let maxNum = 26;
let currNum = 2;

function AddSet() {

    if (currNum < 26) {

        let charNum = 65 + currNum;
        currNum++;
    
        let delBtn = document.querySelectorAll('#delBtn');
        if (delBtn[delBtn.length - 1]) {
            delBtn[delBtn.length - 1].style="display: none;";
        }

        node = document.getElementById('sets');
        node.insertAdjacentHTML('beforeend', `  <div class="field" id="setfield${charNum - 65}">
                                                    <div style="display: flex; align-items: center;">
                                                        <button class="delete is-small mr-1" type="button" onclick="DeleteSet(${charNum - 65})" id="delBtn"></button>
                                                        <label class="label">Set &#${charNum}</label>
                                                    </div>
                                                    <div class="control">
                                                        <input class="input" type="text" placeholder="e.g. 1,2,5" id="set${charNum - 65}">
                                                    </div>
                                                </div>`);
    } else {
        console.log('You have reached a limint of available sets');
    }
}

function DeleteSet(setNum) {
    
    let setField = document.querySelector(`#setfield${setNum}`);
    setField.remove();
    currNum--;

    let delBtn = document.querySelectorAll('#delBtn');
    if (delBtn[delBtn.length - 1]) {
        delBtn[delBtn.length - 1].style="display: inline-block;";
    }
}


let universalSet = new Set();

function Complement (set) {

    let _complement = new Set();

    _complement = Difference(universalSet, set);

    return _complement;
}

function Intersection (set1, set2) {

    let _intersection = new Set();

    set1.forEach(element => {
        if (set2.has(element)) {
            _intersection.add(element);
        }
    });

    return _intersection;
}

function Union (set1, set2) {

    let _union = new Set(set1);

    set2.forEach(element => {
        _union.add(element);
    });

    return _union;
}

function Difference (set1, set2) {

    let _difference = new Set(set1);

    set2.forEach(element => {
        
        if (_difference.has(element)) {
            _difference.delete(element);
        }
    });

    return _difference;
}


const OPERATORS = new Set(['~', '!', '∩', '/', '∪', '+', '-']);
const BRACKETS = new Set(['(', ')']);

let SETSNAMES = new Set();
let SETS = new Array();

function Evaluate() {
        
    FetchSets();

    let formulaString = document.getElementById('formula').value;

    let charArray = formulaString.split('');
    let RPN_Array = ConvertFormulaCharArrayToRPN(charArray);

    let result = SolveRPNFormula(RPN_Array);

    let readableResult = ConvertToReadableResult(result);
        

    let resultField = document.getElementById('result');
    resultField.value = readableResult;


    SETSNAMES.clear();
    SETS = new Array();
    universalSet = new Set();
}

function ConvertFormulaCharArrayToRPN(chars) {

    let setsStack = new Array();
    let actionsStack = new Array();

    chars.forEach(element => {
        
        if (SETSNAMES.has(element)) {

            setsStack.push(GetSetFromIndex(element));
        }

        if (OPERATORS.has(element)) {

            while (GetActionPriority(actionsStack[actionsStack.length - 1]) >= GetActionPriority(element)) {

                let last = actionsStack.pop();

                if (last != '(') {
                    setsStack.push(last);
                } else {
                    break;
                }
            }

            if (actionsStack[0] == undefined || GetActionPriority(actionsStack[actionsStack.length - 1]) < GetActionPriority(element)) {

                actionsStack.push(element);
            }
        }

        if (BRACKETS.has(element)) {

            if (element == '(') {

                actionsStack.push(element);
            }

            if (element == ')') {

                let last = actionsStack.pop();

                while (last != '(') {

                    setsStack.push(last);
                    last = actionsStack.pop();
                }
            }
        }
    });

    while (actionsStack[0] != undefined) {

        setsStack.push(actionsStack.pop());
    }

    return setsStack;
}

function SolveRPNFormula(RPN_Array) {

    let stack =  new Array();

    for (let i = 0; i < RPN_Array.length; i++) {
        const element = RPN_Array[i];

        if (OPERATORS.has(element)) {

            if (element == '~' || element == '!') {
                
                let currSet = stack.pop();

                let result = Complement(currSet);

                stack.push(result);                
            } else if (element == '∩' || element == '/') {
                
                let secondSet = stack.pop();
                let firstSet = stack.pop();
                
                let result = Intersection(firstSet, secondSet);
                
                stack.push(result);
            } else if (element == '∪' || element == '+') {

                let secondSet = stack.pop();
                let firstSet = stack.pop();
                
                let result = Union(firstSet, secondSet);
                
                stack.push(result);
            } else if (element == '-') {

                let secondSet = stack.pop();
                let firstSet = stack.pop();
                
                let result = Difference(firstSet, secondSet);
                
                stack.push(result);
            }
        } else {

            stack.push(element);
        }
    }

    return stack[0];
}



function FetchSets() {

    let universalArray = new Array();

    for (let i = 0; i < currNum; i++) {

        let inputField = document.getElementById(`set${i}`);
        
        let numArray;
        if (inputField != undefined && inputField.value.length != 0) {
            numArray = inputField.value.split(',');

            numArray.sort();
        
            let newSet = new Set();
    
            numArray.forEach(element => {
                
                newSet.add(+element);
                universalArray.push(+element);
            });
    
            SETSNAMES.add(String.fromCharCode(65 + i));
            SETS.push(newSet);
        } else {
            console.log('[WARNING] Some of the sets are not defined');
        }
    }

    universalSet = new Set(universalArray);
}




function GetSetFromIndex(index) {

    let unicode = index.charCodeAt(0);
    
    let num = unicode - 65;

    return SETS[num];
}

function GetActionPriority(action) {

    if (action == '~' || action == '!') {
        return 5;
    } else if (action == '∩' || action == '/') {
        return 4;
    } else if (action == '∪' || action == '+') {
        return 3;
    } else if (action == '-') {
        return 2;
    } else if (action == '(') {
        return 1;
    } else {
        return 0;
    }
}

function ConvertToReadableResult(unconverted) {

    let converted = Array.from(unconverted).sort().join(', ');
    return converted;
}