Function producer_completion_window 

pub fn producer_completion_window(
    current: Option<i16>,
    epoch: i16,
    ends: &[i64],
    incoming: i64,
) -> (bool, Vec<usize>)

Merge a deferred data completion into the current epoch’s retry window.

The returned indices name old batches, or ends.len() for the incoming batch. Equal physical offsets keep the existing metadata. Earlier completions cannot displace a newer batch; only the five greatest distinct offsets survive. A lower epoch preserves the old window and is rejected. The host supplies sorted retained batches and a truthful incoming batch.