/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/
"use strict";

const Watchpack = require("watchpack");
const objectToMap = require("../util/objectToMap");

class NodeWatchFileSystem {
	constructor(inputFileSystem) {
		this.inputFileSystem = inputFileSystem;
		this.watcherOptions = {
			aggregateTimeout: 0
		};
		this.watcher = new Watchpack(this.watcherOptions);
	}

	watch(files, dirs, missing, startTime, options, callback, callbackUndelayed) {
		if (!Array.isArray(files)) {
			throw new Error("Invalid arguments: 'files'");
		}
		if (!Array.isArray(dirs)) {
			throw new Error("Invalid arguments: 'dirs'");
		}
		if (!Array.isArray(missing)) {
			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 cachedFiles = files;
		const cachedDirs = dirs;
		this.watcher.once("aggregated", (changes, removals) => {
			changes = changes.concat(removals);
			if (this.inputFileSystem && this.inputFileSystem.purge) {
				this.inputFileSystem.purge(changes);
			}
			const times = objectToMap(this.watcher.getTimes());
			files = new Set(files);
			dirs = new Set(dirs);
			missing = new Set(missing);
			removals = new Set(removals.filter(file => files.has(file)));
			callback(
				null,
				changes.filter(file => files.has(file)).sort(),
				changes.filter(file => dirs.has(file)).sort(),
				changes.filter(file => missing.has(file)).sort(),
				times,
				times,
				removals
			);
		});

		this.watcher.watch(
			cachedFiles.concat(missing),
			cachedDirs.concat(missing),
			startTime
		);

		if (oldWatcher) {
			oldWatcher.close();
		}
		return {
			close: () => {
				if (this.watcher) {
					this.watcher.close();
					this.watcher = null;
				}
			},
			pause: () => {
				if (this.watcher) {
					this.watcher.pause();
				}
			},
			getFileTimestamps: () => {
				if (this.watcher) {
					return objectToMap(this.watcher.getTimes());
				} else {
					return new Map();
				}
			},
			getContextTimestamps: () => {
				if (this.watcher) {
					return objectToMap(this.watcher.getTimes());
				} else {
					return new Map();
				}
			}
		};
	}
}

module.exports = NodeWatchFileSystem;