fs/lib/ReaderCollection.js

  1. import AbstractReader from "./AbstractReader.js";
  3. /**
  4.  * Resource Locator ReaderCollection
  5.  *
  6.  * @public
  7.  * @class
  8.  * @alias @ui5/fs/ReaderCollection
  9.  * @extends @ui5/fs/AbstractReader
  10.  */
  11. class ReaderCollection extends AbstractReader {
  12. 	/**
  13. 	 * The constructor.
  14. 	 *
  15. 	 * @param {object} parameters Parameters
  16. 	 * @param {string} parameters.name The collection name
  17. 	 * @param {@ui5/fs/AbstractReader[]} [parameters.readers]
  18. 	 *   List of resource readers (all tried in parallel).
  19. 	 *   If none are provided, the collection will never return any results.
  20. 	 */
  21. 	constructor({name, readers}) {
  22. 		super(name);
  24. 		// Remove any undefined (empty) readers from array
  25. 		this._readers = readers.filter(($) => $);
  26. 	}
  28. 	/**
  29. 	 * Locates resources by glob.
  30. 	 *
  31. 	 * @private
  32. 	 * @param {string|string[]} pattern glob pattern as string or an array of
  33. 	 *         glob patterns for virtual directory structure
  34. 	 * @param {object} options glob options
  35. 	 * @param {@ui5/fs/tracing.Trace} trace Trace instance
  36. 	 * @returns {Promise<@ui5/fs/Resource[]>} Promise resolving to list of resources
  37. 	 */
  38. 	_byGlob(pattern, options, trace) {
  39. 		return Promise.all(this._readers.map(function(resourceLocator) {
  40. 			return resourceLocator._byGlob(pattern, options, trace);
  41. 		})).then((result) => {
  42. 			trace.collection(this._name);
  43. 			return Array.prototype.concat.apply([], result);
  44. 		});
  45. 	}
  47. 	/**
  48. 	 * Locates resources by path.
  49. 	 *
  50. 	 * @private
  51. 	 * @param {string} virPath Virtual path
  52. 	 * @param {object} options Options
  53. 	 * @param {@ui5/fs/tracing.Trace} trace Trace instance
  54. 	 * @returns {Promise<@ui5/fs/Resource|null>}
  55. 	 *   Promise resolving to a single resource or <code>null</code> if no resource is found
  56. 	 */
  57. 	_byPath(virPath, options, trace) {
  58. 		const that = this;
  59. 		const resourceLocatorCount = this._readers.length;
  60. 		let resolveCount = 0;
  62. 		if (resourceLocatorCount === 0) {
  63. 			// Short-circuit if there are no readers (Promise.race does not settle for empty arrays)
  64. 			trace.collection(that._name);
  65. 			return Promise.resolve(null);
  66. 		}
  68. 		// Using Promise.race to deliver files that can be found as fast as possible
  69. 		return Promise.race(this._readers.map(function(resourceLocator) {
  70. 			return resourceLocator._byPath(virPath, options, trace).then(function(resource) {
  71. 				return new Promise(function(resolve, reject) {
  72. 					trace.collection(that._name);
  73. 					resolveCount++;
  74. 					if (resource) {
  75. 						resource.pushCollection(that._name);
  76. 						resolve(resource);
  77. 					} else if (resolveCount === resourceLocatorCount) {
  78. 						resolve(null);
  79. 					}
  80. 				});
  81. 			});
  82. 		}));
  83. 	}
  84. }
  86. export default ReaderCollection;