# 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.

"""
RZX based template for CX - RYGate - CX
.. parsed-literal::
                                                       ┌──────────┐
q_0: ──■─────────────■─────────────────────────────────┤0         ├───────────
     ┌─┴─┐┌───────┐┌─┴─┐┌────────┐┌──────────┐┌───────┐│  RZX(-ϴ) │┌─────────┐
q_1: ┤ X ├┤ RY(ϴ) ├┤ X ├┤ RY(-ϴ) ├┤ RZ(-π/2) ├┤ RX(ϴ) ├┤1         ├┤ RZ(π/2) ├
     └───┘└───────┘└───┘└────────┘└──────────┘└───────┘└──────────┘└─────────┘
"""

from __future__ import annotations

import numpy as np

from qiskit.circuit import Parameter, QuantumCircuit
from qiskit.circuit.parameterexpression import ParameterValueType


def rzx_cy(theta: ParameterValueType | None = None):
    """Template for CX - RYGate - CX."""
    if theta is None:
        theta = Parameter("ϴ")

    circ = QuantumCircuit(2)
    circ.cx(0, 1)
    circ.ry(theta, 1)
    circ.cx(0, 1)
    circ.ry(-1 * theta, 1)
    circ.rz(-np.pi / 2, 1)
    circ.rx(theta, 1)
    circ.rzx(-1 * theta, 0, 1)
    circ.rz(np.pi / 2, 1)

    return circ
