document.addEventListener("DOMContentLoaded", function () {

    function getValue(name) {
        var el = document.getElementsByName(name)[0];
        return el ? parseFloat(el.value) || 0 : 0;
    }

    function setValue(name, val) {
        var el = document.getElementsByName(name)[0];
        if (el) el.value = Number(val).toFixed(2);
    }

    // ---- Track last edited field for Tax(A) ----
    let lastEditedTaxA = null;

    document.getElementsByName("per_tax_a")[0].addEventListener("input", () => {
        lastEditedTaxA = "percentage";
    });

    document.getElementsByName("tax_a_cal")[0].addEventListener("input", () => {
        lastEditedTaxA = "amount";
    });

    window.calculate = function () {

        // ---------------- BASIC INPUTS ----------------
        var gross_total_income = getValue("gross_total_income");
        var disallowance_14a = getValue("disallowance_14a");
        var disallowance_37 = getValue("disallowance_37");

        var gross_total = gross_total_income + disallowance_14a + disallowance_37;
        setValue("gti_as_per_ao", gross_total);

        // ---------------- DEDUCTIONS ----------------
        var d80_business = getValue("deduction_80ia_business");
        var d80_misc = getValue("deduction_80ia_misc");
        var d80_other = getValue("deduction_80ia_other");
        var d80_sec37 = getValue("deduction_sec37_disallowance");
        var deduction_80g = getValue("deduction_80g");

        var deduction = d80_business + d80_misc + d80_other + d80_sec37 - 1.35;

        var net_taxable_income = gross_total - deduction - deduction_80g;
        setValue("net_taxable_income", net_taxable_income);

        // ================= TAX (A) – TWO WAY =================
        var per_tax_a = getValue("per_tax_a");
        var tax_a_cal = getValue("tax_a_cal");

        if (net_taxable_income > 0) {
            if (lastEditedTaxA === "percentage") {
                tax_a_cal = net_taxable_income * (per_tax_a / 100);
                setValue("tax_a_cal", tax_a_cal);
            }
            else if (lastEditedTaxA === "amount") {
                per_tax_a = (tax_a_cal / net_taxable_income) * 100;
                setValue("per_tax_a", per_tax_a);
            }
        }

        var per_surcharge_a = getValue("per_surcharge_a");
        var surcharge_a_cal = tax_a_cal * (per_surcharge_a / 100);
        setValue("surcharge_a_cal", surcharge_a_cal);

        var per_cess_a = getValue("per_cess_a");
        var edu_cess_a_cal = (tax_a_cal + surcharge_a_cal) * (per_cess_a / 100);
        setValue("edu_cess_a_cal", edu_cess_a_cal);

        var sum_of_a = tax_a_cal + surcharge_a_cal + edu_cess_a_cal;
        setValue("sum_of_a", sum_of_a);

        // ================= TAX (B) =================
        var tax_b_cal = getValue("tax_b_cal");

        var per_surcharge_b = getValue("per_surcharge_b");
        var surcharge_b_cal = tax_b_cal * (per_surcharge_b / 100);
        setValue("surcharge_b_cal", surcharge_b_cal);

        var per_cess_b = getValue("per_cess_b");
        var edu_cess_b_cal = (tax_b_cal + surcharge_b_cal) * (per_cess_b / 100);
        setValue("edu_cess_b_cal", edu_cess_b_cal);

        var sum_of_b = tax_b_cal + surcharge_b_cal + edu_cess_b_cal;
        setValue("sum_of_b", sum_of_b);

        // ================= TAX PAYABLE =================
        var tax_payable = (sum_of_a > sum_of_b) ? tax_a_cal : tax_b_cal;
        setValue("tax_payable", tax_payable);

        var total_tax_payable = (sum_of_a > sum_of_b) ? sum_of_a : sum_of_b;
        setValue("total_tax_payable", total_tax_payable);

        // ================= MAT CREDIT =================
        var mat_created = 0;
        var mat_utilized = 0;

        if (sum_of_a < sum_of_b) {
            mat_created = sum_of_b - sum_of_a;
        } else {
            mat_utilized = sum_of_a - sum_of_b;
        }

        setValue("mat_credit_created", mat_created);
        setValue("mat_credit_utilized", mat_utilized);

        // ================= Opening Balance and closing =================  
        var opening_balance = getValue("opening_balance");
        var closing_balance = (opening_balance + mat_created) - mat_utilized
        setValue("closing_balance", closing_balance);

        // ================= FINAL TAX =================
        var interest_234c = getValue("interest_234c");

        var total_tax = total_tax_payable + interest_234c - mat_utilized;
        setValue("total_tax", total_tax);

        // ================= ADJUSTMENTS =================
        var adv_tax = getValue("advance_tax");
        var tds = getValue("tds");
        var tcs = getValue("tcs");
        var tax_on_assessment = getValue("tax_on_assessment");
        var interest_244a_per143 = getValue("interest_244a_per143");
        var refund_received = getValue("refund_received");

        var paid_tax = adv_tax + tds + tcs + tax_on_assessment;

        var refund = total_tax - paid_tax;
        setValue("refund", refund);

        var balance_receivable = (refund + interest_244a_per143) - refund_received
        setValue("balance_receivable", balance_receivable);

    };
});