document.addEventListener('DOMContentLoaded', function () {
    const form = document.getElementById('calculator-form');
    const contractTypeSelector = document.getElementById('contract-type-selector');
    const dynamicOptionsContainer = document.getElementById('dynamic-options');
    const resultsContainer = document.getElementById('results');
    const resultsSummary = document.getElementById('results-summary');

    // --- CONFIGURATION & CONSTANTS (for 2025, simplified) ---
    const UOP_CONSTANTS = {
        TAX_FREE_AMOUNT: 30000,
        TAX_THRESHOLD_1: 120000,
        TAX_RATE_1: 0.12,
        TAX_RATE_2: 0.32,
        PENSION_RATE: 0.0976,
        DISABILITY_RATE: 0.015,
        SICKNESS_RATE: 0.0245,
        HEALTH_INSURANCE_RATE: 0.09,
    };

    const B2B_CONSTANTS = {
        BIG_ZUS_HEALTH: 626.93,
        BIG_ZUS_SOCIAL: 1600.32,
        LINEAR_TAX_RATE: 0.19,
    };

    const INKUBATOR_CONSTANTS = {
        FEE: 350,
        ZUS_RATE: 0.0976 + 0.015,
    };

    const UZ_CONSTANTS = {
        COST_OF_INCOME_RATE: 0.20,
    };

    const UOD_CONSTANTS = {
        COST_OF_INCOME_RATE_20: 0.20,
        COST_OF_INCOME_RATE_50: 0.50,
    };


    // --- UI UPDATE FUNCTIONS ---
    function updateDynamicOptions() {
        const contractType = document.querySelector('input[name="contractType"]:checked').value;
        let optionsHtml = '';

        if (contractType === 'b2b') {
            optionsHtml = `
                <div class="dynamic-option-set">
                    <label class="form-label fw-bold">Forma opodatkowania</label>
                    <div class="form-check">
                        <input class="form-check-input" type="radio" name="b2bTaxType" id="b2bLinear" value="linear" checked>
                        <label class="form-check-label" for="b2bLinear">Liniowy (19%)</label>
                    </div>
                    <div class="form-check">
                        <input class="form-check-input" type="radio" name="b2bTaxType" id="b2bScale" value="scale">
                        <label class="form-check-label" for="b2bScale">Skala podatkowa</label>
                    </div>
                </div>
            `;
        } else if (contractType === 'uop') {
            optionsHtml = `
                <div class="dynamic-option-set">
                    <div class="form-check form-switch">
                        <input class="form-check-input" type="checkbox" role="switch" id="uopUnder26" checked>
                        <label class="form-check-label" for="uopUnder26">Mam mniej niż 26 lat (zerowy PIT)</label>
                    </div>
                </div>
            `;
        } else if (contractType === 'uz') {
            optionsHtml = `
                <div class="dynamic-option-set">
                    <div class="form-check form-switch">
                        <input class="form-check-input" type="checkbox" role="switch" id="uzUnder26" checked>
                        <label class="form-check-label" for="uzUnder26">Jestem studentem/uczniem do 26 r.ż.</label>
                    </div>
                    <div class="form-check form-switch">
                        <input class="form-check-input" type="checkbox" role="switch" id="uzVoluntarySickness">
                        <label class="form-check-label" for="uzVoluntarySickness">Dobrowolne ubezp. chorobowe</label>
                    </div>
                </div>
            `;
        } else if (contractType === 'uod') {
            optionsHtml = `
                 <div class="dynamic-option-set">
                    <label class="form-label fw-bold">Koszty uzyskania przychodu</label>
                    <div class="form-check">
                        <input class="form-check-input" type="radio" name="uodCostType" id="uodCost20" value="20" checked>
                        <label class="form-check-label" for="uodCost20">Standardowe (20%)</label>
                    </div>
                    <div class="form-check">
                        <input class="form-check-input" type="radio" name="uodCostType" id="uodCost50" value="50">
                        <label class="form-check-label" for="uodCost50">Prawa autorskie (50%)</label>
                    </div>
                </div>
            `;
        }
        dynamicOptionsContainer.innerHTML = optionsHtml;
    }

    // --- CALCULATION LOGIC ---
    function calculateUoP(amount, amountType, options) {
        let grossAmount, netAmount;
        const isUnder26 = options.under26;

        if (amountType === 'gross') {
            grossAmount = amount;
            const pension = grossAmount * UOP_CONSTANTS.PENSION_RATE;
            const disability = grossAmount * UOP_CONSTANTS.DISABILITY_RATE;
            const sickness = grossAmount * UOP_CONSTANTS.SICKNESS_RATE;
            const socialContributions = pension + disability + sickness;
            
            const healthInsuranceBase = grossAmount - socialContributions;
            const healthInsurance = healthInsuranceBase * UOP_CONSTANTS.HEALTH_INSURANCE_RATE;

            let taxBase = Math.round(healthInsuranceBase);
            let tax = 0;
            if (!isUnder26) {
                const annualIncome = grossAmount * 12;
                if (annualIncome > UOP_CONSTANTS.TAX_THRESHOLD_1) {
                    tax = (taxBase * UOP_CONSTANTS.TAX_RATE_2) / 12; 
                } else {
                    tax = (taxBase * UOP_CONSTANTS.TAX_RATE_1) / 12;
                }
                tax = Math.max(0, tax);
            }

            netAmount = grossAmount - socialContributions - healthInsurance - tax;
            return { gross: grossAmount, net: netAmount, social: socialContributions, health: healthInsurance, tax: tax };
        }
        return { gross: 'Brak obliczeń', net: amount }; 
    }

    function calculateB2B(amount, amountType, options) {
        if (amountType === 'gross') {
            const income = amount;
            const social = B2B_CONSTANTS.BIG_ZUS_SOCIAL;
            const health = B2B_CONSTANTS.BIG_ZUS_HEALTH;
            const taxBase = Math.max(0, income - social);
            let tax = 0;
            if (options.taxType === 'linear') {
                tax = taxBase * B2B_CONSTANTS.LINEAR_TAX_RATE;
            }
            else { 
                tax = (taxBase * UOP_CONSTANTS.TAX_RATE_1);
            }
            const netAmount = income - social - health - tax;
            return { gross: income, net: netAmount, social: social, health: health, tax: tax };
        }
        return { gross: 'Brak obliczeń', net: amount };
    }

    function calculateInkubator(amount, amountType) {
        if (amountType === 'gross') {
            const income = amount;
            const fee = INKUBATOR_CONSTANTS.FEE;
            const zus = 250; // Simplified fixed ZUS
            const tax = (income - fee - zus) * UOP_CONSTANTS.TAX_RATE_1;
            const netAmount = income - fee - zus - tax;
            return { gross: income, net: netAmount, fee: fee, zus: zus, tax: tax };
        }
        return { gross: 'Brak obliczeń', net: amount };
    }

    function calculateUZ(amount, amountType, options) {
        if (amountType === 'gross') {
            const grossAmount = amount;
            if (options.isStudent) {
                return { gross: grossAmount, net: grossAmount, social: 0, health: 0, tax: 0 };
            }

            const costOfIncome = grossAmount * UZ_CONSTANTS.COST_OF_INCOME_RATE;
            
            let socialContributions = 0;
            let healthInsurance = 0;
            let sickness = 0;

            const pension = grossAmount * UOP_CONSTANTS.PENSION_RATE;
            const disability = grossAmount * UOP_CONSTANTS.DISABILITY_RATE;
            socialContributions = pension + disability;

            if (options.voluntarySickness) {
                sickness = grossAmount * UOP_CONSTANTS.SICKNESS_RATE;
                socialContributions += sickness;
            }
            
            const healthInsuranceBase = grossAmount - socialContributions;
            healthInsurance = healthInsuranceBase * UOP_CONSTANTS.HEALTH_INSURANCE_RATE;

            const taxBase = Math.round(grossAmount - costOfIncome - socialContributions);
            const tax = Math.max(0, taxBase * UOP_CONSTANTS.TAX_RATE_1);

            const netAmount = grossAmount - socialContributions - healthInsurance - tax;
            return { gross: grossAmount, net: netAmount, social: socialContributions, health: healthInsurance, tax: tax };
        }
        return { gross: 'Brak obliczeń', net: amount };
    }

    function calculateUOD(amount, amountType, options) {
        if (amountType === 'gross') {
            const grossAmount = amount;
            const costRate = options.costRate === 50 ? UOD_CONSTANTS.COST_OF_INCOME_RATE_50 : UOD_CONSTANTS.COST_OF_INCOME_RATE_20;
            const costOfIncome = grossAmount * costRate;
            const taxBase = Math.round(grossAmount - costOfIncome);
            const tax = Math.max(0, taxBase * UOP_CONSTANTS.TAX_RATE_1);
            const netAmount = grossAmount - tax;
            return { gross: grossAmount, net: netAmount, social: 0, health: 0, tax: tax };
        }
        return { gross: 'Brak obliczeń', net: amount };
    }

    // --- DISPLAY RESULTS ---
    function displayResults(results) {
        let html = '';
        const { gross, net, ...details } = results;

        html += `
            <div class="col-md-6">
                ${createResultItem('Kwota Brutto', gross)}
                ${createResultItem('Składki ZUS', details.social || details.zus)}
                ${createResultItem('Ubezp. zdrowotne', details.health)}
                ${createResultItem('Podatek PIT', details.tax)}
                ${createResultItem('Opłata dla inkubatora', details.fee)}
            </div>
            <div class="col-md-6 d-flex align-items-center justify-content-center">
                <div class="result-total w-100">
                    <span class="label">Na rękę</span>
                    <span class="value">${net.toFixed(2)} PLN</span>
                </div>
            </div>
        `;

        resultsSummary.innerHTML = html;
        resultsContainer.style.display = 'block';
    }

    function createResultItem(label, value) {
        if (value === undefined || value === null) return '';
        const val = typeof value === 'number' ? `${value.toFixed(2)} PLN` : value;
        return `
            <div class="result-item">
                <span class="label">${label}</span>
                <span class="value">${val}</span>
            </div>
        `;
    }

    // --- EVENT HANDLERS ---
    form.addEventListener('submit', function (e) {
        e.preventDefault();

        const contractType = document.querySelector('input[name="contractType"]:checked').value;
        const amount = parseFloat(document.getElementById('amount').value);
        const amountType = document.querySelector('input[name="amountType"]:checked').value;

        if (isNaN(amount) || amount <= 0) {
            alert('Proszę podać poprawną kwotę.');
            return;
        }

        let results;
        if (contractType === 'uop') {
            const options = { under26: document.getElementById('uopUnder26').checked };
            results = calculateUoP(amount, amountType, options);
        } else if (contractType === 'b2b') {
            const options = { taxType: document.querySelector('input[name="b2bTaxType"]:checked').value };
            results = calculateB2B(amount, amountType, options);
        } else if (contractType === 'inkubator') {
            results = calculateInkubator(amount, amountType);
        } else if (contractType === 'uz') {
            const options = { 
                isStudent: document.getElementById('uzUnder26').checked,
                voluntarySickness: document.getElementById('uzVoluntarySickness').checked
            };
            results = calculateUZ(amount, amountType, options);
        } else if (contractType === 'uod') {
            const options = { 
                costRate: parseInt(document.querySelector('input[name="uodCostType"]:checked').value)
            };
            results = calculateUOD(amount, amountType, options);
        }


        if (results) {
            displayResults(results);
        }
    });

    contractTypeSelector.addEventListener('change', updateDynamicOptions);

    // --- INITIALIZATION ---
    updateDynamicOptions();
});