138 lines
3.5 KiB
TypeScript
138 lines
3.5 KiB
TypeScript
/**
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* Money Value Object
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*
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* Encapsulates currency and amount with proper validation
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*
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* Business Rules:
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* - Amount must be non-negative
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* - Currency must be valid ISO 4217 code
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* - Money is immutable
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* - Arithmetic operations return new Money instances
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*/
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export class Money {
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private readonly amount: number;
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private readonly currency: string;
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private static readonly SUPPORTED_CURRENCIES = ['USD', 'EUR', 'GBP', 'CNY', 'JPY'];
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private constructor(amount: number, currency: string) {
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this.amount = amount;
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this.currency = currency;
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}
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static create(amount: number, currency: string): Money {
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if (amount < 0) {
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throw new Error('Amount cannot be negative.');
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}
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const normalizedCurrency = currency.trim().toUpperCase();
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if (!Money.isValidCurrency(normalizedCurrency)) {
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throw new Error(
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`Invalid currency code: ${currency}. Supported currencies: ${Money.SUPPORTED_CURRENCIES.join(', ')}`
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);
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}
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// Round to 2 decimal places to avoid floating point issues
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const roundedAmount = Math.round(amount * 100) / 100;
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return new Money(roundedAmount, normalizedCurrency);
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}
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static zero(currency: string): Money {
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return Money.create(0, currency);
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}
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private static isValidCurrency(currency: string): boolean {
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return Money.SUPPORTED_CURRENCIES.includes(currency);
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}
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getAmount(): number {
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return this.amount;
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}
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getCurrency(): string {
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return this.currency;
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}
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add(other: Money): Money {
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this.ensureSameCurrency(other);
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return Money.create(this.amount + other.amount, this.currency);
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}
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subtract(other: Money): Money {
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this.ensureSameCurrency(other);
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const result = this.amount - other.amount;
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if (result < 0) {
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throw new Error('Subtraction would result in negative amount.');
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}
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return Money.create(result, this.currency);
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}
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multiply(multiplier: number): Money {
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if (multiplier < 0) {
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throw new Error('Multiplier cannot be negative.');
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}
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return Money.create(this.amount * multiplier, this.currency);
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}
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divide(divisor: number): Money {
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if (divisor <= 0) {
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throw new Error('Divisor must be positive.');
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}
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return Money.create(this.amount / divisor, this.currency);
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}
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isGreaterThan(other: Money): boolean {
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this.ensureSameCurrency(other);
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return this.amount > other.amount;
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}
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isLessThan(other: Money): boolean {
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this.ensureSameCurrency(other);
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return this.amount < other.amount;
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}
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isEqualTo(other: Money): boolean {
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return this.currency === other.currency && this.amount === other.amount;
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}
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isZero(): boolean {
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return this.amount === 0;
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}
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private ensureSameCurrency(other: Money): void {
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if (this.currency !== other.currency) {
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throw new Error(`Currency mismatch: ${this.currency} vs ${other.currency}`);
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}
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}
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/**
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* Format as string with currency symbol
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*/
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format(): string {
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const symbols: { [key: string]: string } = {
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USD: '$',
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EUR: '€',
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GBP: '£',
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CNY: '¥',
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JPY: '¥',
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};
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const symbol = symbols[this.currency] || this.currency;
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return `${symbol}${this.amount.toFixed(2)}`;
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}
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toString(): string {
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return this.format();
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}
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toObject(): { amount: number; currency: string } {
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return {
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amount: this.amount,
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currency: this.currency,
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};
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}
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}
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