import re
from ibis.expr import datatypes as dt


def compile_dtype(type: str | dt.DataType, *, dialect: str | None = None) -> str:
    """Compile an ibis.DataType to SQL."""
    # need to ensure nullable so that we can make a literal NULL of this type.
    # No backends that I know of treat nullable and non-nullable types
    # differently, they only care about this during a column definition.
    t = ibis.dtype(type).copy(nullable=True)
    e = ibis.null(t).name("foobar")
    raw = ibis.to_sql(e, dialect=dialect)
    pattern = re.compile(r"^SELECT\s+CAST\(NULL AS (.*)\) AS .+$")
    match = pattern.match(raw)
    assert match, f"Could not match {raw} to SQL type"
    return match.group(1)


compile_dtype("!struct<foo: int64, bar: string>", dialect="duckdb")
compile_dtype("struct<foo: int64, bar: string>", dialect="postgres")