"""Pure subquery LIMIT/OFFSET injection for paging (non-destructive).

Unlike `_inject_limit` (which uses AST rewriting and adds +1 for truncation detection),
`inject_limit_offset` wraps the query as a subquery and applies LIMIT/OFFSET verbatim.
This preserves any existing LIMIT that was part of the user's query (it becomes part
of the inner subquery), and adds paging on top.
"""


def inject_limit_offset(sql: str, *, limit: int, offset: int = 0) -> str:
    """Wrap query as subquery and apply LIMIT/OFFSET non-destructively.

    The original query (including any user LIMIT) becomes the inner subquery,
    so no existing LIMIT clause is overwritten. OFFSET clause is omitted when
    offset == 0 to keep the SQL clean.
    """
    inner = sql.strip().rstrip(";")
    clause = f"LIMIT {int(limit)}"
    if offset:
        clause += f" OFFSET {int(offset)}"
    return f"SELECT * FROM (\n{inner}\n) AS _tht_page {clause}"