Emulate "public path" functionality in React Native

transformAssetLocation.ts

import { Platform } from "react-native";
import getDevServer from "react-native/Libraries/Core/Devtools/getDevServer";

const devServerInfo = getDevServer();

/**
 * Transform a local "public" path location to a URL that works in React Native.
 *
 * When the project is not hosted from a development server, use an offline path from an embedded asset.
 *
 * ```js
 * transformAssetLocation('node_modules/react-native/Libraries/LogBox/UI/LogBoxImages/chevron-left.png')
 * ```
 * 
 * ```jsx
 * <Image style={{ width: 100, height: 100 }} source={{ uri: transformAssetLocation('node_modules/react-native/Libraries/LogBox/UI/LogBoxImages/chevron-left.png') }} />
 * ```
 *
 * Alternatively a project hosted from something like EAS Updates can use the hosted path + public path to retrieve assets.
 *
 * @param assetPath
 * @returns
 */
export function transformAssetLocation(assetPath: string) {
  // Dev server in use
  if (devServerInfo.bundleLoadedFromServer) {
    // Remote
    const url = !devServerInfo.url.endsWith("/")
      ? `${devServerInfo.url}/`
      : devServerInfo.url;
    return url + assetPath;
  } else {
    // Local files bundled in the Android binary
    if (Platform.OS === "android") {
      // Use the same asset resolution code as the `expo bundle` command
      const normalized = getAndroidResourceIdentifier(assetPath);
      // Return a URL for a file in the assets folder.
      return `asset:/${normalized}`;
    } else if (Platform.OS === "ios") {
      // Not sure what the recommended way to retrieve embedded iOS assets is??
      // Maybe some combo of https://github.com/react-native-community/cli/pull/1290 and
      // https://reactnative.dev/docs/images#images-from-hybrid-apps-resources
      throw Error("no imp ios production");
    }
  }
}

function getAndroidResourceIdentifier(asset): string {
  return `${asset}`
    .toLowerCase()
    .replace(/\//g, "_") // Encode folder structure in file name
    .replace(/([^a-z0-9_])/g, "") // Remove illegal chars
    .replace(/^assets_/, ""); // Remove "assets_" prefix
}