/**
 * The contract between the application page and the suite that drives it.
 *
 * It is declared ONCE and imported by both sides — `indexing-app.ts` implements it,
 * `run.ts` calls it — so a method that changes shape breaks the typecheck instead of
 * failing at run time inside a browser, where the only symptom would be `undefined is
 * not a function` three minutes into a broker crossing.
 *
 * Everything crossing `frame.evaluate` must be structured-cloneable, which is why every
 * member below takes and returns plain strings, numbers and object literals. A `Nuri` is
 * a template-literal string type upstream (`did:ng:${string}`), so it crosses as itself;
 * it is declared `string` here because a value that has been through structured clone
 * carries no proof of its shape, and pretending otherwise is how an unvalidated string
 * ends up typed as a reference.
 */

import type { UnionSubject } from "@ng-eventually/polyfill";

/**
 * One entry, as THIS APPLICATION decodes one out of the index document.
 *
 * It is declared here and not imported, because `@ng-helpers/indexing` publishes no
 * such type and no call that produces one: an index is an ordinary document, so its
 * contents are whatever `readUnion` hands back, read with the two published IRIs.
 * A subject carrying several values shows up as several rows — the document's own
 * truth, and the application's business to make something of.
 */
export interface IndexRow {
  readonly object: string;
  readonly value: string;
}

/** What the leak probe observed — see `run.ts`'s last journey. */
export interface BrokenInboxOutcome {
  /** The message `create` rejected with, or `null` if it did not reject. */
  readonly rejected: string | null;
  /** What `create` returned, on the impossible branch where it did not reject. */
  readonly returned: string | null;
  /** The documents that appeared in this identity's public store despite the failure. */
  readonly appeared: readonly string[];
}

/**
 * What one anchored SPARQL SELECT answered — or how it failed.
 *
 * The three fields are kept apart deliberately. "Nothing came back" and "the call failed"
 * are different answers, and a shape that folded them together would let a failure read as
 * an empty index — the defect class this repository keeps finding. `raw` carries the answer
 * BEFORE anything here decodes it, so a decoder that is wrong about the result's shape
 * cannot pass its own blindness off as a query that returned nothing.
 */
export interface SelectOutcome {
  /** The message the query rejected with, or `null` when it returned. */
  readonly failed: string | null;
  /** Whatever came back, rendered as JSON — the answer before any decoding of it. */
  readonly raw: string;
  /** The SELECT's bindings, decoded to plain `variable → value` rows. */
  readonly rows: ReadonlyArray<Readonly<Record<string, string>>>;
}

/**
 * The acts this application can perform — and ONLY acts an application can perform.
 *
 * There is no back door onto the library's internals here. The one method that is not
 * something an application does (`createIndexWithBrokenInbox`) injects a failure and is
 * named for it, because the alternative — leaving the question unanswered — is worse
 * than a probe that says what it is.
 */
export interface IndexingBridge {
  /** `connecting` → `ready`, or `failed`. */
  status(): string;
  /** Why the boot failed, or `null`. */
  error(): string | null;
  /** Who this page signed in as. */
  whoami(): string;
  /**
   * The index this deployment was BUILT to contribute to, read off its own configuration.
   *
   * An index is an ordinary document; what makes it an index is that an application
   * references its NURI in its own source (`src/indexing.ts`). This page is configured
   * through its URL rather than through a compiled-in constant, which is the same thing
   * one build step earlier — and it is how the reference reaches a SECOND identity
   * without the suite handing it over through a variable no application would have.
   */
  configuredIndex(): string | null;

  /** Create an index in this identity's public store, indexing by `field`. */
  createIndex(field: string): Promise<string>;
  /** Publish a public document carrying one value for one predicate. */
  publishObject(predicate: string, value: string): Promise<string>;
  /** Hand the CONFIGURED index a reference to an object. Anyone may. */
  addToConfigured(object: string): Promise<void>;
  /** Hand a NAMED index a reference — used where no identity boundary is crossed. */
  addTo(index: string, object: string): Promise<void>;
  /**
   * Obtain a fresh `Indexing` handle, which is what a page load does.
   *
   * It reaches NOTHING — a handle is a session id and two acts, and building one talks
   * to nobody. That is precisely what one journey asserts: taking a handle again changes
   * nothing an index holds. It is NOT a settle point and cannot be used as one; what a
   * journey waits on after a deposit is the INDEX, read like any other document (`run.ts`,
   * `settled`).
   */
  rebuildHandle(): Promise<void>;
  /**
   * The index's entries, ordered by value — decoded BY THIS APPLICATION, out of an
   * ordinary `readUnion` of the index document, with nothing from the library but the
   * two IRIs it publishes. That the suite can do this at all is the claim under test.
   */
  read(index: string): Promise<IndexRow[]>;

  /** What a document literally holds, straight off `readUnion` — the write-form probe. */
  readRaw(doc: string): Promise<UnionSubject[]>;
  /**
   * Run a SPARQL SELECT anchored on a document, through `docs.sparqlQuery`.
   *
   * An index is claimed to be an ORDINARY document, which means an ordinary query must
   * reach it. Nothing in `src/` ever issues one — this layer composes SPARQL only to
   * write — so this is the one act here that no code of this package performs, and it is
   * on the bridge because the claim had never been measured against a broker.
   */
  select(anchor: string, query: string): Promise<SelectOutcome>;
  /** This identity's public documents. How an owner discovers a document it did not keep. */
  listPublicDocs(): Promise<string[]>;

  /**
   * `create` with its inbox step made to fail — everything else real, against the
   * real broker. Answers whether a half-created index is left behind.
   */
  createIndexWithBrokenInbox(field: string): Promise<BrokenInboxOutcome>;
}

declare global {
  interface Window {
    __indexing: IndexingBridge;
  }
}