expo-asset
Version:
An Expo universal module to download assets and pass them into other APIs
68 lines • 3.32 kB
JavaScript
import { Platform } from 'expo-modules-core';
import { PixelRatio, NativeModules } from 'react-native';
import AssetSourceResolver from './AssetSourceResolver';
import { getManifest2, manifestBaseUrl } from './PlatformUtils';
/**
* Selects the best file for the given asset (ex: choosing the best scale for images) and returns
* a { uri, hash } pair for the specific asset file.
*
* If the asset isn't an image with multiple scales, the first file is selected.
*/
export function selectAssetSource(meta) {
// This logic is based on that of AssetSourceResolver, with additional support for file hashes and
// explicitly provided URIs
const scale = AssetSourceResolver.pickScale(meta.scales, PixelRatio.get());
const index = meta.scales.findIndex((s) => s === scale);
const hash = meta.fileHashes ? (meta.fileHashes[index] ?? meta.fileHashes[0]) : meta.hash;
// Allow asset processors to directly provide the URL to load
const uri = meta.fileUris ? (meta.fileUris[index] ?? meta.fileUris[0]) : meta.uri;
if (uri) {
return { uri: resolveUri(uri), hash };
}
const fileScale = scale === 1 ? '' : `@${scale}x`;
const fileExtension = meta.type ? `.${encodeURIComponent(meta.type)}` : '';
const suffix = `/${encodeURIComponent(meta.name)}${fileScale}${fileExtension}`;
const params = new URLSearchParams({
platform: Platform.OS,
hash: meta.hash,
});
// For assets with a specified absolute URL, we use the existing origin instead of prepending the
// development server or production CDN URL origin
if (/^https?:\/\//.test(meta.httpServerLocation)) {
const uri = meta.httpServerLocation + suffix + '?' + params;
return { uri, hash };
}
// For assets during development using manifest2, we use the development server's URL origin
const manifest2 = getManifest2();
const devServerUrl = manifest2?.extra?.expoGo?.developer
? 'http://' + manifest2.extra.expoGo.debuggerHost
: null;
if (devServerUrl) {
const baseUrl = new URL(meta.httpServerLocation + suffix, devServerUrl);
baseUrl.searchParams.set('platform', Platform.OS);
baseUrl.searchParams.set('hash', meta.hash);
return {
uri: baseUrl.href,
hash,
};
}
// Temporary fallback for loading assets in Expo Go home
if (NativeModules['ExponentKernel']) {
return { uri: `https://classic-assets.eascdn.net/~assets/${encodeURIComponent(hash)}`, hash };
}
// In correctly configured apps, we arrive here if the asset is locally available on disk due to
// being managed by expo-updates, and `getLocalAssetUri(hash)` must return a local URI for this
// hash. Since the asset is local, we don't have a remote URL and specify an invalid URL (an empty
// string) as a placeholder.
return { uri: '', hash };
}
/**
* Resolves the given URI to an absolute URI. If the given URI is already an absolute URI, it is
* simply returned. Otherwise, if it is a relative URI, it is resolved relative to the manifest's
* base URI.
*/
export function resolveUri(uri) {
// `manifestBaseUrl` is always an absolute URL or `null`.
return manifestBaseUrl ? new URL(uri, manifestBaseUrl).href : uri;
}
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