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

import * as UUID from 'vscode-languageclient/lib/utils/uuid';
import * as vscode from 'vscode';
import * as path from 'path';
import * as fs from 'fs-extra';
import * as os from 'os';
import { spawn, ExecOptions, SpawnOptions, ChildProcess } from 'child_process';
import * as nls from 'vscode-nls';
const localize = nls.loadMessageBundle();

import { IServerInstance } from './common';
import JupyterServerInstallation from './jupyterServerInstallation';
import * as utils from '../common/utils';
import * as constants from '../common/constants';
import * as notebookUtils from '../common/notebookUtils';
import * as ports from '../common/ports';

const NotebookConfigFilename = 'jupyter_notebook_config.py';
const CustomJsFilename = 'custom.js';
const defaultPort = 8888;
const JupyterStartedMessage = 'The Jupyter Notebook is running';

type MessageListener = (data: string | Buffer) => void;
type ErrorListener = (err: any) => void;

export interface IInstanceOptions {
	/**
	 * The path to the initial document we want to start this server for
	 */
	documentPath: string;

	/**
	 * Base install information needed in order to start the server instance
	 */
	install: JupyterServerInstallation;

	/**
	 * Optional start directory for the notebook server. If none is set, will use a
	 * path relative to the initial document
	 */
	notebookDirectory?: string;
}

/**
 * Helper class to enable testing without calling into file system or
 * commandline shell APIs
 */
export class ServerInstanceUtils {
	public mkDir(dirPath: string, outputChannel?: vscode.OutputChannel): Promise<void> {
		return utils.mkDir(dirPath, outputChannel);
	}
	public removeDir(dirPath: string): Promise<void> {
		return fs.remove(dirPath);
	}
	public pathExists(dirPath: string): Promise<boolean> {
		return fs.pathExists(dirPath);
	}
	public copy(src: string, dest: string): Promise<void> {
		return fs.copy(src, dest);
	}
	public existsSync(dirPath: string): boolean {
		return fs.existsSync(dirPath);
	}
	public generateUuid(): string {
		return UUID.generateUuid();
	}
	public executeBufferedCommand(cmd: string, options: ExecOptions, outputChannel?: vscode.OutputChannel): Thenable<string> {
		return utils.executeBufferedCommand(cmd, options, outputChannel);
	}

	public spawn(command: string, args?: ReadonlyArray<string>, options?: SpawnOptions): ChildProcess {
		return spawn(command, args, options);
	}

	public ensureProcessEnded(childProcess: ChildProcess): void {
		if (!childProcess) {
			return;
		}
		// Wait 5 seconds and then force kill. Jupyter stop is slow so this seems a reasonable time limit
		setTimeout(() => {
			// Test if the process is still alive. Throws an exception if not
			try {
				process.kill(childProcess.pid, 'SIGKILL');
			} catch (error) {
				if (!error || !error.code || (typeof error.code === 'string' && error.code !== 'ESRCH')) {
					console.log(error);
				}
			}
		}, 5000);
	}
}

export class PerNotebookServerInstance implements IServerInstance {

	/**
	 * Root of the jupyter directory structure. Config and data roots will be
	 * under this, in order to simplify deletion of folders on stop of the instance
	 */
	private baseDir: string;

	/**
	 * Path to configuration folder for this instance. Typically:
	 * %extension_path%/jupyter_config/%server%_config
	 */
	private instanceConfigRoot: string;

	/**
	 * Path to data folder for this instance. Typically:
	 * %extension_path%/jupyter_config/%server%_data
	 */
	private instanceDataRoot: string;

	private _systemJupyterDir: string;
	private _port: string;
	private _uri: vscode.Uri;
	private _isStarted: boolean = false;
	private utils: ServerInstanceUtils;
	private childProcess: ChildProcess;
	private errorHandler: ErrorHandler = new ErrorHandler();

	constructor(private options: IInstanceOptions, fsUtils?: ServerInstanceUtils) {
		this.utils = fsUtils || new ServerInstanceUtils();
	}

	public get isStarted(): boolean {
		return this._isStarted;
	}

	public get port(): string {
		return this._port;
	}

	public get uri(): vscode.Uri {
		return this._uri;
	}

	public async configure(): Promise<void> {
		await this.configureJupyter();
	}

	public async start(): Promise<void> {
		await this.startInternal();
	}

	public async stop(): Promise<void> {
		try {
			if (this.baseDir) {
				let exists = await this.utils.pathExists(this.baseDir);
				if (exists) {
					await this.utils.removeDir(this.baseDir);
				}
			}
			if (this.isStarted) {
				let install = this.options.install;
				let stopCommand = `"${install.pythonExecutable}" -m jupyter notebook stop ${this._port}`;
				await this.utils.executeBufferedCommand(stopCommand, install.execOptions, install.outputChannel);
			}
		} catch (error) {
			// For now, we don't care as this is non-critical
			this.notify(this.options.install, localize('serverStopError', 'Error stopping Notebook Server: {0}', utils.getErrorMessage(error)));
		} finally {
			this._isStarted = false;
			this.utils.ensureProcessEnded(this.childProcess);
			this.handleConnectionClosed();
		}
	}


	private async configureJupyter(): Promise<void> {
		await this.createInstanceFolders();
		let resourcesFolder = path.join(this.options.install.extensionPath, 'resources', constants.jupyterConfigRootFolder);
		await this.copyInstanceConfig(resourcesFolder);
		await this.CopyCustomJs(resourcesFolder);
		await this.copyKernelsToSystemJupyterDirs();
	}

	private async createInstanceFolders(): Promise<void> {
		this.baseDir = path.join(this.getSystemJupyterHomeDir(), 'instances', `${this.utils.generateUuid()}`);
		this.instanceConfigRoot = path.join(this.baseDir, 'config');
		this.instanceDataRoot = path.join(this.baseDir, 'data');
		await this.utils.mkDir(this.baseDir, this.options.install.outputChannel);
		await this.utils.mkDir(this.instanceConfigRoot, this.options.install.outputChannel);
		await this.utils.mkDir(this.instanceDataRoot, this.options.install.outputChannel);
	}

	private async copyInstanceConfig(resourcesFolder: string): Promise<void> {
		let configSource = path.join(resourcesFolder, NotebookConfigFilename);
		let configDest = path.join(this.instanceConfigRoot, NotebookConfigFilename);
		await this.utils.copy(configSource, configDest);
	}

	private async CopyCustomJs(resourcesFolder: string): Promise<void> {
		let customPath = path.join(this.instanceConfigRoot, 'custom');
		await this.utils.mkDir(customPath, this.options.install.outputChannel);
		let customSource = path.join(resourcesFolder, CustomJsFilename);
		let customDest = path.join(customPath, CustomJsFilename);
		await this.utils.copy(customSource, customDest);
	}

	private async copyKernelsToSystemJupyterDirs(): Promise<void> {
		let kernelsExtensionSource = path.join(this.options.install.extensionPath, 'kernels');
		this._systemJupyterDir = path.join(this.getSystemJupyterHomeDir(), 'kernels');
		if (!this.utils.existsSync(this._systemJupyterDir)) {
			await this.utils.mkDir(this._systemJupyterDir, this.options.install.outputChannel);
		}
		await this.utils.copy(kernelsExtensionSource, this._systemJupyterDir);
	}

	private getSystemJupyterHomeDir(): string {
		switch (process.platform) {
			case 'win32':
				let appDataWindows = process.env['APPDATA'];
				return appDataWindows + '\\jupyter';
			case 'darwin':
				return path.resolve(os.homedir(), 'Library/Jupyter');
			default:
				return path.resolve(os.homedir(), '.local/share/jupyter');
		}
	}

	/**
	 * Starts a Jupyter instance using the provided a start command. Server is determined to have
	 * started when the log message with URL to connect to is emitted.
	 */
	protected async startInternal(): Promise<void> {
		if (this.isStarted) {
			return;
		}
		let notebookDirectory = this.getNotebookDirectory();
		// Find a port in a given range. If run into trouble, try another port inside the given range
		let port = await ports.strictFindFreePort(new ports.StrictPortFindOptions(defaultPort, defaultPort + 1000));
		let token = await notebookUtils.getRandomToken();
		this._uri = vscode.Uri.parse(`http://localhost:${port}/?token=${token}`);
		this._port = port.toString();
		let startCommand = `"${this.options.install.pythonExecutable}" -m jupyter notebook --no-browser --notebook-dir "${notebookDirectory}" --port=${port} --NotebookApp.token=${token}`;
		this.notifyStarting(this.options.install, startCommand);

		// Execute the command
		await this.executeStartCommand(startCommand);
	}

	private executeStartCommand(startCommand: string): Promise<void> {
		return new Promise<void>((resolve, reject) => {
			let install = this.options.install;
			this.childProcess = this.spawnJupyterProcess(install, startCommand);
			let stdErrLog: string = '';
			// Add listeners for the process exiting prematurely
			let onErrorBeforeStartup = (err: any) => reject(err);
			let onExitBeforeStart = (err: any) => {
				if (!this.isStarted) {
					reject(localize('notebookStartProcessExitPremature', 'Notebook process exited prematurely with error: {0}, StdErr Output: {1}', err, stdErrLog));
				}
			};
			this.childProcess.on('error', onErrorBeforeStartup);
			this.childProcess.on('exit', onExitBeforeStart);

			// Add listener for the process to emit its web address
			let handleStdout = (data: string | Buffer) => { install.outputChannel.appendLine(data.toString()); };
			let handleStdErr = (data: string | Buffer) => {
				// For some reason, URL info is sent on StdErr
				let [url, port] = this.matchUrlAndPort(data);
				if (url) {
					// For now, will verify port matches
					if (url.authority !== this._uri.authority
						|| url.query !== this._uri.query) {
						this._uri = url;
						this._port = port;
					}
					this.notifyStarted(install, url.toString());
					this._isStarted = true;

					this.updateListeners(handleStdout, handleStdErr, onErrorBeforeStartup, onExitBeforeStart);
					resolve();
				} else {
					stdErrLog += data.toString();
				}
			};
			this.childProcess.stdout.on('data', handleStdout);
			this.childProcess.stderr.on('data', handleStdErr);
		});
	}

	private updateListeners(handleStdout: MessageListener, handleStdErr: MessageListener, onErrorBeforeStartup: ErrorListener, onExitBeforeStart: ErrorListener): void {
		this.childProcess.stdout.removeListener('data', handleStdout);
		this.childProcess.stderr.removeListener('data', handleStdErr);
		this.childProcess.removeListener('error', onErrorBeforeStartup);
		this.childProcess.removeListener('exit', onExitBeforeStart);

		this.childProcess.addListener('error', this.handleConnectionError);
		this.childProcess.addListener('exit', this.handleConnectionClosed);

		process.addListener('exit', this.stop);

		// TODO #897 covers serializing stdout and stderr to a location where we can read from so that user can see if they run into trouble
	}

	private handleConnectionError(error: Error): void {
		let action = this.errorHandler.handleError(error);
		if (action === ErrorAction.Shutdown) {
			this.notify(this.options.install, localize('jupyterError', 'Error sent from Jupyter: {0}', utils.getErrorMessage(error)));
			this.stop();
		}
	}
	private handleConnectionClosed(): void {
		this.childProcess = undefined;
		this._isStarted = false;
	}

	getNotebookDirectory(): string {
		if (this.options.notebookDirectory) {
			if (this.options.notebookDirectory.endsWith('\\')) {
				return this.options.notebookDirectory.substr(0, this.options.notebookDirectory.length - 1) + '/';
			}
			return this.options.notebookDirectory;
		}
		return path.dirname(this.options.documentPath);
	}

	private matchUrlAndPort(data: string | Buffer): [vscode.Uri, string] {
		// regex: Looks for the successful startup log message like:
		//        [C 12:08:51.947 NotebookApp]
		//
		//             Copy/paste this URL into your browser when you connect for the first time,
		//             to login with a token:
		//                http://localhost:8888/?token=f5ee846e9bd61c3a8d835ecd9b965591511a331417b997b7
		let dataString = data.toString();
		let urlMatch = dataString.match(/\[C[\s\S]+ {8}(.+:(\d+)\/.*)$/m);

		if (urlMatch) {
			// Legacy case: manually parse token info if no token/port were passed
			return [vscode.Uri.parse(urlMatch[1]), urlMatch[2]];
		} else if (this._uri && dataString.indexOf(JupyterStartedMessage) > -1) {
			// Default case: detect the notebook started message, indicating our preferred port and token were used
			return [this._uri, this._port];
		}
		return [undefined, undefined];
	}

	private notifyStarted(install: JupyterServerInstallation, jupyterUri: string): void {
		install.outputChannel.appendLine(localize('jupyterOutputMsgStartSuccessful', '... Jupyter is running at {0}', jupyterUri));
	}
	private notify(install: JupyterServerInstallation, message: string): void {
		install.outputChannel.appendLine(message);
	}

	private notifyStarting(install: JupyterServerInstallation, startCommand: string): void {
		install.outputChannel.appendLine(localize('jupyterOutputMsgStart', '... Starting Notebook server'));
		install.outputChannel.appendLine(`    > ${startCommand}`);
	}

	private spawnJupyterProcess(install: JupyterServerInstallation, startCommand: string): ChildProcess {
		// Specify the global environment variables.
		// Note: Get env from the install since it gets used elsewhere
		let env = this.getEnvWithConfigPaths(install.execOptions.env);

		// 'MSHOST_TELEMETRY_ENABLED' and 'MSHOST_ENVIRONMENT' environment variables are set
		// for telemetry purposes used by PROSE in the process where the Jupyter kernel runs
		if (vscode.workspace.getConfiguration('telemetry').get<boolean>('enableTelemetry', true)) {
			env['MSHOST_TELEMETRY_ENABLED'] = true;
		} else {
			env['MSHOST_TELEMETRY_ENABLED'] = false;
		}

		env['MSHOST_ENVIRONMENT'] = 'ADSClient-' + vscode.version;

		// Start the notebook process
		let options: SpawnOptions = {
			shell: true,
			env: env,
			detached: false
		};
		let childProcess = this.utils.spawn(startCommand, [], options);
		return childProcess;
	}

	private getEnvWithConfigPaths(env: {}): any {
		let newEnv: { [key: string]: string } = Object.assign({}, env);
		newEnv['JUPYTER_CONFIG_DIR'] = this.instanceConfigRoot;
		newEnv['JUPYTER_PATH'] = this.instanceDataRoot;
		return newEnv;
	}
}

class ErrorHandler {
	private numErrors: number = 0;

	public handleError(error: Error): ErrorAction {
		this.numErrors++;
		return this.numErrors > 3 ? ErrorAction.Shutdown : ErrorAction.Continue;
	}
}

enum ErrorAction {
	Continue = 1,
	Shutdown = 2
}