cal-sal/index.js

A CLI tool for calculating monthly salary with tax deductions for Sri Lanka (2025 tax scheme)

#!/usr/bin/env node

import * as p from '@clack/prompts';
import color from 'picocolors';
import fs from 'fs';
import path from 'path';
import PDFDocument from 'pdfkit';
import downloadsFolder from 'downloads-folder';
import { exec } from 'child_process';

// Tax Scheme Constants (2025)
const TAX_FREE_THRESHOLD = 1800000;
const TAX_BRACKETS = [
    { upTo: 1000000, rate: 0.06 },
    { upTo: 500000, rate: 0.18 },
    { upTo: 500000, rate: 0.24 },
    { upTo: 500000, rate: 0.30 },
    { upTo: Infinity, rate: 0.36 },
];

const EPF_RATE = 0.08;
const STAMP_DUTY = 25;
const SPORTS_CLUB = 350;

// Utility Functions
const formatValue = (value) => {
    return Number(value).toLocaleString('en-US', {
        minimumFractionDigits: 2,
        maximumFractionDigits: 2,
    });
};

const calculateAnnualTax = (income, taxFreeThreshold, taxBrackets) => {
    const annualIncome = income * 12;
    if (annualIncome <= taxFreeThreshold) return 0;

    let tax = 0, remainingIncome = annualIncome - taxFreeThreshold;

    for (const { upTo, rate } of taxBrackets) {
        const taxableAmount = Math.min(remainingIncome, upTo);
        tax += taxableAmount * rate;
        remainingIncome -= taxableAmount;
        if (remainingIncome <= 0) break;
    }

    return tax / 12; // Monthly tax
};

const calculateEPFContribution = (basicSalary) => basicSalary * EPF_RATE;

const calculateNetSalary = (grossSalary, tax, epf) => {
    const totalDeductions = tax + epf + STAMP_DUTY + SPORTS_CLUB;
    return {
        netSalary: grossSalary - totalDeductions,
        totalDeductions
    };
};

const calculateExtraPayRate = (basicSalary) => {
    const totalHoursPerMonth = 240;
    const extraPayMultiplier = 1.5;
    const normalHourlyRate = basicSalary / totalHoursPerMonth;
    const extraPayRate = normalHourlyRate * extraPayMultiplier;
    return extraPayRate.toFixed(2);
};

const exportToCSV = (filename, data) => {
    const filepath = path.join(downloadsFolder(), filename);
    const content = Object.entries(data)
        .map(([key, value]) => `"${key}","${value}"`)
        .join('\n');
    fs.writeFileSync(filepath, content, 'utf8');
    openFile(filepath);
};

const exportToPDF = (filename, summaryText) => {
    const filepath = path.join(downloadsFolder(), filename);
    const doc = new PDFDocument();

    const stream = fs.createWriteStream(filepath);
    doc.pipe(stream);
    doc.fontSize(12).text(summaryText);
    doc.end();

    stream.on('finish', () => {
        openFile(filepath);
    });
};

const openFile = (filePath) => {
    const platform = process.platform;

    if (platform === 'darwin') {
        exec(`open "${filePath}"`);
    } else if (platform === 'win32') {
        exec(`start "" "${filePath}"`);
    } else if (platform === 'linux') {
        exec(`xdg-open "${filePath}"`);
    } else {
        console.warn('Automatic file opening is not supported on this OS.');
    }
};

// Main Function
async function main() {
    console.clear();
    p.intro(`${color.bgCyan(color.bold(color.black('  CAMMS Monthly Salary Calculator (2025 Tax Scheme) ')))}`);

    const { basicSalary, extraHours } = await p.group(
        {
            basicSalary: () =>
                p.text({
                    message: 'Enter your basic salary (LKR/month):',
                    placeholder: 'e.g., 100000',
                    validate: (value) => {
                        if (!value || isNaN(value) || Number(value) <= 0)
                            return "Please enter a valid non-negative number.";
                    },
                }),
            extraHours: () =>
                p.text({
                    message: 'Enter extra hours worked (OT):',
                    placeholder: 'Enter 0 if none',
                    validate: (value) => {
                        if (!value || isNaN(value) || Number(value) < 0)
                            return "Please enter a valid non-negative number.";
                    },
                    initialValue: '0',
                }),
        },
        { onCancel: () => process.exit(0) }
    );

    const spinner = p.spinner();
    spinner.start('Calculating salary details...');

    // Calculations
    const basic = Number(basicSalary);
    const hours = Number(extraHours);
    let extraPay = 0;
    if (hours > 0) {
        const rate = Number(calculateExtraPayRate(basic));
        extraPay = hours * rate;
    }

    const gross = basic + extraPay;
    const tax = calculateAnnualTax(gross, TAX_FREE_THRESHOLD, TAX_BRACKETS);
    const epf = calculateEPFContribution(basic);
    const { netSalary, totalDeductions } = calculateNetSalary(gross, tax, epf);

    spinner.stop(color.green('Calculation complete!'));

    // Summary
    const formattedOutput = `
${color.bold(color.cyan('Salary Breakdown'))}
----------------------------------------
  Basic Salary:         ${color.green(formatValue(basic))} LKR
  Extra Hours Pay:      ${color.green(formatValue(extraPay))} LKR
----------------------------------------
  Gross Salary:         ${color.green(formatValue(gross))} LKR

${color.bold(color.cyan('Deductions'))}
----------------------------------------
  EPF Contribution:     ${color.red(formatValue(epf))} LKR
  Tax (2025 Scheme):    ${color.red(formatValue(tax))} LKR
  Stamp Duty:           ${color.red(formatValue(STAMP_DUTY))} LKR
  Sports Club Fee:      ${color.red(formatValue(SPORTS_CLUB))} LKR
----------------------------------------
  Total Deductions:     ${color.red(formatValue(totalDeductions))} LKR

${color.bold(color.cyan('Net Salary'))}
----------------------------------------
  ${color.bold(color.green(formatValue(netSalary)))} LKR
`;

    p.note(formattedOutput, 'Summary');

    // Export Option
    const { exportChoice } = await p.group(
        {
            exportChoice: () =>
                p.select({
                    message: 'Do you want to export the results?',
                    options: [
                        { label: 'No Export', value: 'none' },
                        { label: 'CSV', value: 'csv' },
                        // { label: 'PDF', value: 'pdf' },
                    ],
                }),
        },
        { onCancel: () => process.exit(0) }
    );

    const exportData = {
        'Basic Salary': `${formatValue(basic)} LKR`,
        'Extra Hours Pay': `${formatValue(extraPay)} LKR`,
        'Gross Salary': `${formatValue(gross)} LKR`,
        'EPF Contribution': `${formatValue(epf)} LKR`,
        'Tax': `${formatValue(tax)} LKR`,
        'Stamp Duty': `${formatValue(STAMP_DUTY)} LKR`,
        'Sports Club Fee': `${formatValue(SPORTS_CLUB)} LKR`,
        'Total Deductions': `${formatValue(totalDeductions)} LKR`,
        'Net Salary': `${formatValue(netSalary)} LKR`,
    };

    const today = new Date();
    const formatted = today.toISOString().split('T')[0]; // "2025-04-15"
    if (exportChoice === 'csv') {
        exportToCSV(`salary_summary_${formatted}.csv`, exportData);
        p.note(`CSV file saved as ~/Downloads/salary_summary_${formatted}.csv`, 'Export Complete');
    } else if (exportChoice === 'pdf') {
        exportToPDF(`salary_summary_${formatted}.pdf`, formattedOutput);
        p.note(`PDF file saved as ~/Downloads/salary_summary_${formatted}.pdf`, 'Export Complete');
    }

    p.outro(`${color.cyan('Thank you for using the Salary Calculator!')}`);
}

// Execute CLI
main().catch(console.error);