/**
 * Thin wrapper around @bokuweb/zstd-wasm that defers WASM load until the
 * first compress/decompress call and memoises the init promise.
 *
 * The WASM binary lives alongside the package's ESM entrypoint, so Vite's
 * default asset handling picks it up. The extension's CSP already allows
 * `wasm-unsafe-eval` for the existing hash-wasm Argon2id module.
 */

import {
  compress as zstdCompress,
  decompress as zstdDecompress,
  init as zstdInit,
} from "@bokuweb/zstd-wasm";
import { IMPORT_LIMITS, importTooLarge } from "../shared/import-limits";

let initPromise: Promise<void> | null = null;

function ensureInit(): Promise<void> {
  if (!initPromise) {
    initPromise = zstdInit().catch((err) => {
      initPromise = null;
      throw err;
    });
  }
  return initPromise;
}

/** Compress bytes with zstd at the given level (default 19 per spec §4.1). */
export async function compressZstd(bytes: Uint8Array, level = 19): Promise<Uint8Array> {
  await ensureInit();
  return zstdCompress(bytes, level);
}

/**
 * Decompress a zstd frame. Throws if the frame is malformed or if the
 * output exceeds IMPORT_LIMITS.MAX_DECOMPRESSED_BYTES (MV-4 — @bokuweb/
 * zstd-wasm materialises the whole output, so the post-hoc check is the
 * strongest available here; callers must ALSO bound the declared length
 * before calling).
 */
export async function decompressZstd(bytes: Uint8Array): Promise<Uint8Array> {
  await ensureInit();
  const out = zstdDecompress(bytes);
  if (out.byteLength > IMPORT_LIMITS.MAX_DECOMPRESSED_BYTES) {
    throw importTooLarge(
      `decompressed payload ${out.byteLength} bytes exceeds ${IMPORT_LIMITS.MAX_DECOMPRESSED_BYTES}`,
    );
  }
  return out;
}