from __future__ import annotations

import itertools
import typing as t

from sqlglot import exp
from sqlglot.helper import is_date_unit, is_iso_date, is_iso_datetime


def canonicalize(expression: exp.Expression) -> exp.Expression:
    """Converts a sql expression into a standard form.

    This method relies on annotate_types because many of the
    conversions rely on type inference.

    Args:
        expression: The expression to canonicalize.
    """
    exp.replace_children(expression, canonicalize)

    expression = add_text_to_concat(expression)
    expression = replace_date_funcs(expression)
    expression = coerce_type(expression)
    expression = remove_redundant_casts(expression)
    expression = ensure_bools(expression, _replace_int_predicate)
    expression = remove_ascending_order(expression)

    return expression


def add_text_to_concat(node: exp.Expression) -> exp.Expression:
    if isinstance(node, exp.Add) and node.type and node.type.this in exp.DataType.TEXT_TYPES:
        node = exp.Concat(expressions=[node.left, node.right])
    return node


def replace_date_funcs(node: exp.Expression) -> exp.Expression:
    if isinstance(node, exp.Date) and not node.expressions and not node.args.get("zone"):
        return exp.cast(node.this, to=exp.DataType.Type.DATE)
    if isinstance(node, exp.Timestamp) and not node.expression:
        return exp.cast(node.this, to=exp.DataType.Type.TIMESTAMP)
    return node


COERCIBLE_DATE_OPS = (
    exp.Add,
    exp.Sub,
    exp.EQ,
    exp.NEQ,
    exp.GT,
    exp.GTE,
    exp.LT,
    exp.LTE,
    exp.NullSafeEQ,
    exp.NullSafeNEQ,
)


def coerce_type(node: exp.Expression) -> exp.Expression:
    if isinstance(node, COERCIBLE_DATE_OPS):
        _coerce_date(node.left, node.right)
    elif isinstance(node, exp.Between):
        _coerce_date(node.this, node.args["low"])
    elif isinstance(node, exp.Extract) and not node.expression.type.is_type(
        *exp.DataType.TEMPORAL_TYPES
    ):
        _replace_cast(node.expression, exp.DataType.Type.DATETIME)
    elif isinstance(node, (exp.DateAdd, exp.DateSub, exp.DateTrunc)):
        _coerce_timeunit_arg(node.this, node.unit)
    elif isinstance(node, exp.DateDiff):
        _coerce_datediff_args(node)

    return node


def remove_redundant_casts(expression: exp.Expression) -> exp.Expression:
    if (
        isinstance(expression, exp.Cast)
        and expression.to.type
        and expression.this.type
        and expression.to.type.this == expression.this.type.this
    ):
        return expression.this
    return expression


def ensure_bools(
    expression: exp.Expression, replace_func: t.Callable[[exp.Expression], None]
) -> exp.Expression:
    if isinstance(expression, exp.Connector):
        replace_func(expression.left)
        replace_func(expression.right)
    elif isinstance(expression, exp.Not):
        replace_func(expression.this)
        # We can't replace num in CASE x WHEN num ..., because it's not the full predicate
    elif isinstance(expression, exp.If) and not (
        isinstance(expression.parent, exp.Case) and expression.parent.this
    ):
        replace_func(expression.this)
    elif isinstance(expression, (exp.Where, exp.Having)):
        replace_func(expression.this)

    return expression


def remove_ascending_order(expression: exp.Expression) -> exp.Expression:
    if isinstance(expression, exp.Ordered) and expression.args.get("desc") is False:
        # Convert ORDER BY a ASC to ORDER BY a
        expression.set("desc", None)

    return expression


def _coerce_date(a: exp.Expression, b: exp.Expression) -> None:
    for a, b in itertools.permutations([a, b]):
        if isinstance(b, exp.Interval):
            a = _coerce_timeunit_arg(a, b.unit)
        if (
            a.type
            and a.type.this == exp.DataType.Type.DATE
            and b.type
            and b.type.this
            not in (
                exp.DataType.Type.DATE,
                exp.DataType.Type.INTERVAL,
            )
        ):
            _replace_cast(b, exp.DataType.Type.DATE)


def _coerce_timeunit_arg(arg: exp.Expression, unit: t.Optional[exp.Expression]) -> exp.Expression:
    if not arg.type:
        return arg

    if arg.type.this in exp.DataType.TEXT_TYPES:
        date_text = arg.name
        is_iso_date_ = is_iso_date(date_text)

        if is_iso_date_ and is_date_unit(unit):
            return arg.replace(exp.cast(arg.copy(), to=exp.DataType.Type.DATE))

        # An ISO date is also an ISO datetime, but not vice versa
        if is_iso_date_ or is_iso_datetime(date_text):
            return arg.replace(exp.cast(arg.copy(), to=exp.DataType.Type.DATETIME))

    elif arg.type.this == exp.DataType.Type.DATE and not is_date_unit(unit):
        return arg.replace(exp.cast(arg.copy(), to=exp.DataType.Type.DATETIME))

    return arg


def _coerce_datediff_args(node: exp.DateDiff) -> None:
    for e in (node.this, node.expression):
        if e.type.this not in exp.DataType.TEMPORAL_TYPES:
            e.replace(exp.cast(e.copy(), to=exp.DataType.Type.DATETIME))


def _replace_cast(node: exp.Expression, to: exp.DataType.Type) -> None:
    node.replace(exp.cast(node.copy(), to=to))


# this was originally designed for presto, there is a similar transform for tsql
# this is different in that it only operates on int types, this is because
# presto has a boolean type whereas tsql doesn't (people use bits)
# with y as (select true as x) select x = 0 FROM y -- illegal presto query
def _replace_int_predicate(expression: exp.Expression) -> None:
    if isinstance(expression, exp.Coalesce):
        for _, child in expression.iter_expressions():
            _replace_int_predicate(child)
    elif expression.type and expression.type.this in exp.DataType.INTEGER_TYPES:
        expression.replace(expression.neq(0))
