/**
 * Inbox — the ONE deposit + materialization mechanism, reused for BOTH meeting-
 * point registration AND submission to the discovery index (see the discovery-
 * model decision: same `inbox.post` API, same watcher). GENERIC by construction:
 * this module knows no application domain (no meeting-point, no notification).
 * The consumer supplies the inbox document NURI and interprets the `payload`.
 *
 * ── TARGET vs POLYFILL ────────────────────────────────────────────────────
 * Target: `post` seals a reference into the inbox owner's native inbox
 * (`ng.inbox_post_link(...)`), and a SEPARATE curator process (the deferred
 * `@ng-eventually/service` package) MATERIALIZES the deposits into the owned
 * document. Here, in the shared-wallet polyfill (everything is readable),
 * both sides are emulated in-lib:
 *   - `post` appends a deposit `{ from, payload, ts }` as RDF into the inbox
 *     DOCUMENT (in the shared wallet) via the `docs.sparqlUpdate` primitive;
 *   - `read` / `watch` play the CURATOR: they read the deposits back via
 *     `docs.sparqlQuery` and expose them. This in-client emulation is enough
 *     for the polyfill — at migration the real materialization moves to the
 *     separate curator and this read side goes away.
 *
 * All NextGraph I/O routes through the T01.a `docs` primitives (the REAL
 * injected `ng`, never `makeNg`), so this module imports NO `@ng-org` package.
 */

import { sparqlUpdate, sparqlQuery } from "./docs";
import { getCurrentUser, getStoreRegistryDeps } from "./polyfill";
import { escapeLiteral } from "./sparql";
import type { Nuri, PrincipalId } from "./types";

// --- deposit model --------------------------------------------------------

/** One deposit as materialized from an inbox document. */
export interface Deposit {
  /** The sender, if identified; `null` when the deposit was anonymous. */
  from: PrincipalId | null;
  /** The consumer-defined payload (opaque here — JSON-serialized in storage). */
  payload: unknown;
  /** Deposit timestamp (ms epoch). Caller may pass one for determinism. */
  ts: number;
}

/** Options for {@link post}. `from` and `ts` are both optional. */
export interface PostOptions {
  /**
   * Who is depositing. Omit (or pass `null`) for an ANONYMOUS deposit; pass a
   * principal id to identify the sender. Defaults to the current polyfill user
   * ({@link getCurrentUser}) when the property is entirely absent, so callers
   * that want anonymity must pass `from: null` explicitly.
   */
  from?: PrincipalId | null;
  /** The payload to deposit (interpreted only by the consumer). */
  payload: unknown;
  /** Optional deposit timestamp (ms epoch). Omitted → `Date.now()`. Passing it
   *  keeps tests deterministic. */
  ts?: number;
}

const SHIM = "urn:ng-eventually:inbox";
const P = {
  type: `${SHIM}:Deposit`,
  from: `${SHIM}:from`,
  payload: `${SHIM}:payload`,
  ts: `${SHIM}:ts`,
} as const;

// --- session access (shared with the storeRegistry) -----------------------

/** The inbox documents live in the shared wallet, so we reuse the registry's
 *  injected session provider for the sessionId. Disappears at migration. */
async function sessionId(): Promise<string> {
  return (await getStoreRegistryDeps().getSession()).sessionId;
}

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

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

// --- deposit (client side) ------------------------------------------------

/**
 * Deposit a payload into `targetInbox`.
 *
 * Appends `{ from, payload, ts }` into the inbox document via `docs.sparqlUpdate`
 * (the real injected `ng`). Each deposit is a fresh RDF subject in the inbox
 * graph, so concurrent deposits don't collide.
 *
 * `from` is BOUND TO THE CURRENT IDENTITY — it is authenticated, not
 * caller-supplied. Omit it to stamp the current user; pass `null` to deposit
 * ANONYMOUSLY (a legitimate choice — "identified if known, anonymous otherwise").
 * A `from` naming ANOTHER principal is a SPOOF and is REJECTED: in the target the
 * broker seals the sender from the wallet's own key, so a client cannot forge
 * another's identity. (At migration this check is redundant — the seal enforces
 * it — but until then it closes the spoof the shared wallet would otherwise allow.)
 */
export async function post(targetInbox: Nuri, opts: PostOptions): Promise<void> {
  const current = getCurrentUser();
  let from: PrincipalId | null;
  if (opts.from === undefined) {
    from = current; // default: stamp the current identity
  } else if (opts.from === null) {
    from = null; // explicit anonymous deposit
  } else if (opts.from === current) {
    from = opts.from; // identifying as self — allowed
  } else {
    throw new Error(
      "[ng-eventually] inbox.post: `from` must be the current identity or null " +
        "(anonymous) — depositing as another principal is a spoof.",
    );
  }
  const ts = opts.ts ?? Date.now();
  const sid = await sessionId();

  // A unique subject per deposit (in the inbox graph) — no collisions.
  const subject = `${SHIM}:deposit:${ts}:${Math.random().toString(36).slice(2)}`;
  const payloadLiteral = escapeLiteral(JSON.stringify(opts.payload ?? null));
  const fromTriple =
    from == null ? "" : ` ;\n        <${P.from}> "${escapeLiteral(from)}"`;

  const update = `
    INSERT DATA {
      GRAPH <${targetInbox}> {
        <${subject}> a <${P.type}> ;
        <${P.payload}> "${payloadLiteral}" ;
        <${P.ts}> "${ts}"${fromTriple} .
      }
    }`;
  await sparqlUpdate(sid, update, targetInbox);
}

// --- read / materialize (emulated curator) --------------------------------

/**
 * Read (materialize) every deposit currently in `targetInbox`, sorted by `ts`
 * ascending. This is the EMULATED CURATOR: at migration a separate curator
 * process materializes deposits and this in-client read goes away. The consumer
 * interprets each deposit's `payload`.
 */
export async function read(targetInbox: Nuri): Promise<Deposit[]> {
  const sid = await sessionId();
  const query = `
    SELECT ?payload ?ts ?from WHERE {
      GRAPH <${targetInbox}> {
        ?d a <${P.type}> ;
           <${P.payload}> ?payload ;
           <${P.ts}> ?ts .
        OPTIONAL { ?d <${P.from}> ?from }
      }
    }`;
  const result = await sparqlQuery(sid, query, undefined, targetInbox);
  const deposits: Deposit[] = [];
  for (const row of readBindings(result)) {
    const rawPayload = row.payload?.value ?? "null";
    let payload: unknown;
    try {
      payload = JSON.parse(rawPayload);
    } catch {
      payload = rawPayload; // tolerate a non-JSON literal
    }
    const tsRaw = row.ts?.value ?? "0";
    const ts = Number.parseInt(tsRaw, 10) || 0;
    const fromValue = row.from?.value;
    deposits.push({ from: fromValue ? fromValue : null, payload, ts });
  }
  deposits.sort((a, b) => a.ts - b.ts);
  return deposits;
}

/** Alias for {@link read} — the name that reads as "run the curator now". */
export const materialize = read;

/**
 * Subscription over an inbox — the emulated watcher. Polls {@link read} on an
 * interval and invokes `onDeposits` with the full current deposit list whenever
 * it changes (grows). Returns an unsubscribe function. The polyfill has no
 * native reactive inbox subscription, so this emulates one; at migration it is
 * replaced by the real curator's watch. `onDeposits` fires once immediately.
 */
export function watch(
  targetInbox: Nuri,
  onDeposits: (deposits: Deposit[]) => void,
  opts?: { intervalMs?: number },
): () => void {
  let stopped = false;
  let lastCount = -1;
  const intervalMs = opts?.intervalMs ?? 1000;

  const tick = async (): Promise<void> => {
    if (stopped) return;
    try {
      const deposits = await read(targetInbox);
      if (!stopped && deposits.length !== lastCount) {
        lastCount = deposits.length;
        onDeposits(deposits);
      }
    } catch (error) {
      console.error("[inbox] watch read failed:", error);
    }
  };

  void tick(); // fire once immediately
  const handle = setInterval(() => void tick(), intervalMs);
  return () => {
    stopped = true;
    clearInterval(handle);
  };
}