# This code is part of Qiskit.
#
# (C) Copyright IBM 2021.
#
# 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.

"Container to encapsulate all control flow operations."

from __future__ import annotations
from abc import ABC, abstractmethod
from typing import Iterable

from qiskit.circuit import QuantumCircuit, Instruction


class ControlFlowOp(Instruction, ABC):
    """Abstract class to encapsulate all control flow operations."""

    @property
    @abstractmethod
    def blocks(self) -> tuple[QuantumCircuit, ...]:
        """Tuple of QuantumCircuits which may be executed as part of the
        execution of this ControlFlowOp. May be parameterized by a loop
        parameter to be resolved at run time.
        """
        pass

    @abstractmethod
    def replace_blocks(self, blocks: Iterable[QuantumCircuit]) -> "ControlFlowOp":
        """Replace blocks and return new instruction.
        Args:
            blocks: Tuple of QuantumCircuits to replace in instruction.

        Returns:
            New ControlFlowOp with replaced blocks.
        """
        pass