/**
 * Document service — registers ingested documents and emits the §4 events.
 *
 * The ingest pipeline (`src/source/pdf/ingest.ts`) is a pure function over
 * bytes — it does not touch the engine. The app composition root calls
 * `ingestPdf` then hands the result to `documentService.register()`, which
 * is where the engine takes over: persist into the repos, emit
 * `DocumentImported` + `DocumentRepresentationGenerated`.
 */

import type { Document, DocumentRepresentation } from "@shared/document";
import type { DocumentId, RepresentationId } from "@shared/ids";

import type { EventBus } from "../events";
import type { DocumentRepository, RepresentationRepository } from "../repos";

export interface DocumentService {
  register(input: {
    readonly document: Document;
    readonly representation: DocumentRepresentation;
  }): { readonly document: Document; readonly representation: DocumentRepresentation };
  get(id: DocumentId): Document | null;
  list(): readonly Document[];
  getRepresentation(id: RepresentationId): DocumentRepresentation | null;
  listRepresentations(documentId: DocumentId): readonly DocumentRepresentation[];
}

export function createDocumentService(
  documents: DocumentRepository,
  representations: RepresentationRepository,
  bus: EventBus,
): DocumentService {
  return {
    register({ document, representation }) {
      const storedDocument = documents.create(document);
      const storedRepresentation = representations.create(representation);
      bus.emit({
        type: "DocumentImported",
        documentId: storedDocument.id,
        document: storedDocument,
      });
      bus.emit({
        type: "DocumentRepresentationGenerated",
        documentId: storedDocument.id,
        representationId: storedRepresentation.id,
        representation: storedRepresentation,
      });
      return { document: storedDocument, representation: storedRepresentation };
    },
    get(id) {
      return documents.get(id);
    },
    list() {
      return documents.list();
    },
    getRepresentation(id) {
      return representations.get(id);
    },
    listRepresentations(documentId) {
      return representations.listByDocument(documentId);
    },
  };
}