Genarrative/src/services/host-bridge/nativeAppHostBridge.ts

import {
  HOST_BRIDGE_PROTOCOL,
  HOST_BRIDGE_VERSION,
  type HostBridgeError,
  type HostBridgeMethod,
  type HostBridgeRequest,
  type HostBridgeResponse,
} from '../../../packages/shared/src/contracts/hostBridge';

const DEFAULT_NATIVE_APP_BRIDGE_TIMEOUT_MS = 8000;
const MAX_NATIVE_APP_BRIDGE_TIMEOUT_MS = 30000;

type NativeAppBridgeWindow = Window & {
  ReactNativeWebView?: {
    postMessage?: (message: string) => void;
  };
  __TAURI__?: {
    core?: {
      invoke?: <Result = unknown>(
        command: string,
        args?: Record<string, unknown>,
      ) => Promise<Result>;
    };
  };
};

type PendingNativeRequest = {
  resolve: (value: unknown) => void;
  reject: (error: Error) => void;
  timeoutId: ReturnType<typeof setTimeout>;
};

const pendingNativeRequests = new Map<string, PendingNativeRequest>();

let nativeBridgeListenerInstalled = false;
let nextNativeRequestSequence = 0;

function resolveNativeWindow() {
  return typeof window === 'undefined'
    ? null
    : (window as NativeAppBridgeWindow);
}

function buildNativeRequestId(method: HostBridgeMethod) {
  nextNativeRequestSequence += 1;
  return `host_${method.replace(/[^a-z0-9]/gi, '_')}_${Date.now()}_${nextNativeRequestSequence}`;
}

function resolveTimeoutMs(timeoutMs: number | undefined) {
  if (!Number.isFinite(timeoutMs ?? Number.NaN) || !timeoutMs) {
    return DEFAULT_NATIVE_APP_BRIDGE_TIMEOUT_MS;
  }

  return Math.min(
    Math.max(1, Math.trunc(timeoutMs)),
    MAX_NATIVE_APP_BRIDGE_TIMEOUT_MS,
  );
}

function createHostBridgeError(error: HostBridgeError) {
  const result = new Error(error.message);
  result.name = error.code;
  return result;
}

function isHostBridgeResponse(value: unknown): value is HostBridgeResponse {
  if (!value || typeof value !== 'object') {
    return false;
  }

  const candidate = value as Partial<HostBridgeResponse>;
  return (
    candidate.bridge === HOST_BRIDGE_PROTOCOL &&
    candidate.version === HOST_BRIDGE_VERSION &&
    typeof candidate.id === 'string' &&
    typeof candidate.ok === 'boolean'
  );
}

function parseNativeMessage(data: unknown) {
  if (typeof data === 'string') {
    try {
      return JSON.parse(data) as unknown;
    } catch {
      return null;
    }
  }

  return data;
}

function settleNativeResponse(response: HostBridgeResponse) {
  const pending = pendingNativeRequests.get(response.id);
  if (!pending) {
    return;
  }

  pendingNativeRequests.delete(response.id);
  clearTimeout(pending.timeoutId);

  if (response.ok) {
    pending.resolve(response.result);
    return;
  }

  pending.reject(createHostBridgeError(response.error));
}

function ensureNativeBridgeListener() {
  const nativeWindow = resolveNativeWindow();
  if (!nativeWindow || nativeBridgeListenerInstalled) {
    return;
  }

  nativeWindow.addEventListener('message', (event) => {
    const value = parseNativeMessage(event.data);
    if (isHostBridgeResponse(value)) {
      settleNativeResponse(value);
    }
  });

  nativeBridgeListenerInstalled = true;
}

export function canUseReactNativeHostBridge() {
  return (
    typeof resolveNativeWindow()?.ReactNativeWebView?.postMessage ===
    'function'
  );
}

export function canUseTauriHostBridge() {
  return (
    typeof resolveNativeWindow()?.__TAURI__?.core?.invoke === 'function'
  );
}

export function canUseNativeAppHostBridge() {
  return canUseReactNativeHostBridge() || canUseTauriHostBridge();
}

export async function requestNativeAppHostBridge<Result = unknown>(
  method: HostBridgeMethod,
  payload?: unknown,
  options: {
    timeoutMs?: number;
  } = {},
) {
  const nativeWindow = resolveNativeWindow();
  if (!nativeWindow) {
    return null;
  }

  const timeoutMs = resolveTimeoutMs(options.timeoutMs);
  const request: HostBridgeRequest = {
    bridge: HOST_BRIDGE_PROTOCOL,
    version: HOST_BRIDGE_VERSION,
    id: buildNativeRequestId(method),
    method,
    timeoutMs,
    ...(payload === undefined ? {} : { payload }),
  };

  const tauriInvoke = nativeWindow.__TAURI__?.core?.invoke;
  if (typeof tauriInvoke === 'function') {
    const response = await tauriInvoke<HostBridgeResponse<Result>>(
      'host_bridge_request',
      { request },
    );
    if (!isHostBridgeResponse(response)) {
      throw new Error('host_bridge_invalid_response');
    }
    if (response.ok) {
      return response.result as Result;
    }
    throw createHostBridgeError(response.error);
  }

  const postMessage = nativeWindow.ReactNativeWebView?.postMessage;
  if (typeof postMessage !== 'function') {
    return null;
  }

  ensureNativeBridgeListener();

  return await new Promise<Result>((resolve, reject) => {
    const timeoutId = setTimeout(() => {
      pendingNativeRequests.delete(request.id);
      reject(createHostBridgeError({
        code: 'timeout',
        message: 'host_bridge_timeout',
      }));
    }, timeoutMs);

    pendingNativeRequests.set(request.id, {
      resolve: (value) => resolve(value as Result),
      reject,
      timeoutId,
    });

    try {
      postMessage(JSON.stringify(request));
    } catch (error) {
      pendingNativeRequests.delete(request.id);
      clearTimeout(timeoutId);
      reject(error instanceof Error ? error : new Error(String(error)));
    }
  });
}

export function resetNativeAppHostBridgeForTest() {
  for (const pending of pendingNativeRequests.values()) {
    clearTimeout(pending.timeoutId);
  }
  pendingNativeRequests.clear();
  nextNativeRequestSequence = 0;
}