import React, { useState, useEffect } from 'react';
import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
import { Input } from "@/components/ui/input";
import { Label } from "@/components/ui/label";
import { Alert, AlertDescription } from "@/components/ui/alert";

const UKCompanyCalculator = () => {
const [inputs, setInputs] = useState({
companyProfit: 0,
salary: 0,
dividends: 0,
previousLoanBalance: 0,
currentLoanBalance: 0,
investmentPL: 0,
childMaintenanceIncome: 0
});

const [results, setResults] = useState({
corporationTax: 0,
incomeTax: 0,
section455: 0,
payrollCharges: 0,
childMaintenance: 0,
allowancesLost: false,
totalTakeHome: 0
});

// Tax brackets for 2024/25
const TAX_BRACKETS = {
PERSONAL_ALLOWANCE: 12570,
BASIC_RATE_END: 50270,
HIGHER_RATE_END: 125140,
BASIC_RATE: 0.20,
HIGHER_RATE: 0.40,
ADDITIONAL_RATE: 0.45
};

// Constants
const CORPORATION_TAX_RATE = 0.25;
const SECTION_455_RATE = 0.33;
const NI_EMPLOYER_RATE = 0.138; // Employer's NI rate
const DIVIDEND_TAX_RATES = {
BASIC: 0.0875,
HIGHER: 0.3375,
ADDITIONAL: 0.3935
};

const calculateTaxes = () => {
// Calculate Corporation Tax
const corporationTax = Math.max(0, inputs.companyProfit * CORPORATION_TAX_RATE);

// Calculate Section 455 charge on increased loan balance
const loanIncrease = inputs.currentLoanBalance - inputs.previousLoanBalance;
const section455 = Math.max(0, loanIncrease * SECTION_455_RATE);

// Calculate Employer's NI
const employerNI = Math.max(0, (inputs.salary - 9100) * NI_EMPLOYER_RATE);

// Calculate Income Tax
let taxableIncome = inputs.salary + inputs.dividends;
let incomeTax = 0;
let allowancesLost = false;

// Reduce personal allowance for high earners
let personalAllowance = TAX_BRACKETS.PERSONAL_ALLOWANCE;
if (taxableIncome > 100000) {
const reduction = Math.min(personalAllowance, (taxableIncome - 100000) / 2);
personalAllowance -= reduction;
if (personalAllowance === 0) allowancesLost = true;
}

// Calculate tax on salary first
let remainingSalary = inputs.salary;
let remainingDividends = inputs.dividends;

// Tax on salary
if (remainingSalary > personalAllowance) {
const basicRateSalary = Math.min(
TAX_BRACKETS.BASIC_RATE_END - personalAllowance,
remainingSalary - personalAllowance
);
incomeTax += basicRateSalary * TAX_BRACKETS.BASIC_RATE;
remainingSalary -= basicRateSalary + personalAllowance;

if (remainingSalary > 0) {
const higherRateSalary = Math.min(
TAX_BRACKETS.HIGHER_RATE_END - TAX_BRACKETS.BASIC_RATE_END,
remainingSalary
);
incomeTax += higherRateSalary * TAX_BRACKETS.HIGHER_RATE;
remainingSalary -= higherRateSalary;

if (remainingSalary > 0) {
incomeTax += remainingSalary * TAX_BRACKETS.ADDITIONAL_RATE;
}
}
}

// Tax on dividends (using different rates)
const dividendAllowance = 1000; // 2024/25 dividend allowance
if (remainingDividends > dividendAllowance) {
remainingDividends -= dividendAllowance;

const basicRateDividends = Math.min(
TAX_BRACKETS.BASIC_RATE_END - inputs.salary - dividendAllowance,
remainingDividends
);
incomeTax += basicRateDividends * DIVIDEND_TAX_RATES.BASIC;
remainingDividends -= basicRateDividends;

if (remainingDividends > 0) {
const higherRateDividends = Math.min(
TAX_BRACKETS.HIGHER_RATE_END - TAX_BRACKETS.BASIC_RATE_END,
remainingDividends
);
incomeTax += higherRateDividends * DIVIDEND_TAX_RATES.HIGHER;
remainingDividends -= higherRateDividends;

if (remainingDividends > 0) {
incomeTax += remainingDividends * DIVIDEND_TAX_RATES.ADDITIONAL;
}
}
}

// Calculate Child Maintenance
// Note: Dividends ARE included in Child Maintenance calculations as per CMS rules
const weeklyIncome = (inputs.salary + inputs.dividends) / 52;
let maintenanceRate;
if (weeklyIncome <= 200) {
maintenanceRate = 0;
} else if (weeklyIncome <= 800) {
maintenanceRate = 0.17; // 17% for 2 children
} else if (weeklyIncome <= 3000) {
maintenanceRate = 0.16; // 16% for 2 children
} else {
maintenanceRate = 0.15; // 15% for 2 children
}
const childMaintenance = weeklyIncome * maintenanceRate * 52;

// Calculate total take-home
const totalTakeHome = inputs.salary + inputs.dividends - incomeTax;

setResults({
corporationTax,
incomeTax,
section455,
payrollCharges: employerNI,
childMaintenance,
allowancesLost,
totalTakeHome
});
};

useEffect(() => {
calculateTaxes();
}, [inputs]);

const handleInputChange = (e) => {
const { name, value } = e.target;
setInputs(prev => ({
...prev,
[name]: parseFloat(value) || 0
}));
};

const formatCurrency = (amount) => {
return new Intl.NumberFormat('en-GB', {
style: 'currency',
currency: 'GBP'
}).format(amount);
};

return (
<div className="max-w-4xl mx-auto p-4 space-y-6">
    <Card>
        <CardHeader>
            <CardTitle>UK Company Withdrawal Calculator</CardTitle>
        </CardHeader>
        <CardContent className="space-y-6">
            {/* Input Section */}
            <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
                <div className="space-y-2">
                    <Label htmlFor="companyProfit">Company Profit</Label>
                    <Input
                            type="number"
                            id="companyProfit"
                            name="companyProfit"
                            value={inputs.companyProfit}
                            onChange={handleInputChange}
                    />
                </div>
                <div className="space-y-2">
                    <Label htmlFor="salary">Annual Salary</Label>
                    <Input
                            type="number"
                            id="salary"
                            name="salary"
                            value={inputs.salary}
                            onChange={handleInputChange}
                    />
                </div>
                <div className="space-y-2">
                    <Label htmlFor="dividends">Annual Dividends</Label>
                    <Input
                            type="number"
                            id="dividends"
                            name="dividends"
                            value={inputs.dividends}
                            onChange={handleInputChange}
                    />
                </div>
                <div className="space-y-2">
                    <Label htmlFor="previousLoanBalance">Previous Year Loan Balance</Label>
                    <Input
                            type="number"
                            id="previousLoanBalance"
                            name="previousLoanBalance"
                            value={inputs.previousLoanBalance}
                            onChange={handleInputChange}
                    />
                </div>
                <div className="space-y-2">
                    <Label htmlFor="currentLoanBalance">Current Year Loan Balance</Label>
                    <Input
                            type="number"
                            id="currentLoanBalance"
                            name="currentLoanBalance"
                            value={inputs.currentLoanBalance}
                            onChange={handleInputChange}
                    />
                </div>
                <div className="space-y-2">
                    <Label htmlFor="investmentPL">Investment Profit/Loss</Label>
                    <Input
                            type="number"
                            id="investmentPL"
                            name="investmentPL"
                            value={inputs.investmentPL}
                            onChange={handleInputChange}
                    />
                </div>
            </div>

            {/* Results Section */}
            <div className="mt-8 space-y-4">
                <h3 className="text-lg font-semibold">Results</h3>
                <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
                    <div>
                        <p className="font-semibold">Corporation Tax:</p>
                        <p>{formatCurrency(results.corporationTax)}</p>
                    </div>
                    <div>
                        <p className="font-semibold">Income Tax:</p>
                        <p>{formatCurrency(results.incomeTax)}</p>
                    </div>
                    <div>
                        <p className="font-semibold">Section 455 Charge:</p>
                        <p>{formatCurrency(results.section455)}</p>
                    </div>
                    <div>
                        <p className="font-semibold">Employer's NI:</p>
                        <p>{formatCurrency(results.payrollCharges)}</p>
                    </div>
                    <div>
                        <p className="font-semibold">Child Maintenance (Monthly):</p>
                        <p>{formatCurrency(results.childMaintenance / 12)}</p>
                    </div>
                    <div>
                        <p className="font-semibold">Total Take-Home:</p>
                        <p>{formatCurrency(results.totalTakeHome)}</p>
                    </div>
                </div>

                {results.allowancesLost && (
                <Alert className="mt-4">
                    <AlertDescription>
                        Warning: Personal allowances have been reduced or lost due to high income
                    </AlertDescription>
                </Alert>
                )}

                <div className="mt-4 text-sm text-gray-600">
                    <p>Key Notes:</p>
                    <ul className="list-disc pl-5 space-y-1">
                        <li>Dividends are included in Child Maintenance calculations</li>
                        <li>Dividend tax rates differ from salary tax rates</li>
                        <li>Personal allowance reduces by £1 for every £2 earned over £100,000</li>
                        <li>Section 455 tax applies to director's loan account increases</li>
                    </ul>
                </div>
            </div>
        </CardContent>
    </Card>
</div>
);
};

export default UKCompanyCalculator;