"""ORDER BY rendering.

A Pick orders by either the metric or a named dimension; both reference the
SELECT-list *output alias* (the metric's name, or the dimension's output alias),
not the underlying qualified column. Returns an `exp.Ordered` node.
"""

from __future__ import annotations

from sqlglot import exp

from api.composer.types import OrderBy, PickValidationError


def _ordered(alias: str, direction: str) -> exp.Ordered:
    return exp.Ordered(this=exp.column(alias, quoted=True), desc=(direction == "desc"))


def render_order_by(
    ob: OrderBy,
    metric_name: str,
    dim_select: dict[str, str],
) -> exp.Ordered:
    """`metric_name` is the metric SELECT alias; `dim_select` maps a dimension
    ref → its output alias."""
    if ob.by == "metric":
        return _ordered(metric_name, ob.direction)
    if ob.dimension not in dim_select:
        raise PickValidationError(
            f"order_by.dimension={ob.dimension!r} is not in group_by ({list(dim_select)})"
        )
    return _ordered(dim_select[ob.dimension], ob.direction)


def default_order_by(metric_name: str) -> exp.Ordered:
    """Sensible default when a grouped query gives no explicit order: largest
    metric value first."""
    return _ordered(metric_name, "desc")