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Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.
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/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/

"use strict";

const util = require("util");
const Watchpack = require("watchpack");

/** @typedef {import("../../declarations/WebpackOptions").WatchOptions} WatchOptions */
/** @typedef {import("../FileSystemInfo").FileSystemInfoEntry} FileSystemInfoEntry */
/** @typedef {import("../util/fs").InputFileSystem} InputFileSystem */
/** @typedef {import("../util/fs").WatchFileSystem} WatchFileSystem */
/** @typedef {import("../util/fs").WatchMethod} WatchMethod */
/** @typedef {import("../util/fs").Watcher} Watcher */

class NodeWatchFileSystem {
	/**
	 * @param {InputFileSystem} inputFileSystem input filesystem
	 */
	constructor(inputFileSystem) {
		this.inputFileSystem = inputFileSystem;
		this.watcherOptions = {
			aggregateTimeout: 0
		};
		this.watcher = new Watchpack(this.watcherOptions);
	}

	/**
	 * @param {Iterable} files watched files
	 * @param {Iterable} directories watched directories
	 * @param {Iterable} missing watched existence entries
	 * @param {number} startTime timestamp of start time
	 * @param {WatchOptions} options options object
	 * @param {function(Error | null, Map, Map, Set, Set): void} callback aggregated callback
	 * @param {function(string, number): void} callbackUndelayed callback when the first change was detected
	 * @returns {Watcher} a watcher
	 */
	watch(
		files,
		directories,
		missing,
		startTime,
		options,
		callback,
		callbackUndelayed
	) {
		if (!files || typeof files[Symbol.iterator] !== "function") {
			throw new Error("Invalid arguments: 'files'");
		}
		if (!directories || typeof directories[Symbol.iterator] !== "function") {
			throw new Error("Invalid arguments: 'directories'");
		}
		if (!missing || typeof missing[Symbol.iterator] !== "function") {
			throw new Error("Invalid arguments: 'missing'");
		}
		if (typeof callback !== "function") {
			throw new Error("Invalid arguments: 'callback'");
		}
		if (typeof startTime !== "number" && startTime) {
			throw new Error("Invalid arguments: 'startTime'");
		}
		if (typeof options !== "object") {
			throw new Error("Invalid arguments: 'options'");
		}
		if (typeof callbackUndelayed !== "function" && callbackUndelayed) {
			throw new Error("Invalid arguments: 'callbackUndelayed'");
		}
		const oldWatcher = this.watcher;
		this.watcher = new Watchpack(options);

		if (callbackUndelayed) {
			this.watcher.once("change", callbackUndelayed);
		}

		const fetchTimeInfo = () => {
			const fileTimeInfoEntries = new Map();
			const contextTimeInfoEntries = new Map();
			if (this.watcher) {
				this.watcher.collectTimeInfoEntries(
					fileTimeInfoEntries,
					contextTimeInfoEntries
				);
			}
			return { fileTimeInfoEntries, contextTimeInfoEntries };
		};
		this.watcher.once(
			"aggregated",
			/**
			 * @param {Set} changes changes
			 * @param {Set} removals removals
			 */
			(changes, removals) => {
				// pause emitting events (avoids clearing aggregated changes and removals on timeout)
				this.watcher.pause();

				const fs = this.inputFileSystem;
				if (fs && fs.purge) {
					for (const item of changes) {
						fs.purge(item);
					}
					for (const item of removals) {
						fs.purge(item);
					}
				}
				const { fileTimeInfoEntries, contextTimeInfoEntries } = fetchTimeInfo();
				callback(
					null,
					fileTimeInfoEntries,
					contextTimeInfoEntries,
					changes,
					removals
				);
			}
		);

		this.watcher.watch({ files, directories, missing, startTime });

		if (oldWatcher) {
			oldWatcher.close();
		}
		return {
			close: () => {
				if (this.watcher) {
					this.watcher.close();
					this.watcher = null;
				}
			},
			pause: () => {
				if (this.watcher) {
					this.watcher.pause();
				}
			},
			getAggregatedRemovals: util.deprecate(
				() => {
					const items = this.watcher && this.watcher.aggregatedRemovals;
					const fs = this.inputFileSystem;
					if (items && fs && fs.purge) {
						for (const item of items) {
							fs.purge(item);
						}
					}
					return items;
				},
				"Watcher.getAggregatedRemovals is deprecated in favor of Watcher.getInfo since that's more performant.",
				"DEP_WEBPACK_WATCHER_GET_AGGREGATED_REMOVALS"
			),
			getAggregatedChanges: util.deprecate(
				() => {
					const items = this.watcher && this.watcher.aggregatedChanges;
					const fs = this.inputFileSystem;
					if (items && fs && fs.purge) {
						for (const item of items) {
							fs.purge(item);
						}
					}
					return items;
				},
				"Watcher.getAggregatedChanges is deprecated in favor of Watcher.getInfo since that's more performant.",
				"DEP_WEBPACK_WATCHER_GET_AGGREGATED_CHANGES"
			),
			getFileTimeInfoEntries: util.deprecate(
				() => {
					return fetchTimeInfo().fileTimeInfoEntries;
				},
				"Watcher.getFileTimeInfoEntries is deprecated in favor of Watcher.getInfo since that's more performant.",
				"DEP_WEBPACK_WATCHER_FILE_TIME_INFO_ENTRIES"
			),
			getContextTimeInfoEntries: util.deprecate(
				() => {
					return fetchTimeInfo().contextTimeInfoEntries;
				},
				"Watcher.getContextTimeInfoEntries is deprecated in favor of Watcher.getInfo since that's more performant.",
				"DEP_WEBPACK_WATCHER_CONTEXT_TIME_INFO_ENTRIES"
			),
			getInfo: () => {
				const removals = this.watcher && this.watcher.aggregatedRemovals;
				const changes = this.watcher && this.watcher.aggregatedChanges;
				const fs = this.inputFileSystem;
				if (fs && fs.purge) {
					if (removals) {
						for (const item of removals) {
							fs.purge(item);
						}
					}
					if (changes) {
						for (const item of changes) {
							fs.purge(item);
						}
					}
				}
				const { fileTimeInfoEntries, contextTimeInfoEntries } = fetchTimeInfo();
				return {
					changes,
					removals,
					fileTimeInfoEntries,
					contextTimeInfoEntries
				};
			}
		};
	}
}

module.exports = NodeWatchFileSystem;