Web APIs with Express

web_apis_with_express

const express = require('express');
const morgan = require('morgan'); // Morgan logging tool

const app = express();

// This is middleware that requests pass through
// on their way to the final handler
// *** a request can pass through multiple functions before a response is sent ***
app.use(morgan('dev')); // Morgan logging tool

// Morgan documenation:
// https://www.npmjs.com/package/morgan

// This is the final request handler
// add a function that responds with some text to GET request to the root URL (/)
// app.get(PATH, HANDLER)

// Request documentation: https://expressjs.com/en/4x/api.html#req

app.get('/', (req, res) => {
	res.send('Hello Express!');
});

// *************************

// SUM
// http://localhost:8000/sum?a=3&b=4
// Result: The sum of a and b is 7.
app.get('/sum', (req, res) => {
	//1. get values from the request
	// const a = req.query.a;
	// const b = req.query.b;

	const { a, b } = req.query;

	//2. validate the values
	if (!a) {
		//3. a was not provided
		return res.status(400).send('Please provide a');
	}

	if (!b) {
		//3. b was not provided
		return res.status(400).send('Please provide b');
	}

	//4. and 5. if everything is valid  do the processing.

	const numA = parseFloat(a);
	const numB = parseFloat(b);

	if (Number.isNaN(numA)) {
		return res.status(400).send('a must be a number');
	}

	if (Number.isNaN(numB)) {
		return res.status(400).send('b must be a number');
	}

	const numC = numA + numB;

	const result = `The sum of ${numA} and ${numB} is ${numC}.`;

	//6. send the response
	res.send(result);
});

// CIPHER
// EX: http://localhost:8000/cipher?text=abc&shift=1
// Result: BCD
/*
Create an endpoint /cipher. The handler function should accept a query parameter named text and one named shift. Encrypt the text using a simple shift cipher also known as a Caesar Cipher. It is a simple substitution cipher where each letter is shifted a certain number of places down the alphabet. So if the shift was 1 then A would be replaced by B, and B would be replaced by C and C would be replaced by D and so on until finally Z would be replaced by A. using this scheme encrypt the text with the given shift and return the result to the client. Hint - String.fromCharCode(65) is an uppercase A and 'A'.charCodeAt(0) is the number 65. 65 is the integer value of uppercase A in UTF-16. See the documentation for details.

https://learncryptography.com/classical-encryption/caesar-cipher

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/fromCharCode
*/

app.get('/cipher', (req, res) => {
	const { text, shift } = req.query;

	// validation: both values are required, shift must be a number
	if (!text) {
		return res.status(400).send('text is required');
	}

	if (!shift) {
		return res.status(400).send('shift is required');
	}

	const numShift = parseFloat(shift);

	if (Number.isNaN(numShift)) {
		return res.status(400).send('shift must be a number');
	}

	// all valid, perform the task
	// Make the text uppercase for convenience
	// the question did not say what to do with punctuation marks
	// and numbers so we will ignore them and only convert letters.
	// Also just the 26 letters of the alphabet in typical use in the US
	// and UK today. To support an international audience we will have to
	// do more
	// Create a loop over the characters, for each letter, covert
	// using the shift

	const base = 'A'.charCodeAt(0); // get char code

	const cipher = text
		.toUpperCase()
		.split('') // create an array of characters
		.map(char => {
			// map each original char to a converted char
			const code = char.charCodeAt(0); //get the char code

			// if it is not one of the 26 letters ignore it
			if (code < base || code > base + 26) {
				return char;
			}

			// otherwise convert it
			// get the distance from A
			let diff = code - base;
			diff = diff + numShift;

			// in case shift takes the value past Z, cycle back to the beginning
			diff = diff % 26;

			// convert back to a character
			const shiftedChar = String.fromCharCode(base + diff);
			return shiftedChar;
		})
		.join(''); // construct a String from the array

	// Return the response
	res.status(200).send(cipher);
});

// LOTTO (array)
// EX: http://localhost:8000/lotto?numbers=11&numbers=12&numbers=13&numbers=14&numbers=15&numbers=16
/*
Create a new endpoint /lotto that accepts an array of 6 distinct numbers between 1 and 20 named numbers. The function then randomly generates 6 numbers between 1 and 20. Compare the numbers sent in the query with the randomly generated numbers to determine how many match. If fewer than 4 numbers match respond with the string "Sorry, you lose". If 4 numbers match respond with the string "Congratulations, you win a free ticket", if 5 numbers match respond with "Congratulations! You win $100!". If all 6 numbers match respond with "Wow! Unbelievable! You could have won the mega millions!".
*/

app.get('/lotto', (req, res) => {
	const { numbers } = req.query;

	// validation:
	// 1. the numbers array must exist
	// 2. must be an array
	// 3. must be 6 numbers
	// 4. numbers must be between 1 and 20

	if (!numbers) {
		return res.status(200).send('numbers is required');
	}

	if (!Array.isArray(numbers)) {
		return res.status(200).send('numbers must be an array');
	}

	const guesses = numbers
		.map(n => parseInt(n))
		.filter(n => !Number.isNaN(n) && (n >= 1 && n <= 20));

	if (guesses.length != 6) {
		return res
			.status(400)
			.send('numbers must contain 6 integers between 1 and 20');
	}

	// fully validated numbers

	// here are the 20 numbers to choose from
	const stockNumbers = Array(20)
		.fill(1)
		.map((_, i) => i + 1);

	//randomly choose 6
	const winningNumbers = [];
	for (let i = 0; i < 6; i++) {
		const ran = Math.floor(Math.random() * stockNumbers.length);
		winningNumbers.push(stockNumbers[ran]);
		stockNumbers.splice(ran, 1);
	}

	//compare the guesses to the winning number
	let diff = winningNumbers.filter(n => !guesses.includes(n));

	// construct a response
	let responseText;

	switch (diff.length) {
		case 0:
			responseText = 'Wow! Unbelievable! You could have won the mega millions!';
			break;
		case 1:
			responseText = 'Congratulations! You win $100!';
			break;
		case 2:
			responseText = 'Congratulations, you win a free ticket!';
			break;
		default:
			responseText = 'Sorry, you lose';
	}

	// uncomment below to see how the results ran

	// res.json({
	// 	guesses,
	// 	winningNumbers,
	// 	diff,
	// 	responseText
	// });

	res.send(responseText);
});

// *************************
// *************************

// HANDLE QUERYSTRING
// in browser: http://localhost:8000/greetings?name=Legolas&race=elf
app.get('/greetings', (req, res) => {
	//1. get values from the request
	const name = req.query.name;
	const race = req.query.race;

	//2. validate the values
	if (!name) {
		//3. name was not provided
		return res.status(400).send('Please provide a name');
	}

	if (!race) {
		//3. race was not provided
		return res.status(400).send('Please provide a race');
	}

	//4. and 5. both name and race are valid so do the processing.
	const greeting = `Greetings ${name} the ${race}, welcome to our kingdom.`;

	//6. send the response
	res.send(greeting);
});

// SEE QUERY OBJECT IN TERMINAL
app.get('/queryViewer', (req, res) => {
	console.log(req.query);
	res.end(); //do not send any data back to the client
});

// SEE REQUEST OBJECT
app.get('/echo/:name', (req, res) => {
	const thisRoute = JSON.stringify(req.route);
	const thisParams = JSON.stringify(req.params);
	const thisQuery = JSON.stringify(req.query);

	const responseText = `Here are some details of your request:
    Base URL: ${req.baseUrl}
    Host: ${req.hostname}
    Path: ${req.path}
    Route: ${req.route}
    Params: ${req.params.name}
    Query: ${req.query.id}

    RouteObj: ${thisRoute}

    ParamsObj: ${thisParams}

    QueryObj: ${thisQuery}

    Method: ${req.method}
    Body: ${req.body}
    App: ${req.app}
    IP: ${req.ip}
    Fresh: ${req.fresh}
    Stale: ${req.stale}
  `;
	res.send(responseText);
});

/*
// RESULT
// in browser: http://localhost:8000/echo/tami?id=99

Here are some details of your request:
Base URL:
Host: localhost
Path: /echo/tami
Route: [object Object]
Params: tami
Query: 99

RouteObj: {"path":"/echo/:name","stack":[{"name":"<anonymous>
	","keys":[],"regexp":{"fast_star":false,"fast_slash":false},"method":"get"}],"methods":{"get":true}}

	ParamsObj: {"name":"tami"}

	QueryObj: {"id":"99"}

	Method: GET
	Body: undefined
	App: function(req, res, next) {
	app.handle(req, res, next);
	}
	IP: ::1
	Fresh: false
	Stale: true

*/

// TEST ENDPOINTS
app.get('/burgers', (req, res) => {
	res.send('We have juicy cheese burgers!');
});

app.get('/pizza/pepperoni', (req, res) => {
	res.send('Your pizza is on the way!');
});

app.get('/pizza/pineapple', (req, res) => {
	res.send("We don't serve that here. Never call again!");
});

// the console.log is only visible in Terminal
app.listen(8000, () => {
	console.log('Express server is listening on port 8000!');
});

// run this app with:
// node app.js
// then view in browser at:
// http://localhost:8000/
const express = require('express');
const morgan = require('morgan'); // Morgan logging tool

const app = express();

// This is middleware that requests pass through
// on their way to the final handler
// *** a request can pass through multiple functions before a response is sent ***
app.use(morgan('dev')); // Morgan logging tool

// Morgan documenation:
// https://www.npmjs.com/package/morgan

// This is the final request handler
// add a function that responds with some text to GET request to the root URL (/)
// app.get(PATH, HANDLER)

// Request documentation: https://expressjs.com/en/4x/api.html#req

app.get('/', (req, res) => {
	res.send('Hello Express!');
});

// *************************

// SUM
// http://localhost:8000/sum?a=3&b=4
// Result: The sum of a and b is 7.
app.get('/sum', (req, res) => {
	//1. get values from the request
	// const a = req.query.a;
	// const b = req.query.b;

	const { a, b } = req.query;

	//2. validate the values
	if (!a) {
		//3. a was not provided
		return res.status(400).send('Please provide a');
	}

	if (!b) {
		//3. b was not provided
		return res.status(400).send('Please provide b');
	}

	//4. and 5. if everything is valid  do the processing.

	const numA = parseFloat(a);
	const numB = parseFloat(b);

	if (Number.isNaN(numA)) {
		return res.status(400).send('a must be a number');
	}

	if (Number.isNaN(numB)) {
		return res.status(400).send('b must be a number');
	}

	const numC = numA + numB;

	const result = `The sum of ${numA} and ${numB} is ${numC}.`;

	//6. send the response
	res.send(result);
});

// CIPHER
// EX: http://localhost:8000/cipher?text=abc&shift=1
// Result: BCD
/*
Create an endpoint /cipher. The handler function should accept a query parameter named text and one named shift. Encrypt the text using a simple shift cipher also known as a Caesar Cipher. It is a simple substitution cipher where each letter is shifted a certain number of places down the alphabet. So if the shift was 1 then A would be replaced by B, and B would be replaced by C and C would be replaced by D and so on until finally Z would be replaced by A. using this scheme encrypt the text with the given shift and return the result to the client. Hint - String.fromCharCode(65) is an uppercase A and 'A'.charCodeAt(0) is the number 65. 65 is the integer value of uppercase A in UTF-16. See the documentation for details.

https://learncryptography.com/classical-encryption/caesar-cipher

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/fromCharCode
*/

app.get('/cipher', (req, res) => {
	const { text, shift } = req.query;

	// validation: both values are required, shift must be a number
	if (!text) {
		return res.status(400).send('text is required');
	}

	if (!shift) {
		return res.status(400).send('shift is required');
	}

	const numShift = parseFloat(shift);

	if (Number.isNaN(numShift)) {
		return res.status(400).send('shift must be a number');
	}

	// all valid, perform the task
	// Make the text uppercase for convenience
	// the question did not say what to do with punctuation marks
	// and numbers so we will ignore them and only convert letters.
	// Also just the 26 letters of the alphabet in typical use in the US
	// and UK today. To support an international audience we will have to
	// do more
	// Create a loop over the characters, for each letter, covert
	// using the shift

	const base = 'A'.charCodeAt(0); // get char code

	const cipher = text
		.toUpperCase()
		.split('') // create an array of characters
		.map(char => {
			// map each original char to a converted char
			const code = char.charCodeAt(0); //get the char code

			// if it is not one of the 26 letters ignore it
			if (code < base || code > base + 26) {
				return char;
			}

			// otherwise convert it
			// get the distance from A
			let diff = code - base;
			diff = diff + numShift;

			// in case shift takes the value past Z, cycle back to the beginning
			diff = diff % 26;

			// convert back to a character
			const shiftedChar = String.fromCharCode(base + diff);
			return shiftedChar;
		})
		.join(''); // construct a String from the array

	// Return the response
	res.status(200).send(cipher);
});

// LOTTO (array)
// EX: http://localhost:8000/lotto?numbers=11&numbers=12&numbers=13&numbers=14&numbers=15&numbers=16
/*
Create a new endpoint /lotto that accepts an array of 6 distinct numbers between 1 and 20 named numbers. The function then randomly generates 6 numbers between 1 and 20. Compare the numbers sent in the query with the randomly generated numbers to determine how many match. If fewer than 4 numbers match respond with the string "Sorry, you lose". If 4 numbers match respond with the string "Congratulations, you win a free ticket", if 5 numbers match respond with "Congratulations! You win $100!". If all 6 numbers match respond with "Wow! Unbelievable! You could have won the mega millions!".
*/

app.get('/lotto', (req, res) => {
	const { numbers } = req.query;

	// validation:
	// 1. the numbers array must exist
	// 2. must be an array
	// 3. must be 6 numbers
	// 4. numbers must be between 1 and 20

	if (!numbers) {
		return res.status(200).send('numbers is required');
	}

	if (!Array.isArray(numbers)) {
		return res.status(200).send('numbers must be an array');
	}

	const guesses = numbers
		.map(n => parseInt(n))
		.filter(n => !Number.isNaN(n) && (n >= 1 && n <= 20));

	if (guesses.length != 6) {
		return res
			.status(400)
			.send('numbers must contain 6 integers between 1 and 20');
	}

	// fully validated numbers

	// here are the 20 numbers to choose from
	const stockNumbers = Array(20)
		.fill(1)
		.map((_, i) => i + 1);

	//randomly choose 6
	const winningNumbers = [];
	for (let i = 0; i < 6; i++) {
		const ran = Math.floor(Math.random() * stockNumbers.length);
		winningNumbers.push(stockNumbers[ran]);
		stockNumbers.splice(ran, 1);
	}

	//compare the guesses to the winning number
	let diff = winningNumbers.filter(n => !guesses.includes(n));

	// construct a response
	let responseText;

	switch (diff.length) {
		case 0:
			responseText = 'Wow! Unbelievable! You could have won the mega millions!';
			break;
		case 1:
			responseText = 'Congratulations! You win $100!';
			break;
		case 2:
			responseText = 'Congratulations, you win a free ticket!';
			break;
		default:
			responseText = 'Sorry, you lose';
	}

	// uncomment below to see how the results ran

	// res.json({
	// 	guesses,
	// 	winningNumbers,
	// 	diff,
	// 	responseText
	// });

	res.send(responseText);
});

// *************************
// *************************

// HANDLE QUERYSTRING
// in browser: http://localhost:8000/greetings?name=Legolas&race=elf
app.get('/greetings', (req, res) => {
	//1. get values from the request
	const name = req.query.name;
	const race = req.query.race;

	//2. validate the values
	if (!name) {
		//3. name was not provided
		return res.status(400).send('Please provide a name');
	}

	if (!race) {
		//3. race was not provided
		return res.status(400).send('Please provide a race');
	}

	//4. and 5. both name and race are valid so do the processing.
	const greeting = `Greetings ${name} the ${race}, welcome to our kingdom.`;

	//6. send the response
	res.send(greeting);
});

// SEE QUERY OBJECT IN TERMINAL
app.get('/queryViewer', (req, res) => {
	console.log(req.query);
	res.end(); //do not send any data back to the client
});

// SEE REQUEST OBJECT
app.get('/echo/:name', (req, res) => {
	const thisRoute = JSON.stringify(req.route);
	const thisParams = JSON.stringify(req.params);
	const thisQuery = JSON.stringify(req.query);

	const responseText = `Here are some details of your request:
    Base URL: ${req.baseUrl}
    Host: ${req.hostname}
    Path: ${req.path}
    Route: ${req.route}
    Params: ${req.params.name}
    Query: ${req.query.id}

    RouteObj: ${thisRoute}

    ParamsObj: ${thisParams}

    QueryObj: ${thisQuery}

    Method: ${req.method}
    Body: ${req.body}
    App: ${req.app}
    IP: ${req.ip}
    Fresh: ${req.fresh}
    Stale: ${req.stale}
  `;
	res.send(responseText);
});

/*
// RESULT
// in browser: http://localhost:8000/echo/tami?id=99

Here are some details of your request:
Base URL:
Host: localhost
Path: /echo/tami
Route: [object Object]
Params: tami
Query: 99

RouteObj: {"path":"/echo/:name","stack":[{"name":"<anonymous>
	","keys":[],"regexp":{"fast_star":false,"fast_slash":false},"method":"get"}],"methods":{"get":true}}

	ParamsObj: {"name":"tami"}

	QueryObj: {"id":"99"}

	Method: GET
	Body: undefined
	App: function(req, res, next) {
	app.handle(req, res, next);
	}
	IP: ::1
	Fresh: false
	Stale: true

*/

// TEST ENDPOINTS
app.get('/burgers', (req, res) => {
	res.send('We have juicy cheese burgers!');
});

app.get('/pizza/pepperoni', (req, res) => {
	res.send('Your pizza is on the way!');
});

app.get('/pizza/pineapple', (req, res) => {
	res.send("We don't serve that here. Never call again!");
});

// the console.log is only visible in Terminal
app.listen(8000, () => {
	console.log('Express server is listening on port 8000!');
});

// run this app with:
// node app.js
// then view in browser at:
// http://localhost:8000/