text: /** @typedef {import("webpack/lib/Compilation.js")} WebpackCompilation */
  /** @typedef {{timestamp: number, fileDependencies: string[]}} Snapshot */
  'use strict';
  
  /**
   *
   * @param {{fileDependencies: string[], contextDependencies: string[], missingDependencies: string[]}} fileDependencies
   * @param {WebpackCompilation} compilation
   * @param {number} startTime
   */
  function createSnapshot (fileDependencies, compilation, startTime) {
    const flatDependencies = [];
    Object.keys(fileDependencies).forEach((depencyTypes) => {
      fileDependencies[depencyTypes].forEach(fileDependency => {
        flatDependencies.push(fileDependency);
      });
    });
    return {
      fileDependencies: flatDependencies,
      timestamp: startTime
    };
  }
  
  /**
   * Returns true if the files inside this snapshot
   * have not been changed
   *
   * @param {Snapshot} snapshot
   * @param {WebpackCompilation} compilation
   * @returns {Promise<boolean>}
   */
  function isSnapShotValid (snapshot, compilation) {
    // Check if any dependent file was changed after the last compilation
    const fileTimestamps = compilation.fileTimestamps;
    const isCacheOutOfDate = snapshot.fileDependencies.some((fileDependency) => {
      const timestamp = fileTimestamps.get(fileDependency);
      // If the timestamp is not known the file is new
      // If the timestamp is larger then the file has changed
      // Otherwise the file is still the same
      return !timestamp || timestamp > snapshot.timestamp;
    });
    return Promise.resolve(!isCacheOutOfDate);
  }
  
  /**
   * Ensure that the files keep watched for changes
   * and will trigger a recompile
   *
   * @param {WebpackCompilation} mainCompilation
   * @param {{fileDependencies: string[], contextDependencies: string[], missingDependencies: string[]}} fileDependencies
   */
  function watchFiles (mainCompilation, fileDependencies) {
    Object.keys(fileDependencies).forEach((depencyTypes) => {
      fileDependencies[depencyTypes].forEach(fileDependency => {
        mainCompilation.compilationDependencies.add(fileDependency);
      });
    });
  }
  
  module.exports = {
    createSnapshot,
    isSnapShotValid,
    watchFiles
  };
  