eitherIOExercise.js

var _ = require('ramda');
var P = require('pointfree-fantasy');
var map = P.map;
var compose = P.compose;
var Maybe = require('pointfree-fantasy/instances/maybe');
var Identity = P.I;

var Either = require('data.either');
var Left = Either.Left;
var Right = Either.Right;
var IO = require('./IO');
var runIO = IO.runIO;
IO.extendFn();


// Exercise 1
// ==========
// Write a function that uses checkActive() and showWelcome() to grant access or return the error
console.log("--------Start exercise 1--------");

var showWelcome = compose(_.add( "Welcome "), _.prop('name'));

var checkActive = function(user) {
	return user.active ? Right(user) : Left('Your account is not active')
};

var ex1 = compose(map(showWelcome), checkActive);

assertDeepEqual(Left('Your account is not active'), ex1({active: false, name: 'Gary'}));
assertDeepEqual(Right('Welcome Theresa'), ex1({active: true, name: 'Theresa'}));
console.log("exercise 1...ok!");

// Exercise 2
// ==========
// Write a validation function that checks for a length > 3. It should return Right(x)
// if it is greater than 3 and Left("You need > 3") otherwise
console.log("--------Start exercise 2--------");

var ex2 = function(x) {
	if (x.length > 3) {
		return Right(x);
	}

	return Left("You need > 3");
};

assertDeepEqual(Right("fpguy99"), ex2("fpguy99"));
assertDeepEqual(Left("You need > 3"), ex2("..."));
console.log("exercise 2...ok!");

// Exercise 3
// ==========
// Use ex2 above and Either as a functor to save the user if they are valid

var save = function(x){ console.log(`x=${x} SAVED USER!`); return x; };

var ex3 = compose(map(save), ex2);

console.log("--------Start exercise 2--------");
assertDeepEqual(Right("fpguy99"), ex3("fpguy99"));
assertDeepEqual(Left("You need > 3"), ex3("duh"));
console.log("exercise 3...ok!");

// Exercise 4
// ==========
// Get the text from the input and strip the spaces
console.log("--------Start exercise 4--------");

var getValue = function(x){ return 'honkeytonk' }.toIO();
var stripSpaces = function(s){ return s.replace(/\s+/g, ''); };

var ex4 = compose(map(stripSpaces), getValue);

assertEqual("honkeytonk", runIO(ex4('#text')));
console.log("exercise 4...ok!");

// Exercise 5
// ==========
// Use getHref() / getProtocal() and runIO() to get the protocal of the page.
var getHref = function(){ return 'http://localhost:8080'; }.toIO();
var getProtocal = compose(_.head, _.split('/'));
var ex5 = compose(map(getProtocal), getHref);

console.log("--------Start exercise 5--------");
assertEqual('http:', runIO(ex5(null)));
console.log("exercise 5...ok!");

// Exercise 6*
// ==========
// Write a function that returns the Maybe(email) of the User from getCache(). Don't
// forget to JSON.parse once it's pulled from the cache so you can _.get() the email

// setup...
var localStorage = {};
localStorage.user = JSON.stringify({email: "george@foreman.net"});

var getCache = function(x){ return Maybe(localStorage[x]); }.toIO();
var log = function (x) { console.log(x); return x };

var getStringEmail = compose(_.prop('email'), JSON.parse);
var ex6 = compose(map(map(getStringEmail)), getCache);

assertDeepEqual(Maybe("george@foreman.net"), runIO(ex6('user')));
console.log("exercise 6...ok!");

// TEST HELPERS
// =====================
function inspectIt(x){
	return (x.inspect && x.inspect()) || (x.toString && x.toString()) || x.valueOf(); //hacky for teachy.
}

function assertEqual(x,y){
	if(x !== y){ throw("expected "+x+" to equal "+y); }
}
function assertDeepEqual(x,y){
	if(x.val !== y.val) throw("expected "+inspectIt(x)+" to equal "+inspectIt(y));
}