@loaders.gl/core/src/lib/utils/resource-utils.ts

The core API for working with loaders.gl loaders and writers

// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors

import {isResponse, isBlob} from '../../javascript-utils/is-type';
import {parseMIMEType, parseMIMETypeFromURL} from './mime-type-utils';
import {stripQueryString} from './url-utils';

/**
 * A loadable resource. Includes:
 * `Response`, `Blob` (`File` is a subclass), string URLs and data URLs
 */
export type Resource = Response | Blob | string;

/**
 * Returns the URL associated with this resource.
 * The returned value may include a query string and need further processing.
 * If it cannot determine url, the corresponding value will be an empty string
 *
 * @todo string parameters are assumed to be URLs
 */
export function getResourceUrl(resource: unknown): string {
  // If resource is a `Response`, it contains the information directly as a field
  if (isResponse(resource)) {
    const response = resource as Response;
    return response.url;
  }

  // If the resource is a Blob or a File (subclass of Blob)
  if (isBlob(resource)) {
    const blob = resource as Blob;
    // File objects have a "name" property. Blob objects don't have any
    // url (name) information
    return (blob as any).name || '';
  }

  if (typeof resource === 'string') {
    return resource;
  }

  // Unknown
  return '';
}

/**
 * Returns the URL associated with this resource.
 * The returned value may include a query string and need further processing.
 * If it cannot determine url, the corresponding value will be an empty string
 *
 * @todo string parameters are assumed to be URLs
 */
export function getResourceMIMEType(resource: unknown): string {
  // If resource is a response, it contains the information directly
  if (isResponse(resource)) {
    const response = resource as Response;
    const contentTypeHeader = response.headers.get('content-type') || '';
    const noQueryUrl = stripQueryString(response.url);
    return parseMIMEType(contentTypeHeader) || parseMIMETypeFromURL(noQueryUrl);
  }

  // If the resource is a Blob or a File (subclass of Blob)
  if (isBlob(resource)) {
    const blob = resource as Blob;
    return blob.type || '';
  }

  if (typeof resource === 'string') {
    return parseMIMETypeFromURL(resource);
  }

  // Unknown
  return '';
}

/**
  * Returns (approximate) content length for a resource if it can be determined.
  * Returns -1 if content length cannot be determined.
  * @param resource

  * @note string parameters are NOT assumed to be URLs
  */
export function getResourceContentLength(resource: unknown): number {
  if (isResponse(resource)) {
    const response = resource as Response;
    return response.headers['content-length'] || -1;
  }
  if (isBlob(resource)) {
    const blob = resource as Blob;
    return blob.size;
  }
  if (typeof resource === 'string') {
    // TODO - handle data URL?
    return resource.length;
  }
  if (resource instanceof ArrayBuffer) {
    return resource.byteLength;
  }
  if (ArrayBuffer.isView(resource)) {
    return resource.byteLength;
  }
  return -1;
}