// Page-side handle to the vault worker. Every VaultCore method (and the free functions) becomes an
// async call into the worker; errors come back as `CoreError`s with the same `code`s.
//
//   import { connectVault } from "@kestrove/core/client.js";
//   const vault = await connectVault();          // IndexedDB "kestrove"
//   if (!(await vault.hasAccount())) { ... }
//   await vault.unlock(password, secretKey);     // Argon2id runs in the worker
//   const items = await vault.listItems();

export async function connectVault(options = {}) {
  const worker =
    options.worker ?? new Worker(new URL("./worker.js", import.meta.url), { type: "module", name: "kestrove-vault" });
  let next = 1;
  const pending = new Map();

  worker.onmessage = ({ data: { id, ok, err } }) => {
    const p = pending.get(id);
    if (!p) return;
    pending.delete(id);
    if (err) p.reject(Object.assign(new Error(err.message), err));
    else p.resolve(ok);
  };
  worker.onerror = (event) => {
    const e = Object.assign(new Error(event.message || "vault worker failed"), { name: "CoreError", code: "Internal" });
    for (const p of pending.values()) p.reject(e);
    pending.clear();
  };

  const call = (method, args) =>
    new Promise((resolve, reject) => {
      const id = next++;
      pending.set(id, { resolve, reject });
      worker.postMessage({ id, method, args });
    });

  try {
    await call("open", [options.dbName ?? null, Boolean(options.inMemory)]);
  } catch (e) {
    worker.terminate(); // e.g. "InUse": the vault is open in another tab
    throw e;
  }

  const handle = {
    /** Frees the core, releases the tab lock and stops the worker (key material goes with it). */
    async close() {
      try {
        await call("close", []);
      } finally {
        worker.terminate();
      }
    },
  };
  return new Proxy(handle, {
    get(target, prop) {
      if (prop in target) return target[prop];
      if (typeof prop !== "string" || prop === "then") return undefined;
      return (...args) => call(prop, args);
    },
  });
}