top of one shared
 * wallet. It creates one document per (account × scope) inside that shared
 * wallet (via `physical.physicalCreate` — the UNGUARDED primitive, since a store is
 * machinery and its cap is filed here, where it is known whose it is; the public
 * `docs.docCreate` files the creator's cap itself), so the `scope`
 * (`public|protected|private`) is a logical attribute tracked here, not a
 * physical NextGraph store. Isolation is enforced by the app layer + the
 * emulated cap registry, not by crypto.
 *
 * The mapping (account → its 3 document NURIs) is the **sharedWalletShim**. It
 * is persisted as RDF, but NOT in the store-root graph anymore — see the
 * indirection below. That makes login cross-device: another device opening the
 * same wallet reads the same shim and finds the same accounts.
 *
 * ── The indirection: pointer (store-root) → doc-shim (subscribable) ─────────
 * On the real NextGraph platform "findable-without-lookup" and "subscribable"
 * are DISJOINT (verified at the source, see docs/nextgraph-current-state.md
 * § *Findable vs subscribable*):
 *   - the ONLY NURI a fresh session can name WITHOUT a lookup is the store-root
 *     `did:ng:${privateStoreId}` — but a store-root has NO first-`State` sync
 *     BARRIER, so a cold "0 rows" on it is AMBIGUOUS (could be sync-lag, could
 *     be truly empty);
 *   - the ONLY thing that DOES have a first-`State` barrier is a `did:ng:o:<RepoID>`
 *     doc from `doc_create` — but its RepoID is RANDOM, so a fresh session
 *     cannot GUESS it; it must be looked up.
 * So a purely-barrier shim resolution is impossible: you cannot have a doc that
 * is both guessable and authoritative on a cold read. The indirection bridges
 * this: a well-known, write-ONCE **pointer** triple in the store-root names a
 * **doc-shim** (`did:ng:o:...`) that holds all account records and IS
 * subscribable. Resolution reads the pointer (a single oldest write-once triple,
 * near-always synced), then opens the doc-shim through its `ensureRepoOpen`
 * BARRIER and reads the account AUTHORITATIVELY (0 = genuinely absent).
 *
 * A pointer FORK (two devices writing the pointer before either synced) is
 * reconciled to a canonical doc-shim (lexicographically-smallest NURI) so every
 * device converges on the SAME doc-shim. This is why the OLD account-level retry
 * (`resolveAccountReliably` / `provisionRetry`) is GONE: the account read is now
 * barrier-authoritative, so it never needs to be retried to distinguish sync-lag
 * from absence. A micro-guard remains ONLY on the pointer read (one write-once
 * triple) — see resolvePointer.
 *
 * ── Generic by construction ──────────────────────────────────────────────
 * This module knows only the three native scopes; it knows no application
 * entity kind. The consumer maps its entities to a scope and calls
 * `createEntityDoc(scope)` / `listEntityDocs(scope)` with the resulting native
 * scope. No application domain here.
 *
 * ── What disappears at migration ─────────────────────────────────────────
 * At the real multi-store migration the shim vanishes entirely: `(account,
 * scope)` maps to the user's REAL store NURI instead of a document in the
 * shared wallet, `docCreate` targets the real per-user store, and the
 * per-scope index document (the store-container emulation) is replaced by the
 * store itself. The consumer-facing surface (`createEntityDoc`,
 * `listEntityDocs`, resolvers) is designed to survive that swap unchanged.
 *
 * All NextGraph I/O routes through the T01.a `docs` primitive (real injected
 * `ng`), so this module imports **no** `@ng-org` package.
 */

import { sparqlUpdate, sparqlQuery } from "./docs";
import { physicalCreate, physicalQuery, physicalUpdate } from "./physical";
import { getCaps, getCurrentUser, getStoreRegistryDeps } from "./polyfill";
import { ensureRepoOpen, ensurePhysicalRepoOpen } from "./open-repo";
import { escapeLiteral, escapeIri, assertNuri } from "./sparql";
import { hasReadCap, isNuri, mintCap } from "./nuri";
import { mustNotAttempt } from "./reach";
import { accessLogPrefix, logStage, shortNuri } from "./access-log";
import type { Nuri, ReadCap, Scope } from "./types";

// --- sharedWalletShim model ----------------------------------------------

/**
 * A NURI as read back from the shim, where `""` means "absent or corrupt".
 *
 * The empty case is NOT new — `canonicalDoc` has always returned `""` for a missing
 * field, and callers have always had to test for it — but with {@link Nuri} typed it
 * stops hiding inside a `string`. It is kept confined to the shim-reading functions
 * below: `AccountRecord` still promises real NURIs, because a record with an empty
 * scope document is a corrupt record, not a valid state to spread through the API.
 * Tightening that (reject the record rather than let it flow) is a change of
 * behaviour and belongs to its own lot — see `recordFromRows`.
 */
type MaybeNuri = Nuri | "";

/** One account's three scope-document NURIs, as recorded in the shim. */
export interface AccountRecord {
  id: string;
  docPublic: Nuri;
  docProtected: Nuri;
  docPrivate: Nuri;
}

const SHIM = "urn:ng-eventually:shim";
const P = {
  type: `${SHIM}:Account`,
  id: `${SHIM}:id`,
  docPublic: `${SHIM}:docPublic`,
  docProtected: `${SHIM}:docProtected`,
  docPrivate: `${SHIM}:docPrivate`,
  contains: `${SHIM}:contains`, // scope-index → entity document NURI
  docInbox: `${SHIM}:docInbox`, // account → ITS OWN inbox document
  link: `${SHIM}:link`, // user branch → a ReadCap received for an EXTERNAL document
  readCap: `${SHIM}:readCap`, // store branch → the ReadCap of a document IN this store
  inboxCap: `${SHIM}:inboxCap`, // user branch → an inbox this user may READ
  inboxAddress: `${SHIM}:inboxAddress`, // header branch → WHERE to deposit for this document
} as const;
// Fixed subject of the per-(account×scope) index document. The index doc plays
// the role of the future store-container: it lists the NURIs of the entity
// documents (one per entity) that live "in" that scope.
const MAIN_BRANCH_SUBJECT = `${SHIM}:index`;
/**
 * Fixed subject of the **User branch** emulation, inside a user's PRIVATE store
 * document. Upstream, `AddLink { read_cap }` is committed to the User branch of the
 * private store — *"so that a user can share with all its device a new Link they
 * received"*, and *"only external repos are accepted"* (`engine/repo/src/types.rs:1934-1950`).
 * That is where a cap received from someone else durably lives.
 *
 * We have no branches, so the compartment is a distinct SUBJECT in the same
 * document, kept separate from `MAIN_BRANCH_SUBJECT` (which emulates the store's Main
 * branch, the `ldp:contains` listing). Two compartments, two subjects — the
 * separation upstream makes with two branches.
 */
const USER_BRANCH_SUBJECT = `${SHIM}:userBranch`;
/**
 * Fixed subject of the **Store branch** emulation, inside a user's store document.
 *
 * `doc_create` upstream writes TWICE (`engine/verifier/src/request_processor.rs:697-710`):
 * `ldp:contains` on the store's **Main** branch — the listing — and
 * `AddRepo { read_cap }` on its **Store** branch — the key. Two branches, two
 * purposes, deliberately separate; replaying the Store branch is what reloads a
 * store's documents WITH their caps (`AddRepo::verify` → `load_repo_from_read_cap`).
 *
 * We have no branches, so this is a distinct SUBJECT beside {@link MAIN_BRANCH_SUBJECT}
 * in the same document — the same shape already used for {@link USER_BRANCH_SUBJECT}.
 *
 * **Honest about the emulation**: upstream the Store branch carries NO triples at all
 * (`BranchCrdt::None`, `engine/repo/src/types.rs:1420`) — it is a stream of service
 * commits. Representing it as RDF is our invention; what is faithful is *that the cap
 * is stored beside the document rather than recomputed*, and that the listing and the
 * keys stay separate.
 */
const STORE_BRANCH_SUBJECT = `${SHIM}:storeBranch`;
/**
 * Fixed subject of the **Header branch** emulation, inside an ENTITY document — the
 * first compartment we put in a document the consumer also reads, hence the filter in
 * `read-model.ts` (every `${SHIM}:` subject is machinery and never surfaces as data).
 *
 * It carries what must be readable by *whoever can read the document*, as opposed to
 * what belongs to its owner alone. Today that is one thing: the ADDRESS of the
 * document's inbox.
 *
 * Why the address must live here and not on the owner's User branch. Upstream an inbox
 * is a KEYPAIR (`repo.inbox: Option<PrivKey>`, `engine/repo/src/repo.rs:126`) and the
 * two halves have opposite audiences: a depositor seals with the PUBLIC key
 * (`InboxMsg::new` → `crypto_box::seal(&to_inbox.to_dh_slice(), …)`,
 * `engine/net/src/types.rs:4299`) and needs nothing else; only the owner holds the
 * private half (`AddInboxCap`, on the User branch). An address is therefore public by
 * nature — upstream it travels with the profile (`ContactDetails` carries
 * `ng:site_inbox` / `ng:protected_inbox`, `engine/verifier/src/inbox_processor.rs:823`).
 * Keeping it only on the owner's User branch, as this lib first did, made the deposit
 * side unreachable: a third party had no way to learn where to deposit.
 *
 * **Not `BranchType::Header` upstream.** That branch exists (`engine/repo/src/types.rs:1551`)
 * but is CLOSED: `update_header` writes only `title`/`about`
 * (`engine/verifier/src/request_processor.rs:173-211`) and `fetch_header` reads back
 * only `title`/`about`/`class` (`:1240-1284`). It cannot carry an inbox address. The
 * name is borrowed for the shape — a compartment of the document that is not its
 * content — not for the upstream branch's contract.
 */
const HEADER_BRANCH_SUBJECT = `${SHIM}:headerBranch`;

// --- pointer (store-root → doc-shim indirection) --------------------------
//
// The pointer is a SINGLE well-known triple written ONCE into the store-root
// graph on the very first login, then IMMUTABLE. Its object is the NURI of the
// doc-shim (a `did:ng:o:...` repo) where all AccountRecords actually live. The
// store-root is NOT subscribable (no first-`State` barrier), but the pointer is
// the OLDEST triple in that graph and is write-once, so it is near-always synced
// on a cold read — and even a transient miss is bounded by a small guard
// (resolvePointer), NOT by an account-level retry.
const POINTER_SUBJECT = `${SHIM}:root`;
const POINTER_PRED = `${SHIM}:shimDoc`;

function accountSubject(id: string): string {
  // The id is UNTRUSTED and lands in an IRI position. Percent-encode it
  // (escapeIri) so no `>` / `"` / whitespace / control char can break out of
  // the `<...>` and inject triples into the shim graph (the account→doc trust
  // root). accountKey() runs first so the subject stays stable per shim key.
  return `${SHIM}:account:${escapeIri(accountKey(id))}`;
}

// --- reserved accounts -----------------------------------------------------
//
// Some accounts are internal to the lib (e.g. the discovery index owner) and
// must NOT collide with any user-chosen id. A reserved account is created
// via {@link reservedAccount}, which marks the name with a sentinel PREFIX that
// `normalizeId` (consumer-injected) can never produce: it strips a leading
// `@`, trims, and lowercases, so a NUL prefix is unreachable. Reserved
// keys therefore live in a disjoint namespace from every normalized id —
// a real user named "index"/"@index" can never resolve to the reserved
// `reservedAccount("index")` account.
const RESERVED_PREFIX = "\u0000reserved:";

/**
 * Wrap an internal account name so it occupies a key that no user input can
 * produce (see {@link RESERVED_PREFIX}). Pass the result to {@link ensureAccount}
 * (and the other registry calls) instead of a bare id.
 */
export function reservedAccount(name: string): string {
  return `${RESERVED_PREFIX}${name}`;
}

/** Whether a name is a reserved-account sentinel (from {@link reservedAccount}). */
function isReserved(id: string): boolean {
  return id.startsWith(RESERVED_PREFIX);
}

/**
 * The shim/cache key for an account. Reserved accounts bypass `normalizeId`
 * entirely and key on their sentinel-prefixed name, so they cannot collide with
 * a normalized id; everyone else normalizes as usual.
 */
function accountKey(id: string): string {
  return isReserved(id) ? id : normalize(id);
}

// --- session / normalization access (injected by the consumer) ------------

/** Minimal session shape the registry needs — provided by the consumer. */
export interface RegistrySession {
  sessionId: string;
  /** The shared wallet's private store id — the pointer anchor. */
  privateStoreId: string;
  /** The shared wallet's protected store id (native store). Optional: only the
   *  scope resolvers need it; the shim only needs the private anchor. */
  protectedStoreId?: string;
  /** The shared wallet's public store id (native store). Optional. */
  publicStoreId?: string;
}

function normalize(id: string): string {
  return getStoreRegistryDeps().normalizeId(id);
}

async function session(): Promise<RegistrySession> {
  return getStoreRegistryDeps().getSession();
}

/** The pointer lives in the shared wallet's private STORE-ROOT graph (the only
 *  always-known-without-lookup anchor). NOT subscribable — hence the pointer is
 *  a write-once triple, and the actual account records live in the doc-shim it
 *  names (see rootNuri vs the doc-shim). */
async function rootNuri(): Promise<Nuri> {
  const s = await session();
  return `did:ng:${s.privateStoreId}`;
}

// --- cache ----------------------------------------------------------------

// Per-account cache, keyed by account key. Populated by the TARGETED resolver
// (resolveAccount) and by loadShim(). Independent of `cache` so a single
// targeted resolve never forces a full shim scan. Both are cleared together.
const accountCache = new Map<string, AccountRecord>();

// The resolved doc-shim NURI for the current session (cached: the pointer read +
// barrier open happen once, then every account read reuses this doc). Cleared on
// resetRegistryCache / wallet switch.
let shimDocNuri: Nuri | null = null;
// De-dupe concurrent pointer-resolutions so a fresh page firing many parallel
// ensureAccount/resolveAccount calls opens the doc-shim exactly once.
let shimDocInFlight: Promise<Nuri> | null = null;

/** Reset cache (e.g. after switching the shared wallet). Mostly for tests. */
export function resetRegistryCache(): void {
  accountCache.clear();
  inboxCache.clear();
  inboxInFlight.clear();
  shimDocNuri = null;
  shimDocInFlight = null;
}

// --- SPARQL result helpers ------------------------------------------------

/** Tolerant extraction of SPARQL SELECT bindings across possible shapes. */
function readBindings(result: unknown): Array<Record<string, { value: string }>> {
  if (!result) return [];
  const anyRes = result as {
    results?: { bindings?: Array<Record<string, { value: string }>> };
  };
  if (Array.isArray(result)) return result as Array<Record<string, { value: string }>>;
  if (anyRes.results?.bindings) return anyRes.results.bindings;
  return [];
}

function bindingValue(row: Record<string, { value: string }>, key: string): string {
  return row[key]?.value ?? "";
}

/**
 * DETERMINISTIC resolution of an account's scope docs from a set of SPARQL
 * bindings (all bindings for ONE account subject).
 *
 * ── Why this is load-bearing (residual fork residue) ───────────────────────
 * A corrupted shim can carry the SAME account subject with MULTIPLE values for a
 * scope predicate (e.g. 5 `shim:docPublic`) — the residue of past account FORKS
 * (each stray provision appended another doc NURI). A query then returns several
 * bindings (the cross-product of the duplicate values). Picking `rows[0]` is
 * NON-DETERMINISTIC (binding order is not stable across sessions), so the session
 * that WROTE an entity into one docPublic and a later fresh page that RESOLVED a
 * DIFFERENT docPublic would disagree → the anchored `readUserStore` returns 0 →
 * the home reads empty. When both happen to pick the same doc, it "works".
 *
 * The fix: for each scope field, collect EVERY distinct value across the bindings
 * and choose the SAME one every time — the lexicographically-smallest NURI. NURIs
 * are content-addressed and stable, so lexicographic order is a total, stable,
 * session-independent order: writer and reader converge on the SAME canonical doc
 * even on a wallet already corrupted by duplicates. (No creation timestamp is
 * recorded in the shim, so lexicographic-min is the available deterministic key.)
 *
 * With the barrier-authoritative doc-shim read, account FORKS no longer occur (a
 * fresh page reads the doc-shim through its first-`State` barrier, so a cold 0 is
 * definitive and never triggers a fork-provision). `canonicalDoc` is RETAINED to
 * stay robust against the residue of PAST forks already persisted in a wallet, and
 * to reconcile a benign pointer fork the same content-addressed way.
 */
function canonicalDoc(rows: Array<Record<string, { value: string }>>, key: string): MaybeNuri {
  let chosen: MaybeNuri = "";
  const distinct = new Set<string>();
  for (const row of rows) {
    const v = bindingValue(row, key);
    // The SPARQL boundary: a binding is an untrusted string. Narrowing here (rather
    // than casting) also discards a value that is not a NextGraph reference at all —
    // shim corruption that used to flow straight through as a "document NURI".
    if (!v || !isNuri(v)) continue;
    distinct.add(v);
    if (chosen === "" || v < chosen) chosen = v;
  }
  // Stage trace: which doc got picked, and out of how many DISTINCT candidate
  // values — >1 flags residual fork residue (see the module doc above) even
  // when resolution still converges correctly on the canonical (smallest) one.
  logStage(
    "canonicalDoc(" + key + ") → " + (chosen ? shortNuri(chosen) : "none") +
      " (" + distinct.size + (distinct.size === 1 ? " candidate)" : " candidates)"),
  );
  return chosen;
}

/** Build an AccountRecord by picking the canonical (lexicographically-smallest)
 *  doc NURI per scope across all bindings for one account. See {@link canonicalDoc}. */
function recordFromRows(
  rows: Array<Record<string, { value: string }>>,
  fallbackId: string,
): AccountRecord {
  let id = "";
  for (const row of rows) {
    const v = bindingValue(row, "id");
    if (v) { id = v; break; }
  }
  // The ONE place the `""`-for-corrupt case is absorbed. `AccountRecord` promises
  // real NURIs; a shim missing a scope document yields `""` here, exactly as it
  // always has, and the cast records that this is a KNOWN gap rather than a proven
  // invariant. Callers already test for the empty value (e.g. `watchShape` skips a
  // falsy container). Rejecting such a record outright would be the right fix and is
  // a behaviour change — its own lot, not this one.
  return {
    id: id || fallbackId,
    docPublic: canonicalDoc(rows, "docPublic") as Nuri,
    docProtected: canonicalDoc(rows, "docProtected") as Nuri,
    docPrivate: canonicalDoc(rows, "docPrivate") as Nuri,
  };
}

// --- pointer resolution + doc-shim bootstrap ------------------------------

const sleep = (ms: number): Promise<void> => new Promise((r) => setTimeout(r, ms));

/**
 * Read the pointer(s) from the store-root graph → the canonical doc-shim NURI, or
 * `""` if no pointer exists yet.
 *
 * The store-root is NOT subscribable, so this read has no first-`State` barrier:
 * a cold 0 is ambiguous. But the pointer is ONE write-once triple (the OLDEST in
 * that graph), so it is near-always synced. The ONLY residual guard is a small
 * bounded re-read here (NOT an account retry): a handful of quick re-reads of that
 * single triple. It is bounded, benign, and — crucially — it can never re-provision
 * an account or fork data; the worst it can do is take a couple extra reads to see a
 * pointer that is still landing. The account records themselves are read
 * authoritatively through the doc-shim barrier, never through this guard.
 *
 * If MULTIPLE pointers exist (a pointer fork: two devices each wrote a pointer to
 * their own freshly-created doc-shim before either synced), reconcile to the
 * canonical (lexicographically-smallest) doc-shim NURI — content-addressed and
 * stable, so every device converges on the SAME doc-shim.
 */
async function resolvePointer(): Promise<MaybeNuri> {
  const s = await session();
  const root = await rootNuri();
  // COLD-START heal: open the store-root repo before the anchored read, so a fresh
  // wallet whose store-root isn't yet in `self.repos` resolves instead of throwing
  // `RepoNotFound`. Idempotent; a no-op with the unit fake ng. The store-root has no
  // barrier, so this open cannot make the read authoritative — the guard below does.
  await ensurePhysicalRepoOpen(root);
  const query = `
    SELECT ?shimDoc WHERE {
      GRAPH <${assertNuri(root)}> {
        <${POINTER_SUBJECT}> <${POINTER_PRED}> ?shimDoc .
      }
    }`;

  // Micro-guard (POINTER only): a small bounded re-read to bridge the store-root
  // sync-lag window on the ONE write-once pointer triple. Bounded, and it can only
  // ever DELAY seeing an existing pointer — never provision, never fork. Uses the
  // injected pointerGuard budget (defaults to a single read when unset, so unit
  // fakes stay synchronous). NB this is NOT the deleted account-level provisionRetry.
  const budget = getStoreRegistryDeps().pointerGuard;
  const attempts = Math.max(1, budget.attempts ?? 1);
  const baseMs = budget.baseMs ?? 150;
  const maxStepMs = budget.maxStepMs ?? 2000;

  let step = baseMs;
  for (let i = 0; i < attempts; i++) {
    try {
      const result = await physicalQuery(s.sessionId, query, undefined, root, "resolvePointer");
      const doc = canonicalDoc(readBindings(result), "shimDoc");
      if (doc) {
        logStage("resolvePointer → 1 target: " + shortNuri(doc));
        return doc;
      }
    } catch (error) {
      console.error(accessLogPrefix() + " resolvePointer failed:", error);
    }
    if (i < attempts - 1) {
      await sleep(step);
      step = Math.min(step * 2, maxStepMs);
    }
  }
  logStage("resolvePointer → 0 targets");
  return "";
}

/** Write the pointer (store-root → doc-shim), once, at first login. Idempotent in
 *  practice (only called when no pointer was found); a concurrent double-write is
 *  reconciled by canonicalDoc on read. */
async function writePointer(doc: Nuri): Promise<void> {
  const s = await session();
  const root = await rootNuri();
  await ensurePhysicalRepoOpen(root);
  const update = `
    INSERT DATA {
      GRAPH <${assertNuri(root)}> {
        <${POINTER_SUBJECT}> <${POINTER_PRED}> <${assertNuri(doc)}> .
      }
    }`;
  try {
    await physicalUpdate(s.sessionId, update, root, "writePointer");
  } catch (error) {
    console.error(accessLogPrefix() + " writePointer failed:", error);
  }
}

/** Create one graph document in the shared wallet's private store (→ a NURI). */
async function createDoc(): Promise<Nuri> {
  const s = await session();
  // crdt="Graph" (RDF/SPARQL/ORM), class="data:graph", destination="store",
  // store_repo=undefined → shared wallet's private store.
  return physicalCreate(s.sessionId);
}

/**
 * Resolve (or on first login, create) the doc-shim NURI for this session — the
 * `did:ng:o:...` repo that holds every AccountRecord and IS subscribable.
 *
 * Steps (cached; runs at most once per session, concurrent callers share one):
 *   1. Read the pointer from the store-root (resolvePointer). If present → that is
 *      the doc-shim; open it through its first-`State` BARRIER so subsequent account
 *      reads are AUTHORITATIVE.
 *   2. No pointer → FIRST login:
 *        a. create a fresh doc-shim (`doc_create`), which bootstraps the repo into the
 *           session (`self.repos`) — so it is already open/synced in-session;
 *        b. publish the pointer (store-root → the new doc-shim), once;
 *        c. open it (barrier — trivially satisfied for a just-created in-session repo).
 *      The BARRIER matters on RECONNECT (step 1, reading an EXISTING remote doc-shim);
 *      on first-login creation it is a no-op, so the pointer is published first.
 */
async function resolveShimDoc(): Promise<Nuri> {
  if (shimDocNuri) return shimDocNuri;
  if (shimDocInFlight) return shimDocInFlight;

  const p = (async (): Promise<Nuri> => {
    const existing = await resolvePointer();
    if (existing) {
      // Open the doc-shim through its first-`State` barrier BEFORE any account read,
      // so a cold 0 on the doc-shim is authoritative (genuinely absent), not sync-lag.
      await ensurePhysicalRepoOpen(existing);
      shimDocNuri = existing;
      logStage("resolveShimDoc → " + shortNuri(existing));
      return existing;
    }

    // FIRST login (no pointer): create the doc-shim (bootstrapped in-session), publish
    // the pointer, then open (no-op barrier for a just-created repo).
    const doc = await createDoc();
    await writePointer(doc);
    await ensurePhysicalRepoOpen(doc);
    shimDocNuri = doc;
    logStage("resolveShimDoc → " + shortNuri(doc));
    return doc;
  })();

  shimDocInFlight = p;
  try {
    return await p;
  } finally {
    shimDocInFlight = null;
  }
}

// --- shim load / account bootstrap ----------------------------------------

/**
 * Resolve ONE account by its shim key with a BOUNDED query — O(1), independent
 * of the number of accounts in the shim. This is the HOT-PATH lookup: it hits
 * the account record at its known subject (`accountSubject(id)`) directly in the
 * doc-shim, instead of scanning EVERY account like {@link loadShim}. Returns the
 * account's record or `null` if it does not exist yet.
 *
 * ── Barrier-AUTHORITATIVE (the reconnection fix) ────────────────────────────
 * The read targets the DOC-SHIM (`did:ng:o:...`), which resolveShimDoc opened
 * through its first-`State` barrier. So a cold 0 rows here is DEFINITIVE ("account
 * genuinely absent"), not ambiguous sync-lag — no account-level retry is needed or
 * used. This is what replaced the old `resolveAccountReliably` / `provisionRetry`
 * loop: the store-root ambiguity that forced the retry is gone once the read moves
 * behind the doc-shim barrier.
 *
 * Cached per account (in `accountCache`); a hit skips the query entirely, so
 * repeated resolves of the same account are free. `resetRegistryCache` clears it.
 */
export async function resolveAccount(id: string): Promise<AccountRecord | null> {
  const key = accountKey(id);
  const cached = accountCache.get(key);
  if (cached) return cached;

  const s = await session();
  const doc = await resolveShimDoc();
  // `subj` is already IRI-safe (accountSubject → escapeIri). The read is anchored to
  // the doc-shim's default graph (opened through its barrier by resolveShimDoc), so
  // it is authoritative. The query is bounded to this one subject.
  const subj = accountSubject(id);
  const query = `
    SELECT ?id ?docPublic ?docProtected ?docPrivate WHERE {
      <${subj}> a <${P.type}> ;
           <${P.id}> ?id ;
           <${P.docPublic}> ?docPublic ;
           <${P.docProtected}> ?docProtected ;
           <${P.docPrivate}> ?docPrivate .
    }`;
  try {
    const result = await physicalQuery(s.sessionId, query, undefined, doc, "resolveAccount");
    const rows = readBindings(result);
    if (rows.length === 0) {
      logStage("resolveAccount(" + key + ") → null");
      return null;
    }
    // DETERMINISTIC: a corrupted shim may return SEVERAL bindings for this one
    // account subject (duplicate scope-doc values from past forks). Pick the
    // canonical (lexicographically-smallest) doc per scope so writer and reader
    // always resolve the SAME docPublic (robustness against PAST fork residue).
    const record = recordFromRows(rows, id);
    accountCache.set(key, record);
    logStage("resolveAccount(" + key + ") → 1 record");
    return record;
  } catch (error) {
    console.error(accessLogPrefix() + " resolveAccount failed:", error);
    return null;
  }
}

/** Persist one AccountRecord into the doc-shim (anchored default-graph write, the
 *  canonical always-safe shape — same convention as createEntityDoc). */
async function writeRecord(doc: Nuri, record: AccountRecord): Promise<void> {
  const s = await session();
  const subj = `${SHIM}:account:${escapeIri(accountKey(record.id))}`;
  // `subj` is IRI-safe (escapeIri). `id` is UNTRUSTED text in a LITERAL position →
  // escapeLiteral. The doc NURIs come from `ng` but are stored as literals here, so
  // they are escaped as literals too (defence in depth). NO explicit `GRAPH <…>`
  // wrapper: write the anchored DEFAULT graph (the `doc` anchor scopes it) — the
  // canonical, always-safe shape the anchored default-graph read queries match.
  const update = `
    INSERT DATA {
      <${subj}> a <${P.type}> ;
        <${P.id}> "${escapeLiteral(record.id)}" ;
        <${P.docPublic}> "${escapeLiteral(record.docPublic)}" ;
        <${P.docProtected}> "${escapeLiteral(record.docProtected)}" ;
        <${P.docPrivate}> "${escapeLiteral(record.docPrivate)}" .
    }`;
  try {
    await physicalUpdate(s.sessionId, update, doc, "writeRecord");
  } catch (error) {
    console.error(accessLogPrefix() + " writeRecord persist failed:", error);
  }
}

/**
 * In-flight `ensureAccount` promises, keyed by account key — so CONCURRENT
 * `ensureAccount(id)` calls for the SAME account share ONE resolve-or-provision.
 *
 * ── Why this is load-bearing (concurrent-provision de-dup) ──────────────────
 * On a fresh page over the persistent wallet, SEVERAL independent callers hit
 * `ensureAccount(A)` near-simultaneously (watchShape public/protected, the container
 * subscriptions, the app's owned-events effect). With the barrier-authoritative
 * resolveAccount a fresh page NO LONGER mistakes sync-lag for absence — but if the
 * account is GENUINELY new, N concurrent callers would still each see 0 and each
 * provision a set of scope docs (an in-session fork). De-duping concurrent provisions
 * collapses those N into ONE: the first caller resolves-or-provisions; every
 * concurrent caller awaits the SAME promise and gets the SAME record. Not polling: a
 * bounded in-memory promise map (mirrors open-repo.ts `inFlight`), cleared the instant
 * it settles.
 */
const ensureInFlight = new Map<string, Promise<AccountRecord>>();

/**
 * Ensure an account exists in the shim, creating its 3 scope documents on
 * first sight. Idempotent — returns the existing record if already present.
 * Concurrency-safe: concurrent calls for the same account share one provision
 * (see {@link ensureInFlight}) so a fresh page never FORKS the account.
 */
export async function ensureAccount(id: string): Promise<AccountRecord> {
  const key = accountKey(id);
  // A completed provision/resolve is cached → no query, no fork risk.
  const cached = accountCache.get(key);
  if (cached) {
    fileOwnStructure(id, cached);
    return cached;
  }
  // A concurrent provision for the SAME account is already running → await it,
  // instead of racing a second (forking) provision. This is the anti-fork guard.
  const pending = ensureInFlight.get(key);
  if (pending) return pending;

  const p = (async (): Promise<AccountRecord> => {
    // HOT PATH: targeted O(1) lookup — does THIS account already exist? — instead
    // of a full-shim scan (loadShim). Off the read/write hot path entirely.
    //
    // Barrier-AUTHORITATIVE: resolveAccount reads the doc-shim behind its first-`State`
    // barrier (opened by resolveShimDoc), so a 0 here means the account is GENUINELY
    // absent — not sync-lag. No account-level retry: the store-root ambiguity that
    // forced the old provisionRetry loop is gone once the read moves behind the barrier.
    const existing = await resolveAccount(id);
    if (existing) {
      fileOwnStructure(id, existing);
      return existing;
    }

    const doc = await resolveShimDoc();
    const [docPublic, docProtected, docPrivate] = await Promise.all([
      createDoc(),
      createDoc(),
      createDoc(),
    ]);
    const record: AccountRecord = { id, docPublic, docProtected, docPrivate };
    // Persist the record INTO the doc-shim (not the store-root anymore).
    await writeRecord(doc, record);
    // Feed the per-account cache, and the full-shim cache if it is already loaded
    // (so allAccounts / the fan-out see the freshly-created account too).
    accountCache.set(key, record);
    fileOwnStructure(id, record);
    return record;
  })();

  ensureInFlight.set(key, p);
  try {
    return await p;
  } finally {
    ensureInFlight.delete(key);
  }
}

// --- resolvers ------------------------------------------------------------

/** The index document NURI of an account for a scope (the store-container). */
function storeOf(record: AccountRecord, scope: Scope): Nuri {
  return scope === "public"
    ? record.docPublic
    : scope === "protected"
    ? record.docProtected
    : record.docPrivate;
}

/**
 * NURI of the document where `id` writes GROUPED entities of `scope` (a single
 * per-scope index document, for entities that need no per-entity document / no
 * inbox). For per-entity scopes use {@link createEntityDoc} instead.
 */
export async function resolveWriteGraph(id: string, scope: Scope): Promise<Nuri> {
  const record = await ensureAccount(id);
  return storeOf(record, scope);
}

// --- SDK-shaped scope resolvers (no store-id ever leaves the lib) ----------
//
// The consumer asks by SCOPE ("give me the graph to write/read entities of
// scope X", "give me the inbox anchor") and NEVER constructs a `did:ng:${…}`
// store NURI itself. The lib owns the physical placement — which is the whole
// point of the SDK boundary. In THIS polyfill the placement is the shared
// wallet's native stores (Axis A, per the two-axes doctrine in
// docs/simulation.md): a scope maps to a native store NURI resolved from the
// injected session. `public` currently co-locates with `protected` because
// `doc_create`/ORM cannot target a non-private/protected native store today
// (the SDK blocker recorded in migration-guide.md); at migration each scope
// resolves to the user's REAL per-scope store and this mapping changes here,
// in the lib, with no consumer change.

/** The native store NURI backing `scope`, resolved from the injected session.
 *  Requires `protectedStoreId` on the session for the non-private scopes. */
async function scopeStoreNuri(scope: Scope): Promise<Nuri> {
  const s = await session();
  if (scope === "private") return `did:ng:${s.privateStoreId}`;
  // public + protected → the protected native store (see note above). Falls
  // back to the private store if the session didn't carry a protected id.
  const store = s.protectedStoreId ?? s.privateStoreId;
  return `did:ng:${store}`;
}

/**
 * The graph NURI where the current session WRITES entities of `scope`, and
 * whose repo `useShape` must subscribe to read them back. SDK-shaped: the
 * consumer passes a logical scope and gets an opaque graph NURI — it holds no
 * store-id and builds no NURI. Use the returned value as both the read scope
 * (`useShape(shape, nuri)`) and the `@graph` write target.
 */
export async function resolveScopeGraph(scope: Scope): Promise<Nuri> {
  return scopeStoreNuri(scope);
}

/**
 * In-flight `walletInbox` resolutions, keyed by account key — so concurrent callers
 * for the SAME wallet share ONE resolve-or-create instead of racing two documents
 * into existence (mirrors {@link ensureInFlight}).
 */
const inboxInFlight = new Map<string, Promise<Nuri>>();
/** Resolved wallet inboxes, keyed by account key. Cleared with the registry cache. */
const inboxCache = new Map<string, Nuri>();

/**
 * The NURI of a virtual user's OWN inbox — where deposits addressed to that
 * identity land, ReadCaps among them.
 *
 * ── Why a wallet owns an inbox, and why that is load-bearing ───────────────
 * You cannot discover in NextGraph; you can only follow links. So a link crosses
 * from one wallet to another through exactly one channel: a deposit into the
 * recipient's inbox. That makes the inbox the **bootstrap of the whole
 * reachability graph** rather than a side feature — and it is why an inbox has to
 * BELONG to someone. Before this existed, an inbox was any NURI a caller passed,
 * so "read the inbox" meant "read anyone's inbox", and since P1a routes caps
 * through it, reading someone else's collected the caps addressed to them.
 *
 * Created on first sight and stable thereafter. Recorded in the doc-shim under its
 * own predicate, read by its OWN query rather than added to the account SELECT: an
 * account record written before this existed must keep resolving, which it would
 * not if the fixed account pattern grew a fourth required field.
 *
 * Concurrency-safe (see {@link inboxInFlight}), and a fork is reconciled the same
 * content-addressed way as everything else ({@link canonicalDoc}).
 *
 * At migration this becomes the identity's native inbox and the resolution moves
 * here — the consumer-facing act (deposit to an inbox, process my own) is unchanged.
 */
export async function walletInbox(id: string): Promise<Nuri> {
  const key = accountKey(id);
  const cached = inboxCache.get(key);
  if (cached) {
    fileOwnInbox(id, cached);
    return cached;
  }
  const pending = inboxInFlight.get(key);
  if (pending) return pending;

  const p = (async (): Promise<Nuri> => {
    const s = await session();
    const shimDoc = await resolveShimDoc();
    await ensureAccount(id); // the account must exist before it can own an inbox
    const subj = accountSubject(id);
    try {
      // The doc-shim is machinery: this reads WHICH inbox a virtual user owns,
      // which is exactly the kind of question that cannot be confined to that user.
      const res = await physicalQuery(
        s.sessionId,
        `SELECT ?d WHERE { <${subj}> <${P.docInbox}> ?d }`,
        undefined,
        shimDoc,
        "walletInbox",
      );
      const existing = canonicalDoc(readBindings(res), "d");
      if (existing) {
        inboxCache.set(key, existing);
        fileOwnInbox(id, existing);
        return existing;
      }
    } catch (error) {
      console.error(accessLogPrefix() + " walletInbox read failed:", error);
    }

    const doc = await createDoc();
    fileOwnInbox(id, doc);
    try {
      await physicalUpdate(
        s.sessionId,
        `INSERT DATA { <${subj}> <${P.docInbox}> "${escapeLiteral(doc)}" }`,
        shimDoc,
        "walletInbox",
      );
    } catch (error) {
      console.error(accessLogPrefix() + " walletInbox persist failed:", error);
    }
    inboxCache.set(key, doc);
    logStage("walletInbox(" + key + ") → " + shortNuri(doc));
    return doc;
  })();

  inboxInFlight.set(key, p);
  try {
    return await p;
  } finally {
    inboxInFlight.delete(key);
  }
}

/**
 * Does `nuri` belong to the CURRENT wallet as one of its inboxes? The predicate the
 * inbox read guard consults (`inbox.ts`). Anonymous holds no inbox, so it is false
 * for everyone until an identity is set.
 */
export async function isOwnInbox(nuri: Nuri): Promise<boolean> {
  const holder = getCurrentUser();
  if (holder === null) return false;
  if ((await walletInbox(holder)) === nuri) return true;
  // …and the inbox of any document this user opened one on (the emulated
  // `AddInboxCap` records on its User branch).
  return (await readInboxCapPairs()).some((p) => p.inbox === nuri);
}

// --- the cap side of a user's store ----------------------------------

/**
 * File the caps of documents the CURRENT holder owns into what they hold — the
 * emulated `AddRepo { read_cap }`.
 *
 * Upstream, creating a document commits an `AddRepo { read_cap }` into a typed
 * branch of the store, and that branch — listing the store's documents, each with
 * its read key — carries the owner's caps. Here the per-(account × scope) index
 * document plays the store-container role, so it carries the caps too: a
 * document appended to it on creation, or read back from it on a later session,
 * puts its cap in the owner's hands with nothing for the consumer to do. That is
 * what makes the invariant hold both ways — you never derive a cap from a bare
 * reference, and yet a document's own creator is never locked out of it.
 *
 * Scoped to the current holder ON PURPOSE: another account's documents are listed
 * by the cross-account fan-out (`listEntityDocs`), and those caps are emphatically
 * not ours to hold. `id` is compared through the shim key, so it matches however
 * the consumer spells the identity.
 */
function holdOwnCap(id: string, scope: Scope, doc: Nuri, cap: ReadCap): void {
  const holder = getCurrentUser();
  if (holder === null || accountKey(holder) !== accountKey(id)) return;
  const caps = getCaps();
  // `learn(cap)`, not `open(doc, scope)` — the cap must be the SAME value that was
  // written to the Store branch, not a second one minted from the NURI. They agree
  // today only because the stand-in value is a constant; with a real key (P1b) a
  // second mint would produce a DIFFERENT key and the document would be unreadable
  // by the very session that created it. Mint once, store it, hold that one.
  caps.learn(cap);
  // Publication is a registry fact, not a stored one, so it is applied separately.
  if (scope === "public") caps.publishRepoLink(doc);
}

/**
 * File the caps of the documents a virtual user owns BY BEING one: its three
 * stores, and its inbox. They are as much its documents as any entity it creates,
 * and without them it cannot even list its own content — the boundary would lock a
 * user out of itself.
 *
 * Scoped to the current holder, like {@link holdOwnCap}: another user's stores are
 * emphatically not ours to hold.
 */
function fileOwnStructure(id: string, record: AccountRecord): void {
  const holder = getCurrentUser();
  if (holder === null || accountKey(holder) !== accountKey(id)) return;
  const caps = getCaps();
  if (record.docPublic) caps.open(record.docPublic, "public");
  if (record.docProtected) caps.open(record.docProtected, "protected");
  if (record.docPrivate) caps.open(record.docPrivate, "private");
}

/** Same, for the user's own inbox — it is its document, and it must be able to
 *  read it. Depositing into someone else's needs no cap (see `docs.depositInto`). */
function fileOwnInbox(id: string, inbox: Nuri): void {
  const holder = getCurrentUser();
  if (holder === null || accountKey(holder) !== accountKey(id)) return;
  getCaps().open(inbox, "private");
}

// --- per-entity documents + per-scope index -------------------------------

/**
 * Create a dedicated document for ONE entity — mirrors the target, where each
 * such entity is its own document/repo (addressable, future inbox). The new
 * document's NURI is appended to the account's scope index document (the
 * store-container). Returns the entity document NURI (use it as `@graph`) — a
 * CAP-LESS reference, exactly like `doc_create` upstream: it names the document,
 * it does not carry its key. The key goes to what the creator holds (see
 * {@link holdOwnCap}), which is where you look it up.
 */
export async function createEntityDoc(id: string, scope: Scope): Promise<Nuri> {
  const record = await ensureAccount(id);
  const indexDoc = storeOf(record, scope);
  const entityNuri = await createDoc();
  const s = await session();
  try {
    await sparqlUpdate(
      s.sessionId,
      // NO explicit `GRAPH <…>` wrapper: write the anchored DEFAULT graph (the
      // `indexDoc` anchor scopes it) — the CANONICAL, always-safe shape the
      // anchored default-graph read queries (readUserStore below, same as
      // read-model.ts). Not a round-trip necessity on the current broker: the e2e
      // harness (`packages/client/e2e/`) verified an anchored `GRAPH <plainNuri>`
      // write ALSO round-trips here (same repo graph, no phantom graph); no-GRAPH
      // is kept as a simplicity/safety convention. entityNuri is a NURI stored as
      // a literal → escapeLiteral.
      `INSERT DATA { <${MAIN_BRANCH_SUBJECT}> <${P.contains}> "${escapeLiteral(entityNuri)}" }`,
      indexDoc,
      "createEntityDoc",
    );
  } catch (error) {
    console.error(accessLogPrefix() + " createEntityDoc index append failed:", error);
  }
  // The second write: `AddRepo { read_cap }` on the Store branch. A separate
  // statement, not a second triple in the one above, because upstream these are two
  // commits on two branches — and because the cap must be recoverable even if the
  // listing write failed.
  //
  // One literal suffices: a ReadCap CARRIES its document (`targetOf`), so storing the
  // cap stores the pair.
  const cap = mintCap(entityNuri);
  try {
    await sparqlUpdate(
      s.sessionId,
      `INSERT DATA { <${STORE_BRANCH_SUBJECT}> <${P.readCap}> "${escapeLiteral(cap)}" }`,
      indexDoc,
      "createEntityDoc:addRepo",
    );
  } catch (error) {
    console.error(accessLogPrefix() + " createEntityDoc cap append failed:", error);
  }
  // …and the creator holds THAT cap for this session.
  holdOwnCap(id, scope, entityNuri, cap);
  // NO inbox here, and NOT the owner's own inbox published as this document's address.
  // Upstream an inbox belongs to exactly ONE repo: the verifier routes an incoming
  // message by `inboxes: PubKey → RepoId` (`engine/verifier/src/verifier.rs:1677,1928`)
  // and unseals it with THAT repo's private half, while `InboxMsgBody` carries no
  // target document at all (`engine/net/src/types.rs:4265`) — because it needs none,
  // the address IS the identification. Pointing several documents at one inbox would
  // emulate a many-to-one relation the model cannot express, and would teach consumers
  // to tag deposits with their document, a habit that has to be unlearned at migration.
  //
  // So a document gets an inbox only when its owner opens one
  // ({@link openDocumentInbox}), which is also what keeps the cost proportional: only
  // documents meant to RECEIVE pay for one (see
  // `docs/briefs/2026-08-03-document-inbox-addressing.md`).
  return entityNuri;
}

/**
 * Publish WHERE to deposit for `doc`, on its Header branch — the compartment any
 * holder of the document can read.
 *
 * Replacement, not addition: a document has exactly ONE inbox upstream (the verifier's
 * `inboxes: PubKey → RepoId` is a function, and `repo.inbox` a single `Option<PrivKey>`),
 * so two addresses on one document is a state the model has no meaning for — and a
 * depositor picking the stale one writes where nobody reads.
 */
async function publishInboxAddress(doc: Nuri, inbox: Nuri): Promise<void> {
  const s = await session();
  try {
    // Two separate updates, not one compound statement: `DELETE WHERE { … }` is the
    // form verified against the real broker (see
    // `docs/decisions/sparql-delete-for-orm-objects.md`), whereas a `;`-joined update
    // is not exercised anywhere in this lib.
    await sparqlUpdate(
      s.sessionId,
      `DELETE WHERE { <${HEADER_BRANCH_SUBJECT}> <${P.inboxAddress}> ?a }`,
      doc,
      "publishInboxAddress:clear",
    );
    await sparqlUpdate(
      s.sessionId,
      `INSERT DATA { <${HEADER_BRANCH_SUBJECT}> <${P.inboxAddress}> "${escapeLiteral(inbox)}" }`,
      doc,
      "publishInboxAddress",
    );
  } catch (error) {
    console.error(accessLogPrefix() + " publishInboxAddress failed:", error);
  }
}

/**
 * The ReadCaps recorded on a store's Store branch — its documents, each with its
 * key. The emulated replay of `AddRepo`, and the reason a fresh session recovers
 * what it owns without recomputing anything.
 */
async function readStoreCaps(storeDoc: Nuri): Promise<ReadCap[]> {
  const s = await session();
  const out: ReadCap[] = [];
  try {
    const res = await sparqlQuery(
      s.sessionId,
      `SELECT ?c WHERE { <${STORE_BRANCH_SUBJECT}> <${P.readCap}> ?c }`,
      undefined,
      storeDoc,
      "readStoreCaps",
    );
    for (const row of readBindings(res)) {
      const v = bindingValue(row, "c");
      if (v && hasReadCap(v)) out.push(v);
    }
  } catch (error) {
    console.error(accessLogPrefix() + " readStoreCaps failed:", error);
  }
  return out;
}

/** Read the entity-document NURIs contained in ONE scope index document. */
async function readUserStore(indexDoc: Nuri): Promise<Nuri[]> {
  const s = await session();
  const out: Nuri[] = [];
  // COLD-START heal (polyfill-era): on a fresh session over a persistent wallet the
  // scope-index repo (public OR protected — the protected one carries participations
  // and is the one that most often reads empty) is not yet in `self.repos`, so this
  // anchored read would return 0 NURIs → nothing gets listed → nothing gets
  // subscribed (the self-inflicted circularity). Open/subscribe the index repo ONCE
  // before reading it. Idempotent per session; no-op with the unit fake ng. See
  // open-repo.ts.
  await ensureRepoOpen(indexDoc);
  try {
    const res = await sparqlQuery(
      s.sessionId,
      // NO explicit `GRAPH <…>` clause — read the anchored DEFAULT graph (see
      // the note in createEntityDoc). The `indexDoc` anchor scopes the query.
      `SELECT ?e WHERE { <${MAIN_BRANCH_SUBJECT}> <${P.contains}> ?e }`,
      undefined,
      indexDoc,
      "readUserStore",
    );
    for (const row of readBindings(res)) {
      // SPARQL boundary again (see canonicalDoc): narrow, do not cast — a stored
      // value that is not a NextGraph reference is not an entity document.
      const v = bindingValue(row, "e");
      if (v && isNuri(v)) out.push(v);
    }
  } catch (error) {
    console.error(accessLogPrefix() + " readUserStore failed:", error);
  }
  logStage("readUserStore(" + shortNuri(indexDoc) + ") → " + out.length + " entities");
  return out;
}

/**
 * The scope-INDEX document NURI of ONE account (`id`) for `scope` — the
 * store-container document that LISTS the account's per-entity document NURIs
 * (what {@link listMyEntityDocs} reads). Exposed so a reactive reader
 * ({@link watchShape}) can SUBSCRIBE to this index document and re-resolve the
 * entity-doc set when the index changes (a new entity created appends a NURI
 * here). Idempotent via `ensureAccount`'s cache. At migration this becomes the
 * user's real per-scope store NURI (the container the store itself provides).
 */
export async function userStoreDoc(id: string, scope: Scope): Promise<Nuri> {
  const record = await ensureAccount(id);
  return storeOf(record, scope);
}

/**
 * The entity-document NURIs of `scope` belonging to ONE account (`id`) —
 * the read-by-need path for one account's own entities. Bounded to a SINGLE
 * account: it resolves only that account's scope index doc (via `ensureAccount`)
 * and reads the contained NURIs — NO cross-account fan-out, so it never touches
 * another account's unsynced docs. This is the helper a consumer application uses
 * for its own my-entities path, instead of the all-accounts `listEntityDocs`.
 */
/**
 * The inbox of a document this user owns — resolved, and created on first ask.
 *
 * Upstream a repo carries `inbox: Option<PrivKey>` (`engine/repo/src/repo.rs:126`):
 * an inbox is a keypair on the repo, whose PRIVATE half its owner holds. That half is
 * recorded with `AddInboxCap { repo_id, overlay, priv_key }` — *"into the user branch,
 * so that a user can share with all its device"* (`engine/repo/src/types.rs:1973`), the
 * same branch that carries `AddLink`. So "which inboxes may I read" is answered by the
 * User branch, and that is what this emulates.
 *
 * **The engine SUPPORTS this; nothing exercises it automatically.** Those are two
 * different statements, and conflating them is what made an earlier version of this
 * comment call the feature an "anticipation". It is not. `inbox: Option<PrivKey>` is a
 * field of EVERY `Repo` (`engine/repo/src/repo.rs:126`), not of a store structure;
 * `AddInboxCapV0` is keyed by `repo_id` (`engine/repo/src/types.rs:1973`); and
 * `update_inbox_cap_v0` applies it with `self.repos.get_mut(repo_id)` and **no
 * `is_store` check of any kind** (`engine/verifier/src/verifier.rs:1920`). Generic by
 * construction, and at any time (see the User-branch note above).
 *
 * What is true is narrower: no code path CREATES one for a document — `new_store_default`
 * attaches one only `if !private` (`verifier.rs:2994`), `doc_create` leaves `inbox: None`
 * (`repo.rs:574`), and the only two `AddInboxCap` commits in the engine are for the
 * public and protected STORE repos (`engine/verifier/src/site.rs:128,149`). So the
 * capability exists and is simply unexposed above level 1: this function is aligned on
 * the engine's model, it does not bet past it.
 *
 * Lazy on purpose, for the same reason: creating an inbox document for every entity up
 * front would double every `createEntityDoc` for inboxes most documents never receive
 * anything in. Upstream the keypair is cheap; here an inbox is a document, so it is
 * minted when first asked for.
 *
 * *(Not covered: ROTATING an inbox key — the engine's "update" case with a new
 * `priv_key`. This function is idempotent and returns the existing inbox instead. A
 * known limit, not an oversight.)*
 *
 * Only for a document this user OWNS — see {@link ownsDocument}. Opening an inbox on
 * someone else's document would be usurpation, not a courtesy: the opener keeps the
 * reading half, so it would silently divert to itself the deposits meant for the
 * owner. To deposit into someone else's document, resolve
 * {@link documentInboxAddress} and `inbox.post` into it.
 */
export async function openDocumentInbox(doc: Nuri): Promise<Nuri> {
  const holder = getCurrentUser();
  if (holder === null) throw new Error("[ng-eventually] openDocumentInbox: no identity is set");
  const known = (await readInboxCapsFor(doc)) ?? null;
  if (known) return known;

  // OWNERSHIP is the criterion, and holding a cap is NOT ownership — a cap can be
  // received. Opening an inbox is what PUBLISHES this document's address, so a
  // non-owner doing it would route the owner's deposits to itself, silently, on a
  // document it merely reads. Upstream the equivalent act is the owner committing
  // `AddInboxCap` with the repo's own key; nobody else can.
  if (!(await ownsDocument(doc))) {
    throw new Error(
      "[ng-eventually] openDocumentInbox: refused — you may only open an inbox on a document " +
        `you own. Deposit into its published address instead (storeRegistry.documentInboxAddress ` +
        `then inbox.post): ${JSON.stringify(doc)}`,
    );
  }

  const inbox = await createDoc();
  const s = await session();
  const record = await ensureAccount(holder);
  const store = record.docPrivate;
  getCaps().open(inbox, "private"); // its owner holds it, like any document of theirs
  if (store) {
    try {
      await sparqlUpdate(
        s.sessionId,
        `INSERT DATA { <${USER_BRANCH_SUBJECT}> <${P.inboxCap}> "${escapeLiteral(doc + " " + inbox)}" }`,
        store,
        "openDocumentInbox",
      );
    } catch (error) {
      console.error(accessLogPrefix() + " openDocumentInbox persist failed:", error);
    }
  }
  // …and the PUBLIC half, in the document itself, so a depositor can find it at all.
  // Without this the inbox is reachable only by its owner — the opposite of what an
  // inbox is for, and the bug this path shipped with.
  await publishInboxAddress(doc, inbox);
  return inbox;
}

/**
 * WHERE to deposit for `doc` — its inbox address, or `undefined` if its owner never
 * opened one. The deposit-side counterpart of {@link openDocumentInbox}, and the
 * function an app calls before `inbox.post`.
 *
 * Readable by whoever can read the document, because it lives on its Header branch —
 * an address is public by nature (upstream a depositor needs only the inbox PUBLIC
 * key). Conversely someone who cannot read the document learns nothing, which is
 * faithful too: upstream the inbox pubkey is not derivable from a RepoId, it has to
 * reach you.
 *
 * **Never creates.** Asking where to deposit must not bring an inbox into existence —
 * only its owner opens one, and only on its own document.
 */
export async function documentInboxAddress(doc: Nuri): Promise<Nuri | undefined> {
  // RULE 2 — do not even attempt. Not holding the document, we have no address to
  // find: upstream the inbox pubkey travels WITH what you can read, so "where do I
  // deposit for a document I cannot read" is not a refused question, it is a question
  // with no referent. Answering `undefined` here keeps the caller's shape (an address
  // or none) instead of turning the boundary into an exception it must catch.
  if (mustNotAttempt(doc)) return undefined;
  const s = await session();
  try {
    const res = await sparqlQuery(
      s.sessionId,
      `SELECT ?a WHERE { <${HEADER_BRANCH_SUBJECT}> <${P.inboxAddress}> ?a }`,
      undefined,
      doc,
      "documentInboxAddress",
    );
    for (const row of readBindings(res)) {
      const a = bindingValue(row, "a");
      if (a && isNuri(a)) return a;
    }
  } catch (error) {
    // Unreadable document (no cap) or not synced → no address to give. Refusing to
    // read is the boundary doing its job, not an error to propagate here.
    console.error(accessLogPrefix() + " documentInboxAddress failed:", error);
  }
  return undefined;
}

/**
 * Does the connected user own `doc`? Answered from its **Store branches** — the
 * register of the documents it created — across the three scopes, which is the only
 * place that records authorship. Holding a cap is NOT ownership: a cap can be
 * received, and a recipient must not be able to open an inbox on what it merely reads.
 */
async function ownsDocument(doc: Nuri): Promise<boolean> {
  const holder = getCurrentUser();
  if (holder === null) return false;
  const record = await resolveAccount(holder);
  if (record === null) return false;
  for (const scope of ["public", "protected", "private"] as const) {
    const store = storeOf(record, scope);
    if (!store) continue;
    if ((await readUserStore(store)).includes(doc)) return true;
  }
  return false;
}

/** The `(document, inbox)` pairs recorded on this user's User branch. */
async function readInboxCapPairs(): Promise<Array<{ doc: Nuri; inbox: Nuri }>> {
  const holder = getCurrentUser();
  if (holder === null) return [];
  const record = await resolveAccount(holder);
  const store = record?.docPrivate;
  if (!store) return [];
  const s = await session();
  const out: Array<{ doc: Nuri; inbox: Nuri }> = [];
  try {
    const res = await sparqlQuery(
      s.sessionId,
      `SELECT ?c WHERE { <${USER_BRANCH_SUBJECT}> <${P.inboxCap}> ?c }`,
      undefined,
      store,
      "readInboxCaps",
    );
    for (const row of readBindings(res)) {
      const [doc, inbox] = bindingValue(row, "c").split(" ");
      if (doc && inbox && isNuri(doc) && isNuri(inbox)) out.push({ doc, inbox });
    }
  } catch (error) {
    console.error(accessLogPrefix() + " readInboxCaps failed:", error);
  }
  return out;
}

/** The inbox recorded for one document, if this user opened one. */
async function readInboxCapsFor(doc: Nuri): Promise<Nuri | undefined> {
  return (await readInboxCapPairs()).find((p) => p.doc === doc)?.inbox;
}

/**
 * Every inbox this user may READ: its own, plus one per document it opened an
 * inbox on. What `connect.connectedUser` drains, and what `isOwnInbox` answers from.
 */
export async function myInboxes(): Promise<Nuri[]> {
  const holder = getCurrentUser();
  if (holder === null) return [];
  const out: Nuri[] = [];
  if ((await resolveAccount(holder)) !== null) out.push(await walletInbox(holder));
  for (const { inbox } of await readInboxCapPairs()) out.push(inbox);
  return out;
}

/**
 * File a cap received for someone ELSE's document — the emulated
 * `AddLink { read_cap }` on the User branch of the current user's private store.
 *
 * This is what makes a received cap DURABLE. Before it, a shared document survived
 * only by re-reading the inbox every session, which uses a queue as a database:
 * upstream an inbox is consumed, and processing a message *applies* it. Applying a
 * Link means writing it here.
 *
 * Idempotent — re-applying the same Link is a no-op, so re-processing an inbox
 * (a second tab, a reconnect) costs nothing.
 */
export async function addLink(cap: ReadCap): Promise<void> {
  const holder = getCurrentUser();
  if (holder === null) return;
  const record = await ensureAccount(holder);
  const store = record.docPrivate;
  if (!store) return;
  if ((await readLinks()).includes(cap)) return;
  const s = await session();
  try {
    await sparqlUpdate(
      s.sessionId,
      `INSERT DATA { <${USER_BRANCH_SUBJECT}> <${P.link}> "${escapeLiteral(cap)}" }`,
      store,
      "addLink",
    );
  } catch (error) {
    console.error(accessLogPrefix() + " addLink failed:", error);
  }
}

/**
 * The caps this user has received and applied — the User branch read back. Called
 * at connection to restore what was shared with them, without touching any inbox.
 */
export async function readLinks(): Promise<ReadCap[]> {
  const holder = getCurrentUser();
  if (holder === null) return [];
  const record = await ensureAccount(holder);
  const store = record.docPrivate;
  if (!store) return [];
  const s = await session();
  const out: ReadCap[] = [];
  await ensureRepoOpen(store);
  try {
    const res = await sparqlQuery(
      s.sessionId,
      `SELECT ?c WHERE { <${USER_BRANCH_SUBJECT}> <${P.link}> ?c }`,
      undefined,
      store,
      "readLinks",
    );
    for (const row of readBindings(res)) {
      const v = bindingValue(row, "c");
      if (v && hasReadCap(v)) out.push(v);
    }
  } catch (error) {
    console.error(accessLogPrefix() + " readLinks failed:", error);
  }
  return out;
}

export async function listMyEntityDocs(id: string, scope: Scope): Promise<Nuri[]> {
  const record = await ensureAccount(id);
  const store = storeOf(record, scope);
  const docs = await readUserStore(store);
  // Recover the caps by READING the Store branch, never by recomputing them from
  // the NURIs — that is the whole point of storing them. A fresh session gets back
  // exactly what was recorded, and the day the stand-in value becomes a real key
  // (P1b) this path needs no change at all.
  //
  // Scoped to the current holder: another user's store caps are not ours to hold.
  const holder = getCurrentUser();
  if (holder !== null && accountKey(holder) === accountKey(id)) {
    const caps = getCaps();
    for (const cap of await readStoreCaps(store)) caps.learn(cap);
    // A `public` store's documents are also published links — the publication fact
    // lives in the registry, not in the store, so it is re-applied here.
    if (scope === "public") for (const d of docs) caps.publishRepoLink(d);
  }
  return docs;
}