tiberius-ng 0.13.1

use crate::{sql_read_bytes::SqlReadBytes, time::DateTimeOffset, ColumnData};

pub(crate) async fn decode<R>(src: &mut R, len: usize) -> crate::Result<ColumnData<'static>>
where
    R: SqlReadBytes + Unpin,
{
    let rlen = src.read_u8().await?;

    let dto = match rlen {
        0 => ColumnData::DateTimeOffset(None),
        _ => {
            // A datetimeoffset value is a `time` portion (rlen - 5 bytes) then a
            // 3-byte `date` and a 2-byte offset. A server rlen < 5 would underflow.
            let time_len = rlen.checked_sub(5).ok_or_else(|| {
                crate::Error::Protocol(
                    format!("datetimeoffset: invalid value length {rlen}").into(),
                )
            })?;
            let dto = DateTimeOffset::decode(src, len, time_len).await?;
            ColumnData::DateTimeOffset(Some(dto))
        }
    };

    Ok(dto)
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::sql_read_bytes::test_utils::IntoSqlReadBytes;
    use bytes::BytesMut;

    #[tokio::test]
    async fn rejects_underlength_value_instead_of_panicking() {
        // rlen in 1..=4 (non-NULL but < 5): must be a protocol error, not a panic.
        let mut buf = BytesMut::new();
        buf.extend_from_slice(&[4u8]);
        let err = decode(&mut buf.into_sql_read_bytes(), 8)
            .await
            .expect_err("rlen < 5 must be rejected");
        assert!(matches!(err, crate::Error::Protocol(_)));
    }
}