# This code is part of Qiskit.
#
# (C) Copyright IBM 2018, 2019.
#
# 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.

"""
AerSimulator readout error NoiseModel integration tests
"""

from test.terra.utils.utils import list2dict

from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
from qiskit_aer.noise import NoiseModel
from qiskit_aer.noise.errors.standard_errors import pauli_error

# Backwards compatibility for Terra <= 0.13
if not hasattr(QuantumCircuit, "i"):
    QuantumCircuit.i = QuantumCircuit.iden


# ==========================================================================
# Pauli Gate Errors
# ==========================================================================


def pauli_gate_error_circuits():
    """Local Pauli gate error noise model circuits"""
    circuits = []

    qr = QuantumRegister(2, "qr")
    cr = ClassicalRegister(2, "cr")

    # 100% all-qubit Pauli error on "id" gate
    circuit = QuantumCircuit(qr, cr)
    circuit.i(qr)
    circuit.barrier(qr)
    circuit.measure(qr, cr)
    circuits.append(circuit)

    # 25% all-qubit Pauli error on "id" gates
    circuit = QuantumCircuit(qr, cr)
    circuit.i(qr)
    circuit.barrier(qr)
    circuit.measure(qr, cr)
    circuits.append(circuit)

    # 100% Pauli error on "id" gates on qubit-1
    circuit = QuantumCircuit(qr, cr)
    circuit.i(qr)
    circuit.barrier(qr)
    circuit.measure(qr, cr)
    circuits.append(circuit)

    # 25% all-qubit Pauli error on "id" gates on qubit-0
    circuit = QuantumCircuit(qr, cr)
    circuit.i(qr)
    circuit.barrier(qr)
    circuit.measure(qr, cr)
    circuits.append(circuit)

    # 50% Pauli error on conditional gate that doesn't get applied
    circuit = QuantumCircuit(qr, cr)
    circuit.x(qr).c_if(cr, 1)
    circuit.barrier(qr)
    circuit.measure(qr, cr)
    circuits.append(circuit)

    # 50% Pauli error on conditional gate that does get applied
    circuit = QuantumCircuit(qr, cr)
    circuit.x(qr).c_if(cr, 0)
    circuit.barrier(qr)
    circuit.measure(qr, cr)
    circuits.append(circuit)

    return circuits


def pauli_gate_error_noise_models():
    """Local Pauli gate error noise models"""
    noise_models = []

    # 100% all-qubit Pauli error on "id" gates
    error = pauli_error([("X", 1)])
    noise_model = NoiseModel()
    noise_model.add_all_qubit_quantum_error(error, "id")
    noise_models.append(noise_model)

    # 25% all-qubit Pauli error on "id" gates
    error = pauli_error([("X", 0.25), ("I", 0.75)])
    noise_model = NoiseModel()
    noise_model.add_all_qubit_quantum_error(error, "id")
    noise_models.append(noise_model)

    # 100% Pauli error on "id" gates on qubit-1
    error = pauli_error([("X", 1)])
    noise_model = NoiseModel()
    noise_model.add_quantum_error(error, "id", [1])
    noise_models.append(noise_model)

    # 25% all-qubit Pauli error on "id" gates on qubit-0
    error = pauli_error([("X", 0.25), ("I", 0.75)])
    noise_model = NoiseModel()
    noise_model.add_quantum_error(error, "id", [0])
    noise_models.append(noise_model)

    # 50% Pauli error on conditional gate that doesn't get applied
    error = pauli_error([("X", 0.5), ("I", 0.5)])
    noise_model = NoiseModel()
    noise_model.add_all_qubit_quantum_error(error, "x")
    noise_models.append(noise_model)

    # 50% Pauli error on conditional gate that does get applied
    error = pauli_error([("X", 0.5), ("I", 0.5)])
    noise_model = NoiseModel()
    noise_model.add_all_qubit_quantum_error(error, "x")
    noise_models.append(noise_model)

    return noise_models


def pauli_gate_error_counts(shots, hex_counts=True):
    """Pauli gate error circuits reference counts"""
    counts_lists = []

    # 100% all-qubit Pauli error on "id" gates
    counts = [0, 0, 0, shots]
    counts_lists.append(counts)

    # 25% all-qubit Pauli error on "id" gates
    counts = [9 * shots / 16, 3 * shots / 16, 3 * shots / 16, shots / 16]
    counts_lists.append(counts)

    # 100% Pauli error on "id" gates on qubit-1
    counts = [0, 0, shots, 0]
    counts_lists.append(counts)

    # 25% all-qubit Pauli error on "id" gates on qubit-0
    counts = [3 * shots / 4, shots / 4, 0, 0]
    counts_lists.append(counts)

    # 50% Pauli error on conditional gate that doesn't get applied
    counts = [shots, 0, 0, 0]
    counts_lists.append(counts)

    # 50% Pauli error on conditional gate that does get applied
    counts = 4 * [shots / 4]
    counts_lists.append(counts)

    return [list2dict(i, hex_counts) for i in counts_lists]


# ==========================================================================
# Pauli Measure Errors
# ==========================================================================


def pauli_measure_error_circuits():
    """Local Pauli measure error noise model circuits"""
    circuits = []

    qr = QuantumRegister(2, "qr")
    cr = ClassicalRegister(2, "cr")

    # 25% all-qubit Pauli error on measure
    circuit = QuantumCircuit(qr, cr)
    circuit.measure(qr, cr)
    circuits.append(circuit)

    # 25% local Pauli error on measure of qubit 1
    circuit = QuantumCircuit(qr, cr)
    circuit.measure(qr, cr)
    circuits.append(circuit)

    return circuits


def pauli_measure_error_noise_models():
    """Local Pauli measure error noise models"""
    noise_models = []

    # 25% all-qubit Pauli error on measure
    error = pauli_error([("X", 0.25), ("I", 0.75)])
    noise_model = NoiseModel()
    noise_model.add_all_qubit_quantum_error(error, "measure")
    noise_models.append(noise_model)

    # 25% local Pauli error on measure of qubit 1
    error = pauli_error([("X", 0.25), ("I", 0.75)])
    noise_model = NoiseModel()
    noise_model.add_quantum_error(error, "measure", [1])
    noise_models.append(noise_model)

    return noise_models


def pauli_measure_error_counts(shots, hex_counts=True):
    """Local Pauli measure error circuits reference counts"""
    counts_lists = []

    # 25% all-qubit Pauli error on measure
    counts = [9 * shots / 16, 3 * shots / 16, 3 * shots / 16, shots / 16]
    counts_lists.append(counts)

    # 25% local Pauli error on measure of qubit 1
    counts = [3 * shots / 4, 0, shots / 4, 0]
    counts_lists.append(counts)

    # Convert to counts dict
    return [list2dict(i, hex_counts) for i in counts_lists]


# ==========================================================================
# Pauli Reset Errors
# ==========================================================================


def pauli_reset_error_circuits():
    """Local Pauli reset error noise model circuits"""
    circuits = []

    qr = QuantumRegister(2, "qr")
    cr = ClassicalRegister(2, "cr")

    # 25% all-qubit Pauli error on reset
    circuit = QuantumCircuit(qr, cr)
    circuit.barrier(qr)
    circuit.reset(qr)
    circuit.barrier(qr)
    circuit.measure(qr, cr)
    circuits.append(circuit)

    # 25% local Pauli error on reset of qubit 1
    circuit = QuantumCircuit(qr, cr)
    circuit.barrier(qr)
    circuit.reset(qr)
    circuit.barrier(qr)
    circuit.measure(qr, cr)
    circuits.append(circuit)

    return circuits


def pauli_reset_error_noise_models():
    """Local Pauli reset error noise models"""
    noise_models = []

    # 25% all-qubit Pauli error on reset
    error = pauli_error([("X", 0.25), ("I", 0.75)])
    noise_model = NoiseModel()
    noise_model.add_all_qubit_quantum_error(error, "reset")
    noise_models.append(noise_model)

    # 25% local Pauli error on reset of qubit 1
    error = pauli_error([("X", 0.25), ("I", 0.75)])
    noise_model = NoiseModel()
    noise_model.add_quantum_error(error, "reset", [1])
    noise_models.append(noise_model)

    return noise_models


def pauli_reset_error_counts(shots, hex_counts=True):
    """Local Pauli reset error circuits reference counts"""
    counts_lists = []

    # 25% all-qubit Pauli error on reset
    counts = [9 * shots / 16, 3 * shots / 16, 3 * shots / 16, shots / 16]
    counts_lists.append(counts)

    # 25% local Pauli error on reset of qubit 1
    counts = [3 * shots / 4, 0, shots / 4, 0]
    counts_lists.append(counts)

    # Convert to counts dict
    return [list2dict(i, hex_counts) for i in counts_lists]
