/**
 * What differs between running in a browser and running as an installed app.
 *
 * The interface is the same code either way — that is the whole reason Electron
 * was chosen over a shell that replaces the engine (docs/desktop-client-v1.md
 * §2). What genuinely differs is small and lives here:
 *
 *   · **where the hub is.** Served from the hub, it is the current origin. Ship
 *     the interface in a package and it becomes a configured URL, because the
 *     page is loaded from disk and has no hub origin of its own.
 *   · **where a downloaded file goes**, and whether a native dialog picks it.
 *   · **what the app can do at all** — managing a local node, choosing folders
 *     on this machine. Features gated on these render nowhere in a browser
 *     rather than failing when clicked.
 *
 * The browser implementation below is exactly today's behaviour, so nothing
 * changes for anyone until an app is installed. That is the acceptance
 * criterion for this split: **the browser SPA behaves identically.**
 *
 * The native side arrives through `window.meshbay`, which the Electron preload
 * exposes over a context bridge. Absent, everything falls back to the browser
 * path — so this file is safe to load anywhere and there is no build flag.
 */

const bridge = (typeof window !== 'undefined' && window.meshbay) || null;

export const isNative = Boolean(bridge);

/**
 * The hub's base URL, prefixed to every API path.
 *
 * Empty string in a browser: the hub served this page, so a relative path goes
 * to the right place and no configuration can be wrong. In the app it is
 * whatever the user signed in against, and it is deliberately *not* guessed —
 * a client that picks its own hub is a client that can be pointed at one.
 */
export function hubBase() {
  return bridge ? (bridge.hubBase() || '') : '';
}

/** Native-only capabilities. A browser renders none of what these gate. */
export const capabilities = {
  // Install, configure and drive a node running on this machine.
  nodeAdmin: Boolean(bridge && bridge.capabilities && bridge.capabilities.nodeAdmin),
  // Choose directories on this machine to share.
  localFolders: Boolean(bridge && bridge.capabilities && bridge.capabilities.localFolders),
  // A real save dialog and a write that does not pass through the page.
  nativeSave: Boolean(bridge && bridge.capabilities && bridge.capabilities.nativeSave),
};

/**
 * Where the identity keys live.
 *
 * In a browser: exactly where they live today — IndexedDB and sessionStorage,
 * with the keypair bundle on the node as the way a second browser recovers
 * them, which is finding C4 and is the reason the app exists.
 *
 * In the app: the OS keychain, and no bundle is stored anywhere. That is what
 * closes C4 for a native device — unconditionally for that device, and for the
 * account only once it stops signing in from a browser too.
 */
export const secrets = {
  available: Boolean(bridge && bridge.secrets),
  async get(name) {
    if (!bridge || !bridge.secrets) return null;
    return bridge.secrets.get(name);
  },
  async set(name, value) {
    if (!bridge || !bridge.secrets) return false;
    return bridge.secrets.set(name, value);
  },
  async clear(name) {
    if (!bridge || !bridge.secrets) return false;
    return bridge.secrets.clear(name);
  },
  /**
   * Whether the OS is really protecting them.
   *
   * Electron's safeStorage falls back to a fixed key when no keyring is
   * running — a headless session, a minimal desktop — and silently. A user who
   * believes their keys are protected by the OS deserves to be told when they
   * are not, so this is surfaced rather than swallowed.
   */
  async backend() {
    if (!bridge || !bridge.secrets) return 'browser';
    return bridge.secrets.backend();
  },
};

/**
 * This device's key for signing in to the hub.
 *
 * Ed25519, generated and held by the main process — the interface asks for a
 * signature and never sees a key. The passphrase is still the account's
 * credential and its only recovery path; this is what saves deriving a key from
 * it on every launch.
 *
 * Not a per-node identity key. Those are generated per node, pinned there, and
 * never leave that relationship: nothing here correlates a person across
 * operators, and nothing wraps a group key for it.
 *
 * Absent in a browser, where a passphrase is entered every time and the
 * keypair bundle on each node is what a second browser recovers — which is
 * finding C4, and the reason the application exists.
 */
/**
 * The sentence out of a bridge error.
 *
 * Electron wraps anything thrown in the main process as
 * "Error invoking remote method 'hub:set': Error: …", which puts plumbing in
 * front of a message written for a person. The message is the part that was
 * written for them.
 */
export function bridgeMessage(err) {
  const raw = (err && err.message) || String(err);
  const m = raw.match(/^Error invoking remote method '[^']*':\s*(?:\w*Error:\s*)?(.*)$/s);
  return m ? m[1] : raw;
}

export const device = {
  available: Boolean(bridge && bridge.device),
  async ensure() {
    return bridge && bridge.device ? bridge.device.ensure() : null;
  },
  async publicKey() {
    return bridge && bridge.device ? bridge.device.publicKey() : null;
  },
  /** `{timestamp, signature}` over `meshbay:user_auth:<username>:<ts>`. */
  async sign(username) {
    return bridge && bridge.device ? bridge.device.sign(username) : null;
  },
  async forget() {
    return bridge && bridge.device ? bridge.device.forget() : false;
  },
};

/**
 * Call the hub.
 *
 * In a browser this is `fetch`, unchanged — the page came from the hub, so the
 * request is same-origin and nothing is in the way.
 *
 * In the application the page's origin is `app://meshbay`, and a browser fetch
 * from it is refused by CORS. The hub has **no CORS middleware at all**, and
 * that is worth keeping: its API is reachable from no web origin whatever.
 * Widening it for `app://meshbay` would be worse than it appears, because that
 * origin is not a credential — any Electron application can claim the same
 * scheme and host name.
 *
 * So the main process makes the call. It returns a small object rather than a
 * Response, and this shapes it back into something with `.ok`, `.status` and
 * `.json()`, so callers do not have to know which one they got.
 */
export async function apiFetch(url, init) {
  if (!bridge || !bridge.fetch) return fetch(url, init);
  const raw = await bridge.fetch(String(url), init && {
    method: init.method,
    headers: init.headers,
    body: init.body,
  });
  return {
    ok: raw.ok,
    status: raw.status,
    statusText: String(raw.status),
    headers: new Headers(raw.headers || {}),
    text: async () => raw.body,
    json: async () => JSON.parse(raw.body),
  };
}

/**
 * Save a decrypted file to disk.
 *
 * Returns null when there is no native path, so the caller keeps today's
 * behaviour — File System Access, a service worker stream, or a blob, decided
 * in `downloads.js`. Adding a native writer must not remove the three that
 * already work.
 */
export async function nativeSave(suggestedName, size) {
  if (!bridge || !bridge.saveFile) return null;
  return bridge.saveFile(suggestedName, size);
}

export default { isNative, hubBase, capabilities, secrets, nativeSave,
                 apiFetch, device, bridgeMessage };

// Also a global, because `transport.js` is loaded as a classic script — it
// predates the module graph and exposes `MeshBayTransport` the same way. The
// alternative was a second fetch path there, which is how two callers of one
// hub end up disagreeing about how to reach it.
if (typeof window !== 'undefined') {
  window.MeshBayPlatform = { isNative, hubBase, capabilities, secrets,
                             nativeSave, apiFetch, device,
                             bridgeMessage };
}