/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

'use strict';

import paths = require('path');
import fs = require('fs');
import os = require('os');
import crypto = require('crypto');
import assert = require('assert');

import { isParent, FileOperation, FileOperationEvent, IContent, IFileService, IResolveFileOptions, IResolveContentOptions, IFileStat, IStreamContent, IFileOperationResult, FileOperationResult, IUpdateContentOptions, FileChangeType, IImportResult, MAX_FILE_SIZE, FileChangesEvent, IFilesConfiguration } from 'vs/platform/files/common/files';
import { isEqualOrParent } from 'vs/base/common/paths';
import { ResourceMap } from 'vs/base/common/map';
import arrays = require('vs/base/common/arrays');
import baseMime = require('vs/base/common/mime');
import { TPromise } from 'vs/base/common/winjs.base';
import types = require('vs/base/common/types');
import objects = require('vs/base/common/objects');
import extfs = require('vs/base/node/extfs');
import { nfcall, Limiter, ThrottledDelayer } from 'vs/base/common/async';
import uri from 'vs/base/common/uri';
import nls = require('vs/nls');
import { isWindows, isLinux } from 'vs/base/common/platform';
import { dispose, IDisposable, toDisposable } from 'vs/base/common/lifecycle';
import { IWorkspaceContextService } from 'vs/platform/workspace/common/workspace';

import pfs = require('vs/base/node/pfs');
import encoding = require('vs/base/node/encoding');
import { IMimeAndEncoding, detectMimesFromFile } from 'vs/base/node/mime';
import flow = require('vs/base/node/flow');
import { FileWatcher as UnixWatcherService } from 'vs/workbench/services/files/node/watcher/unix/watcherService';
import { FileWatcher as WindowsWatcherService } from 'vs/workbench/services/files/node/watcher/win32/watcherService';
import { toFileChangesEvent, normalize, IRawFileChange } from 'vs/workbench/services/files/node/watcher/common';
import Event, { Emitter } from 'vs/base/common/event';
import { FileWatcher as NsfwWatcherService } from 'vs/workbench/services/files/node/watcher/nsfw/watcherService';
import { IConfigurationService } from "vs/platform/configuration/common/configuration";

export interface IEncodingOverride {
	resource: uri;
	encoding: string;
}

export interface IFileServiceOptions {
	tmpDir?: string;
	errorLogger?: (msg: string) => void;
	encodingOverride?: IEncodingOverride[];
	watcherIgnoredPatterns?: string[];
	disableWatcher?: boolean;
	verboseLogging?: boolean;
	useExperimentalFileWatcher?: boolean;
}

function etag(stat: fs.Stats): string;
function etag(size: number, mtime: number): string;
function etag(arg1: any, arg2?: any): string {
	let size: number;
	let mtime: number;
	if (typeof arg2 === 'number') {
		size = arg1;
		mtime = arg2;
	} else {
		size = (<fs.Stats>arg1).size;
		mtime = (<fs.Stats>arg1).mtime.getTime();
	}

	return `"${crypto.createHash('sha1').update(String(size) + String(mtime)).digest('hex')}"`;
}

export class FileService implements IFileService {

	public _serviceBrand: any;

	private static FS_EVENT_DELAY = 50; // aggregate and only emit events when changes have stopped for this duration (in ms)
	private static FS_REWATCH_DELAY = 300; // delay to rewatch a file that was renamed or deleted (in ms)
	private static MAX_DEGREE_OF_PARALLEL_FS_OPS = 10; // degree of parallel fs calls that we accept at the same time

	private tmpPath: string;
	private options: IFileServiceOptions;

	private _onFileChanges: Emitter<FileChangesEvent>;
	private _onAfterOperation: Emitter<FileOperationEvent>;

	private toDispose: IDisposable[];

	private activeFileChangesWatchers: ResourceMap<fs.FSWatcher>;
	private fileChangesWatchDelayer: ThrottledDelayer<void>;
	private undeliveredRawFileChangesEvents: IRawFileChange[];

	constructor(
		private contextService: IWorkspaceContextService,
		private configurationService: IConfigurationService,
		options: IFileServiceOptions,
	) {
		this.toDispose = [];
		this.options = options || Object.create(null);
		this.tmpPath = this.options.tmpDir || os.tmpdir();

		this._onFileChanges = new Emitter<FileChangesEvent>();
		this.toDispose.push(this._onFileChanges);

		this._onAfterOperation = new Emitter<FileOperationEvent>();
		this.toDispose.push(this._onAfterOperation);

		if (!this.options.errorLogger) {
			this.options.errorLogger = console.error;
		}

		if (contextService.hasWorkspace() && !this.options.disableWatcher) {

			// new watcher: use it if setting tells us so or we run in multi-root environment
			if (this.options.useExperimentalFileWatcher || contextService.getWorkspace2().roots.length > 1) {
				this.setupNsfwWorkspceWatching();
			}

			// old watcher
			else {
				if (isWindows) {
					this.setupWin32WorkspaceWatching();
				} else {
					this.setupUnixWorkspaceWatching();
				}
			}
		}

		this.activeFileChangesWatchers = new ResourceMap<fs.FSWatcher>();
		this.fileChangesWatchDelayer = new ThrottledDelayer<void>(FileService.FS_EVENT_DELAY);
		this.undeliveredRawFileChangesEvents = [];
	}

	public get onFileChanges(): Event<FileChangesEvent> {
		return this._onFileChanges.event;
	}

	public get onAfterOperation(): Event<FileOperationEvent> {
		return this._onAfterOperation.event;
	}

	public updateOptions(options: IFileServiceOptions): void {
		if (options) {
			objects.mixin(this.options, options); // overwrite current options
		}
	}

	private setupWin32WorkspaceWatching(): void {
		this.toDispose.push(toDisposable(new WindowsWatcherService(this.contextService, this.options.watcherIgnoredPatterns, e => this._onFileChanges.fire(e), this.options.errorLogger, this.options.verboseLogging).startWatching()));
	}

	private setupUnixWorkspaceWatching(): void {
		this.toDispose.push(toDisposable(new UnixWatcherService(this.contextService, this.options.watcherIgnoredPatterns, e => this._onFileChanges.fire(e), this.options.errorLogger, this.options.verboseLogging).startWatching()));
	}

	private setupNsfwWorkspceWatching(): void {
		this.toDispose.push(toDisposable(new NsfwWatcherService(this.contextService, this.configurationService, e => this._onFileChanges.fire(e), this.options.errorLogger, this.options.verboseLogging).startWatching()));
	}

	public resolveFile(resource: uri, options?: IResolveFileOptions): TPromise<IFileStat> {
		return this.resolve(resource, options);
	}

	public resolveFiles(toResolve: { resource: uri, options?: IResolveFileOptions }[]): TPromise<IFileStat[]> {
		return TPromise.join(toResolve.map(resourceAndOptions => this.resolve(resourceAndOptions.resource, resourceAndOptions.options)));
	}

	public existsFile(resource: uri): TPromise<boolean> {
		return this.resolveFile(resource).then(() => true, () => false);
	}

	public resolveContent(resource: uri, options?: IResolveContentOptions): TPromise<IContent> {
		return this.doResolveContent(resource, options, (stat, enc) => this.resolveFileContent(stat, enc));
	}

	public resolveStreamContent(resource: uri, options?: IResolveContentOptions): TPromise<IStreamContent> {
		return this.doResolveContent(resource, options, (stat, enc) => this.resolveFileStreamContent(stat, enc));
	}

	private doResolveContent<IStreamContent>(resource: uri, options: IResolveContentOptions, contentResolver: (stat: IFileStat, enc?: string) => TPromise<IStreamContent>): TPromise<IStreamContent> {
		const absolutePath = this.toAbsolutePath(resource);

		// Guard early against attempts to resolve an invalid file path
		if (resource.scheme !== 'file' || !resource.fsPath) {
			return TPromise.wrapError<IStreamContent>(<IFileOperationResult>{
				message: nls.localize('fileInvalidPath', "Invalid file resource ({0})", resource.toString()),
				fileOperationResult: FileOperationResult.FILE_INVALID_PATH
			});
		}

		// 1.) resolve resource
		return this.resolve(resource).then((model): TPromise<IStreamContent> => {

			// Return early if resource is a directory
			if (model.isDirectory) {
				return TPromise.wrapError<IStreamContent>(<IFileOperationResult>{
					message: nls.localize('fileIsDirectoryError', "File is directory ({0})", absolutePath),
					fileOperationResult: FileOperationResult.FILE_IS_DIRECTORY
				});
			}

			// Return early if file not modified since
			if (options && options.etag && options.etag === model.etag) {
				return TPromise.wrapError<IStreamContent>(<IFileOperationResult>{
					fileOperationResult: FileOperationResult.FILE_NOT_MODIFIED_SINCE
				});
			}

			// Return early if file is too large to load
			if (types.isNumber(model.size) && model.size > MAX_FILE_SIZE) {
				return TPromise.wrapError<IStreamContent>(<IFileOperationResult>{
					fileOperationResult: FileOperationResult.FILE_TOO_LARGE
				});
			}

			// 2.) detect mimes
			const autoGuessEncoding = (options && options.autoGuessEncoding) || this.configuredAutoGuessEncoding(resource);
			return detectMimesFromFile(absolutePath, { autoGuessEncoding }).then((detected: IMimeAndEncoding) => {
				const isText = detected.mimes.indexOf(baseMime.MIME_BINARY) === -1;

				// Return error early if client only accepts text and this is not text
				if (options && options.acceptTextOnly && !isText) {
					return TPromise.wrapError<IStreamContent>(<IFileOperationResult>{
						message: nls.localize('fileBinaryError', "File seems to be binary and cannot be opened as text"),
						fileOperationResult: FileOperationResult.FILE_IS_BINARY
					});
				}

				let preferredEncoding: string;
				if (options && options.encoding) {
					if (detected.encoding === encoding.UTF8 && options.encoding === encoding.UTF8) {
						preferredEncoding = encoding.UTF8_with_bom; // indicate the file has BOM if we are to resolve with UTF 8
					} else {
						preferredEncoding = options.encoding; // give passed in encoding highest priority
					}
				} else if (detected.encoding) {
					if (detected.encoding === encoding.UTF8) {
						preferredEncoding = encoding.UTF8_with_bom; // if we detected UTF-8, it can only be because of a BOM
					} else {
						preferredEncoding = detected.encoding;
					}
				} else if (this.configuredEncoding(resource) === encoding.UTF8_with_bom) {
					preferredEncoding = encoding.UTF8; // if we did not detect UTF 8 BOM before, this can only be UTF 8 then
				}

				// 3.) get content
				return contentResolver(model, preferredEncoding);
			});
		}, (error) => {

			// bubble up existing file operation results
			if (!types.isUndefinedOrNull((<IFileOperationResult>error).fileOperationResult)) {
				return TPromise.wrapError<IStreamContent>(error);
			}

			// check if the file does not exist
			return pfs.exists(absolutePath).then(exists => {

				// Return if file not found
				if (!exists) {
					return TPromise.wrapError<IStreamContent>(<IFileOperationResult>{
						message: nls.localize('fileNotFoundError', "File not found ({0})", absolutePath),
						fileOperationResult: FileOperationResult.FILE_NOT_FOUND
					});
				}

				// otherwise just give up
				return TPromise.wrapError<IStreamContent>(error);
			});
		});
	}

	public resolveContents(resources: uri[]): TPromise<IContent[]> {
		const limiter = new Limiter(FileService.MAX_DEGREE_OF_PARALLEL_FS_OPS);

		const contentPromises = <TPromise<IContent>[]>[];
		resources.forEach(resource => {
			contentPromises.push(limiter.queue(() => this.resolve(resource).then(model => this.resolveFileContent(model)).then(content => content, error => TPromise.as(null /* ignore errors gracefully */))));
		});

		return TPromise.join(contentPromises).then(contents => {
			return arrays.coalesce(contents);
		});
	}

	public updateContent(resource: uri, value: string, options: IUpdateContentOptions = Object.create(null)): TPromise<IFileStat> {
		const absolutePath = this.toAbsolutePath(resource);

		// 1.) check file
		return this.checkFile(absolutePath, options).then(exists => {
			let createParentsPromise: TPromise<boolean>;
			if (exists) {
				createParentsPromise = TPromise.as(null);
			} else {
				createParentsPromise = pfs.mkdirp(paths.dirname(absolutePath));
			}

			// 2.) create parents as needed
			return createParentsPromise.then(() => {
				const encodingToWrite = this.getEncoding(resource, options.encoding);
				let addBomPromise: TPromise<boolean> = TPromise.as(false);

				// UTF_16 BE and LE as well as UTF_8 with BOM always have a BOM
				if (encodingToWrite === encoding.UTF16be || encodingToWrite === encoding.UTF16le || encodingToWrite === encoding.UTF8_with_bom) {
					addBomPromise = TPromise.as(true);
				}

				// Existing UTF-8 file: check for options regarding BOM
				else if (exists && encodingToWrite === encoding.UTF8) {
					if (options.overwriteEncoding) {
						addBomPromise = TPromise.as(false); // if we are to overwrite the encoding, we do not preserve it if found
					} else {
						addBomPromise = encoding.detectEncodingByBOM(absolutePath).then(enc => enc === encoding.UTF8); // otherwise preserve it if found
					}
				}

				// 3.) check to add UTF BOM
				return addBomPromise.then(addBom => {
					let writeFilePromise: TPromise<void>;

					// Write fast if we do UTF 8 without BOM
					if (!addBom && encodingToWrite === encoding.UTF8) {
						writeFilePromise = pfs.writeFile(absolutePath, value, encoding.UTF8);
					}

					// Otherwise use encoding lib
					else {
						const encoded = encoding.encode(value, encodingToWrite, { addBOM: addBom });
						writeFilePromise = pfs.writeFile(absolutePath, encoded);
					}

					// 4.) set contents
					return writeFilePromise.then(() => {

						// 5.) resolve
						return this.resolve(resource);
					});
				});
			});
		});
	}

	public createFile(resource: uri, content: string = ''): TPromise<IFileStat> {

		// Create file
		return this.updateContent(resource, content).then(result => {

			// Events
			this._onAfterOperation.fire(new FileOperationEvent(resource, FileOperation.CREATE, result));

			return result;
		});
	}

	public createFolder(resource: uri): TPromise<IFileStat> {

		// 1.) Create folder
		const absolutePath = this.toAbsolutePath(resource);
		return pfs.mkdirp(absolutePath).then(() => {

			// 2.) Resolve
			return this.resolve(resource).then(result => {

				// Events
				this._onAfterOperation.fire(new FileOperationEvent(resource, FileOperation.CREATE, result));

				return result;
			});
		});
	}

	public touchFile(resource: uri): TPromise<IFileStat> {
		const absolutePath = this.toAbsolutePath(resource);

		// 1.) check file
		return this.checkFile(absolutePath).then(exists => {
			let createPromise: TPromise<IFileStat>;
			if (exists) {
				createPromise = TPromise.as(null);
			} else {
				createPromise = this.createFile(resource);
			}

			// 2.) create file as needed
			return createPromise.then(() => {

				// 3.) update atime and mtime
				return pfs.touch(absolutePath).then(() => {

					// 4.) resolve
					return this.resolve(resource);
				});
			});
		});
	}

	public rename(resource: uri, newName: string): TPromise<IFileStat> {
		const newPath = paths.join(paths.dirname(resource.fsPath), newName);

		return this.moveFile(resource, uri.file(newPath));
	}

	public moveFile(source: uri, target: uri, overwrite?: boolean): TPromise<IFileStat> {
		return this.moveOrCopyFile(source, target, false, overwrite);
	}

	public copyFile(source: uri, target: uri, overwrite?: boolean): TPromise<IFileStat> {
		return this.moveOrCopyFile(source, target, true, overwrite);
	}

	private moveOrCopyFile(source: uri, target: uri, keepCopy: boolean, overwrite: boolean): TPromise<IFileStat> {
		const sourcePath = this.toAbsolutePath(source);
		const targetPath = this.toAbsolutePath(target);

		// 1.) move / copy
		return this.doMoveOrCopyFile(sourcePath, targetPath, keepCopy, overwrite).then(() => {

			// 2.) resolve
			return this.resolve(target).then(result => {

				// Events
				this._onAfterOperation.fire(new FileOperationEvent(source, keepCopy ? FileOperation.COPY : FileOperation.MOVE, result));

				return result;
			});
		});
	}

	private doMoveOrCopyFile(sourcePath: string, targetPath: string, keepCopy: boolean, overwrite: boolean): TPromise<boolean /* exists */> {

		// 1.) check if target exists
		return pfs.exists(targetPath).then(exists => {
			const isCaseRename = sourcePath.toLowerCase() === targetPath.toLowerCase();
			const isSameFile = sourcePath === targetPath;

			// Return early with conflict if target exists and we are not told to overwrite
			if (exists && !isCaseRename && !overwrite) {
				return TPromise.wrapError<boolean>(<IFileOperationResult>{
					fileOperationResult: FileOperationResult.FILE_MOVE_CONFLICT
				});
			}

			// 2.) make sure target is deleted before we move/copy unless this is a case rename of the same file
			let deleteTargetPromise = TPromise.as<void>(void 0);
			if (exists && !isCaseRename) {
				if (isEqualOrParent(sourcePath, targetPath, !isLinux /* ignorecase */)) {
					return TPromise.wrapError<boolean>(nls.localize('unableToMoveCopyError', "Unable to move/copy. File would replace folder it is contained in.")); // catch this corner case!
				}

				deleteTargetPromise = this.del(uri.file(targetPath));
			}

			return deleteTargetPromise.then(() => {

				// 3.) make sure parents exists
				return pfs.mkdirp(paths.dirname(targetPath)).then(() => {

					// 4.) copy/move
					if (isSameFile) {
						return TPromise.as(null);
					} else if (keepCopy) {
						return nfcall(extfs.copy, sourcePath, targetPath);
					} else {
						return nfcall(extfs.mv, sourcePath, targetPath);
					}
				}).then(() => exists);
			});
		});
	}

	public importFile(source: uri, targetFolder: uri): TPromise<IImportResult> {
		const sourcePath = this.toAbsolutePath(source);
		const targetResource = uri.file(paths.join(targetFolder.fsPath, paths.basename(source.fsPath)));
		const targetPath = this.toAbsolutePath(targetResource);

		// 1.) resolve
		return pfs.stat(sourcePath).then(stat => {
			if (stat.isDirectory()) {
				return TPromise.wrapError<IImportResult>(nls.localize('foldersCopyError', "Folders cannot be copied into the workspace. Please select individual files to copy them.")); // for now we do not allow to import a folder into a workspace
			}

			// 2.) copy
			return this.doMoveOrCopyFile(sourcePath, targetPath, true, true).then(exists => {

				// 3.) resolve
				return this.resolve(targetResource).then(stat => {

					// Events
					this._onAfterOperation.fire(new FileOperationEvent(source, FileOperation.IMPORT, stat));

					return <IImportResult>{ isNew: !exists, stat: stat };
				});
			});
		});
	}

	public del(resource: uri): TPromise<void> {
		const absolutePath = this.toAbsolutePath(resource);

		return pfs.del(absolutePath, this.tmpPath).then(() => {

			// Events
			this._onAfterOperation.fire(new FileOperationEvent(resource, FileOperation.DELETE));
		});
	}

	// Helpers

	private toAbsolutePath(arg1: uri | IFileStat): string {
		let resource: uri;
		if (arg1 instanceof uri) {
			resource = <uri>arg1;
		} else {
			resource = (<IFileStat>arg1).resource;
		}

		assert.ok(resource && resource.scheme === 'file', 'Invalid resource: ' + resource);

		return paths.normalize(resource.fsPath);
	}

	private resolve(resource: uri, options: IResolveFileOptions = Object.create(null)): TPromise<IFileStat> {
		return this.toStatResolver(resource)
			.then(model => model.resolve(options));
	}

	private toStatResolver(resource: uri): TPromise<StatResolver> {
		const absolutePath = this.toAbsolutePath(resource);

		return pfs.stat(absolutePath).then(stat => {
			return new StatResolver(resource, stat.isDirectory(), stat.mtime.getTime(), stat.size, this.options.verboseLogging);
		});
	}

	private resolveFileStreamContent(model: IFileStat, enc?: string): TPromise<IStreamContent> {

		// Return early if file is too large to load
		if (types.isNumber(model.size) && model.size > MAX_FILE_SIZE) {
			return TPromise.wrapError<IStreamContent>(<IFileOperationResult>{
				fileOperationResult: FileOperationResult.FILE_TOO_LARGE
			});
		}

		const absolutePath = this.toAbsolutePath(model);
		const fileEncoding = this.getEncoding(model.resource, enc);

		const reader = fs.createReadStream(absolutePath).pipe(encoding.decodeStream(fileEncoding)); // decode takes care of stripping any BOMs from the file content

		const content = model as IFileStat & IStreamContent;
		content.value = reader;
		content.encoding = fileEncoding; // make sure to store the encoding in the model to restore it later when writing

		return TPromise.as(content);
	}

	private resolveFileContent(model: IFileStat, enc?: string): TPromise<IContent> {
		return this.resolveFileStreamContent(model, enc).then(streamContent => {
			return new TPromise<IContent>((c, e) => {
				let done = false;
				const chunks: string[] = [];

				streamContent.value.on('data', buf => {
					chunks.push(buf);
				});

				streamContent.value.on('error', error => {
					if (!done) {
						done = true;
						e(error);
					}
				});

				streamContent.value.on('end', () => {
					const content: IContent = <any>streamContent;
					content.value = chunks.join('');

					if (!done) {
						done = true;
						c(content);
					}
				});
			});
		});
	}

	public getEncoding(resource: uri, preferredEncoding?: string): string {
		let fileEncoding: string;

		const override = this.getEncodingOverride(resource);
		if (override) {
			fileEncoding = override;
		} else if (preferredEncoding) {
			fileEncoding = preferredEncoding;
		} else {
			fileEncoding = this.configuredEncoding(resource);
		}

		if (!fileEncoding || !encoding.encodingExists(fileEncoding)) {
			fileEncoding = encoding.UTF8; // the default is UTF 8
		}

		return fileEncoding;
	}

	private configuredAutoGuessEncoding(resource: uri): boolean {
		const config = this.configurationService.getConfiguration(void 0, { resource }) as IFilesConfiguration;

		return config && config.files && config.files.autoGuessEncoding === true;
	}

	private configuredEncoding(resource: uri): string {
		const config = this.configurationService.getConfiguration(void 0, { resource }) as IFilesConfiguration;

		return config && config.files && config.files.encoding;
	}

	private getEncodingOverride(resource: uri): string {
		if (resource && this.options.encodingOverride && this.options.encodingOverride.length) {
			for (let i = 0; i < this.options.encodingOverride.length; i++) {
				const override = this.options.encodingOverride[i];

				// check if the resource is a child of the resource with override and use
				// the provided encoding in that case
				if (isParent(resource.fsPath, override.resource.fsPath, !isLinux /* ignorecase */)) {
					return override.encoding;
				}
			}
		}

		return null;
	}

	private checkFile(absolutePath: string, options: IUpdateContentOptions = Object.create(null)): TPromise<boolean /* exists */> {
		return pfs.exists(absolutePath).then(exists => {
			if (exists) {
				return pfs.stat(absolutePath).then(stat => {
					if (stat.isDirectory()) {
						return TPromise.wrapError<boolean>(new Error('Expected file is actually a directory'));
					}

					// Dirty write prevention
					if (typeof options.mtime === 'number' && typeof options.etag === 'string' && options.mtime < stat.mtime.getTime()) {

						// Find out if content length has changed
						if (options.etag !== etag(stat.size, options.mtime)) {
							return TPromise.wrapError<boolean>(<IFileOperationResult>{
								message: 'File Modified Since',
								fileOperationResult: FileOperationResult.FILE_MODIFIED_SINCE
							});
						}
					}

					let mode = stat.mode;
					const readonly = !(mode & 128);

					// Throw if file is readonly and we are not instructed to overwrite
					if (readonly && !options.overwriteReadonly) {
						return TPromise.wrapError<boolean>(<IFileOperationResult>{
							message: nls.localize('fileReadOnlyError', "File is Read Only"),
							fileOperationResult: FileOperationResult.FILE_READ_ONLY
						});
					}

					if (readonly) {
						mode = mode | 128;
						return pfs.chmod(absolutePath, mode).then(() => exists);
					}

					return TPromise.as<boolean>(exists);
				});
			}

			return TPromise.as<boolean>(exists);
		});
	}

	public watchFileChanges(resource: uri): void {
		assert.ok(resource && resource.scheme === 'file', `Invalid resource for watching: ${resource}`);

		// Create or get watcher for provided path
		let watcher = this.activeFileChangesWatchers.get(resource);
		if (!watcher) {
			const fsPath = resource.fsPath;

			try {
				watcher = fs.watch(fsPath); // will be persistent but not recursive
			} catch (error) {
				return; // the path might not exist anymore, ignore this error and return
			}

			this.activeFileChangesWatchers.set(resource, watcher);

			// eventType is either 'rename' or 'change'
			const fsName = paths.basename(resource.fsPath);
			watcher.on('change', (eventType: string, filename: string) => {
				const renamedOrDeleted = ((filename && filename !== fsName) || eventType === 'rename');

				// The file was either deleted or renamed. Many tools apply changes to files in an
				// atomic way ("Atomic Save") by first renaming the file to a temporary name and then
				// renaming it back to the original name. Our watcher will detect this as a rename
				// and then stops to work on Mac and Linux because the watcher is applied to the
				// inode and not the name. The fix is to detect this case and trying to watch the file
				// again after a certain delay.
				// In addition, we send out a delete event if after a timeout we detect that the file
				// does indeed not exist anymore.
				if (renamedOrDeleted) {

					// Very important to dispose the watcher which now points to a stale inode
					this.unwatchFileChanges(resource);

					// Wait a bit and try to install watcher again, assuming that the file was renamed quickly ("Atomic Save")
					setTimeout(() => {
						this.existsFile(resource).done(exists => {

							// File still exists, so reapply the watcher
							if (exists) {
								this.watchFileChanges(resource);
							}

							// File seems to be really gone, so emit a deleted event
							else {
								this.onRawFileChange({
									type: FileChangeType.DELETED,
									path: fsPath
								});
							}
						});
					}, FileService.FS_REWATCH_DELAY);
				}

				// Handle raw file change
				this.onRawFileChange({
					type: FileChangeType.UPDATED,
					path: fsPath
				});
			});

			// Errors
			watcher.on('error', (error: string) => {
				this.options.errorLogger(error);
			});
		}
	}

	private onRawFileChange(event: IRawFileChange): void {

		// add to bucket of undelivered events
		this.undeliveredRawFileChangesEvents.push(event);

		if (this.options.verboseLogging) {
			console.log('%c[node.js Watcher]%c', 'color: green', 'color: black', event.type === FileChangeType.ADDED ? '[ADDED]' : event.type === FileChangeType.DELETED ? '[DELETED]' : '[CHANGED]', event.path);
		}

		// handle emit through delayer to accommodate for bulk changes
		this.fileChangesWatchDelayer.trigger(() => {
			const buffer = this.undeliveredRawFileChangesEvents;
			this.undeliveredRawFileChangesEvents = [];

			// Normalize
			const normalizedEvents = normalize(buffer);

			// Logging
			if (this.options.verboseLogging) {
				normalizedEvents.forEach(r => {
					console.log('%c[node.js Watcher]%c >> normalized', 'color: green', 'color: black', r.type === FileChangeType.ADDED ? '[ADDED]' : r.type === FileChangeType.DELETED ? '[DELETED]' : '[CHANGED]', r.path);
				});
			}

			// Emit
			this._onFileChanges.fire(toFileChangesEvent(normalizedEvents));

			return TPromise.as(null);
		});
	}

	public unwatchFileChanges(resource: uri): void;
	public unwatchFileChanges(path: string): void;
	public unwatchFileChanges(arg1: any): void {
		const resource = (typeof arg1 === 'string') ? uri.parse(arg1) : arg1 as uri;

		const watcher = this.activeFileChangesWatchers.get(resource);
		if (watcher) {
			watcher.close();
			this.activeFileChangesWatchers.delete(resource);
		}
	}

	public dispose(): void {
		this.toDispose = dispose(this.toDispose);

		this.activeFileChangesWatchers.forEach(watcher => watcher.close());
		this.activeFileChangesWatchers.clear();
	}
}

export class StatResolver {
	private resource: uri;
	private isDirectory: boolean;
	private mtime: number;
	private name: string;
	private etag: string;
	private size: number;
	private verboseLogging: boolean;

	constructor(resource: uri, isDirectory: boolean, mtime: number, size: number, verboseLogging: boolean) {
		assert.ok(resource && resource.scheme === 'file', 'Invalid resource: ' + resource);

		this.resource = resource;
		this.isDirectory = isDirectory;
		this.mtime = mtime;
		this.name = paths.basename(resource.fsPath);
		this.etag = etag(size, mtime);
		this.size = size;

		this.verboseLogging = verboseLogging;
	}

	public resolve(options: IResolveFileOptions): TPromise<IFileStat> {

		// General Data
		const fileStat: IFileStat = {
			resource: this.resource,
			isDirectory: this.isDirectory,
			hasChildren: undefined,
			name: this.name,
			etag: this.etag,
			size: this.size,
			mtime: this.mtime
		};

		// File Specific Data
		if (!this.isDirectory) {
			return TPromise.as(fileStat);
		}

		// Directory Specific Data
		else {

			// Convert the paths from options.resolveTo to absolute paths
			let absoluteTargetPaths: string[] = null;
			if (options && options.resolveTo) {
				absoluteTargetPaths = [];
				options.resolveTo.forEach(resource => {
					absoluteTargetPaths.push(resource.fsPath);
				});
			}

			return new TPromise<IFileStat>((c, e) => {

				// Load children
				this.resolveChildren(this.resource.fsPath, absoluteTargetPaths, options && options.resolveSingleChildDescendants, (children) => {
					children = arrays.coalesce(children); // we don't want those null children (could be permission denied when reading a child)
					fileStat.hasChildren = children && children.length > 0;
					fileStat.children = children || [];

					c(fileStat);
				});
			});
		}
	}

	private resolveChildren(absolutePath: string, absoluteTargetPaths: string[], resolveSingleChildDescendants: boolean, callback: (children: IFileStat[]) => void): void {
		extfs.readdir(absolutePath, (error: Error, files: string[]) => {
			if (error) {
				if (this.verboseLogging) {
					console.error(error);
				}

				return callback(null); // return - we might not have permissions to read the folder
			}

			// for each file in the folder
			flow.parallel(files, (file: string, clb: (error: Error, children: IFileStat) => void) => {
				const fileResource = uri.file(paths.resolve(absolutePath, file));
				let fileStat: fs.Stats;
				const $this = this;

				flow.sequence(
					function onError(error: Error): void {
						if ($this.verboseLogging) {
							console.error(error);
						}

						clb(null, null); // return - we might not have permissions to read the folder or stat the file
					},

					function stat(): void {
						fs.stat(fileResource.fsPath, this);
					},

					function countChildren(fsstat: fs.Stats): void {
						fileStat = fsstat;

						if (fileStat.isDirectory()) {
							extfs.readdir(fileResource.fsPath, (error, result) => {
								this(null, result ? result.length : 0);
							});
						} else {
							this(null, 0);
						}
					},

					function resolve(childCount: number): void {
						const childStat: IFileStat = {
							resource: fileResource,
							isDirectory: fileStat.isDirectory(),
							hasChildren: childCount > 0,
							name: file,
							mtime: fileStat.mtime.getTime(),
							etag: etag(fileStat),
							size: fileStat.size
						};

						// Return early for files
						if (!fileStat.isDirectory()) {
							return clb(null, childStat);
						}

						// Handle Folder
						let resolveFolderChildren = false;
						if (files.length === 1 && resolveSingleChildDescendants) {
							resolveFolderChildren = true;
						} else if (childCount > 0 && absoluteTargetPaths && absoluteTargetPaths.some(targetPath => isEqualOrParent(targetPath, fileResource.fsPath, !isLinux /* ignorecase */))) {
							resolveFolderChildren = true;
						}

						// Continue resolving children based on condition
						if (resolveFolderChildren) {
							$this.resolveChildren(fileResource.fsPath, absoluteTargetPaths, resolveSingleChildDescendants, children => {
								children = arrays.coalesce(children);  // we don't want those null children
								childStat.hasChildren = children && children.length > 0;
								childStat.children = children || [];

								clb(null, childStat);
							});
						}

						// Otherwise return result
						else {
							clb(null, childStat);
						}
					});
			}, (errors, result) => {
				callback(result);
			});
		});
	}
}