Entities and Rules

Core entities

• User: identity, email validity, password/google constraints.
• Wallet: currency, balance, and member management.
• Category: scoped categorization for transactions.
• Transaction: non-zero amount, valid date/currency, ownership fields.
• Budget: period/status/timeframe rules and collaboration fields.

Source files:

• backend/src/Domain/Entities/User.ts
• backend/src/Domain/Entities/Wallet.ts
• backend/src/Domain/Entities/Category.ts
• backend/src/Domain/Entities/Transaction.ts
• backend/src/Domain/Entities/Budget.ts

Rule examples

• Budget endDate cannot be before startDate.
• Transaction amount cannot be zero.
• Wallet currency must be in SupportedCurrencies.

Internal snippet

if (typeof amount !== 'number' || Number.isNaN(amount) || amount === 0) {
  throw domainError('INVALID_PAYLOAD', { message: 'Amount must be a non zero number' });
}

From backend/src/Domain/Entities/Transaction.ts.