react-native-macos/packager/src/node-haste/FilesByDirNameIndex.js

A framework for building native macOS apps using React

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @flow
 */

'use strict';

const path = require('path');

/**
 * This is a way to find files quickly given a RegExp, in a specific directory.
 * This is must faster than iterating over all the files and matching both
 * directory and RegExp at the same time.
 *
 * This was first implemented to support finding assets fast, for which we know
 * the directory, but we want to identify all variants (ex. @2x, @1x, for
 * a picture's different definition levels).
 */
class FilesByDirNameIndex {
  _filesByDirName: Map<string, Array<string>>;

  constructor(allFilePaths: Array<string>) {
    this._filesByDirName = new Map();
    for (let i = 0; i < allFilePaths.length; ++i) {
      const filePath = allFilePaths[i];
      const dirName = path.dirname(filePath);
      let dir = this._filesByDirName.get(dirName);
      if (dir === undefined) {
        dir = [];
        this._filesByDirName.set(dirName, dir);
      }
      dir.push(path.basename(filePath));
    }
  }

  match(dirName: string, pattern: RegExp): Array<string> {
    const results = [];
    const dir = this._filesByDirName.get(dirName);
    if (dir === undefined) {
      return [];
    }
    for (let i = 0; i < dir.length; ++i) {
      if (pattern.test(dir[i])) {
        results.push(path.join(dirName, dir[i]));
      }
    }
    return results;
  }
}

module.exports = FilesByDirNameIndex;