import pytest
import random
import time

import nidaqmx
from nidaqmx.constants import AcquisitionType
from nidaqmx.tests.fixtures import x_series_device
from nidaqmx.tests.helpers import generate_random_seed


class TestEvents(object):
    """
    Contains a collection of pytest tests that validate the NI-DAQmx events
    functionality in the Python NI-DAQmx API.
    """

    @pytest.mark.parametrize('seed', [generate_random_seed()])
    def test_every_n_samples_event(self, x_series_device, seed):
        # Reset the pseudorandom number generator with seed.
        random.seed(seed)

        samples_chunk = 100
        sample_rate = 5000

        with nidaqmx.Task() as task:
            task.ai_channels.add_ai_voltage_chan(
                x_series_device.ai_physical_chans[0].name)

            samples_multiple = random.randint(2, 5)
            num_samples = samples_chunk * samples_multiple

            task.timing.cfg_samp_clk_timing(
                sample_rate, sample_mode=AcquisitionType.FINITE,
                samps_per_chan=num_samples)

            # Python 2.X does not have nonlocal keyword.
            non_local_var = {'samples_read': 0}

            def callback(task_handle, every_n_samples_event_type,
                         number_of_samples, callback_data):
                samples = task.read(
                    number_of_samples_per_channel=samples_chunk, timeout=2.0)
                non_local_var['samples_read'] += len(samples)
                return 0

            task.register_every_n_samples_acquired_into_buffer_event(
                samples_chunk, callback)

            task.start()
            task.wait_until_done(timeout=2)

            # Wait until done doesn't wait for all callbacks to be processed.
            time.sleep(1)
            task.stop()

            assert non_local_var['samples_read'] == num_samples

            samples_multiple = random.randint(2, 5)
            num_samples = samples_chunk * samples_multiple

            task.timing.cfg_samp_clk_timing(
                sample_rate, sample_mode=AcquisitionType.FINITE,
                samps_per_chan=num_samples)

            non_local_var = {'samples_read': 0}

            # Unregister event callback function by passing None.
            task.register_every_n_samples_acquired_into_buffer_event(
                samples_chunk, None)

            task.start()
            task.wait_until_done(timeout=2)

            # Wait until done doesn't wait for all callbacks to be processed.
            time.sleep(1)
            task.stop()

            assert non_local_var['samples_read'] == 0