import { Db, Document, MongoServerError } from "mongodb";
import { getDb } from "../index";
import {
  MUNI_ISSUES_COLLECTION,
  NAMESPACE_EXISTS,
  VALIDATION_LEVEL,
  VALIDATION_ACTION,
} from "./muniIssues.constants";
import { muniIssuesIndexes, muniIssuesJsonSchema } from "./muniIssues.schema";

const applyValidator = (db: Db, validator: Document): Promise<unknown> =>
  db.command({
    collMod: MUNI_ISSUES_COLLECTION,
    validator,
    validationLevel: VALIDATION_LEVEL,
    validationAction: VALIDATION_ACTION,
  });

// Provisions validator and indexes: createCollection first, collMod if already exists.
export const ensureMuniIssuesCollection = async (): Promise<void> => {
  const db = getDb();
  const validator = { $jsonSchema: muniIssuesJsonSchema };

  const existing = await db
    .listCollections({ name: MUNI_ISSUES_COLLECTION })
    .toArray();

  if (existing.length === 0) {
    try {
      await db.createCollection(MUNI_ISSUES_COLLECTION, {
        validator,
        validationLevel: VALIDATION_LEVEL,
        validationAction: VALIDATION_ACTION,
      });
    } catch (err) {
      // NamespaceExists race: collection exists — apply validator via collMod.
      if (err instanceof MongoServerError && err.code === NAMESPACE_EXISTS) {
        await applyValidator(db, validator);
      } else {
        throw err;
      }
    }
  } else {
    await applyValidator(db, validator);
  }

  await db.collection(MUNI_ISSUES_COLLECTION).createIndexes(muniIssuesIndexes);
};

// Per-Db cache so each test's in-memory Db re-provisions.
const provisioningByDb = new WeakMap<Db, Promise<void>>();

// Once per Db; evicts failed run so the next call retries.
export const ensureMuniIssuesCollectionOnce = (): Promise<void> => {
  const db = getDb();
  let provisioning = provisioningByDb.get(db);
  if (!provisioning) {
    provisioning = ensureMuniIssuesCollection().catch((err) => {
      provisioningByDb.delete(db);
      throw err;
    });
    provisioningByDb.set(db, provisioning);
  }
  return provisioning;
};