const True  = K;
const False = KI;

const not = C;

not(True);         // False (Function)
not(False);        // True  (Function)
not(not(True));    // True  (Function)

const and = p => q => p(q)(False);

and(True)(True)         // True
and(False)(True)        // False
and(True)(False)        // False
and(False)(False)       // False

const or = p => q => p(True)(q);

or(True)(True)         // True
or(False)(True)        // True
or(True)(False)        // True
or(False)(False)       // False

const beq = p => q => p(q)(not(q));

beq(True)(True)         // True
beq(False)(True)        // False
beq(True)(False)        // False
beq(False)(False)       // True

const showBoolean = b => b("True")("False");

showBoolean(True);        // 'True'
showBoolean(False);       // 'False'

const convertToJsBool = b => b(true)(false);

convertToJsBool(True)        // true
convertToJsBool(False)       // false

// Implementation n1
const n1 = f => a => f(a);

// Demonstration
n1(x => x + 1)(0)      // 1

n1(x => x + '!')('λ')  // 'λ!'

// Implementation n2...n9
const n2 = f => a => f(f(a));
const n3 = f => a => f(f(f(a)));
const n4 = f => a => f(f(f(f(a))));
const n5 = f => a => f(f(f(f(f(a)))));
const n6 = f => a => f(f(f(f(f(f(a))))));
const n7 = f => a => f(f(f(f(f(f(f(a)))))));
const n8 = f => a => f(f(f(f(f(f(f(f(a))))))));
const n9 = f => a => f(f(f(f(f(f(f(f(f(a)))))))));

// Demonstration
n2(x => x + 1)(0)      // 2
n3(x => x + 1)(0)      // 3
n4(x => x + 1)(0)      // 4

n3(x => x + '!')('λ')  // 'λ!!!'

// Implementation n0
const n0 = f => a => a;

// Demonstration
n0(x => x + 1)(0)      // 0

n0(x => x + '!')('λ')  // 'λ'

// Implementaion
const jsNum = n => n(x => x + 1)(0);

// Anwendung
jsNum(n0)     // 0
jsNum(n1)     // 1
jsNum(n2)     // 2

// Implementaion
const churchNum = n => n === 0 ? n0 : successor(churchNum(n - 1));

// Anwendung
jsNum(0)     // n0
jsNum(1)     // n1
jsNum(2)     // n2

const successor = n => f => a => f(n(f)(a));

successor(n0)        // n1
successor(n5)        // n6

const phi = p => pair(p(snd))(succ(p(snd)));

const testPair  = pair(n1)(n2);
const testPhi   = phi(testPair);

testPhiPair(fst)    // n2
testPhiPair(snd)    // n3

const pred = n => n(phi)(pair(n0)(n0))(fst);

 pred(n0)   // n0
 pred(n1)   // n0
 pred(n2)   // n1
 pred(n9)   // n8

const churchAddition = n => k => n(successor)(k);

churchAddition(n0)(n0)     //  0
churchAddition(n1)(n0)     //  1
churchAddition(n2)(n5)     //  7
churchAddition(n9)(n9)     // 18

const churchSubtraction = n => k => k(pred)(n);

churchSubtraction(n2)(n1)     // 1
churchSubtraction(n2)(n0)     // 2
churchSubtraction(n2)(n5)     // 0
churchSubtraction(n9)(n4)     // 5

const churchMultiplication = B;    // Bluebird

churchMultiplication(n2)(n1)     //  1
churchMultiplication(n2)(n0)     //  0
churchMultiplication(n2)(n5)     // 10
churchMultiplication(n9)(n4)     // 36

const churchPotency = T;    // Thrush

churchPotency(n2)(n1)     //    2
churchPotency(n2)(n0)     //    1
churchPotency(n2)(n5)     //   32
churchPotency(n9)(n4)     // 6561

const is0 = n => n(K(False))(True);

is0(n0)     // True
is0(n1)     // False
is0(n2)     // False
is0(n7)     // False

const leq = n => k => is0(churchSubtraction(n)(k));

leq(n0)(n0)     // True
leq(n0)(n3)     // True
leq(n5)(n5)     // True
leq(n5)(n1)     // False

const eq = n => k => and(leq(n)(k))(leq(k)(n));

 eq(n0)(n0)  // True
 eq(n0)(n1)  // False
 eq(n1)(n1)  // True
 eq(n2)(n1)  // False

const gt = Blackbird(not)(leq);

gt(n0)(n0)     // False
gt(n0)(n1)     // False
gt(n1)(n1)     // False
gt(n2)(n1)     // True 

const calculatorHandler = op => n => k => f => f(op(n)(k));

const plus              = n => k => n + k;
const multiplication    = n => k => n * k;
const subtraction       = n => k => n - k;
const exponentiation    = n => k => n ** k;
const division          = n => k => n / k;

// example
plus(1)(2)            // 3
multiplication(2)(3)  // 6 
subtraction(5)(2)     // 3

const add   = calculatorHandler(plus);            
const multi = calculatorHandler(multiplication);  
const sub   = calculatorHandler(subtraction);
const pow   = calculatorHandler(exponentiation);
const div   = calculatorHandler(division);

T(1)(add)(2)(pow)(6)(sub)(2)(div)(8)(add)(7)(multi)(4)(sub)...

T(1)(add)(2)(id)                     //   3
T(1)(sub)(2)(id)                     //  -1
T(5)(multi)(4)(add)(2)(id)           //  22
T(5)(div)(5)(multi)(100)(add)(1)(id) // 101

const calc   = T;
const result = id;

calc(5)(multi)(4)(sub)(4)(pow)(2)(div)(8)(add)(10)(result) // 42

const churchAdd     = calculatorHandler(churchAddition);
const churchMulti   = calculatorHandler(churchMultiplication);
const churchPow     = calculatorHandler(churchPotency);
const churchSub     = calculatorHandler(churchSubtraction);

calc(n5)(churchMulti)(n9)(churchAdd)(n4)(churchSub)(n7)(result) // n42

f => a => f(f(f(f(f(f(f(a))))))); //n7

jsNum(n42) // 42

calc(1)(sub)(7)(result)         // -6

calc(n1)(churchSub)(n7)(result) // 0 bzw. n0

calc(n5)(cpow)(n8)(cmulti)(n6)(cadd)(n8)(csub)(n9) ... // Maximum call stack size exceeded

const id = x => x;

id(10);           // 10
id(id);           // id
id("Hello");      // "Hello"

const K = x => y => x;

K(1)(2);         // 1
K(8)(id);        // 8
K('q')('t');     // 'q'

const KI = x => y => y;

KI(1)(2);                // 2
KI(id)(3);               // 3
KI("Hello")("World");    // "World"

const M = f => f(f);

M(id);        // id
M(id)(5);     // 5
M(M);         // stack overflow, da M(M) ==> M(M) ==> M(M) ....

const C = f => x => y => f(y)(x);

const diff = x => y => x - y;

C(diff)(2)(3);        //  1
C(diff)(3)(2);        // -1

const B = f => g => x => f(g(x));

    const f = x => x + 1;
    const g = x => x * 2;
    
    B(f)(g)(4);      // 9
    B(g)(f)(4);      // 10
    B(id)(id)(5);    // 5

const T = x => f => f(x);

const f = x => x + 1;

T(2)(f);            // 3
T(2)(id);           // 2 

const V = x => y => f => f(x)(y);

const pair    =    V;    // immutable datastructure pair

const fst     =    K;    // get first element from pair
const snd     =   KI;    // get second element from pair

const pairOfNumbers = pair(1)(2);
const pairOfStrings = pair("Hello")("World");
    
pairOfNumbers(fst);        // 1
pairOfNumbers(snd);        // 2
    
pairOfStrings(fst);        // "Hello"
pairOfStrings(snd);        // "World"

const mapPair = f => p => pair(f(p(fst)))(f(p(snd)));

const mapFunction = x => x * 2;
const pairOfNNumbers = pair(5)(6);

const mappedPair = mapPair(mapFunction)(pairOfNNumbers); // pair(10)(12)

const showPair = p => `${p(fst)} | ${p(snd)}`;

const pairOfNNumbers = pair(5)(6);

const stringOfPair = showPair(pairOfNNumbers); // '5 | 6'

const triple = x => y => z => f => f(x)(y)(z);

// getter functions of triple
const firstOfTriple  = x => y => z => x;
const secondOfTriple = x => y => z => y;
const thirdOfTriple  = x => y => z => z;

// triple with 3 numbers
const tripleOfNumbers = triple(1)(2)(3);

tripleOfNumbers( firstOfTriple  );    // 1
tripleOfNumbers( secondOfTriple );    // 2
tripleOfNumbers( thirdOfTriple  );    // 3

const Blackbird = f => g => x => y => f(g(x)(y));

const add = x => y => x + y;
const multiplyWithTwo = x => x * 2;

Blackbird(multiplyWithTwo)(add)(2)(3);      // 10
Blackbird(multiplyWithTwo)(add)(10)(20);    // 60

// User-Object
const user = {
    firstName: "Donald",
    lastName: "Duck",
    address: {
        city: "Entenhausen",
        street: {
            name: "WaltStreet",
            nr: 10
        }
    }
}

// Anwendungs Ziel
streetName(user) // "WALTSTREET"

const streetName = user => {
    if (user){
        const address = user.address;
        if(address){
            const street = address.street;
            if(street){
                const name = street.name;
                if (name){
                    return name.toUpperCase();
                }
            }
        }
    }
    return "no street"
}

const streetName = user =>
    Box(maybeNotNullAndUndefined(user))
        (chainMaybe)(u => maybeNotNullAndUndefined(u.address))
        (chainMaybe)(a => maybeNotNullAndUndefined(a.street))
        (chainMaybe)(s => maybeNotNullAndUndefined(s.name))
        (foldMaybe)(n => n.toUpperCase())
    (_ => "no street")
    (id)

const push = s => stack( succ( s(stackIndex) ) )(s);

const push = s => (x => y => z => f => f(x)(y)(z))((n => f => x => (f)(n(f)(x)))(s(x => _ => _ => x)))(s)

const push = s => z => f => f( f => x => f( s(x => _ => _ => x)(f)(x) ))(s)(z);

// reduce in mehreren Funktionen unterteilt
const reduce = reduceFn => initialValue => s => {

    const reduceIteration = argsTriple => {
        const stack = argsTriple(firstOfTriple);

        const getTriple = argsTriple => {
            const reduceFunction    = argsTriple(secondOfTriple);
            const preAcc            = argsTriple(thirdOfTriple);
            const curr              = head(stack);
            const acc               = reduceFunction(preAcc)(curr);
            const preStack          = stack(stackPredecessor);
            return triple(preStack)(reduceFunction)(acc);
        }

        return If( hasPre(stack) )
                (Then( getTriple(argsTriple) ))
                (Else(           argsTriple  ));
    };

    const times = size(s);
    const reversedStack = times
                            (reduceIteration)
                                (triple
                                  (s)
                                  (acc => curr => push(acc)(curr))
                                  (emptyStack)
                                )
                                (thirdOfTriple);

    return times
            (reduceIteration)
                (triple
                  (reversedStack)
                  (reduceFn)
                  (initialValue)
            )(thirdOfTriple);
};

// reduce in reinem Lambda Kalkül 
const reduce = reduceFn => initialValue => s => s(x => _ => _ => x)(t => t(x => _ => _ => x)(x => _ => _ => x)(_ => (_ => y => y))(x => _ => x)(t)((t => f => f(t(x => _ => _ => x)(_ => y => _ => y))(t(_ => y => _ => y))(t(_ => y => _ => y)(t(_ => _ => z => z))((t(x => _ => _ => x))(_ => _ => z => z))))(t)))(f => f(s(x => _ => _ => x)(t => t(x => _ => _ => x)(x => _ => _ => x)(_ => (_ => y => y))(x => _ => x)(t)((t => f => f(t(x => _ => _ => x)(_ => y => _ => y))(t(_ => y => _ => y))(t(_ => y => _ => y)(t(_ => _ => z => z))((t(x => _ => _ => x))(_ => _ => z => z))))(t)))(f => f(s)(acc => curr =>  f => f( f => x => f(s(x => _ => _ => x)(f)(x)))(acc)(curr))(f => f(_ => a => a)(x => x)(x => x)))(_ => _ => z => z))(reduceFn)(initialValue))(_ => _ => z => z);

const stack = x => y => z => f => f(x)(y)(z);

const emptyStack = stack(n0)(id)(id);

const stackWithOneValue = push(emptyStack)(1);

const resultPair = pop(stackWithOneValue); 

const predecessorStack = resultPair(fst);    // empty stack
const poppedValue = resultPair(snd);         // 1

const sizeOfStack = size(stackWithOneValue); // n1

const headValue = head(stackWithOneValue); // 1

const result = hasPre(stackWithOneValue); // false (as church-boolean)

const stackWithTwoElements = push(push(emptyStack)("Hello"))("World");

getElementByIndex(stackWithTwoElements)(n1); // "Hello"
getElementByIndex(stackWithTwoElements)(n2); // "World"

getElementByIndex(stackWithTwoElements)(1); // "Hello"
getElementByIndex(stackWithTwoElements)(2); // "World"

getElementByIndex(stackWithTwoElements)(999); // Error "invalid index"

const stackWithTwoElements = push(push(emptyStack)(1))(2);
const arrayWithTwoElements = convertStackToArray(stackWithTwoElements); // [1, 2]

const array = [1, 2, 3];
const stack = convertArrayToStack(array); // stack: 1, 2, 3

const stackWithTwoElements = push(push(emptyStack)(1))(2);
const reversedStack = reverseStack(stackWithTwoElements); // stack: 2, 1

const stackWithNumbers  = convertArrayToStack([0,1,2]);

const reduceFunctionSum = acc => curr => acc + curr;
reduce( reduceFunctionSum )( 0 )( stackWithNumbers )          // returns  3
reduce( reduceFunctionSum )( 0 )( push(stackWithNumbers)(3) ) // returns  5
reduce( reduceFunctionSum )( 5 )( stackWithNumbers )          // returns  8
reduce( reduceFunctionSum )( 5 )( push(stackWithNumbers)(3) ) // returns 10

const reduceToArray = acc => curr => [...acc, curr];
reduce( reduceToArray )( [] )( stackWithNumbers )              // returns [0, 1, 2]

const stackWithTwoElements = push(push(emptyStack)(1))(2);
const multiplyWithTwo = x => x * 2;

const mappedStack = map(stackWithTwoElements)(multiplyWith2); // stack: 2, 4

const mapWithReduce = s => map => reduce(s)(pair(acc => curr => push(acc)(map(curr)))(emptyStack));

const stackWithThreeElements = push(push(push(emptyStack)(1))(2))(3);
const filterFunction = x => x > 1 && x < 3;

const filteredStack = filter(stackWithTwoElements)(filterFunction); // stack: 2

const filterWithReduce = s => filter => reduce(s)(pair(acc => curr => filter(curr) ? push(acc)(curr) : acc)(emptyStack));

const stackWithNumbers = startStack(pushToStack)(5)(pushToStack)(10)(id);

const callbackFunc = (element, index) => {
    console.log('element at: ' + index + ': ' + element);
};

forEach(stackWithNumbers)(callbackFunc); // element at: 1: 5
                                         // element at: 2: 10

const stackWithThreeElements = push(push(push(emptyStack)(1))(2))(3);
logStackToConsole(stackWithThreeElements);

const result = startStack(pushToStack)(2)(pushToStack)(3)(pushToStack)(4)(id); // Stack: 2, 3, 4

let listenerVariable; // undefined
const listenerExample = newListener( newValue => oldValue  => listenerVariable = newValue );

let obsExample = Observable(42)                     // new Observable with initValue 42
                  (addListener)( listenerExample ); // append Listener to the Observable

obsExample( getValue );  // 42

obsExample = obsExample( setValue )(11) // set new value and update all listeners

listenerVariable         // 11
obsExample( getValue );  // 11

obsExample = obsExample( removeListener )( listenerExample ); 

let listenerVariable; // undefined
const listenerExample = newListener( nVal => oVal => listenerVariable = nVal );

// create observable and add listener
let obsExample = Observable(42)
                    (addListener)(listenerExample); 

listenerVariable // 42 <- get the value from initialValue

// set new value and update listeners
obsExample = obsExample(setValue)(11);

// receive the update
listenerVariable // 11 

// remove listener
obsExample = obsExample(removeListener)(lisExample);  

// set new value and update listeners
obsExample = obsExample(setValue)(67); 

// receive no updates anymore 
listenerVariable // 11  

// Get the elements from the Dom
const [inputText, newValue, oldValue, sizes] = getDomElements("inputText", "newValue", "oldValue", "sizes");

// Create Listener
const listenerNewValue      = newListener( listenerNewValueToDomElementTextContent     (newValue) );
const listenerOldValue      = newListener( listenerOldValueToDomElementTextContent     (oldValue) );
const listenerNewValueSize  = newListener( listenerNewValueLengthToElementTextContent  (sizes)    );
const listenerConsoleLog    = newListener( listenerLogToConsole                                   );

// Create Observable-Object, define the Initial-Value and append the Listeners
let textInputObservables = Observable("")
                            (addListener)( listenerNewValue     )
                            (addListener)( listenerOldValue     )
                            (addListener)( listenerNewValueSize )
                            (addListener)( listenerConsoleLog   );

// Connect the Observables with the Input-Text-Field.
// Every change in the Input-Field execute the 'setValue'-Function with the new value from Input-Field.
inputText.oninput = _ =>
    textInputObservables = textInputObservables(setValue)(inputText.value);

// Get the elements from the Dom
const [resultColor, rgbValue, hex, hsl] = getDomElements("resultColor", "rgbValue", "hex", "hsl");
const [inputR, inputG, inputB]          = getDomElements("inputR", "inputG", "inputB");
const [rangeR, rangeG, rangeB]          = getDomElements("rangeR", "rangeG", "rangeB");

// Getter methods for the RPG-Values (triple)
const getRed    = firstOfTriple;
const getGreen  = secondOfTriple;
const getBlue   = thirdOfTriple;

// Create Listeners for every color (red, green, blue) to Text- & Slider-Input
const listenerInputR       = newListener( nVal => _ => inputR.value  =  nVal( getRed   ));
const listenerRangeR       = newListener( nVal => _ => rangeR.value  =  nVal( getRed   ));
const listenerInputG       = newListener( nVal => _ => inputG.value  =  nVal( getGreen ));
const listenerRangeG       = newListener( nVal => _ => rangeG.value  =  nVal( getGreen ));
const listenerInputB       = newListener( nVal => _ => inputB.value  =  nVal( getBlue  ));
const listenerRangeB       = newListener( nVal => _ => rangeB.value  =  nVal( getBlue  ));

// Create Listeners for the Background-Result, RGB- & Hex-Labels
const listenerBgColorRGB   = newListener( nVal => _ => resultColor.style.backgroundColor = toRGBString( nVal(getRed), nVal(getGreen), nVal(getBlue) ));
const listenerRgbTextRGB   = newListener( nVal => _ => rgbValue.value                    = toRGBString( nVal(getRed), nVal(getGreen), nVal(getBlue) ));
const listenerHexTextRGB   = newListener( nVal => _ => hex.textContent                   = toHexString( nVal(getRed), nVal(getGreen), nVal(getBlue) ));

// Create Observable-Object, define the three initial-Values RGB and append the Listeners
let rgbObservable = Observable(triple(55)(215)(150))
                                (addListener)( listenerInputR     )
                                (addListener)( listenerRangeR     )
                                (addListener)( listenerInputG     )
                                (addListener)( listenerRangeG     )
                                (addListener)( listenerInputB     )
                                (addListener)( listenerRangeB     )
                                (addListener)( listenerBgColorRGB )
                                (addListener)( listenerRgbTextRGB )
                                (addListener)( listenerHexTextRGB );
                                
// Connecting the Observables with every Input-Field (Range and Text).
inputR.oninput = _ =>
    rgbObservable = rgbObservable(setValue)(
        triple
            (inputR.value)
            (rgbObservable(getValue)(getGreen))
            (rgbObservable(getValue)(getBlue))
    );

rangeR.oninput = _ =>
    rgbObservable = rgbObservable(setValue)(
        triple
            (rangeR.value)
            (rgbObservable(getValue)(getGreen))
            (rgbObservable(getValue)(getBlue))
    );

...

// Either all the necessary Dom-Element exist and or display all missed Element
eitherElementsOrErrorsByFunction(eitherDomElement)("jokeHistory", "norrisBtn", "nerdyBtn", "trumpBtn")
(err => document.body.innerHTML = Box(err)(mapf)(convertStackToArray)(mapf)(s => s.join(", <br>"))(fold)(txt => `<div style="background: orangered"> <br> ${txt}</div>`))
(result => {

    // receive founded the elements
    const [jokeHistory, norrisBtn, nerdyBtn, trumpBtn] = convertListMapToArray(result)

    // create the Listeners (text-to-speech & display to view)
    const listenerSpeak     = newListener(nValue => oValue => speak(nValue(snd)));

    const listenerJokeToDom = newListener(nValue => oValue => {
        const template = document.createElement('fieldset');
        template.className = "joke"
        template.innerHTML = `<legend>${nValue(fst)}</legend><p class="jokeText">${nValue(snd)}</p>`
        jokeHistory.insertAdjacentElement('afterbegin', template)
    });

    // create the Observable with pair data structure ("Title")("Joke")
    const jokePairObserver = Observable( pair("nobody")("tell me a joke") )
                                    (addListener)( listenerSpeak )
                                    (addListener)( listenerJokeToDom )


    // Jokes-API-URLs
    const jokeNorrisUrl = "https://api.chucknorris.io/jokes/random";            // jsonKey: value
    const jokeNerdUrl   = "https://v2.jokeapi.dev/joke/Programming?type=single" // jsonKey: joke
    const trumpTweetUrl = "https://www.tronalddump.io/random/quote";            // jsonKey: value


    // Constructor for a Joke-Object
    const jokeCtor = name => btn => url => jsonKey => convertObjToListMap({name, btn, url, jsonKey});

    // creat Joke-Object
    const norrisJoke = jokeCtor("Chuck Norris - Joke")(norrisBtn)(jokeNorrisUrl)("value");
    const nerdJoke   = jokeCtor("Nerd - Joke"        )(nerdyBtn )(jokeNerdUrl  )("joke" );
    const trumpTweet = jokeCtor("Trump Tweet"        )(trumpBtn )(trumpTweetUrl)("value");

    // combine the Joke-Objects into a stack
    const jokes = convertElementsToStack(norrisJoke, nerdJoke, trumpTweet);

    // add the Joke-Buttons a on-click event listener for request the Jokes and update the Observable
    forEach(jokes)((joke, _) =>
        getElementByKey(joke)("btn").onclick = _ =>
            HttpGet( getElementByKey(joke)("url") )(resp =>
                jokePairObserver(setValue)(Box(resp)
                                            (mapf)(JSON.parse)
                                            (fold)(x => pair( getElementByKey(joke )( "name"))( x[getElementByKey(joke)("jsonKey")] )))));
})

// Implementation
const Observable = initialValue =>
    observableBody(emptyListMap)(initialValue)(setValue)(initialValue);
    
// Anwendung
const obsExample = Observable(0)

// Implementation
const observableBody = listeners => value => observableFn =>
    observableFn(listeners)(value);

// Implementation
const addListener = listeners => value => newListener => {
    newListener(snd)(value)(value)
    return observableBody( push(listeners)(newListener) )(value)
    
// Anwedung
const obsExample = Observable(0)
                    (addListener)( listenerLogToConsole      )
                    (addListener)( listenerNewValueToElement );

// Implementation
const removeListener = listeners => value => givenListener =>
    observableBody( removeByKey(listeners)(givenListener(fst)) )(value)

  
// Anwendung
const listenerLog = newListener(listenerLogToConsole);

let obsExample = Observable(0)
                     (addListener)( listenerLog );
                     
obsExample = obsExample(removeListener)( listenerLog );    

// Implementation
const removeListenerByKey = listeners => value => listenerKey =>
    observableBody(removeByKey(listeners)(listenerKey))(value)

  
// Anwendung
const listenerLog = newListenerWithCustomKey(42)(listenerLogToConsole);

let obsExample = Observable(0)
                     (addListener)( listenerLog );
                     
obsExample = obsExample(removeListenerByKey)(42)   

// Implementation
const setValue = listeners => oldValue => newValue => {
    forEach(listeners)((listener, _) => (listener(snd))(newValue)(oldValue))
    return observableBody(listeners)(newValue)
}


// Anwendung
let obsExample = Observable(0)
testObs(getValue)                // 0
testObs = testObs(setValue)(42)
testObs(getValue)                // 42

// Implementation
const getValue = listeners => value => value;

  
// Anwendung
let obsExample = Observable(0)
testObs(getValue)                // 0
testObs = testObs(setValue)(42)
testObs(getValue)                // 42

// Implementation
const newListener = listenerFn => pair(generateRandomKey())(listenerFn);

  
// Anwendung
const listenerLog = newListenerWithCustomKey(42)(listenerLogToConsole);

// Implementation
const newListener = listenerFn => pair(generateRandomKey())(listenerFn);

  
// Anwendung
const listenerLog = newListener(listenerLogToConsole);

// Implementation
const setListenerKey = newKey => listener => pair(newKey)(listener(snd));

  
// Anwendung
let listenerLog = newListener(listenerLogToConsole);
listenerLog = setListenerKey( listenerLog  )(42)

// Implementation
const getListenerKey = listener => listener(fst);

  
// Anwendung
const listenerLog = newListenerWithCustomKey(42)(listenerLogToConsole);
getListenerKey( listenerLog )  // 42

const stack1  = convertArrayToStack( ["Hello", "Haskell"] );
const stack2  = convertArrayToStack( ["World", "Random"] );

concat(stack1)(stack2); // [ "Hello", "Haskell", "World", "Random" ]


const stack3 = convertArrayToStack( [1, 2, 3] );
const stack4 = convertArrayToStack( [4] );
concat(stack3)(stack4)  // [ 1, 2, 3, 4 ]

const s1 = convertArrayToStack( [1, 2] );
const s2 = convertArrayToStack( [3, 4] );
const s3 = convertArrayToStack( [5, 6] );

const stackWithStacks = convertArrayToStack( [s1, s2, s3] ); // [ [1, 2], [3, 4], [5, 6] ]

flatten(stackWithStacks) // [ 1, 2, 3, 4, 5, 6]

const add = x => y => x + y;

const s1 = convertArrayToStack( [1, 2] );
const s2 = convertArrayToStack( [4, 5] );

zipWith(add)(s1)(s2) // [ 5, 7 ]

const s1 = convertArrayToStack( [1, 2] );
const s2 = convertArrayToStack( [3, 4] );

zip(s1)(s2)  // [ (1, 3), (2, 4) ]

const s1 = convertArrayToStack( [1, 2] );
const s2 = convertArrayToStack( [1, 2] );

stackEquals(s1)(s2)  // True (Church Boolean)

const stackWithStrings = convertArrayToStack(["Hello", "World"]);

getElementByIndex(stackWithStrings)(n1) // "Hello"
getElementByIndex(stackWithStrings)(n2) // "World"

getElementByIndex(stackWithStrings)( 1)  // "Hello"
getElementByIndex(stackWithStrings)( 2)  // "World"

getElementByIndex(stackWithStrings)(999) // Error "invalid index" 

const stackWithStrings = convertArrayToStack( ["Hello", "Haskell", "World"] );

removeByIndex(stackWithStrings)( 2) // [ "Hello", "World" ]
removeByIndex(stackWithStrings)(n2) // [ "Hello", "World" ]

removeByIndex(stackWithStrings)(999) // [ "Hello", "Haskell", "World" ]

const stackWithNumbers = convertArrayToStack( [7, 34, 10] );

getIndexOfElement(stackWithNumbers)(7)    // 1
getIndexOfElement(stackWithNumbers)(34)   // 2
getIndexOfElement(stackWithNumbers)(10)   // 3
getIndexOfElement(stackWithNumbers)(100)  // undefined

const stackWithNumbers = convertArrayToStack( [7, 34, 10] );

maybeIndexOfElement(stackWithNumbers)(7)    // Just(1)
maybeIndexOfElement(stackWithNumbers)(34)   // Just(2)
maybeIndexOfElement(stackWithNumbers)(10)   // Just(3)
maybeIndexOfElement(stackWithNumbers)(100)  // Nothing

const stackWithNumbers = convertArrayToStack( [0, 11, 22, 33] );

containsElement(stackWithNumbers)(-1) === False
containsElement(stackWithNumbers)( 0) === True
containsElement(stackWithNumbers)(11) === True
containsElement(stackWithNumbers)(22) === True
containsElement(stackWithNumbers)(33) === True
containsElement(stackWithNumbers)(44) === False

const stackWithValues = convertElementsToStack(1,2,3);

convertStackToArray( stackWithValues ) === [1,2,3]


const stackWithValues2 = convertElementsToStack(1,2,3,...['a','b','c']);

convertStackToArray( stackWithValues2 ) === [1,2,3,'a','b','c']

const listMap = stack; // triple

const emptyListMap = listMap(n0)(id)( pair(id)(id) );

const p1 = pair(1)("Michael")
const p2 = pair(2)("Peter")
const p3 = pair(3)("Hans")

const testListMap = convertArrayToStack([p1, p2, p3]) // [ ("1", "Michael"), ("2", "Peter"),("3", "Hans") ]

getElementByKey( testListMap )( 1 )   // "Michael"
getElementByKey( testListMap )( 2 )   // "Peter"
getElementByKey( testListMap )( 3 )   // "Hans"

const p1 = pair(1)("Michael")
const p2 = pair(2)("Peter")
const p3 = pair(3)("Hans")

const testListMap   = convertArrayToStack( [p1, p2, p3] )
const resultListMap = removeByKey(testListMap)(2); // [ ("1", "Michael"), ("3", "Hans") ]

getElementByKey( resultListMap )( 1 )   // "Michael"
getElementByKey( resultListMap )( 3 )   // "Hans"

// Implementation
const convertObjToListMap = obj => 
    Object.entries(obj).reduce((acc, [key, value]) => push(acc)(pair(key)(value)), emptyListMap);

// Anwendung
const personObject = {firstName: "George", lastName: "Lucas"}

const result = convertObjToListMap(personObject); // [ ("firstName", "George"), ("lastName","Lucas") ]

getElementByKey( result )( "firstName" )   // "George"
getElementByKey( result )( "lastName"  )   // "Lucas"

// Implementation
const convertListMapToArray = listMap => 
    reduceListMap(acc => curr => [...acc, curr])([])(listMap);

// Anwendung
const personObject  = {firstName: "George", lastName: "Lucas"}

const personListMap = convertListMapToArray( personObject ); // [ ("firstName", "George"), ("lastName","Lucas") ]

convertListMapToArray( personListMap ) // [ "George", "Lucas" ]

// Implementation
const mapListMap = f => map(p => pair( p(fst) )( f(p(snd)) ));

// Anwendung
const toUpperCase      = str => str.toUpperCase();
const listMapWithNames = convertObjToListMap({name1: "Peter", name2: "Hans"});

const mappedListMap    = mapListMap(toUpperCase)(listMapWithNames); // [ ("name1", "PETER"), ("name2", "HANS") ]

getElementByKey( mappedListMap )( "name1" ) // "PETER"
getElementByKey( mappedListMap )( "name2" )  // "HANS"

// Implementation
const filterListMap    = f => filter(p => f(p(snd)));

// Anwendung
const startsWithP      = str => str.startsWith('P');

const listMapWithNames = convertObjToListMap( {name1: "Peter", name2: "Hans", name3: "Paul"} );
const filteredListMap  = filterListMap( startsWithP )( listMapWithNames ); // [ ("name1", "Peter"), ("name3", "Paul") ]

getElementByKey( filteredListMap )( "name1" );  // "Peter"
getElementByKey( filteredListMap )( "name3" );  // "Paul"

// Implementation
const reduceListMap = f => reduce(acc => curr => f(acc => curr(snd)));

// Anwendung
const reduceFunc = acc => curr => acc + curr.income;

const listMapWithPersons = convertObjToListMap({
              p1: {firstName: 'Peter', income: 1000},
              p2: {firstName: 'Michael', income: 500}
        });
    
reduceListMap(reduceFunc)(0)(listMapWithPersons); // 1500

// Implementation
const logListMapToConsole = listMap =>
    forEach(listMap)( (element, index) => console.log("At Index " + index + " is  Key and Element " + JSON.stringify(element(fst)) + " | " + JSON.stringify(element(snd)) ));
    
// Anwendung
const listMapWithPersons = convertObjToListMap( {firstName: "George", lastName: "Lucas"} );

logListMapToConsole( listMapWithPersons );

// Logs to Console:
// Index 1 (Key, Element): ("firstName", "George")
// Index 2 (Key, Element): ("lastName", "Lucas")

const p = {firstName: "Lukas", lastName: "Mueller"};

const addSalutation = fullName => male => (male ? "Mr. " : "Mrs. ") + fullName;

const fullName           = p.firstName + " " + p.lastName;
const fullNameUpperCase  = fullName.toUpperCase();
const nameWithSalutation = addSalutation(fullNameUpperCase)(true); // Mr. LUKAS MUELLER

const p = {firstName: "Lukas", lastName: "Mueller"};

const addSalutation = fullName => male => (male ? "Mr. " : "Mrs. ") + fullName;

const nameWithSalutation = Box(p)
                             (fmap)(p => p.firstName + " " + p.lastName)
                             (fmap)(fullName => fullName.toUpperCase())
                             (fold)(fullNameUpperCase => addSalutation(fullNameUpperCase)(true)); // Mr. LUKAS MUELLER

// Implementation
const fmap  = x => f => g => g(f(x));  

const Box   = x => fmap(x)(id);        // Box.of

// Anwendung
Box(10);                 // { 10 }
Box("Hello World");      // { "Hello World" }
Box(p);                  // { p }

// Implementation
const fmap = x => f => g => g(f(x));

// Anwendung
Box(5)                                 // { 5 }
 (fmap)(n => n * 10)                   // { 50 }
 (fmap)(n => n + 15)                   // { 65 }
 (fmap)(n => String.fromCharCode(n));  // { 'A' }

// Implementation
const fold  = x => f => f(x);

// Anwendung
Box(5)                                 // { 5 }
 (fmap)(n => n * 10)                   // { 50 }
 (fmap)(n => n + 15)                   // { 65 }
 (fold)(n => String.fromCharCode(n));  // 'A'

// Implementation
const chain = x => f => g => g((f(x)(id)));

// Anwendung
Box(5)                                     // { 5 }
 (fmap)(num => num + 5)                    // { 10 }
 (chain)(num => Box(num * 2)
                 (fmap)(num => num + 1))   // { 21 }
 (chain)(num => Box(num * 3)
                 (fmap)(num => num + 1))   // { 64 }

// Implementation
const getContent = b => b(id);

// Anwendung
const p = { firstName: "Tyrion", lastName: "Lannister" };

const box1 = Box(p);

const mapped1 = box1(fmap)(p => p.firstName);

const mapped2 = mapped1(fmap)(firstName => firstName.toUpperCase());

getContent( box1    )   // { firstName: "Tyrion", lastName: "Lannister" } 
getContent( mapped1 )   // "Tyrion"
getContent( mapped2 )   // "TYRION"

// Implementation
const app = x => f => g => g(f(fmap)(x)(id));

// Anwendung
Box(x => x + 5)          // { 10 + 5 }
 (app)( Box(10) );       // { 10 }
 
Box( x => y => x + y)    // { 10 + 24 }
 (app)( Box(10) )        // { 10 }
 (app)( Box(14) );       // { 24 }

// Implementation
const liftA2 = f => fx => fy => fx(fmap)(f)(app)(fy);

// Anwendung
liftA2(name1 => name2 => name1 + " " + name2)  // { "Tyrion Lannister" }
 ( Box("Tyrion"   ) )
 ( Box("Lannister") );

// Implementation
const debug = x => {
    console.log(x);
    return x;
}

// Anwendung
Box(10)
 (fmap)(debug)        // Ausgabe auf der Konsole: 10
 (fmap)(n => n + 2)
 (fold)(debug);       // Ausgabe auf der Konsole: 12

const Stream = (...elements) => Box(convertArrayToStack(elements));

Stream(1,2,3,4)
 (fmap)( map(x => x * 2)    )
 (fold)( filter(x => x > 4) )

// Synchron
Box( HttpGetSync( URL ) )
 (fmap)( JSON.parse   )
 (fold)( x => x.value )
 
 
// Asynchron
HttpGet( URL )(resp => Box(resp)
                        (fmap)(JSON.parse   )
                        (fold)(x => x.value ))

// Implementation
const fmapMaybe = x => f => g => g(mapMaybe(x)(f));

// Anwendung
 const maybePerson = () => Just( {firstName: "Tyrion", lastName: "Lannister"} );
 
 const maybeFirstName = obj =>
      obj && obj.hasOwnProperty('firstName')
          ? Just(obj.firstName)
          : Nothing;
          
 Box( maybePerson() )                                  // { Just({firstName: "Tyrion", lastName: "Lannister"}) }
  (chainMaybe)( maybeFirstName )                       // { Just("Tyrion") }
  (foldMaybe)( firstName => firstName.toUpperCase() )  //   Just("TYRION")

// Implementation
const foldMaybe = mapMaybe;

// Anwendung
Box( Just(10) )                   // { Just(10) }
 (fmapMaybe)(x => x + 10)         // { Just(20) }
 (foldMaybe)(num => num + '$')    // Just("20$")

// Implementation
const chainMaybe    = x => f => g => g(flatMapMaybe(x)(f));

// Anwendung
const maybePerson = () => Just({firstName: "Tyrion", lastName: "Lannister"});

const maybeFirstName = obj =>
        obj && obj.hasOwnProperty('firstName')
            ? Just(obj.firstName)
            : Nothing;

Box( maybePerson() )                                  // { Just({firstName: "Tyrion", lastName: "Lannister"}) 
 (chainMaybe)( maybeFirstName )                       // { Just("Tyrion") }
 (foldMaybe)( firstName => firstName.toUpperCase() )  //   Just("TYRION")

// Implementation
const apMaybe = x => f => g => g(flatMapMaybe(x)(func => mapMaybe(f)(func)));

// Anwendung
Box( Just(x => x + 5) )          // { Just(15 + 5) }
 (appMaybe)( Just(10) );         // { Just(10) }

// Implementation
const liftA2Maybe = f => fx => fy =>
    Box(fx)
     (fmapMaybe)(f)
     (appMaybe)(fy);
        
// Anwendung
liftA2Maybe( x => y => x + y )  // (10 + 5)
 ( Just(10) )
 ( Just(5)  );

const Left   = x => f => _ => f (x);
const Right  = x => _ => g => g (x);

// Anwendung        
eitherXYZ(someParam)
    (error  => doSomethingInErrorCase(error)    )  // Left Case
    (result => doSomethingInSuccessCase(result) )  // Right Case

const eitherTruthy = value =>
    value
        ? Right(value)
        : Left(`'${value}' is a falsy value`);

const eitherNotNullAndUndefined = value =>
    value !== null && value !== undefined
        ? Right(value)
        : Left(`element is '${value}'`);

// Implementation
const eitherElementOrCustomErrorMessage = errorMessage => element =>
    eitherNotNullAndUndefined(element)
     (_ => Left(errorMessage))
     (_ => Right(element));
 
// Anwendung       
eitherElementOrCustomErrorMessage("Der Wert ist Null")(null); // Left ("Der Wert ist null")

const eitherDomElement = elemId =>
    eitherElementOrCustomErrorMessage
     (`no element exist with id: ${elemId}`)
     (document.getElementById(elemId));

const eitherNumber = val =>
    Number.isInteger(val)
        ? Right(val)
        : Left(`'${val}' is not a integer`);

const eitherNaturalNumber = val =>
    Number.isInteger(val) && val >= 0
        ? Right(val)
        : Left(`'${val}' is not a natural number`);

const eitherFunction = val =>
    typeof val === "function"
        ? Right(val)
        : Left(`'${val}' is not a function`);

const eitherTryCatch = f => {
    try {
        return Right(f());
    } catch (error) {
        return Left(error);
    }
}

eitherElementsOrErrorsByFunction(eitherDomElement)("inputText", "output")
(err    => doSomethingWithErrorMessages) // stack mit Fehlermeldungen
(result => {                             // listMap mit den Resultaten

   // Die Resultate als einzelne Variablen
   const [inputText, output] = convertListMapToArray(result);
   
   doSomethingWithResult(inputText, output);
   
})

const textInputObservables = Observable("")(addListener)(listenerNewValue)(addListener)(listenerOldValue)(addListener)(listenerNewValueSize)(addListener)(listenerConsoleLog)

const textInputObservables = Observable("")
(addListener)(listenerNewValue)
(addListener)(listenerOldValue)
(addListener)(listenerNewValueSize)
(addListener)(listenerConsoleLog)

const textInputObservables = Observable("")
                              (addListener)(listenerNewValue)
                              (addListener)(listenerOldValue)
                              (addListener)(listenerNewValueSize)
                              (addListener)(listenerConsoleLog)

const textInputObservables = Observable("")
                              (addListener)( listenerNewValue     )
                              (addListener)( listenerOldValue     )
                              (addListener)( listenerNewValueSize )
                              (addListener)( listenerConsoleLog   )

const textInputObservables = Observable("")
                              (addListener)( listenerNewValue     )
                              (addListener)( listenerOldValue     )
                              (addListener)( listenerNewValueSize )
                              (addListener)( listenerConsoleLog   );

// unformatiert
const listenerNewValue = newListener(listenerNewValueToDomElementTextContent(newValue));
const listenerOldValue = newListener(listenerOldValueToDomElementTextContent(oldValue));
const listenerNewValueSize = newListener(listenerNewValueLengthToElementTextContent(sizes));
const listenerConsoleLog = newListener(listenerLogToConsole);

// formatiert
const listenerNewValue     = newListener( listenerNewValueToDomElementTextContent    (newValue) );
const listenerOldValue     = newListener( listenerOldValueToDomElementTextContent    (oldValue) );
const listenerNewValueSize = newListener( listenerNewValueLengthToElementTextContent (sizes)    );
const listenerConsoleLog   = newListener( listenerLogToConsole                                  );

// unformatiert
forEach(jokes)((joke, _) => getElementByKey(joke)("btn").onclick = _ => HttpGet(getElementByKey(joke)("url"))(resp => jokePairObserver(setValue)(Box(resp)(mapf)(JSON.parse)(fold)(x => pair(getElementByKey(joke)("name"))(x[getElementByKey(joke)("jsonKey")])))));

// formatiert
forEach(jokes)( (joke, _) =>
    getElementByKey(joke)("btn").onclick = _ =>
        HttpGet( getElementByKey(joke)("url") )( resp =>
            jokePairObserver(setValue)( Box(resp)
                                         (mapf)( JSON.parse )
                                         (fold)( x => pair( getElementByKey(joke)("name") )( x[getElementByKey(joke)("jsonKey")] )))));

// unformatiert
const nextCharForNumberString = str => Box(str)(chain)(s => Box(s)(mapf)(s => s.trim()))(mapf)(r => parseInt(r))(mapf)(i => i + 1)(mapf)(i => String.fromCharCode(i))(fold)(c => c.toLowerCase())

// formatiert
const nextCharForNumberString = str =>
    Box(str)
     (chain)(s => Box(s)
                   (mapf)(s => s.trim()))
     (mapf)(r => parseInt(r))
     (mapf)(i => i + 1)
     (mapf)(i => String.fromCharCode(i))
     (fold)(c => c.toLowerCase());

/**
 * A function that takes a stack and an index (as Church- or JS-Number).
 * The function returns the element at the passed index or undefined incl. a Error-Log to the Console
 *
 * @haskell getElementByIndex :: stack -> number -> a
 * @sideeffect Logs a error if index is no Church- or JS-Number or valid number
 * @function
 * @param  {stack} stack
 * @return {function(index:churchNumber|number) : * } stack-value or undefined when not exist or invalid
 * @example
 * const stackWithNumbers  = convertArrayToStack([0,1,2]);
 *
 * getElementByIndex( stackWithNumbers )( n0 ) === id
 * getElementByIndex( stackWithNumbers )( n1 ) ===  0
 * getElementByIndex( stackWithNumbers )( n2 ) ===  1
 * getElementByIndex( stackWithNumbers )( n3 ) ===  2
 *
 * getElementByIndex( stackWithNumbers )( 0 ) === id
 * getElementByIndex( stackWithNumbers )( 1 ) ===  0
 * getElementByIndex( stackWithNumbers )( 2 ) ===  1
 * getElementByIndex( stackWithNumbers )( 3 ) ===  2
 *
 * getElementByIndex( stackWithNumbers )( "im a string" ) === undefined // strings not allowed, throws a Console-Warning
 */
const getElementByIndex = stack => index =>
    eitherElementByIndex(stack)(index)
     (console.error)
     (id);

assert.equals(1, 1);

lambdaCTest.add("identity", assert => {
    assert.equals(id(1), 1);
    assert.equals(id(n1), n1);
    assert.equals(id(true), true);
    assert.equals(id(id), id);
    assert.equals(id === id, true);
});

const forEach = stack => callbackFunc => {
    const times         = size(stack);
    const reversedStack = reverseStack(stack);

    const iteration = s => {
        if( convertToJsBool(hasPre(s)) ) {
            const element = head(s);
            const index   = jsnum( succ( churchSubtraction(times)(size(s) )));

            callbackFunc(element, index);

            return ( pop(s) )(fst);
        }
        return s;
    };

    times
        (iteration)
        (reversedStack);
};

const forEach = stack => callbackFunc => {
    const times         = size(stack);
    const reversedStack = reverseStack(stack);

    const invokeCallback = p => {
        const s       = p(fst);
        const index   = p(snd);
        const element = head(s);

        callbackFunc(element, index);

        return pair( getPreStack(s) )( index + 1 );
    }

    const iteration = p =>
        If( hasPre( p(fst) ))
            ( Then( invokeCallback(p) ))
            ( Else(                p  ));

    times
        (iteration)
        (pair( reversedStack)(1) );
};

// either type
const Left   = x => f => _ => f (x);
const Right  = x => _ => g => g (x);

// maybe type
const Nothing  = Left();
const Just     = Right ;

// Anwendung        
maybeXYZ(someParam)
 ( ()     => doSomethingInNothingCase(error) )    // Nothing Case
 ( result => doSomethingInJustCase(result)   )    // Just Case

// Implementation
const getOrDefault = maybe => defaultVal =>
    maybe
        (() => defaultVal)
        (id);
   
// Anwendung     
getOrDefault ( Just(10) )(20) // 10
getOrDefault ( Nothing  )(20) // 20

const maybeDivision = dividend => divisor =>
    Number.isInteger(dividend) &&
    Number.isInteger(divisor)  &&
    divisor !== 0
        ? Just(dividend / divisor)
        : Nothing;

const maybeTruthy = value =>
    eitherTruthy(value)
     (_ => Nothing)
     (_ => Just(value));

const maybeNotNullAndUndefined = value =>
    eitherNotNullAndUndefined(value)
     (_ => Nothing)
     (_ => Just(value));

const maybeDomElement = elemId =>
    eitherDomElement(elemId)
     (_ => Nothing)
     (e => Just(e));

const maybeNumber = val =>
    eitherNumber(val)
     (_ => Nothing)
     (_ => Just(val));

const maybeFunction = value =>
    eitherFunction(value)
     (_ => Nothing)
     (_ => Just(value));

// Implementation
const mapMaybe = maybe => f => maybe (() => maybe) (x => Just(f(x)));

// Anwendung
mapMaybe( Just(10) )(x => x * 4) // Just (40)
mapMaybe( Nothing  )(x => x * 4) // Nothing

// Implementation
const flatMapMaybe = maybe => f => maybe (() => maybe) (x => f(x));

// Anwendung
flatMapMaybe( Just(10) )(num => Just(num * 2));    // Just (20)
flatMapMaybe( Just(10) )(num => Nothing      );    // Nothing
flatMapMaybe( Nothing  )(num => Just(num * 2));    // Nothing