Banking Ledger

// Banking ledger: customers, accounts (joint ownership via explicit M2M),
// transactions (debit/credit), transfers (double-entry style), statements.
// All monetary amounts stored in minor currency units (cents).
// Provenance: Synthetic (modeled after the standard banking ledger design pattern)

Customer {
  id: +uuid
  first_name: string @length(1, 50)
  last_name: string @length(1, 50)
  email: &string @email
  phone: string?
  date_of_birth: timestamp?
  account_owners: [AccountOwner]
  created_at: +timestamp
}

// kind: checking | savings | credit | investment
Account {
  id: +uuid
  // human-readable account number, e.g. "1234567890"
  account_number: &string @length(10, 20)
  kind: string @length(1, 20)
  // balance in minor currency units (cents)
  balance: i64
  // ISO 4217 currency code stored as fixed 3 bytes, e.g. "USD"
  currency: char(3)
  opened_at: +timestamp
  closed_at: timestamp?
  owners: [AccountOwner]
  transactions: [Transaction]
  statements: [Statement]
  created_at: +timestamp
}

// Explicit join model enabling joint accounts (Customer <-> Account M2M).
// role: primary | joint | authorized
AccountOwner {
  id: +uuid
  customer: *Customer
  account: *Account
  role: string @length(1, 20)
  added_at: +timestamp
  @index(customer, account)
}

// kind: debit | credit
Transaction {
  id: +uuid
  account: *Account
  kind: string @length(1, 10)
  // amount in minor currency units (cents); always positive
  amount: i64 @min(1)
  description: string?
  reference: string?
  occurred_at: +timestamp
  created_at: +timestamp
  @index(account, occurred_at)
}

// A transfer represents a debit on from_account and a credit on to_account.
Transfer {
  id: +uuid
  from_account: *Account
  to_account: *Account
  // amount in minor currency units (cents)
  amount: i64 @min(1)
  description: string?
  occurred_at: +timestamp
  created_at: +timestamp
  @index(from_account, occurred_at)
}

Statement {
  id: +uuid
  account: *Account
  period_start: timestamp
  period_end: timestamp
  opening_balance: i64
  closing_balance: i64
  generated_at: +timestamp
  created_at: +timestamp
  @index(account, period_start)
}