index.js

const npmPackage = require('./package.json');
const crypto = require('crypto');
const express = require('express');
const proxy = require('express-http-proxy');
const cors = require('cors');
const bodyParser = require('body-parser');
const urlUtil = require('url');
const chalk = require('chalk');

/** The caching proxy server. */
class JsonCachingProxy {
	/**
	 * @param {Object} options - Options passed into the ctor will override defaults if defined
	 */
	constructor(options = {}) {
		this.defaultOptions = {
			remoteServerUrl: 'http://localhost:8080',
			proxyPort: 3001,
			harObject: null,
			commandPrefix: 'proxy',
			proxyHeaderIdentifier: 'caching-proxy-playback',
			middlewareList: [],
			excludedRouteMatchers: [],
			excludedStatusMatchers: [],
			cacheBustingParams: [],
			cacheEverything: false,
			dataPlayback: true,
			dataRecord: true,
			showConsoleOutput: false,
			proxyTimeout: 3600000, // one hour
			deleteCookieDomain: false, // Removes the domain portion from all cookies
			overrideCors: false,
			useCorsCredentials: false
		};

		// Ignore undefined values and combine the options with defaults
		this.options = Object.assign({},
			this.defaultOptions,
			Object.keys(options).reduce(function (passedOpts, key) {
				if (typeof options[key] !== 'undefined' && options[key] !== null) passedOpts[key] = options[key];
				return passedOpts;
			}, {}));

		// Will be set when the app starts
		this.server = null;

		this.app = express();
		this.routeCache = {};

		this.excludedParamMap = this.options.cacheBustingParams.reduce((map, param) => { map[param] = true; return map }, {});

		if (this.options.overrideCors) {
			this.app.use(cors({credentials: this.options.useCorsCredentials, origin: this.options.overrideCors}));
			this.app.options('*', cors({credentials: this.options.useCorsCredentials, origin: this.options.overrideCors}));
		}

		if (this.options.showConsoleOutput) {
			this.log = console.log;
			this.err = console.error;
		} else {
			this.log = () => false;
			this.err = () => false;
		}
	}

	/**
	* Remove the domain portion of any cookies from the object. Remove the secure attribute so we can set cookies to https targets
	* @param {Object} cookies - Express cookies array
	* @returns {Object[]} - Cookies with domain portion removed
	*/
	removeCookiesDomain(cookies) {
		return cookies.map(c => {
			let cookieParts = c.split(';');
			let newCookieParts = [];

			cookieParts.forEach(c => {
				if (c.indexOf('domain') === -1 && c.indexOf('secure') === -1) {
					newCookieParts.push(c);
        }
			});

			return newCookieParts.join(';');
		});
	}

	/**
	 * Returns an Object's own  properties into an array of name-value pair objects
	 * @param {Object} obj
	 * @returns {Object[]}
	 */
	convertToNameValueList(obj) {
		return typeof obj === 'object' ? Object.keys(obj).map(key => { return { name: key, value: obj[key] }; }) : [];
	}

	/**
	 * Generate a unique hash key from a har file entry's request object: TODO: Include headers?
	 * @param {Object} harEntryReq - HAR request object
	 * @returns {Object} A unique key, hash tuple that identifies the request
	 */
	genKeyFromHarReq(harEntryReq) {
		let { method, url, queryString = [], postData = { text: '' } } = harEntryReq;
		let uri = urlUtil.parse(url).pathname;
		let postParams = postData.text;

		queryString = queryString.filter(param => !this.excludedParamMap[param.name]);

		let plainText = `${method} ${uri} ${JSON.stringify(queryString)} ${postParams}`;
		let hash = crypto.createHash('md5').update(plainText).digest("hex");
		let key = `${method} ${uri} ${hash}`;

		return { key, hash };
	}

	/**
	 * Takes a generic express request and convert it into a HAR request so that a unique key can be generated
	 * @param {Object} req - An express IncomingMessage request
	 * @returns {string} A unique hash key that identifies the request
	 */
	genKeyFromExpressReq(req) {
		return this.genKeyFromHarReq({
			method: req.method,
			url: req.url,
			queryString: this.convertToNameValueList(req.query),
			postData: { text: req.body && req.body.length > 0 ? req.body.toString('utf8') : '' }
		});
	}

	/**
	 * Build a HAR entry object from an express Request and response
	 * @param {string} startedDateTime - An ISO Datetime String
	 * @param {Object} req - An express IncomingMessage request
	 * @param {Object} res - An express ServerResponse response
	 * @param {Object} data - An express response body (the content)
	 * @returns {Object} A HAR entry object
	 */
	createHarEntry(startedDateTime, req, res, data) {
		let reqMimeType = req.get('Content-Type');
		let resMimeType = res.get('Content-Type') || 'text/plain';
		let encoding = (/^text\/|^application\/(javascript|json)/).test(resMimeType) ? 'utf8' : 'base64';

		let entry = {
			request: {
				startedDateTime: startedDateTime,
				method: req.method.toUpperCase(),
				url: req.url,
				cookies: this.convertToNameValueList(req.cookies),
				headers: this.convertToNameValueList(req.headers),
				queryString: this.convertToNameValueList(req.query),
				headersSize: -1,
				bodySize: -1
			},
			response: {
				status: res.statusCode,
				statusText: res.statusMessage,
				cookies: this.convertToNameValueList(res.cookies),
				headers: this.convertToNameValueList(res._headers).filter(header => header.name.toLowerCase() !== 'content-encoding'), // Not  compressed
				content: {
					size: -1,
					mimeType: resMimeType,
					text: data.toString(encoding),
					encoding: encoding
				},
				headersSize: -1,
				bodySize: -1
			}
		};

		// Add the request body if it exists
		if (req.body && req.body.length > 0) {
			entry.request.postData = {
				mimeType: reqMimeType,
				text: req.body.toString(encoding)
			};
		}

		return entry;
	}

	/**
	 * Check to see if the pieces of a request are excluded. This checks only the method and the uri. It uses the list
	 * of regExp matchers to test
	 * @param {string} method - e.g. GET, POST, PUT, etc.
	 * @param {string} uri - e.g. http://www.api.com/rest/accounts
	 * @returns {boolean} Whether the test is true for some matcher
	 */
	isRouteExcluded(method, uri) {
		return this.options.excludedRouteMatchers.some(regExp => regExp.test(`${method} ${uri}`))
	}

	/**
	 * Check to see if the status of a response is excluded. It uses the list of regExp matchers to test
	 * @param {number} status - e.g. 404, 503, etc.
	 * @returns {boolean} Whether the test is true for some matcher
	 */
	isStatusExcluded(status) {
		return this.options.excludedStatusMatchers.some(regExp => regExp.test(status))
	}

	/**
	 * Add express routes for each entry in a harObject. The harObject would have been read in from a har file at some point
	 * @param {Object} harObject - A standard HAR file object that contains a collection of entries
	 * @returns {JsonCachingProxy}
	 */
	addHarEntriesToCache(harObject) {
		if (harObject) {
			harObject.log.entries.forEach(entry => {
				let { key, hash } = this.genKeyFromHarReq(entry.request);

				if (this.isRouteExcluded(entry.request.method, entry.request.url)) {
					this.log(chalk.red('Excluded from Cache', chalk.bold(entry.request.method, entry.request.url)));
					return;
				}

				if (this.isStatusExcluded(entry.response.status)) {
					this.log(chalk.red('Excluded from Cache', chalk.bold(entry.request.method, entry.request.url, `\tStatus: ${entry.response.status}`)));
					return;
				}

				// Only cache things that have content. Some times HAR files generated elsewhere will be missing this parameter
				if (entry.response.content.text) {
					let mimeType = entry.response.content.mimeType;

					if (entry.response.headers && (this.options.cacheEverything || !this.options.cacheEverything && mimeType && mimeType.indexOf('application/json') >= 0)) {
						// Remove content-encoding. gzip compression won't be used
						entry.response.headers = entry.response.headers.filter(header => header.name.toLowerCase() !== 'content-encoding');
						this.routeCache[key] = entry;

						this.log(chalk.yellow('Saved to Cache', hash, chalk.bold(entry.request.method, entry.request.url)));
					}
				}
			});
		}

		return this;
	}

	/**
	 * Add the admin express routes for controlling the proxy server through a browser. Allows one to make GET requests to clear
	 * the cache, disable/enable playback/recording, and generate a har file of the cache to download for later use.
	 * @returns {JsonCachingProxy}
	 */
	addAdminRoutes() {
		// These are not really restful because the GET is changing state. But it's easier to use in a browser
		this.app.get(`/${this.options.commandPrefix}/playback`, (req, res) => {
			this.options.dataPlayback = typeof req.query.enabled !== 'undefined' ? req.query.enabled === 'true'.toLowerCase() : this.options.dataPlayback;
			this.log(chalk.blue(`Replay from cache: ${this.options.dataPlayback}`));
			res.send(`Replay from cache: ${this.options.dataPlayback}`);
		});

		this.app.get(`/${this.options.commandPrefix}/record`, (req, res) => {
			this.options.dataRecord = typeof req.query.enabled !== 'undefined' ? req.query.enabled === 'true'.toLowerCase() : this.options.dataRecord;
			this.log(chalk.blue('Saving to cache: ' + this.options.dataRecord));
			res.send(`Saving to cache: ${this.options.dataRecord}`);
		});

		this.app.get(`/${this.options.commandPrefix}/clear`, (req, res) => {
			this.routeCache = {};
			this.log(chalk.blue('Cleared cache'));
			res.send('Cleared cache');
		});

		this.app.get(`/${this.options.commandPrefix}/har`, (req, res) => {
			this.log(chalk.blue('Generating har file'));

			let har = {
				log: {
					version: "1.2",
					creator: {
						name: npmPackage.name,
						version: npmPackage.version
					},
					entries: []
				}
			};

			Object.keys(this.routeCache).forEach(key => har.log.entries.push(this.routeCache[key]));

			res.setHeader('Content-disposition', 'attachment; filename=json-caching-proxy.har');
			res.setHeader('Content-type', 'application/json');
			res.json(har);
		});

		return this;
	}

	/**
	 * Add user supplied middleware routes to express in order to handle special cases (browser-sync middleware options)
	 * @param {Object[]} middlewareList - A list of route/handler pairs
	 * @returns {JsonCachingProxy}
	 */
	addMiddleWareRoutes(middlewareList) {
		middlewareList.forEach(mw => {
			if (mw.route) {
				this.app.use(mw.route, mw.handle);
			} else {
				this.app.use(mw.handle);
			}
		});

		return this;
	}

	/**
	 * Add Request body parsing into RAW if there is actual body content
	 * @returns {JsonCachingProxy}
	 */
	addBodyParser() {
		this.app.use(bodyParser.raw({ type: '*/*', limit: '100mb' }));

		// Remove the body if there is no body content. Some sites check for malformed requests
		this.app.use((req, res, next) => {
			if (!req.headers['content-length']) {
				delete req.body;
			}

			next();
		});

		return this;
	}

	/**
	 * An express route that reads from the cache if possible for any routes persisted in cache memory
	 * @returns {JsonCachingProxy}
	 */
	addCachingRoute() {
		this.app.use('/', (req, res, next) => {
			if (!this.options.dataPlayback) {
				next();
			} else {
				let { key, hash } = this.genKeyFromExpressReq(req);
				let entry = this.routeCache[key];

				if (!(entry && entry.response && entry.response.content)) {
					next();
				} else {
					let response = entry.response;
					let headerList = response.headers || [];
					let text = response.content.text || '';
					let encoding = response.content.encoding || 'utf8';

					headerList.forEach(function (header) {
						res.set(header.name, header.value);
					});

					// Use our header identifier to signal that this response is cached
					res.set(this.options.proxyHeaderIdentifier, true);

					if (text.length === 0) {
						res.sendStatus(response.status);
					} else {
						if (encoding === 'base64') {
							let bin = new Buffer(text, 'base64');
							res.writeHead(response.status, {
								'Content-Type': response.content.mimeType,
								'Content-Length': bin.length
							});
							res.end(bin);
						} else {
							res.status(response.status);
							res.type(response.content.mimeType);
							res.send(text);
						}
					}

					this.log(chalk.green('Reading From Cache', hash, chalk.bold(entry.request.method, entry.request.url)));
				}
			}
		});

		return this;
	}

	/**
	 * Add the proxy route that makes the actual request to the target server and cache the response when it comes back.
	 * Modifies locations on redirects.
	 * @returns {JsonCachingProxy}
	 */
	addProxyRoute() {
		this.app.use('/', proxy(this.options.remoteServerUrl, {
			userResDecorator: (rsp, rspData, req, res) => {
				// Handle Redirects by modifying the location property of the response header
				let location = res.get('location');
				if (location) {
					res.location(urlUtil.parse(location).path);
				}

				if (this.options.overrideCors && this.options.overrideCors !== '*') {
					res.header('access-control-allow-origin', this.options.overrideCors);
				}

				if (this.options.deleteCookieDomain && res._headers['set-cookie']) {
					res.header('set-cookie', this.removeCookiesDomain(res._headers['set-cookie'] || []));
				}

				if (this.isRouteExcluded(req.method, req.url)) {
					this.log(chalk.red('Exclude Proxied Resource', chalk.bold(req.method, req.url)));
				} else if (this.isStatusExcluded(res.statusCode)) {
					this.log(chalk.red('Exclude Proxied Resource', chalk.bold(req.method, req.url, `\tStatus: ${res.statusCode}`)));
				} else {
					let mimeType = res._headers['content-type'];

					if (this.options.dataRecord && (this.options.cacheEverything || !this.options.cacheEverything && mimeType && mimeType.indexOf('application/json') >= 0)) {
						let { key, hash } = this.genKeyFromExpressReq(req);
						let entry = this.createHarEntry(new Date().toISOString(), req, res, rspData);
						this.routeCache[key] = entry;
						this.log(chalk.yellow('Saved to Cache', hash, chalk.bold(entry.request.method, entry.request.url)));
					} else {
						this.log(chalk.gray('Proxied Resource', chalk.bold(req.method, req.url)));
					}
				}

				return rspData;
			}
		}));

		return this;
	}

	/**
	 * Start the server and generate any log output if needed
	 * @param {Function} callback fn executed after the server has started
	 * @returns {JsonCachingProxy}
	 */
	start(onStarted) {
		this.server = this.app.listen(this.options.proxyPort);
		this.server.setTimeout(this.options.proxyTimeout);

		this.log(chalk.bold(`\JSON Caching Proxy Started:`));
		this.log(chalk.gray(`===========================\n`));
		this.log(`Remote server url: \t${chalk.bold(this.options.remoteServerUrl)}`);
		this.log(`Proxy running on port: \t${chalk.bold(this.options.proxyPort)}`);
		this.log(`Proxy Timeout: \t\t${chalk.bold(this.options.proxyTimeout)}`);
		this.log(`Replay cache: \t\t${chalk.bold(this.options.dataPlayback)}`);
		this.log(`Save to cache: \t\t${chalk.bold(this.options.dataRecord)}`);
		this.log(`Command prefix: \t${chalk.bold(this.options.commandPrefix)}`);
		this.log(`Proxy response header: \t${chalk.bold(this.options.proxyHeaderIdentifier)}`);
		this.log(`Cache all: \t\t${chalk.bold(this.options.cacheEverything)}`);
		this.log(`Delete cookies domain: \t${chalk.bold(this.options.deleteCookieDomain)}`);
		this.log(`Override CORS origin: \t${chalk.bold(this.options.overrideCors)}`);
		this.log(`Use CORS Credentials: \t${chalk.bold(this.options.useCorsCredentials)}`);
		this.log(`Cache busting params: \t${chalk.bold(this.options.cacheBustingParams)}`);
		this.log(`Excluded routes: `);
		this.options.excludedRouteMatchers.forEach((regExp) => {
			this.log(`\t\t\t${chalk.bold(regExp)}`)
		});
		this.log(`Excluded statuses: `);
		this.options.excludedStatusMatchers.forEach((regExp) => {
			this.log(`\t\t\t${chalk.bold(regExp)}`)
		});

		this.log('\nListening...\n');

		// The order of these routes is important
		this.addHarEntriesToCache(this.options.harObject);
		this.addAdminRoutes();
		this.addMiddleWareRoutes(this.options.middlewareList);
		this.addBodyParser();
		this.addCachingRoute();
		this.addProxyRoute();

		onStarted && onStarted();

		return this;
	}

	/**
	 * Stops the proxy server
		* @param {Function} callback fn executed after the server has stopped
	 * @returns {JsonCachingProxy}
	 */
	stop(onStopped) {
		if (this.server) {
			this.server.close(onStopped);
			this.log(chalk.bold('\nStopping Proxy Server'));
		}

		return this;
	}

	/**
	 * Returns the options passed into the proxy
	 * @returns {Object}
	 */
	getOptions() { return this.options; }

	/**
	 * Returns the default options that are used when no options are passed in
	 * @returns {Object}
	 */
	getDefaultOptions() { return this.defaultOptions; }

	/**
	 * Returns the Express App
	 * @returns {Object}
	 */
	getApp() { return this.app; }

	/**
	 * Returns the Node server object
	 * @returns {Object}
	 */
	getServer() { return this.server; }

	/**
	 * Returns the key value map of all the excluded params
	 * @returns {Object}
	 */
	getExcludedParamMap() { return this.excludedParamMap; }

	/**
	 * Count of total cached routes in memory
	 * @returns {number}
	 */
	getTotalCachedRoutes() { return Object.keys(this.routeCache).length; }

	/**
	 * Determines if we have anything in the cache
	 * @returns {boolean}
	 */
	isRouteCacheEmpty() { return this.getTotalCachedRoutes() === 0; }

	/**
	 * Is the server sending us cached responses
	 * @returns {boolean}
	 */
	isReplaying() { return this.options.dataPlayback; }

	/**
	 * Is the server saving to the cache
	 * @returns {JsonCachingProxy}
	 */
	isRecording() { return this.options.dataRecord; }
}

module.exports = JsonCachingProxy;