Module position 

Module: position

Responsibility

Tracks individual positions per symbol and a multi-position ledger with cash accounting. Computes realized and unrealized P&L from fills.

Guarantees

• Position::apply_fill returns realized PnL (non-zero only when reducing position)
• PositionLedger::apply_fill debits/credits cash correctly including commissions
• Position::is_flat is true iff quantity == 0

NOT Responsible For

• Risk checks (see risk module)
• Order management

Structs

Fill

A single trade execution event.

Position

A single-symbol position tracking quantity, average cost, and realized P&L.

PositionLedger

A multi-symbol ledger tracking positions and a cash balance.

Enums

PositionDirection

Direction of an open position.