Function calculate_reconciliation_price 

pub fn calculate_reconciliation_price(
    current_position_qty: Decimal,
    current_position_avg_px: Option<Decimal>,
    target_position_qty: Decimal,
    target_position_avg_px: Option<Decimal>,
    target_avg_px_reconciliation: AvgPxReconciliation,
    target_avg_px_precision: Option<u8>,
) -> Option<Decimal>

Calculate the price needed for a reconciliation order to achieve target position.

This is a pure function that calculates what price a fill would need to have to move from the current position state to the target position state. By default, a reduction uses the reported average price but cannot change the remaining position’s entry average.

A same-side reduction or accumulation instead keeps the current average as its price when the target average is [AvgPxReconciliation::OpeningOnly], or when the target average carries a precision and already matches the current average, so neither a different averaging method nor venue rounding fabricates a fill price. This override takes precedence over scenarios 4 and 5 below.

Returns

Returns Some(Decimal) if a valid reconciliation price can be calculated, None otherwise.

Notes

The function handles five scenarios:

1. Position to flat: reconciliation_px = current_avg_px (close at current average)
2. Flat to position: reconciliation_px = target_avg_px
3. Position flip (sign change): reconciliation_px = target_avg_px (due to value reset in simulation)
4. Reduction: target average price by default (remaining entry average is unchanged)
5. Accumulation: weighted average formula by default