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

import * as fs from 'fs';
import * as stream from 'stream';
import { tmpdir } from 'os';
import { promisify } from 'util';
import { ResourceQueue } from 'vs/base/common/async';
import { isEqualOrParent, isRootOrDriveLetter, randomPath } from 'vs/base/common/extpath';
import { normalizeNFC } from 'vs/base/common/normalization';
import { join } from 'vs/base/common/path';
import { isLinux, isMacintosh, isWindows } from 'vs/base/common/platform';
import { extUriBiasedIgnorePathCase } from 'vs/base/common/resources';
import type { CoordinationArgs } from 'vs/base/common/resources';
import { URI } from 'vs/base/common/uri';

//#region rimraf

export enum RimRafMode {

	/**
	 * Slow version that unlinks each file and folder.
	 */
	UNLINK,

	/**
	 * Fast version that first moves the file/folder
	 * into a temp directory and then deletes that
	 * without waiting for it.
	 */
	MOVE
}

/**
 * Allows to delete the provided path (either file or folder) recursively
 * with the options:
 * - `UNLINK`: direct removal from disk
 * - `MOVE`: faster variant that first moves the target to temp dir and then
 *           deletes it in the background without waiting for that to finish.
 */
async function rimraf(path: string, mode = RimRafMode.UNLINK): Promise<void> {
	if (isRootOrDriveLetter(path)) {
		throw new Error('rimraf - will refuse to recursively delete root');
	}

	/*
	 * (modification for file-explorer https://github.com/pkerschbaum/file-explorer):
	 * always use rimrafUnlink (since rimrafMove causes problems with some devices on windows, e.g. external drives, network drives)
	 * 
	 * original code is here:
	// delete: via rmDir
	if (mode === RimRafMode.UNLINK) {
		return rimrafUnlink(path);
	}

	// delete: via move
	return rimrafMove(path);
	 */
	return rimrafUnlink(path);
}

async function rimrafMove(path: string): Promise<void> {
	try {
		const pathInTemp = randomPath(tmpdir());
		try {
			await Promises.rename(path, pathInTemp);
		} catch (error) {
			return rimrafUnlink(path); // if rename fails, delete without tmp dir
		}

		// Delete but do not return as promise
		rimrafUnlink(pathInTemp).catch(error => {/* ignore */ });
	} catch (error) {
		if (error.code !== 'ENOENT') {
			throw error;
		}
	}
}

async function rimrafUnlink(path: string): Promise<void> {
	return Promises.rm(path, { recursive: true, maxRetries: 3 });
}

export function rimrafSync(path: string): void {
	if (isRootOrDriveLetter(path)) {
		throw new Error('rimraf - will refuse to recursively delete root');
	}

	fs.rmdirSync(path, { recursive: true });
}

//#endregion

//#region readdir with NFC support (macos)

export interface IDirent {
	name: string;

	isFile(): boolean;
	isDirectory(): boolean;
	isSymbolicLink(): boolean;
}

/**
 * Drop-in replacement of `fs.readdir` with support
 * for converting from macOS NFD unicon form to NFC
 * (https://github.com/nodejs/node/issues/2165)
 */
async function readdir(path: string): Promise<string[]>;
async function readdir(path: string, options: { withFileTypes: true }): Promise<IDirent[]>;
async function readdir(path: string, options?: { withFileTypes: true }): Promise<(string | IDirent)[]> {
	return handleDirectoryChildren(await (options ? safeReaddirWithFileTypes(path) : promisify(fs.readdir)(path)));
}

async function safeReaddirWithFileTypes(path: string): Promise<IDirent[]> {
	try {
		return await promisify(fs.readdir)(path, { withFileTypes: true });
	} catch (error) {
		console.warn('[node.js fs] readdir with filetypes failed with error: ', error);
	}

	// Fallback to manually reading and resolving each
	// children of the folder in case we hit an error
	// previously.
	// This can only really happen on exotic file systems
	// such as explained in #115645 where we get entries
	// from `readdir` that we can later not `lstat`.
	const result: IDirent[] = [];
	const children = await readdir(path);
	for (const child of children) {
		let isFile = false;
		let isDirectory = false;
		let isSymbolicLink = false;

		try {
			const lstat = await Promises.lstat(join(path, child));

			isFile = lstat.isFile();
			isDirectory = lstat.isDirectory();
			isSymbolicLink = lstat.isSymbolicLink();
		} catch (error) {
			console.warn('[node.js fs] unexpected error from lstat after readdir: ', error);
		}

		result.push({
			name: child,
			isFile: () => isFile,
			isDirectory: () => isDirectory,
			isSymbolicLink: () => isSymbolicLink
		});
	}

	return result;
}

/**
 * Drop-in replacement of `fs.readdirSync` with support
 * for converting from macOS NFD unicon form to NFC
 * (https://github.com/nodejs/node/issues/2165)
 */
export function readdirSync(path: string): string[] {
	return handleDirectoryChildren(fs.readdirSync(path));
}

function handleDirectoryChildren(children: string[]): string[];
function handleDirectoryChildren(children: IDirent[]): IDirent[];
function handleDirectoryChildren(children: (string | IDirent)[]): (string | IDirent)[];
function handleDirectoryChildren(children: (string | IDirent)[]): (string | IDirent)[] {
	return children.map(child => {

		// Mac: uses NFD unicode form on disk, but we want NFC
		// See also https://github.com/nodejs/node/issues/2165

		if (typeof child === 'string') {
			return isMacintosh ? normalizeNFC(child) : child;
		}

		child.name = isMacintosh ? normalizeNFC(child.name) : child.name;

		return child;
	});
}

/**
 * A convenience method to read all children of a path that
 * are directories.
 */
async function readDirsInDir(dirPath: string): Promise<string[]> {
	const children = await readdir(dirPath);
	const directories: string[] = [];

	for (const child of children) {
		if (await SymlinkSupport.existsDirectory(join(dirPath, child))) {
			directories.push(child);
		}
	}

	return directories;
}

//#endregion

//#region whenDeleted()

/**
 * A `Promise` that resolves when the provided `path`
 * is deleted from disk.
 */
export function whenDeleted(path: string, intervalMs = 1000): Promise<void> {
	return new Promise<void>(resolve => {
		let running = false;
		const interval = setInterval(() => {
			if (!running) {
				running = true;
				fs.access(path, err => {
					running = false;

					if (err) {
						clearInterval(interval);
						resolve(undefined);
					}
				});
			}
		}, intervalMs);
	});
}

//#endregion

//#region Methods with symbolic links support

export namespace SymlinkSupport {

	export interface IStats {

		// The stats of the file. If the file is a symbolic
		// link, the stats will be of that target file and
		// not the link itself.
		// If the file is a symbolic link pointing to a non
		// existing file, the stat will be of the link and
		// the `dangling` flag will indicate this.
		stat: fs.Stats;

		// Will be provided if the resource is a symbolic link
		// on disk. Use the `dangling` flag to find out if it
		// points to a resource that does not exist on disk.
		symbolicLink?: { dangling: boolean };
	}

	/**
	 * Resolves the `fs.Stats` of the provided path. If the path is a
	 * symbolic link, the `fs.Stats` will be from the target it points
	 * to. If the target does not exist, `dangling: true` will be returned
	 * as `symbolicLink` value.
	 */
	export async function stat(path: string): Promise<IStats> {

		// First stat the link
		let lstats: fs.Stats | undefined;
		try {
			lstats = await Promises.lstat(path);

			// Return early if the stat is not a symbolic link at all
			if (!lstats.isSymbolicLink()) {
				return { stat: lstats };
			}
		} catch (error) {
			/* ignore - use stat() instead */
		}

		// If the stat is a symbolic link or failed to stat, use fs.stat()
		// which for symbolic links will stat the target they point to
		try {
			const stats = await Promises.stat(path);

			return { stat: stats, symbolicLink: lstats?.isSymbolicLink() ? { dangling: false } : undefined };
		} catch (error) {

			// If the link points to a nonexistent file we still want
			// to return it as result while setting dangling: true flag
			if (error.code === 'ENOENT' && lstats) {
				return { stat: lstats, symbolicLink: { dangling: true } };
			}

			// Windows: workaround a node.js bug where reparse points
			// are not supported (https://github.com/nodejs/node/issues/36790)
			if (isWindows && error.code === 'EACCES') {
				try {
					const stats = await Promises.stat(await Promises.readlink(path));

					return { stat: stats, symbolicLink: { dangling: false } };
				} catch (error) {

					// If the link points to a nonexistent file we still want
					// to return it as result while setting dangling: true flag
					if (error.code === 'ENOENT' && lstats) {
						return { stat: lstats, symbolicLink: { dangling: true } };
					}

					throw error;
				}
			}

			throw error;
		}
	}

	/**
	 * Figures out if the `path` exists and is a file with support
	 * for symlinks.
	 *
	 * Note: this will return `false` for a symlink that exists on
	 * disk but is dangling (pointing to a nonexistent path).
	 *
	 * Use `exists` if you only care about the path existing on disk
	 * or not without support for symbolic links.
	 */
	export async function existsFile(path: string): Promise<boolean> {
		try {
			const { stat, symbolicLink } = await SymlinkSupport.stat(path);

			return stat.isFile() && symbolicLink?.dangling !== true;
		} catch (error) {
			// Ignore, path might not exist
		}

		return false;
	}

	/**
	 * Figures out if the `path` exists and is a directory with support for
	 * symlinks.
	 *
	 * Note: this will return `false` for a symlink that exists on
	 * disk but is dangling (pointing to a nonexistent path).
	 *
	 * Use `exists` if you only care about the path existing on disk
	 * or not without support for symbolic links.
	 */
	export async function existsDirectory(path: string): Promise<boolean> {
		try {
			const { stat, symbolicLink } = await SymlinkSupport.stat(path);

			return stat.isDirectory() && symbolicLink?.dangling !== true;
		} catch (error) {
			// Ignore, path might not exist
		}

		return false;
	}
}

//#endregion

//#region Write File

// According to node.js docs (https://nodejs.org/docs/v14.16.0/api/fs.html#fs_fs_writefile_file_data_options_callback)
// it is not safe to call writeFile() on the same path multiple times without waiting for the callback to return.
// Therefor we use a Queue on the path that is given to us to sequentialize calls to the same path properly.
const writeQueues = new ResourceQueue();

/**
 * Same as `fs.writeFile` but with an additional call to
 * `fs.fdatasync` after writing to ensure changes are
 * flushed to disk.
 *
 * In addition, multiple writes to the same path are queued.
 */
function writeFile(path: string, data: string, options?: IWriteFileOptions): Promise<void>;
function writeFile(path: string, data: Buffer, options?: IWriteFileOptions): Promise<void>;
function writeFile(path: string, data: Uint8Array, options?: IWriteFileOptions): Promise<void>;
function writeFile(path: string, data: string | Buffer | Uint8Array, options?: IWriteFileOptions): Promise<void>;
function writeFile(path: string, data: string | Buffer | Uint8Array, options?: IWriteFileOptions): Promise<void> {
	return writeQueues.queueFor(URI.file(path), extUriBiasedIgnorePathCase).queue(() => {
		const ensuredOptions = ensureWriteOptions(options);

		return new Promise((resolve, reject) => doWriteFileAndFlush(path, data, ensuredOptions, error => error ? reject(error) : resolve()));
	});
}

interface IWriteFileOptions {
	mode?: number;
	flag?: string;
}

interface IEnsuredWriteFileOptions extends IWriteFileOptions {
	mode: number;
	flag: string;
}

let canFlush = true;

// Calls fs.writeFile() followed by a fs.sync() call to flush the changes to disk
// We do this in cases where we want to make sure the data is really on disk and
// not in some cache.
//
// See https://github.com/nodejs/node/blob/v5.10.0/lib/fs.js#L1194
function doWriteFileAndFlush(path: string, data: string | Buffer | Uint8Array, options: IEnsuredWriteFileOptions, callback: (error: Error | null) => void): void {
	if (!canFlush) {
		return fs.writeFile(path, data, { mode: options.mode, flag: options.flag }, callback);
	}

	// Open the file with same flags and mode as fs.writeFile()
	fs.open(path, options.flag, options.mode, (openError, fd) => {
		if (openError) {
			return callback(openError);
		}

		// It is valid to pass a fd handle to fs.writeFile() and this will keep the handle open!
		fs.writeFile(fd, data, writeError => {
			if (writeError) {
				return fs.close(fd, () => callback(writeError)); // still need to close the handle on error!
			}

			// Flush contents (not metadata) of the file to disk
			// https://github.com/microsoft/vscode/issues/9589
			fs.fdatasync(fd, (syncError: Error | null) => {

				// In some exotic setups it is well possible that node fails to sync
				// In that case we disable flushing and warn to the console
				if (syncError) {
					console.warn('[node.js fs] fdatasync is now disabled for this session because it failed: ', syncError);
					canFlush = false;
				}

				return fs.close(fd, closeError => callback(closeError));
			});
		});
	});
}

/**
 * Same as `fs.writeFileSync` but with an additional call to
 * `fs.fdatasyncSync` after writing to ensure changes are
 * flushed to disk.
 */
export function writeFileSync(path: string, data: string | Buffer, options?: IWriteFileOptions): void {
	const ensuredOptions = ensureWriteOptions(options);

	if (!canFlush) {
		return fs.writeFileSync(path, data, { mode: ensuredOptions.mode, flag: ensuredOptions.flag });
	}

	// Open the file with same flags and mode as fs.writeFile()
	const fd = fs.openSync(path, ensuredOptions.flag, ensuredOptions.mode);

	try {

		// It is valid to pass a fd handle to fs.writeFile() and this will keep the handle open!
		fs.writeFileSync(fd, data);

		// Flush contents (not metadata) of the file to disk
		try {
			fs.fdatasyncSync(fd); // https://github.com/microsoft/vscode/issues/9589
		} catch (syncError) {
			console.warn('[node.js fs] fdatasyncSync is now disabled for this session because it failed: ', syncError);
			canFlush = false;
		}
	} finally {
		fs.closeSync(fd);
	}
}

function ensureWriteOptions(options?: IWriteFileOptions): IEnsuredWriteFileOptions {
	if (!options) {
		return { mode: 0o666 /* default node.js mode for files */, flag: 'w' };
	}

	return {
		mode: typeof options.mode === 'number' ? options.mode : 0o666 /* default node.js mode for files */,
		flag: typeof options.flag === 'string' ? options.flag : 'w'
	};
}

//#endregion

//#region Move / Copy

/**
 * A drop-in replacement for `fs.rename` that:
 * - updates the `mtime` of the `source` after the operation
 * - allows to move across multiple disks
 */
async function move(source: string, target: string, coordinationArgs?: CoordinationArgs): Promise<void> {
	if (source === target) {
		return;  // simulate node.js behaviour here and do a no-op if paths match
	}

	/*
	 * (modification for file-explorer https://github.com/pkerschbaum/file-explorer):
	 * report that the progress for this source is indeterminate (`Promises.rename` does not allow to track progress)
	 */
	if (coordinationArgs?.reportProgress) {
		coordinationArgs.reportProgress({ forSource: URI.file(source), progressDeterminateType: 'INDETERMINATE' });
	}

	// We have been updating `mtime` for move operations for files since the
	// beginning for reasons that are no longer quite clear, but changing
	// this could be risky as well. As such, trying to reason about it:
	// It is very common as developer to have file watchers enabled that watch
	// the current workspace for changes. Updating the `mtime` might make it
	// easier for these watchers to recognize an actual change. Since changing
	// a source code file also updates the `mtime`, moving a file should do so
	// as well because conceptually it is a change of a similar category.
	async function updateMtime(path: string): Promise<void> {
		try {
			const stat = await Promises.lstat(path);
			if (stat.isDirectory() || stat.isSymbolicLink()) {
				return; // only for files
			}

			await Promises.utimes(path, stat.atime, new Date());
		} catch (error) {
			// Ignore any error
		}
	}

	try {
		await Promises.rename(source, target);
		await updateMtime(target);
	} catch (error) {

		// In two cases we fallback to classic copy and delete:
		//
		// 1.) The EXDEV error indicates that source and target are on different devices
		// In this case, fallback to using a copy() operation as there is no way to
		// rename() between different devices.
		//
		// 2.) The user tries to rename a file/folder that ends with a dot. This is not
		// really possible to move then, at least on UNC devices.
		if (source.toLowerCase() !== target.toLowerCase() && error.code === 'EXDEV' || source.endsWith('.')) {
			await copy(source, target, { preserveSymlinks: false /* copying to another device */ }, coordinationArgs);
			await rimraf(source, RimRafMode.MOVE);
			await updateMtime(target);
		} else {
			throw error;
		}
	}
}

interface ICopyPayload {
	readonly root: { source: string, target: string };
	readonly options: { preserveSymlinks: boolean };
	readonly handledSourcePaths: Set<string>;
}

/**
 * Recursively copies all of `source` to `target`.
 *
 * The options `preserveSymlinks` configures how symbolic
 * links should be handled when encountered. Set to
 * `false` to not preserve them and `true` otherwise.
 */
async function copy(source: string, target: string, options: { preserveSymlinks: boolean }, coordinationArgs?: CoordinationArgs): Promise<void> {
	return doCopy(source, target, { root: { source, target }, options, handledSourcePaths: new Set<string>() }, coordinationArgs);
}

// When copying a file or folder, we want to preserve the mode
// it had and as such provide it when creating. However, modes
// can go beyond what we expect (see link below), so we mask it.
// (https://github.com/nodejs/node-v0.x-archive/issues/3045#issuecomment-4862588)
const COPY_MODE_MASK = 0o777;

async function doCopy(source: string, target: string, payload: ICopyPayload, coordinationArgs?: CoordinationArgs): Promise<void> {

	// Keep track of paths already copied to prevent
	// cycles from symbolic links to cause issues
	if (payload.handledSourcePaths.has(source)) {
		return;
	} else {
		payload.handledSourcePaths.add(source);
	}

	const { stat, symbolicLink } = await SymlinkSupport.stat(source);

	// Symlink
	if (symbolicLink) {

		// Try to re-create the symlink unless `preserveSymlinks: false`
		if (payload.options.preserveSymlinks) {
			try {
				return await doCopySymlink(source, target, payload);
			} catch (error) {
				// in any case of an error fallback to normal copy via dereferencing
				console.warn('[node.js fs] copy of symlink failed: ', error);
			}
		}

		if (symbolicLink.dangling) {
			return; // skip dangling symbolic links from here on (https://github.com/microsoft/vscode/issues/111621)
		}
	}

	// Folder
	if (stat.isDirectory()) {
		return doCopyDirectory(source, target, stat.mode & COPY_MODE_MASK, payload, coordinationArgs);
	}

	// File or file-like
	else {
		return doCopyFile(source, target, stat.mode & COPY_MODE_MASK, coordinationArgs);
	}
}

async function doCopyDirectory(source: string, target: string, mode: number, payload: ICopyPayload, coordinationArgs?: CoordinationArgs): Promise<void> {

	// Create folder
	await Promises.mkdir(target, { recursive: true, mode });

	// Copy each file recursively
	const files = await readdir(source);
	for (const file of files) {
		await doCopy(join(source, file), join(target, file), payload, coordinationArgs);
	}
}

const COPY_FILE_HIGHWATERMARK = 1024 * 1024; // 1 MB
async function doCopyFile(source: string, target: string, mode: number, coordinationArgs?: CoordinationArgs): Promise<void> {

	/*
	 * (modification for file-explorer https://github.com/pkerschbaum/file-explorer):
	 * - report that the progress for this source is determinate now
	 * - if cancellation token got cancelled, abort
	 * - instead of using fs.promises.copyFile, copy the file manually in order to be able to track 
	 *   the progress on byte level
	 */
	if (coordinationArgs?.reportProgress) {
		coordinationArgs.reportProgress({ forSource: URI.file(source), progressDeterminateType: 'DETERMINATE' });
	}
	if (!!coordinationArgs?.token?.isCancellationRequested) {
		return;
	}

	return new Promise((resolve, reject) => {
		const reader = fs.createReadStream(source, { highWaterMark: COPY_FILE_HIGHWATERMARK });
		const writer = fs.createWriteStream(target, { mode, highWaterMark: COPY_FILE_HIGHWATERMARK });
		const progressWatcher = new stream.Transform({
			highWaterMark: COPY_FILE_HIGHWATERMARK,
			transform(chunk: Buffer, _, callback) {
				if (coordinationArgs?.reportProgress) {
					coordinationArgs.reportProgress({ forSource: sourceUri, newBytesRead: chunk.byteLength });
				}
				if (!!coordinationArgs?.token?.isCancellationRequested) {
					callback(new Error(`aborted doCopyFile due to cancellation`));
				} else {
					callback(undefined, chunk);
				}
			}
		});
		const sourceUri = URI.file(source);

		let finished = false;
		const finish = (error?: Error) => {
			if (!finished) {
				finished = true;
				reader.destroy();
				writer.destroy();
				progressWatcher.destroy();

				// in error cases, pass to callback
				if (error) {
					return reject(error);
				}

				// we need to explicitly chmod because of https://github.com/nodejs/node/issues/1104
				fs.chmod(target, mode, error => error ? reject(error) : resolve());
			}
		};

		// handle errors properly
		reader.once('error', error => finish(error));
		writer.once('error', error => finish(error));

		// we are done (underlying fd has been closed)
		writer.once('close', () => finish());

		progressWatcher.once('error', error => finish(error));

		// start piping
		reader.pipe(progressWatcher).pipe(writer);
	});

	// (modification for file-explorer https://github.com/pkerschbaum/file-explorer) original code of vscode is here:
	// Copy file
	// await Promises.copyFile(source, target);

	// // restore mode (https://github.com/nodejs/node/issues/1104)
	// await Promises.chmod(target, mode);
}

async function doCopySymlink(source: string, target: string, payload: ICopyPayload): Promise<void> {

	// Figure out link target
	let linkTarget = await Promises.readlink(source);

	// Special case: the symlink points to a target that is
	// actually within the path that is being copied. In that
	// case we want the symlink to point to the target and
	// not the source
	if (isEqualOrParent(linkTarget, payload.root.source, !isLinux)) {
		linkTarget = join(payload.root.target, linkTarget.substr(payload.root.source.length + 1));
	}

	// Create symlink
	await Promises.symlink(linkTarget, target);
}

//#endregion

//#region Promise based fs methods

/**
 * Prefer this helper class over the `fs.promises` API to
 * enable `graceful-fs` to function properly. Given issue
 * https://github.com/isaacs/node-graceful-fs/issues/160 it
 * is evident that the module only takes care of the non-promise
 * based fs methods.
 *
 * Another reason is `realpath` being entirely different in
 * the promise based implementation compared to the other
 * one (https://github.com/microsoft/vscode/issues/118562)
 *
 * Note: using getters for a reason, since `graceful-fs`
 * patching might kick in later after modules have been
 * loaded we need to defer access to fs methods.
 * (https://github.com/microsoft/vscode/issues/124176)
 */
export const Promises = new class {

	//#region Implemented by node.js

	get access() { return promisify(fs.access); }

	get stat() { return promisify(fs.stat); }
	get lstat() { return promisify(fs.lstat); }
	get utimes() { return promisify(fs.utimes); }

	get read() { return promisify(fs.read); }
	get readFile() { return promisify(fs.readFile); }

	get write() { return promisify(fs.write); }

	get appendFile() { return promisify(fs.appendFile); }

	get fdatasync() { return promisify(fs.fdatasync); }
	get truncate() { return promisify(fs.truncate); }

	get rename() { return promisify(fs.rename); }
	get copyFile() { return promisify(fs.copyFile); }

	get open() { return promisify(fs.open); }
	get close() { return promisify(fs.close); }

	get symlink() { return promisify(fs.symlink); }
	get readlink() { return promisify(fs.readlink); }

	get chmod() { return promisify(fs.chmod); }

	get mkdir() { return promisify(fs.mkdir); }

	get unlink() { return promisify(fs.unlink); }
	get rmdir() { return promisify(fs.rmdir); }
	get rm() { return promisify(fs.rm); }

	get realpath() { return promisify(fs.realpath); }

	//#endregion

	//#region Implemented by us

	async exists(path: string): Promise<boolean> {
		try {
			await Promises.access(path);

			return true;
		} catch {
			return false;
		}
	}

	get readdir() { return readdir; }
	get readDirsInDir() { return readDirsInDir; }

	get writeFile() { return writeFile; }

	get rimraf() { return rimraf; }

	get move() { return move; }
	get copy() { return copy; }

	//#endregion
};

//#endregion