validator

voucher.ts

export class Voucher {
  description: string;
  rows: VoucherRow[];

  constructor(description: string, rows: VoucherRow[]) {
    this.description = description;
    this.rows = rows;
  }

  get isBalanced(): boolean {
    return this.rows.reduce((sum, row) => sum + row.credit + row.debit, 0) === 0;
  }

  addRow(row: VoucherRow) {
    this.rows.push(row);
  }
}

export class VoucherRow {
  accountNumber: AccountNumber;
  amount: number;
  category: 'debit' | 'credit';

  constructor(accountNumber: AccountNumber, amount: number, category: 'debit' | 'credit') {
    this.accountNumber = accountNumber;
    this.amount = amount;
    this.category = category;
  }

  static create(accountNumber: string, amount: number, category: 'debit' | 'credit'): VoucherRow | ParseError {
    const parsed = AccountNumber.fromString(accountNumber);
    if (parsed instanceof ParseError) {
      return parsed;
    }
    return new VoucherRow(parsed, amount, category);
  }

  get debit(): number {
    return this.category === 'debit' ? -this.amount : 0;
  }

  get credit(): number {
    return this.category === 'credit' ? this.amount : 0;
  }
}

export class AccountNumber {
  number: number;

  private constructor(number: number) {
    this.number = number;
  }

  // usage:
  // const accountNumber = AccountNumber.fromString('1900');
  // if (accountNumber instanceof ParseError) {
  //   console.log(accountNumber.message);
  // } else {
  //   console.log(accountNumber.number);
  // }
  static fromString(str: string): AccountNumber | ParseError {
    const number = parseInt(str);
    if (isNaN(number) || number < 1900 || number > 1999) {
      return new ParseError(`Invalid account number: ${str}`);
    }
    return new AccountNumber(number);
  }
}

export class ParseError {
  message: string;

  constructor(message: string) {
    this.message = message;
  }
}