# This code is part of Qiskit.
#
# (C) Copyright IBM 2023.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.

"""Abstract class for generating ODE functions."""
from __future__ import annotations

from abc import ABC, abstractmethod
from collections.abc import Mapping, Iterable

from qiskit.circuit import Parameter

from ..var_qte_linear_solver import VarQTELinearSolver


class AbstractOdeFunction(ABC):
    """Abstract class for generating ODE functions."""

    def __init__(
        self,
        varqte_linear_solver: VarQTELinearSolver,
        param_dict: Mapping[Parameter, float],
        t_param: Parameter | None = None,
    ) -> None:

        self._varqte_linear_solver = varqte_linear_solver
        self._param_dict = param_dict
        self._t_param = t_param

    @abstractmethod
    def var_qte_ode_function(self, time: float, parameter_values: Iterable) -> Iterable:
        """
        Evaluates an ODE function for a given time and parameter values. It is used by an ODE
        solver.

        Args:
            time: Current time of evolution.
            parameter_values: Current values of parameters.

        Returns:
            ODE gradient arising from solving a system of linear equations.
        """
        pass