// src/init/initializeDuckDb.ts

import * as duckdb from "@duckdb/duckdb-wasm";
import { AsyncDuckDB, type DuckDBConfig } from "@duckdb/duckdb-wasm";
import { logElapsedTime } from "../util/perf";

export let DEBUG: boolean | undefined;

let DB: Promise<AsyncDuckDB> | undefined;

/**
 * Initialize DuckDB, ensuring we only initialize it once.
 *
 * @param debug If true, log DuckDB logs and elapsed times to the console.
 * @param config An optional DuckDBConfig object.
 */
export default async function initializeDuckDb(options?: {
  debug?: boolean;
  config?: DuckDBConfig;
}): Promise<AsyncDuckDB> {
  const { debug = false, config } = options || {};
  DEBUG = debug;

  if (DB === undefined) {
    DB = _initializeDuckDb(config);
  }
  return DB;
}

/**
 * Initialize DuckDB with a browser-specific Wasm bundle.
 */
const _initializeDuckDb = async (config?: DuckDBConfig): Promise<AsyncDuckDB> => {
  const start = performance.now();

  // Select a bundle based on browser checks
  const JSDELIVR_BUNDLES = duckdb.getJsDelivrBundles();
  const bundle = await duckdb.selectBundle(JSDELIVR_BUNDLES);

  const worker_url = URL.createObjectURL(
    new Blob([`importScripts("${bundle.mainWorker!}");`], {
      type: "text/javascript",
    }),
  );

  // Instantiate the async version of DuckDB-wasm
  const worker = new Worker(worker_url);
  const logger = DEBUG ? new duckdb.ConsoleLogger() : new duckdb.VoidLogger();
  const db = new AsyncDuckDB(logger, worker);
  await db.instantiate(bundle.mainModule, bundle.pthreadWorker);
  URL.revokeObjectURL(worker_url);

  if (config) {
    if (config.path) {
      const res = await fetch(config.path);
      const buffer = await res.arrayBuffer();
      const fileNameMatch = config.path.match(/[^/]*$/);
      if (fileNameMatch) {
        config.path = fileNameMatch[0];
      }
      await db.registerFileBuffer(config.path, new Uint8Array(buffer));
    }
    await db.open(config);
  }

  if (DEBUG) {
    logElapsedTime("DuckDB initialized", start);
    if (config) {
      console.debug(`DuckDbConfig: ${JSON.stringify(config, null, 2)}`);
    }
  }
  return db;
};

/**
 * Get the instance of DuckDB, initializing it if needed.
 *
 * Typically `useDuckDB` is used in React components instead, but this
 * method provides access outside of React contexts.
 */
export const getDuckDB = async (): Promise<AsyncDuckDB> => {
  if (DB) {
    return DB;
  }
  return await initializeDuckDb();
};