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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 Stats = require("./Stats");

/** @typedef {import("../declarations/WebpackOptions").WatchOptions} WatchOptions */
/** @typedef {import("./Compilation")} Compilation */
/** @typedef {import("./Compiler")} Compiler */
/** @typedef {import("./FileSystemInfo").FileSystemInfoEntry} FileSystemInfoEntry */
/** @typedef {import("./WebpackError")} WebpackError */
/** @typedef {import("./logging/Logger").Logger} Logger */
/** @typedef {import("./util/fs").WatchFileSystem} WatchFileSystem */

/**
 * @template T
 * @callback Callback
 * @param {Error | null} err
 * @param {T=} result
 */

class Watching {
	/**
	 * @param {Compiler} compiler the compiler
	 * @param {WatchOptions} watchOptions options
	 * @param {Callback} handler completion handler
	 */
	constructor(compiler, watchOptions, handler) {
		this.startTime = null;
		this.invalid = false;
		this.handler = handler;
		/** @type {Callback[]} */
		this.callbacks = [];
		/** @type {Callback[] | undefined} */
		this._closeCallbacks = undefined;
		this.closed = false;
		this.suspended = false;
		this.blocked = false;
		this._isBlocked = () => false;
		this._onChange = () => {};
		this._onInvalid = () => {};
		if (typeof watchOptions === "number") {
			this.watchOptions = {
				aggregateTimeout: watchOptions
			};
		} else if (watchOptions && typeof watchOptions === "object") {
			this.watchOptions = { ...watchOptions };
		} else {
			this.watchOptions = {};
		}
		if (typeof this.watchOptions.aggregateTimeout !== "number") {
			this.watchOptions.aggregateTimeout = 20;
		}
		this.compiler = compiler;
		this.running = false;
		this._initial = true;
		this._invalidReported = true;
		this._needRecords = true;
		this.watcher = undefined;
		this.pausedWatcher = undefined;
		/** @type {Set | undefined} */
		this._collectedChangedFiles = undefined;
		/** @type {Set | undefined} */
		this._collectedRemovedFiles = undefined;
		this._done = this._done.bind(this);
		process.nextTick(() => {
			if (this._initial) this._invalidate();
		});
	}

	/**
	 * @param {ReadonlySet=} changedFiles changed files
	 * @param {ReadonlySet=} removedFiles removed files
	 */
	_mergeWithCollected(changedFiles, removedFiles) {
		if (!changedFiles) return;
		if (!this._collectedChangedFiles) {
			this._collectedChangedFiles = new Set(changedFiles);
			this._collectedRemovedFiles = new Set(removedFiles);
		} else {
			for (const file of changedFiles) {
				this._collectedChangedFiles.add(file);
				/** @type {Set} */
				(this._collectedRemovedFiles).delete(file);
			}
			for (const file of /** @type {ReadonlySet} */ (removedFiles)) {
				this._collectedChangedFiles.delete(file);
				/** @type {Set} */
				(this._collectedRemovedFiles).add(file);
			}
		}
	}

	/**
	 * @param {ReadonlyMap=} fileTimeInfoEntries info for files
	 * @param {ReadonlyMap=} contextTimeInfoEntries info for directories
	 * @param {ReadonlySet=} changedFiles changed files
	 * @param {ReadonlySet=} removedFiles removed files
	 * @returns {void}
	 */
	_go(fileTimeInfoEntries, contextTimeInfoEntries, changedFiles, removedFiles) {
		this._initial = false;
		if (this.startTime === null) this.startTime = Date.now();
		this.running = true;
		if (this.watcher) {
			this.pausedWatcher = this.watcher;
			this.lastWatcherStartTime = Date.now();
			this.watcher.pause();
			this.watcher = null;
		} else if (!this.lastWatcherStartTime) {
			this.lastWatcherStartTime = Date.now();
		}
		this.compiler.fsStartTime = Date.now();
		if (
			changedFiles &&
			removedFiles &&
			fileTimeInfoEntries &&
			contextTimeInfoEntries
		) {
			this._mergeWithCollected(changedFiles, removedFiles);
			this.compiler.fileTimestamps = fileTimeInfoEntries;
			this.compiler.contextTimestamps = contextTimeInfoEntries;
		} else if (this.pausedWatcher) {
			if (this.pausedWatcher.getInfo) {
				const {
					changes,
					removals,
					fileTimeInfoEntries,
					contextTimeInfoEntries
				} = this.pausedWatcher.getInfo();
				this._mergeWithCollected(changes, removals);
				this.compiler.fileTimestamps = fileTimeInfoEntries;
				this.compiler.contextTimestamps = contextTimeInfoEntries;
			} else {
				this._mergeWithCollected(
					this.pausedWatcher.getAggregatedChanges &&
						this.pausedWatcher.getAggregatedChanges(),
					this.pausedWatcher.getAggregatedRemovals &&
						this.pausedWatcher.getAggregatedRemovals()
				);
				this.compiler.fileTimestamps =
					this.pausedWatcher.getFileTimeInfoEntries();
				this.compiler.contextTimestamps =
					this.pausedWatcher.getContextTimeInfoEntries();
			}
		}
		this.compiler.modifiedFiles = this._collectedChangedFiles;
		this._collectedChangedFiles = undefined;
		this.compiler.removedFiles = this._collectedRemovedFiles;
		this._collectedRemovedFiles = undefined;

		const run = () => {
			if (this.compiler.idle) {
				return this.compiler.cache.endIdle(err => {
					if (err) return this._done(err);
					this.compiler.idle = false;
					run();
				});
			}
			if (this._needRecords) {
				return this.compiler.readRecords(err => {
					if (err) return this._done(err);

					this._needRecords = false;
					run();
				});
			}
			this.invalid = false;
			this._invalidReported = false;
			this.compiler.hooks.watchRun.callAsync(this.compiler, err => {
				if (err) return this._done(err);
				/**
				 * @param {Error | null} err error
				 * @param {Compilation=} _compilation compilation
				 * @returns {void}
				 */
				const onCompiled = (err, _compilation) => {
					if (err) return this._done(err, _compilation);

					const compilation = /** @type {Compilation} */ (_compilation);

					if (this.invalid) return this._done(null, compilation);

					if (this.compiler.hooks.shouldEmit.call(compilation) === false) {
						return this._done(null, compilation);
					}

					process.nextTick(() => {
						const logger = compilation.getLogger("webpack.Compiler");
						logger.time("emitAssets");
						this.compiler.emitAssets(compilation, err => {
							logger.timeEnd("emitAssets");
							if (err) return this._done(err, compilation);
							if (this.invalid) return this._done(null, compilation);

							logger.time("emitRecords");
							this.compiler.emitRecords(err => {
								logger.timeEnd("emitRecords");
								if (err) return this._done(err, compilation);

								if (compilation.hooks.needAdditionalPass.call()) {
									compilation.needAdditionalPass = true;

									compilation.startTime = /** @type {number} */ (
										this.startTime
									);
									compilation.endTime = Date.now();
									logger.time("done hook");
									const stats = new Stats(compilation);
									this.compiler.hooks.done.callAsync(stats, err => {
										logger.timeEnd("done hook");
										if (err) return this._done(err, compilation);

										this.compiler.hooks.additionalPass.callAsync(err => {
											if (err) return this._done(err, compilation);
											this.compiler.compile(onCompiled);
										});
									});
									return;
								}
								return this._done(null, compilation);
							});
						});
					});
				};
				this.compiler.compile(onCompiled);
			});
		};

		run();
	}

	/**
	 * @param {Compilation} compilation the compilation
	 * @returns {Stats} the compilation stats
	 */
	_getStats(compilation) {
		const stats = new Stats(compilation);
		return stats;
	}

	/**
	 * @param {(Error | null)=} err an optional error
	 * @param {Compilation=} compilation the compilation
	 * @returns {void}
	 */
	_done(err, compilation) {
		this.running = false;

		const logger =
			/** @type {Logger} */
			(compilation && compilation.getLogger("webpack.Watching"));

		/** @type {Stats | undefined} */
		let stats = undefined;

		/**
		 * @param {Error} err error
		 * @param {Callback[]=} cbs callbacks
		 */
		const handleError = (err, cbs) => {
			this.compiler.hooks.failed.call(err);
			this.compiler.cache.beginIdle();
			this.compiler.idle = true;
			this.handler(err, /** @type {Stats} */ (stats));
			if (!cbs) {
				cbs = this.callbacks;
				this.callbacks = [];
			}
			for (const cb of cbs) cb(err);
		};

		if (
			this.invalid &&
			!this.suspended &&
			!this.blocked &&
			!(this._isBlocked() && (this.blocked = true))
		) {
			if (compilation) {
				logger.time("storeBuildDependencies");
				this.compiler.cache.storeBuildDependencies(
					compilation.buildDependencies,
					err => {
						logger.timeEnd("storeBuildDependencies");
						if (err) return handleError(err);
						this._go();
					}
				);
			} else {
				this._go();
			}
			return;
		}

		if (compilation) {
			compilation.startTime = /** @type {number} */ (this.startTime);
			compilation.endTime = Date.now();
			stats = new Stats(compilation);
		}
		this.startTime = null;
		if (err) return handleError(err);

		const cbs = this.callbacks;
		this.callbacks = [];
		logger.time("done hook");
		this.compiler.hooks.done.callAsync(/** @type {Stats} */ (stats), err => {
			logger.timeEnd("done hook");
			if (err) return handleError(err, cbs);
			this.handler(null, stats);
			logger.time("storeBuildDependencies");
			this.compiler.cache.storeBuildDependencies(
				/** @type {Compilation} */
				(compilation).buildDependencies,
				err => {
					logger.timeEnd("storeBuildDependencies");
					if (err) return handleError(err, cbs);
					logger.time("beginIdle");
					this.compiler.cache.beginIdle();
					this.compiler.idle = true;
					logger.timeEnd("beginIdle");
					process.nextTick(() => {
						if (!this.closed) {
							this.watch(
								/** @type {Compilation} */
								(compilation).fileDependencies,
								/** @type {Compilation} */
								(compilation).contextDependencies,
								/** @type {Compilation} */
								(compilation).missingDependencies
							);
						}
					});
					for (const cb of cbs) cb(null);
					this.compiler.hooks.afterDone.call(/** @type {Stats} */ (stats));
				}
			);
		});
	}

	/**
	 * @param {Iterable} files watched files
	 * @param {Iterable} dirs watched directories
	 * @param {Iterable} missing watched existence entries
	 * @returns {void}
	 */
	watch(files, dirs, missing) {
		this.pausedWatcher = null;
		this.watcher =
			/** @type {WatchFileSystem} */
			(this.compiler.watchFileSystem).watch(
				files,
				dirs,
				missing,
				/** @type {number} */ (this.lastWatcherStartTime),
				this.watchOptions,
				(
					err,
					fileTimeInfoEntries,
					contextTimeInfoEntries,
					changedFiles,
					removedFiles
				) => {
					if (err) {
						this.compiler.modifiedFiles = undefined;
						this.compiler.removedFiles = undefined;
						this.compiler.fileTimestamps = undefined;
						this.compiler.contextTimestamps = undefined;
						this.compiler.fsStartTime = undefined;
						return this.handler(err);
					}
					this._invalidate(
						fileTimeInfoEntries,
						contextTimeInfoEntries,
						changedFiles,
						removedFiles
					);
					this._onChange();
				},
				(fileName, changeTime) => {
					if (!this._invalidReported) {
						this._invalidReported = true;
						this.compiler.hooks.invalid.call(fileName, changeTime);
					}
					this._onInvalid();
				}
			);
	}

	/**
	 * @param {Callback=} callback signals when the build has completed again
	 * @returns {void}
	 */
	invalidate(callback) {
		if (callback) {
			this.callbacks.push(callback);
		}
		if (!this._invalidReported) {
			this._invalidReported = true;
			this.compiler.hooks.invalid.call(null, Date.now());
		}
		this._onChange();
		this._invalidate();
	}

	/**
	 * @param {ReadonlyMap=} fileTimeInfoEntries info for files
	 * @param {ReadonlyMap=} contextTimeInfoEntries info for directories
	 * @param {ReadonlySet=} changedFiles changed files
	 * @param {ReadonlySet=} removedFiles removed files
	 * @returns {void}
	 */
	_invalidate(
		fileTimeInfoEntries,
		contextTimeInfoEntries,
		changedFiles,
		removedFiles
	) {
		if (this.suspended || (this._isBlocked() && (this.blocked = true))) {
			this._mergeWithCollected(changedFiles, removedFiles);
			return;
		}

		if (this.running) {
			this._mergeWithCollected(changedFiles, removedFiles);
			this.invalid = true;
		} else {
			this._go(
				fileTimeInfoEntries,
				contextTimeInfoEntries,
				changedFiles,
				removedFiles
			);
		}
	}

	suspend() {
		this.suspended = true;
	}

	resume() {
		if (this.suspended) {
			this.suspended = false;
			this._invalidate();
		}
	}

	/**
	 * @param {Callback} callback signals when the watcher is closed
	 * @returns {void}
	 */
	close(callback) {
		if (this._closeCallbacks) {
			if (callback) {
				this._closeCallbacks.push(callback);
			}
			return;
		}
		/**
		 * @param {WebpackError | null} err error if any
		 * @param {Compilation=} compilation compilation if any
		 */
		const finalCallback = (err, compilation) => {
			this.running = false;
			this.compiler.running = false;
			this.compiler.watching = undefined;
			this.compiler.watchMode = false;
			this.compiler.modifiedFiles = undefined;
			this.compiler.removedFiles = undefined;
			this.compiler.fileTimestamps = undefined;
			this.compiler.contextTimestamps = undefined;
			this.compiler.fsStartTime = undefined;
			/**
			 * @param {WebpackError | null} err error if any
			 */
			const shutdown = err => {
				this.compiler.hooks.watchClose.call();
				const closeCallbacks =
					/** @type {Callback[]} */
					(this._closeCallbacks);
				this._closeCallbacks = undefined;
				for (const cb of closeCallbacks) cb(err);
			};
			if (compilation) {
				const logger = compilation.getLogger("webpack.Watching");
				logger.time("storeBuildDependencies");
				this.compiler.cache.storeBuildDependencies(
					compilation.buildDependencies,
					err2 => {
						logger.timeEnd("storeBuildDependencies");
						shutdown(err || err2);
					}
				);
			} else {
				shutdown(err);
			}
		};

		this.closed = true;
		if (this.watcher) {
			this.watcher.close();
			this.watcher = null;
		}
		if (this.pausedWatcher) {
			this.pausedWatcher.close();
			this.pausedWatcher = null;
		}
		this._closeCallbacks = [];
		if (callback) {
			this._closeCallbacks.push(callback);
		}
		if (this.running) {
			this.invalid = true;
			this._done = finalCallback;
		} else {
			finalCallback(null);
		}
	}
}

module.exports = Watching;