fs/lib/ReaderCollection.js

  1. const AbstractReader = require("./AbstractReader");
  3. /**
  4.  * Resource Locator ReaderCollection
  5.  *
  6.  * @public
  7.  * @memberof module:@ui5/fs
  8.  * @augments module:@ui5/fs.AbstractReader
  9.  */
  10. class ReaderCollection extends AbstractReader {
  11. 	/**
  12. 	 * The constructor.
  13. 	 *
  14. 	 * @param {object} parameters Parameters
  15. 	 * @param {module:@ui5/fs.AbstractReader[]} parameters.readers List of resource readers (all tried in parallel)
  16. 	 * @param {string} parameters.name The collection name
  17. 	 */
  18. 	constructor({readers, name}) {
  19. 		super();
  20. 		this._name = name;
  21. 		this._readers = readers;
  22. 	}
  24. 	/**
  25. 	 * Locates resources by glob.
  26. 	 *
  27. 	 * @private
  28. 	 * @param {string|string[]} pattern glob pattern as string or an array of
  29. 	 *         glob patterns for virtual directory structure
  30. 	 * @param {object} options glob options
  31. 	 * @param {module:@ui5/fs.tracing.Trace} trace Trace instance
  32. 	 * @returns {Promise<module:@ui5/fs.Resource[]>} Promise resolving to list of resources
  33. 	 */
  34. 	_byGlob(pattern, options, trace) {
  35. 		return Promise.all(this._readers.map(function(resourceLocator) {
  36. 			return resourceLocator._byGlob(pattern, options, trace);
  37. 		})).then((result) => {
  38. 			trace.collection(this._name);
  39. 			return Array.prototype.concat.apply([], result);
  40. 		});
  41. 	}
  43. 	/**
  44. 	 * Locates resources by path.
  45. 	 *
  46. 	 * @private
  47. 	 * @param {string} virPath Virtual path
  48. 	 * @param {object} options Options
  49. 	 * @param {module:@ui5/fs.tracing.Trace} trace Trace instance
  50. 	 * @returns {Promise<module:@ui5/fs.Resource>} Promise resolving to a single resource
  51. 	 */
  52. 	_byPath(virPath, options, trace) {
  53. 		const that = this;
  54. 		const resourceLocatorCount = this._readers.length;
  55. 		let resolveCount = 0;
  57. 		if (this._readers.length === 0) {
  58. 			// Promise.race doesn't resolve for empty arrays
  59. 			return Promise.resolve();
  60. 		}
  62. 		/* Promise.race to cover the following (self defined) requirement:
  63. 			Deliver files that can be found fast at the cost of slower response times for files that cannot be found.
  64. 		*/
  65. 		return Promise.race(this._readers.map(function(resourceLocator) {
  66. 			return resourceLocator._byPath(virPath, options, trace).then(function(resource) {
  67. 				return new Promise(function(resolve, reject) {
  68. 					trace.collection(that._name);
  69. 					resolveCount++;
  70. 					if (resource) {
  71. 						resource.pushCollection(that._name);
  72. 						resolve(resource);
  73. 					} else if (resolveCount === resourceLocatorCount) {
  74. 						resolve(null);
  75. 					}
  76. 				});
  77. 			});
  78. 		}));
  79. 	}
  80. }
  82. module.exports = ReaderCollection;