from timeit import default_timer as timer

import config
import cupy as cp
import numpy as np
import pytest
import qibo
from qibo.models import QFT


def qibo_qft(nqubits, swaps):
    circ_qibo = QFT(nqubits, swaps)
    state_vec = circ_qibo().state(numpy=True)
    return circ_qibo, state_vec


def time(func):
    start = timer()
    res = func()
    end = timer()
    time = end - start
    return time, res


@pytest.mark.gpu
@pytest.mark.parametrize("nqubits", [1, 2, 5, 10])
def test_eval(nqubits: int, dtype="complex128"):
    """Evaluate QASM with cuQuantum.

    Args:
        nqubits (int): Total number of qubits in the system.
        dtype (str): The data type for precision, 'complex64' for single,
            'complex128' for double.
    """
    import qibotn.eval

    # Test qibo
    qibo.set_backend(backend=config.qibo.backend, platform=config.qibo.platform)
    qibo_time, (qibo_circ, result_sv) = time(lambda: qibo_qft(nqubits, swaps=True))

    # Test Cuquantum
    cutn_time, result_tn = time(
        lambda: qibotn.eval.dense_vector_tn(qibo_circ, dtype).flatten()
    )

    assert 1e-2 * qibo_time < cutn_time < 1e2 * qibo_time
    assert np.allclose(result_sv, result_tn), "Resulting dense vectors do not match"


@pytest.mark.gpu
@pytest.mark.parametrize("nqubits", [2, 5, 10])
def test_mps(nqubits: int, dtype="complex128"):
    """Evaluate MPS with cuQuantum.

    Args:
        nqubits (int): Total number of qubits in the system.
        dtype (str): The data type for precision, 'complex64' for single,
            'complex128' for double.
    """
    import qibotn.eval

    # Test qibo
    qibo.set_backend(backend=config.qibo.backend, platform=config.qibo.platform)

    qibo_time, (circ_qibo, result_sv) = time(lambda: qibo_qft(nqubits, swaps=True))

    result_sv_cp = cp.asarray(result_sv)

    # Test of MPS
    gate_algo = {
        "qr_method": False,
        "svd_method": {
            "partition": "UV",
            "abs_cutoff": 1e-12,
        },
    }

    cutn_time, result_tn = time(
        lambda: qibotn.eval.dense_vector_mps(circ_qibo, gate_algo, dtype).flatten()
    )

    print(f"State vector difference: {abs(result_tn - result_sv_cp).max():0.3e}")

    assert cp.allclose(result_tn, result_sv_cp)