Function assemble_chunks

nodedb-array/src/sync/snapshot.rs:209–243

Reassemble a [`TileSnapshot`] from a header and a slice of chunks. Sorts chunks by `chunk_index`, validates that exactly `0..total_chunks` are present (no gaps, no duplicates), concatenates their payloads, and reconstructs the snapshot. Validation failures → [`ArrayError::SegmentCorruption`].

(
    header: &SnapshotHeader,
    chunks: &mut [SnapshotChunk],
)

///
/// Validation failures → [`ArrayError::SegmentCorruption`].
pub fn assemble_chunks(
    header: &SnapshotHeader,
    chunks: &mut [SnapshotChunk],
) -> ArrayResult<TileSnapshot> {
    chunks.sort_by_key(|c| c.chunk_index);

    let expected = header.total_chunks as usize;

    if chunks.len() != expected {
        return Err(ArrayError::SegmentCorruption {
            detail: format!("expected {} chunks, got {}", expected, chunks.len()),
        });
    }

    for (i, chunk) in chunks.iter().enumerate() {
        if chunk.chunk_index as usize != i {
            return Err(ArrayError::SegmentCorruption {
                detail: format!("chunk index gap: expected {i}, got {}", chunk.chunk_index),
            });
        }
    }

    let tile_blob: Vec<u8> = chunks
        .iter()
        .flat_map(|c| c.payload.iter().copied())
        .collect();

    Ok(TileSnapshot {
        array: header.array.clone(),
        coord_range: header.coord_range.clone(),
        tile_blob,
        snapshot_hlc: header.snapshot_hlc,
        schema_hlc: header.schema_hlc,
    })
}

// ─── Sink trait ──────────────────────────────────────────────────────────────