Function apply_budget

atomic-cli/src/commands/vault/context.rs:736–763

Truncate bodies so their combined length fits `budget_chars`. Start with an even allocation, then give unused capacity from short bodies to higher-ranked items instead of silently discarding available context.

(mut items: Vec<MemoryItem>, budget_chars: usize)

/// even allocation, then give unused capacity from short bodies to higher-ranked
/// items instead of silently discarding available context.
fn apply_budget(mut items: Vec<MemoryItem>, budget_chars: usize) -> Vec<MemoryItem> {
    if items.is_empty() {
        return items;
    }
    let lengths: Vec<usize> = items.iter().map(|item| item.body.chars().count()).collect();
    let baseline = budget_chars / items.len();
    let mut allocations: Vec<usize> = lengths
        .iter()
        .map(|length| (*length).min(baseline))
        .collect();
    let mut remaining = budget_chars.saturating_sub(allocations.iter().sum());
    for (allocation, length) in allocations.iter_mut().zip(&lengths) {
        let extra = length.saturating_sub(*allocation).min(remaining);
        *allocation += extra;
        remaining -= extra;
        if remaining == 0 {
            break;
        }
    }

    for ((item, allocation), length) in items.iter_mut().zip(allocations).zip(lengths) {
        if allocation < length {
            item.body = truncate_chars(&item.body, allocation);
            item.truncated = true;
        }
    }
    items
}

/// Truncate to at most `max_chars` characters on a char boundary.
fn truncate_chars(s: &str, max_chars: usize) -> String {