# Copyright 2023 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from __future__ import annotations

import abc
import dataclasses
import functools
import itertools
import typing
from typing import Callable, Mapping, Tuple, TypeVar

from bigframes import dtypes
from bigframes.core import expression, window_spec
import bigframes.core.identifiers as ids
import bigframes.operations.aggregations as agg_ops

TExpression = TypeVar("TExpression", bound="Aggregation")


@dataclasses.dataclass(frozen=True)
class Aggregation(expression.Expression):
    """Represents windowing or aggregation over a column."""

    op: agg_ops.WindowOp = dataclasses.field()

    @property
    def column_references(self) -> typing.Tuple[ids.ColumnId, ...]:
        return tuple(
            itertools.chain.from_iterable(
                map(lambda x: x.column_references, self.inputs)
            )
        )

    @functools.cached_property
    def is_resolved(self) -> bool:
        return all(input.is_resolved for input in self.inputs)

    @functools.cached_property
    def output_type(self) -> dtypes.ExpressionType:
        if not self.is_resolved:
            raise ValueError(f"Type of expression {self.op} has not been fixed.")

        input_types = [input.output_type for input in self.inputs]

        return self.op.output_type(*input_types)

    @property
    @abc.abstractmethod
    def inputs(
        self,
    ) -> typing.Tuple[expression.Expression, ...]:
        ...

    @property
    def children(self) -> Tuple[expression.Expression, ...]:
        return self.inputs

    @property
    def free_variables(self) -> typing.Tuple[str, ...]:
        return tuple(
            itertools.chain.from_iterable(map(lambda x: x.free_variables, self.inputs))
        )

    @property
    def is_const(self) -> bool:
        return all(child.is_const for child in self.inputs)

    @functools.cached_property
    def is_scalar_expr(self) -> bool:
        return False

    @abc.abstractmethod
    def replace_args(self: TExpression, *arg) -> TExpression:
        ...

    def transform_children(
        self: TExpression, t: Callable[[expression.Expression], expression.Expression]
    ) -> TExpression:
        return self.replace_args(*(t(arg) for arg in self.inputs))

    def bind_variables(
        self: TExpression,
        bindings: Mapping[str, expression.Expression],
        allow_partial_bindings: bool = False,
    ) -> TExpression:
        return self.transform_children(
            lambda x: x.bind_variables(bindings, allow_partial_bindings)
        )

    def bind_refs(
        self: TExpression,
        bindings: Mapping[ids.ColumnId, expression.Expression],
        allow_partial_bindings: bool = False,
    ) -> TExpression:
        return self.transform_children(
            lambda x: x.bind_refs(bindings, allow_partial_bindings)
        )


@dataclasses.dataclass(frozen=True)
class NullaryAggregation(Aggregation):
    op: agg_ops.NullaryWindowOp = dataclasses.field()

    @property
    def inputs(
        self,
    ) -> typing.Tuple[expression.Expression, ...]:
        return ()

    def replace_args(self, *arg) -> NullaryAggregation:
        return self


@dataclasses.dataclass(frozen=True)
class UnaryAggregation(Aggregation):
    op: agg_ops.UnaryWindowOp
    arg: expression.Expression

    @property
    def inputs(
        self,
    ) -> typing.Tuple[expression.Expression, ...]:
        return (self.arg,)

    def replace_args(self, arg: expression.Expression) -> UnaryAggregation:
        return UnaryAggregation(
            self.op,
            arg,
        )


@dataclasses.dataclass(frozen=True)
class BinaryAggregation(Aggregation):
    op: agg_ops.BinaryAggregateOp = dataclasses.field()
    left: expression.Expression = dataclasses.field()
    right: expression.Expression = dataclasses.field()

    @property
    def inputs(
        self,
    ) -> typing.Tuple[expression.Expression, ...]:
        return (self.left, self.right)

    def replace_args(
        self, larg: expression.Expression, rarg: expression.Expression
    ) -> BinaryAggregation:
        return BinaryAggregation(self.op, larg, rarg)


@dataclasses.dataclass(frozen=True)
class WindowExpression(expression.Expression):
    analytic_expr: Aggregation
    window: window_spec.WindowSpec

    @property
    def column_references(self) -> typing.Tuple[ids.ColumnId, ...]:
        return tuple(
            itertools.chain.from_iterable(
                map(lambda x: x.column_references, self.inputs)
            )
        )

    @functools.cached_property
    def is_resolved(self) -> bool:
        return all(input.is_resolved for input in self.inputs)

    @property
    def output_type(self) -> dtypes.ExpressionType:
        return self.analytic_expr.output_type

    @property
    def inputs(
        self,
    ) -> typing.Tuple[expression.Expression, ...]:
        # TODO: Maybe make the window spec itself an expression?
        return (self.analytic_expr, *self.window.expressions)

    @property
    def children(self) -> Tuple[expression.Expression, ...]:
        return self.inputs

    @property
    def free_variables(self) -> typing.Tuple[str, ...]:
        return tuple(
            itertools.chain.from_iterable(map(lambda x: x.free_variables, self.inputs))
        )

    @property
    def is_const(self) -> bool:
        return all(child.is_const for child in self.inputs)

    @functools.cached_property
    def is_scalar_expr(self) -> bool:
        return False

    def transform_children(
        self: WindowExpression,
        t: Callable[[expression.Expression], expression.Expression],
    ) -> WindowExpression:
        return WindowExpression(
            t(self.analytic_expr),  # type: ignore
            self.window.transform_exprs(t),
        )

    def bind_variables(
        self: WindowExpression,
        bindings: Mapping[str, expression.Expression],
        allow_partial_bindings: bool = False,
    ) -> WindowExpression:
        return self.transform_children(
            lambda x: x.bind_variables(bindings, allow_partial_bindings)
        )

    def bind_refs(
        self: WindowExpression,
        bindings: Mapping[ids.ColumnId, expression.Expression],
        allow_partial_bindings: bool = False,
    ) -> WindowExpression:
        return self.transform_children(
            lambda x: x.bind_refs(bindings, allow_partial_bindings)
        )
