feat(core): initial release of financial calculation package with decimal precision

2025-07-29 09:20:06 +00:00
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+# @fin.cx/calculation
+
+> Professional financial calculations with decimal precision for JavaScript and TypeScript
+
+[![npm version](https://img.shields.io/npm/v/@fin.cx/calculation.svg)](https://www.npmjs.com/package/@fin.cx/calculation)
+[![TypeScript](https://img.shields.io/badge/TypeScript-Ready-blue.svg)](https://www.typescriptlang.org/)
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
+
+## 🎯 Why @fin.cx/calculation?
+
+JavaScript's floating-point arithmetic can lead to precision errors in financial calculations:
+
+```javascript
+// JavaScript floating point problem
+0.1 + 0.2 // 0.30000000000000004 ❌
+
+// With @fin.cx/calculation
+calculator.add(0.1, 0.2) // 0.3 ✅
+```
+
+This package provides **accurate financial calculations** using decimal arithmetic, making it perfect for:
+
+- 🏦 Banking applications
+- 💰 Investment analysis tools
+- 📊 Financial reporting systems
+- 🏢 Accounting software
+- 💳 Payment processing systems
+- 📈 Trading platforms
+
+## ✨ Features
+
+- **🔢 Decimal Precision**: Built on decimal.js for accurate calculations
+- **📐 Comprehensive Functions**: Time value of money, interest calculations, loan amortization, and more
+- **💱 Currency Support**: Built-in currency formatting and conversion
+- **🌍 Cross-Platform**: Works in Node.js and browsers
+- **📘 TypeScript First**: Full type safety and IntelliSense support
+- **🧪 Battle-Tested**: Extensive test suite ensures reliability
+- **🚀 Zero Dependencies**: Only depends on decimal.js for core functionality
+
+## 📦 Installation
+
+```bash
+npm install @fin.cx/calculation
+# or
+yarn add @fin.cx/calculation
+# or
+pnpm add @fin.cx/calculation
+```
+
+## 🚀 Quick Start
+
+```typescript
+import { Calculator, Financial, Currency } from '@fin.cx/calculation';
+
+// Basic calculations with precision
+const calc = new Calculator();
+const result = calc.add(0.1, 0.2); // 0.3 (exact)
+
+// Financial calculations
+const financial = new Financial();
+const payment = financial.payment(200000, 0.045/12, 360); // Monthly mortgage payment
+
+// Currency operations
+const currency = new Currency();
+currency.setExchangeRate('USD', 'EUR', 0.85);
+const euros = currency.convert(100, 'USD', 'EUR'); // Convert $100 to €85
+```
+
+## 📚 Core Classes
+
+### Calculator - Precision Arithmetic
+
+```typescript
+const calc = new Calculator({ precision: 10 });
+
+// Basic operations
+calc.add(10.5, 20.3);           // 30.8
+calc.subtract(100, 45.5);       // 54.5
+calc.multiply(15, 3.5);         // 52.5
+calc.divide(100, 3);            // 33.3333333333...
+
+// Advanced operations
+calc.power(2, 8);               // 256
+calc.sqrt(16);                  // 4
+calc.ln(Math.E);                // 1
+calc.round(3.14159, 2);         // 3.14
+```
+
+### Financial - Time Value of Money
+
+```typescript
+const financial = new Financial();
+
+// Present Value - How much is $10,000 in 5 years worth today at 5% interest?
+const pv = financial.presentValue(10000, 0.05, 5); // $7,835.26
+
+// Future Value - How much will $5,000 be worth in 10 years at 7% interest?
+const fv = financial.futureValue(5000, 0.07, 10); // $9,835.76
+
+// Loan Payment - Monthly payment for $200,000 mortgage at 4.5% for 30 years
+const pmt = financial.payment(200000, 0.045/12, 360); // $1,013.37
+
+// Net Present Value - Is this investment worth it?
+const cashFlows = [-50000, 15000, 15000, 15000, 15000, 20000];
+const npv = financial.npv(0.1, cashFlows); // $7,946.11 (positive = good investment)
+
+// Internal Rate of Return - What's the return rate?
+const irr = financial.irr(cashFlows); // 16.89%
+```
+
+### Interest - Various Interest Calculations
+
+```typescript
+const interest = new Interest();
+
+// Simple Interest - $1,000 at 5% for 2 years
+const simple = interest.simple(1000, 0.05, 2); // $100
+
+// Compound Interest - $1,000 at 5% for 2 years, compounded monthly
+const compound = interest.compound(1000, 0.05, 2, 'monthly'); // $104.94
+
+// Effective Annual Rate - What's the real rate with monthly compounding?
+const ear = interest.effectiveAnnualRate(0.12, 'monthly'); // 12.68%
+
+// Rule of 72 - How long to double your money at 8%?
+const years = interest.ruleOf72(8); // ~9 years
+```
+
+### Amortization - Loan Schedules
+
+```typescript
+const amortization = new Amortization();
+
+// Generate complete loan schedule
+const schedule = amortization.schedule({
+  principal: 250000,
+  annualRate: 0.045,
+  termYears: 30,
+  extraPayment: 200 // Optional extra monthly payment
+});
+
+// Analyze the schedule
+console.log(`Monthly Payment: $${schedule.monthlyPayment.toFixed(2)}`);
+console.log(`Total Interest: $${schedule.totalInterest.toFixed(2)}`);
+console.log(`Payoff in ${schedule.payments.length} months`);
+
+// Each payment includes:
+schedule.payments[0]; // {
+//   period: 1,
+//   payment: 1266.71,
+//   principal: 329.21,
+//   interest: 937.50,
+//   balance: 249670.79,
+//   cumulativePrincipal: 329.21,
+//   cumulativeInterest: 937.50
+// }
+```
+
+### Currency - Money Formatting & Conversion
+
+```typescript
+const currency = new Currency();
+
+// Set exchange rates
+currency.setExchangeRates([
+  { from: 'USD', to: 'EUR', rate: 0.85 },
+  { from: 'USD', to: 'GBP', rate: 0.73 },
+  { from: 'USD', to: 'JPY', rate: 110 }
+]);
+
+// Convert currencies
+const euros = currency.convert(1000, 'USD', 'EUR'); // €850
+
+// Format currency for display
+currency.format(1234.56, 'USD'); // "$1,234.56"
+currency.format(1234.56, 'EUR'); // "€1.234,56"
+currency.format(1234.56, 'JPY'); // "¥1,235"
+
+// Money operations (ensures same currency)
+const total = currency.addMoney(
+  currency.money(100, 'USD'),
+  currency.money(50, 'USD')
+); // $150
+
+// Percentage calculations
+currency.percentage(200, 15);           // 30 (15% of 200)
+currency.discount(100, 20);             // 80 (20% off)
+currency.withTax(100, 0.08);           // 108 (8% tax)
+```
+
+## Precision and Accuracy
+
+All calculations use decimal.js internally to avoid floating-point precision errors common in JavaScript:
+
+```typescript
+// JavaScript floating point error
+console.log(0.1 + 0.2); // 0.30000000000000004
+
+// @fin.cx/calculation precision
+const calc = new Calculator();
+const result = calc.add(0.1, 0.2);
+console.log(calc.toString(result)); // "0.3"
+```
+
+## API Reference
+
+### Calculator Options
+
+```typescript
+interface ICalculatorOptions {
+  precision?: number;    // Decimal places (default: 10)
+  rounding?: number;     // Rounding mode (default: ROUND_HALF_UP)
+}
+```
+
+### Compounding Frequencies
+
+- `'annually'` - Once per year
+- `'semiannually'` - Twice per year
+- `'quarterly'` - Four times per year
+- `'monthly'` - Twelve times per year
+- `'weekly'` - 52 times per year
+- `'daily'` - 365 times per year
+- `'continuous'` - Continuous compounding
+
+### Currency Options
+
+```typescript
+interface ICurrencyOptions {
+  code: string;
+  symbol?: string;
+  decimals?: number;
+  thousandsSeparator?: string;
+  decimalSeparator?: string;
+  symbolPosition?: 'before' | 'after';
+  spaceBetweenSymbolAndValue?: boolean;
+}
+```
+
+## 🏗️ Real-World Examples
+
+### Mortgage Calculator
+
+```typescript
+import { Financial, Amortization } from '@fin.cx/calculation';
+
+function calculateMortgage(homePrice: number, downPayment: number, rate: number, years: number) {
+  const financial = new Financial();
+  const amortization = new Amortization();
+  
+  const loanAmount = homePrice - downPayment;
+  const monthlyRate = rate / 12;
+  const months = years * 12;
+  
+  const monthlyPayment = financial.payment(loanAmount, monthlyRate, months);
+  const totalPaid = monthlyPayment.mul(months);
+  const totalInterest = totalPaid.sub(loanAmount);
+  
+  const schedule = amortization.schedule({
+    principal: loanAmount,
+    annualRate: rate,
+    termYears: years
+  });
+  
+  return {
+    monthlyPayment,
+    totalInterest,
+    schedule
+  };
+}
+```
+
+### Investment Analysis
+
+```typescript
+import { Financial } from '@fin.cx/calculation';
+
+function analyzeInvestment(initialInvestment: number, cashFlows: number[], discountRate: number) {
+  const financial = new Financial();
+  
+  // Add initial investment as negative cash flow
+  const allCashFlows = [-initialInvestment, ...cashFlows];
+  
+  const npv = financial.npv(discountRate, allCashFlows);
+  const irr = financial.irr(allCashFlows);
+  const paybackPeriod = calculatePaybackPeriod(allCashFlows);
+  
+  return {
+    npv: npv.toFixed(2),
+    irr: (irr.mul(100)).toFixed(2) + '%',
+    profitable: npv.greaterThan(0),
+    paybackPeriod
+  };
+}
+```
+
+### Multi-Currency Invoice System
+
+```typescript
+import { Currency } from '@fin.cx/calculation';
+
+class InvoiceSystem {
+  private currency = new Currency();
+  
+  constructor() {
+    // Set up exchange rates (in production, fetch from API)
+    this.currency.setExchangeRates([
+      { from: 'USD', to: 'EUR', rate: 0.85 },
+      { from: 'USD', to: 'GBP', rate: 0.73 }
+    ]);
+  }
+  
+  calculateInvoice(items: Array<{price: number, quantity: number}>, currency: string, taxRate: number) {
+    const subtotal = items.reduce((sum, item) => 
+      this.currency.add(sum, this.currency.multiply(item.price, item.quantity)), 
+      0
+    );
+    
+    const tax = this.currency.tax(subtotal, taxRate);
+    const total = this.currency.add(subtotal, tax);
+    
+    return {
+      subtotal: this.currency.format(subtotal, currency),
+      tax: this.currency.format(tax, currency),
+      total: this.currency.format(total, currency),
+      // Provide total in other currencies
+      totalUSD: this.currency.format(this.currency.convert(total, currency, 'USD'), 'USD'),
+      totalEUR: this.currency.format(this.currency.convert(total, currency, 'EUR'), 'EUR')
+    };
+  }
+}
+```
+
+## 🔧 Configuration
+
+### Calculator Precision
+
+```typescript
+// Default precision is 10 decimal places
+const calc = new Calculator();
+
+// Custom precision for specific use cases
+const highPrecision = new Calculator({ precision: 20 });
+const moneyCalc = new Calculator({ precision: 4, rounding: Decimal.ROUND_HALF_UP });
+```
+
+### Custom Currencies
+
+```typescript
+const currency = new Currency();
+
+// Register a custom currency
+currency.registerCurrency({
+  code: 'BTC',
+  symbol: '₿',
+  decimals: 8,
+  thousandsSeparator: ',',
+  decimalSeparator: '.',
+  symbolPosition: 'before'
+});
+
+// Use it like any other currency
+currency.format(0.00042, 'BTC'); // "₿0.00042000"
+```
+
+## 🧪 Testing
+
+The package includes comprehensive tests for all calculations:
+
+```bash
+# Run tests
+npm test
+
+# Run tests with coverage
+npm run test:coverage
+```
+
+## 🤝 Contributing
+
+Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.
+
+1. Fork the repository
+2. Create your feature branch (`git checkout -b feature/AmazingFeature`)
+3. Commit your changes (`git commit -m 'Add some AmazingFeature'`)
+4. Push to the branch (`git push origin feature/AmazingFeature`)
+5. Open a Pull Request
+
+## 📄 License
+
+This project is licensed under the MIT License - see the [LICENSE](license.md) file for details.
+
+## 🙏 Acknowledgments
+
+- Built on top of [decimal.js](https://github.com/MikeMcl/decimal.js/) for decimal arithmetic
+- Inspired by financial calculation needs in modern web applications
+- Thanks to all contributors who have helped shape this library
+
+## 📞 Support
+
+- 📧 Email: support@fin.cx
+- 🐛 Issues: [GitHub Issues](https://github.com/fin-cx/calculation/issues)
+- 💬 Discussions: [GitHub Discussions](https://github.com/fin-cx/calculation/discussions)
+
+---
+
+Made with ❤️ by the fin.cx team