reallyme-foundationdb-kit 0.3.2

// SPDX-FileCopyrightText: 2026 ReallyMe LLC
// SPDX-License-Identifier: MIT OR Apache-2.0

//! Range helpers for FoundationDB scans.

use crate::fdb::error::{FdbError, FdbQueryErrorReason, FdbResult};
use bytes::{Bytes, BytesMut};

/// Computes the exclusive range end for a prefix scan.
///
/// This legacy API returns an owned `Vec<u8>` for existing call sites and older
/// adapters. Prefer [`range_end_for_prefix_bytes`] in new or performance-critical
/// paths so key buffers stay in `bytes`-owned form end-to-end.
pub fn range_end_for_prefix(prefix: &[u8]) -> FdbResult<Vec<u8>> {
    range_end_for_prefix_bytes(prefix).map(|value| value.to_vec())
}

/// Computes the exclusive range end for a prefix scan using a `bytes` key buffer.
///
/// The caller receives `Bytes`, which aligns with this kit's preference for key
/// ownership and reduces conversion churn in hot scan paths.
pub fn range_end_for_prefix_bytes(prefix: &[u8]) -> FdbResult<Bytes> {
    if prefix.is_empty() {
        return Err(FdbError::Query {
            reason: FdbQueryErrorReason::InvalidRangePrefix,
        });
    }

    let mut end = BytesMut::from(prefix);
    for index in (0..end.len()).rev() {
        if end[index] != 0xff {
            end[index] = end[index].checked_add(1).ok_or(FdbError::Query {
                reason: FdbQueryErrorReason::IntegerOverflow,
            })?;
            end.truncate(index.checked_add(1).ok_or(FdbError::Query {
                reason: FdbQueryErrorReason::IntegerOverflow,
            })?);
            return Ok(end.freeze());
        }
    }

    Err(FdbError::Query {
        reason: FdbQueryErrorReason::InvalidRangePrefix,
    })
}

#[cfg(test)]
#[path = "range_tests.rs"]
mod tests;