let currentLang = 'ru';


function updateLanguage() {
    const language = langData[currentLang];

    document.getElementById("header").textContent = language.header;
    document.getElementById("description").textContent = language.description;
    document.getElementById("dTaxLabel").textContent = language.dTaxLabel;
    document.getElementById("dPriceLabel").textContent = language.dPriceLabel;
    document.getElementById("dConsLabel").textContent = language.dConsLabel;
    document.getElementById("pTaxLabel").textContent = language.pTaxLabel;
    document.getElementById("pPriceLabel").textContent = language.pPriceLabel;
    document.getElementById("pConsLabel").textContent = language.pConsLabel;
    document.getElementById("annualKmLabel").textContent = language.annualKmLabel;
    document.getElementById("resultText1").textContent = language.resultText1;
    document.getElementById("resultText2").textContent = language.resultText2;
    document.getElementById("resultText3").textContent = language.resultText3;
    document.getElementById("resultText4").textContent = language.resultText4;
    document.getElementById("tableDistance").textContent = language.tableDistance;
    document.getElementById("tableDieselTotal").textContent = language.tableDieselTotal;
    document.getElementById("tablePetrolTotal").textContent = language.tablePetrolTotal;
    document.getElementById("tableDifference").textContent = language.tableDifference;

    calculate();
}


document.querySelector('#language-toggle').addEventListener('click', () => {
    currentLang = (currentLang === 'en') ? 'ru' : 'en';
    updateLanguage();
});

document.querySelector('#dark-mode-toggle').addEventListener('click', () => {
    document.body.classList.toggle('dark-mode');
});

function calculate() {
    const dTax = parseFloat(document.getElementById("dTax").value);
    const dPrice = parseFloat(document.getElementById("dPrice").value);
    const dCons = parseFloat(document.getElementById("dCons").value);
    const pTax = parseFloat(document.getElementById("pTax").value);
    const pPrice = parseFloat(document.getElementById("pPrice").value);
    const pCons = parseFloat(document.getElementById("pCons").value);
    const annualKm = parseFloat(document.getElementById("annualKm").value);

   
    // 1. Calculate Break-Even Petrol Consumption
    // Formula: P_Cons = (100 * (dTax - pTax) / (annualKm * pPrice)) + (dCons * dPrice / pPrice)
    const taxDiff = dTax - pTax;
    const breakEven = (100 * taxDiff / (annualKm * pPrice)) + (dCons * dPrice / pPrice);
    

    // 2. Generate Table
    // 2. Calculate Minimum Diesel Price where user's pCons equals break-even consumption
    // We want to solve for dPrice such that: pCons = (100 * taxDiff / (annualKm * pPrice)) + (dCons * dPrice / pPrice)
    // Rearranging for dPrice:
    // pCons - (100 * taxDiff / (annualKm * pPrice)) = (dCons * dPrice / pPrice)
    // dPrice = (pCons - (100 * taxDiff / (annualKm * pPrice))) * pPrice / dCons
    
    let minDieselPrice = 0;
    if (dCons > 0 && annualKm > 0 && pPrice > 0) {
        const firstTerm = 100 * taxDiff / (annualKm * pPrice);
        const secondTerm = pCons - firstTerm;
        minDieselPrice = secondTerm * pPrice / dCons;
    }
    
    document.getElementById("displayKm").textContent = annualKm.toLocaleString();
    document.getElementById("breakEvenCons").textContent = breakEven.toFixed(2);
    document.getElementById("minDieselPrice").textContent = minDieselPrice.toFixed(2);

    const tbody = document.getElementById("comparisonTable").getElementsByTagName('tbody')[0];
    tbody.innerHTML = '';

    for (let i = 5000; i <= 50000; i += 5000) {
        const row = tbody.insertRow();
        const cell1 = row.insertCell(0);
        const cell2 = row.insertCell(1);
        const cell3 = row.insertCell(2);
        const cell4 = row.insertCell(3);

        const dCost = (dTax + ((dPrice * dCons) / 100 * i)).toFixed(2);
        const pCost = (pTax + ((pPrice * pCons) / 100 * i)).toFixed(2);
        const diffCost = (parseFloat(pCost) - parseFloat(dCost)).toFixed(2);

        cell1.innerHTML = "<strong>" + i.toLocaleString() + "</strong>";
        cell2.innerHTML = dCost + " €";
        cell3.innerHTML = pCost + " €";
        cell4.innerHTML = diffCost + " €";

        if (diffCost > 0) {
            cell4.className = "saving";
        } else {
            cell4.className = "loss";
        }
    }
}

calculate();
updateLanguage();