import textwrap
from contextlib import ExitStack
from functools import partial
from typing import Sequence, Tuple, Any, Optional
from distutils.version import LooseVersion
from bisect import bisect_left

import numpy as np

import qcodes.utils.validators as vals
from qcodes import VisaInstrument, InstrumentChannel
from qcodes.instrument_drivers.Keysight.private.error_handling import \
    KeysightErrorQueueMixin
from qcodes.instrument.parameter import Parameter, ParameterWithSetpoints
from qcodes.instrument.base import Instrument


class Trigger(InstrumentChannel):
    """Implements triggering parameters and methods of Keysight 344xxA."""

    def __init__(self, parent: '_Keysight_344xxA', name: str, **kwargs: Any):
        super().__init__(parent, name, **kwargs)

        if self.parent.is_34465A_34470A:
            _max_trigger_count = 1e9
        else:
            _max_trigger_count = 1e6

        self.add_parameter('count',
                           label='Trigger Count',
                           set_cmd='TRIGger:COUNt {}',
                           get_cmd='TRIGger:COUNt?',
                           get_parser=float,
                           vals=vals.MultiType(
                               vals.Numbers(1, _max_trigger_count),
                               vals.Enum('MIN', 'MAX', 'DEF', 'INF')),
                           docstring=textwrap.dedent("""\
            Selects the number of triggers that are accepted by the
            instrument before returning to the "idle" trigger state.

            You can use the specified trigger count in conjunction with
            `sample_count`. In this case, the number of measurements
            returned is the sample count multiplied by the trigger count.

            A variable trigger count is not available from the front panel.
            However, when you return to remote control of the instrument,
            the trigger count returns to the previous value you selected."""))

        self.add_parameter('delay',
                           label='Trigger Delay',
                           unit='s',
                           set_cmd='TRIGger:DELay {}',
                           get_cmd='TRIGger:DELay?',
                           vals=vals.MultiType(vals.Numbers(0, 3600),
                                               vals.Enum('MIN', 'MAX', 'DEF')),
                           get_parser=float,
                           docstring=textwrap.dedent("""\
            Sets the delay between the trigger signal and the first
            measurement. This may be useful in applications where you want
            to allow the input to settle before taking a measurement or for
            pacing a burst of measurements.

            Step size for DC measurements is approximately 1 µs. For AC
            measurements, step size depends on AC bandwidth.

            Selecting a specific trigger delay disables the automatic
            trigger delay."""))

        self.add_parameter('auto_delay_enabled',
                           label='Auto Trigger Delay Enabled',
                           set_cmd='TRIGger:DELay:AUTO {}',
                           get_cmd='TRIGger:DELay:AUTO?',
                           get_parser=int,
                           val_mapping={True: 1, False: 0},
                           docstring=textwrap.dedent("""\
            Disables or enables automatic trigger delay. If enabled,
            the instrument determines the delay based on function, range,
            and integration time or bandwidth.

            Selecting a specific trigger delay using `trigger.delay` disables
            the automatic trigger delay."""))

        self.add_parameter('slope',
                           label='Trigger Slope',
                           set_cmd='TRIGger:SLOPe {}',
                           get_cmd='TRIGger:SLOPe?',
                           vals=vals.Enum('POS', 'NEG'))

        if self.parent.is_34465A_34470A and self.parent.has_DIG:
            self.add_parameter('level',
                               label='Trigger Level',
                               unit='V',
                               set_cmd='TRIGger:LEVel {}',
                               get_cmd='TRIGger:LEVel?',
                               get_parser=float,
                               vals=vals.MultiType(
                                   vals.Numbers(-1000, 1000),
                                   vals.Enum('MIN', 'MAX', 'DEF')),
                               docstring=textwrap.dedent("""\
                Sets the level on which a trigger occurs when level
                triggering is enabled (`trigger.source` set to "INT").

                Note that for 100 mV to 100 V ranges and autorange is off,
                the trigger level can only be set within ±120% of the
                range."""))

        _trigger_source_docstring = textwrap.dedent("""\
            Selects the trigger source for measurements.

            IMMediate: The trigger signal is always present. When you place
                the instrument in the "wait-for-trigger" state, the trigger is
                issued immediately.

            BUS: The instrument is triggered by `trigger.force` method of this
                driver once the DMM is in the "wait-for-trigger" state.

            EXTernal: The instrument accepts hardware triggers applied to
                the rear-panel Ext Trig input and takes the specified number
                of measurements (`sample_count`), each time a TTL pulse
                specified by `trigger.slope` is received. If the
                instrument receives an external trigger before it is ready,
                it buffers one trigger.""")
        _trigger_source_vals = vals.Enum('IMM', 'EXT', 'BUS')

        if self.parent.has_DIG:
            _trigger_source_vals = vals.Enum('IMM', 'EXT', 'BUS', 'INT')
            # extra empty lines are needed for readability of the docstring
            _trigger_source_docstring += textwrap.dedent("""\


            INTernal: Provides level triggering capability. To trigger on a
                level on the input signal, select INTernal for the source,
                and set the level and slope with the `trigger.level` and
                `trigger.slope` parameters.""")

        self.add_parameter('source',
                           label='Trigger Source',
                           set_cmd='TRIGger:SOURce {}',
                           get_cmd='TRIGger:SOURce?',
                           vals=_trigger_source_vals,
                           docstring=_trigger_source_docstring)

    def force(self) -> None:
        """Triggers the instrument if `trigger.source` is "BUS"."""
        self.write('*TRG')


class Sample(InstrumentChannel):
    """Implements sampling parameters of Keysight 344xxA."""

    def __init__(self, parent: '_Keysight_344xxA', name: str, **kwargs: Any):
        super().__init__(parent, name, **kwargs)

        if self.parent.is_34465A_34470A:
            _max_sample_count = int(1e9)
        elif self.parent.model == "34410A":
            _max_sample_count = 50_000
        else:
            _max_sample_count = int(1e6)

        self.add_parameter('count',
                           label='Sample Count',
                           set_cmd='SAMPle:COUNt {}',
                           get_cmd='SAMPle:COUNt?',
                           vals=vals.MultiType(
                               vals.Numbers(1, _max_sample_count),
                               vals.Enum('MIN', 'MAX', 'DEF')),
                           get_parser=int,
                           docstring=textwrap.dedent("""\
            Specifies the number of measurements (samples) the instrument
            takes per trigger.

            MAX selects 1 billion readings. However, when pretrigger is
            selected, the maximum is 50,000 readings (without the MEM
            option) or 2,000,000 readings (with the MEM option)"""))

        if self.parent.has_DIG:
            if self.parent.has_MEM:
                _max_pretrig_count = int(2e6) - 1
            else:
                _max_pretrig_count = int(5e4) - 1

            self.add_parameter('pretrigger_count',
                               label='Sample Pretrigger Count',
                               set_cmd='SAMPle:COUNt:PRETrigger {}',
                               get_cmd='SAMPle:COUNt:PRETrigger?',
                               vals=vals.MultiType(
                                   vals.Numbers(0, _max_pretrig_count),
                                   vals.Enum('MIN', 'MAX', 'DEF')),
                               get_parser=int,
                               docstring=textwrap.dedent("""\
                Allows collection of the data being digitized the trigger.
                Reserves memory for pretrigger samples up to the specified
                num. of pretrigger samples.

                Note that the maximum number of pretrigger counts is bounded
                by the current number of sample counts as specified via the
                ``sample.count`` parameter. Refer to the doc of the
                ``sample.count`` parameter for information on the maximum
                number of sample counts."""))

        if self.parent.is_34465A_34470A:
            self.add_parameter('source',
                               label='Sample Timing Source',
                               set_cmd='SAMPle:SOURce {}',
                               get_cmd='SAMPle:SOURce?',
                               vals=vals.Enum('IMM', 'TIM'),
                               docstring=('Determines sampling time, '
                                          'immediate or using `sample.timer`'))

        self.add_parameter('timer',
                           label='Sample Timer',
                           set_cmd='SAMPle:TIMer {}',
                           get_cmd='SAMPle:TIMer?',
                           unit='s',
                           vals=vals.MultiType(vals.Numbers(0, 3600),
                                               vals.Enum('MIN', 'MAX', 'DEF')),
                           get_parser=float,
                           docstring=textwrap.dedent("""\
            The value is rounded by the instrument to the nearest step. For DC
            measurements, the step size is 1 µs. For AC measurements,
            it is AC bandwidth dependent.

            Special values are: MIN - recommended minimum, MAX - maximum,
            DEF - default. In order to obtain the actual value of the
            parameter that gets set when setting it to one of these special
            values, just call the get method of the parameter, or use
            corresponding parameters in this driver,
            like `sample.timer_minimum`.

            Specifying a value that is between the absolute minimum (assumes
            no range changes) and the recommended minimum value,
            may generate a timing violation error when making measurements.

            Applying a value less than the absolute minimum will generate an
            error."""))

        self.add_parameter('timer_minimum',
                           label='Minimal recommended sample time',
                           get_cmd='SAMPle:TIMer? MIN',
                           get_parser=float,
                           unit='s',
                           docstring=textwrap.dedent("""\
            This value is measurement dependent. It depends on such things
            as the integration time, autozero on or off, autorange on or
            off, and the measurement range. Basically, the minimum is
            automatically determined by the instrument so that the sample
            interval is always greater than the sampling time.

            Since the minimum value changes depending on configuration, a
            command order dependency exists. You must completely configure
            the measurement before setting the sample timer to minimum,
            or you may generate an error. A complete configuration includes
            such things as math statistics or scaling.

            When using autorange, the minimum value is the recommended value,
            not the absolute minimum value. With autorange enabled, minimum
            value is calculated assuming a single range change will occur
            for every measurement (not multiple ranges, just one range up or
            down per measurement)."""))


class Display(InstrumentChannel):
    """Implements interaction with the display of Keysight 344xxA."""

    def __init__(self, parent: '_Keysight_344xxA', name: str, **kwargs: Any):
        super().__init__(parent, name, **kwargs)

        self.add_parameter('enabled',
                           label='Display enabled',
                           set_cmd='DISPlay:STATe {}',
                           get_cmd='DISPlay:STATe?',
                           val_mapping={True: 1, False: 0},
                           docstring=textwrap.dedent("""\
            Disables or enables the front panel display. When disabled,
            the display dims, and all annunciators are disabled. However,
            the screen remains on.

            Disabling the display improves command execution speed from the
            remote interface and provides basic security.

            Displaying text with `display.text` parameter will work even
            when the display is disabled."""))

        self.add_parameter('text',
                           label='Display text',
                           set_cmd='DISPLAY:TEXT "{}"',
                           get_cmd='DISPLAY:TEXT?',
                           initial_value="",
                           get_parser=lambda s: s.strip('"'),
                           vals=vals.Strings(),
                           docstring=textwrap.dedent("""\
            Displays the given text on the screen. Specifying empty string
            moves the display back to its normal state. The same can be
            achieved by calling `display.clear`."""))

    def clear(self) -> None:
        """
        Clear text from display. Depending on the display being
        enabled/disabled, this either returns to display's normal state or
        leaves it black, respectively.
        """
        self.write('DISPLay:TEXT:CLEar')
        self.text.get()  # also update the parameter value


class TimeTrace(ParameterWithSetpoints): # pylint: disable=abstract-method
    """
    A parameter class that holds the data for a time trace type measurement,
    i.e. a measurement of N voltage or current values measured at fixed time
    intervals
    """

    def __init__(self, name: str, instrument: Instrument, **kwargs: Any):

        self.instrument: Instrument  # needed for mypy
        super().__init__(name=name, instrument=instrument, **kwargs)

        # the extra time needed to avoid timeouts during acquisition
        self._acquire_timeout_fudge_factor = 1.25

    def _validate_dt(self) -> None:
        """
        Validate that the specified dt (measurement time interval) can be
        realized by the instrument with the present settings

        Raises:
            RuntimeError: If the present measurement settings prevent reaching
                the specified dt.
        """

        minimum_time = self.instrument.sample.timer_minimum()
        dt = self.instrument.timetrace_dt()
        if  dt < minimum_time:
            raise RuntimeError(f"Can not realize a time trace dt of {dt} s "
                               f"With the present settings. The minimal "
                               f"allowed dt is {minimum_time} s. To allow "
                               "for a shorter dt, try changing the NPLC or "
                               "aperture time.")


    def _set_units_and_labels(self) -> None:
        """
        A helper function to set correct units and labels for the parameter
        """

        units_and_labels = {'AC Voltage': ('V', 'Voltage'),
                            'DC Voltage': ('V', 'Voltage'),
                            'AC Current': ('A', 'Current'),
                            'DC Current': ('A', 'Current'),
                            '2 Wire Resistance': ('Ohm', 'Resistance'),
                            '4 Wire Resistance': ('Ohm', 'Resistance')}

        conf = self.instrument.sense_function()
        self.unit, self.label = units_and_labels[conf]

    def _acquire_time_trace(self) -> np.ndarray:
        """
        The function that prepares the measurement and fetches the data
        """
        dt = self.instrument.timetrace_dt()
        npts = self.instrument.timetrace_npts()
        meas_time = npts*dt
        disp_text = f"Acquiring {npts} samples"  # display limit: 40 characters
        new_timeout = max(self._acquire_timeout_fudge_factor * meas_time,
                          self.instrument.timeout())

        param_settings = [(self.instrument.trigger.count, 1),
                          (self.instrument.trigger.source, "BUS"),
                          (self.instrument.sample.source, "TIM"),
                          (self.instrument.sample.timer, dt),
                          (self.instrument.sample.count, npts),
                          (self.instrument.timeout, new_timeout),
                          (self.instrument.display.text, disp_text)]

        if self.instrument.has_DIG:
            param_settings.append((self.instrument.sample.pretrigger_count,
                                   0))

        with ExitStack() as stack:
            for ps in param_settings:
                stack.enter_context(ps[0].set_to(ps[1]))

            self.instrument.init_measurement()
            self.instrument.trigger.force()
            data = self.instrument.fetch()

        return data

    def get_raw(self) -> np.ndarray:  # pylint: disable=method-hidden

        self._validate_dt()
        self._set_units_and_labels()
        data = self._acquire_time_trace()

        return data


class TimeAxis(Parameter): # pylint: disable=abstract-method
    """
    A simple :class:`.Parameter` that holds all the times (relative to the
    measurement start) at which the points of the time trace were acquired.
    """

    def get_raw(self) -> np.ndarray:  # pylint: disable=method-hidden
        """
        Construct a time axis by querying the number of points and step size
        from the instrument.
        """
        if self.instrument is None:
           raise RuntimeError("No instrument attached to Parameter.")

        npts = self.instrument.timetrace_npts()
        dt = self.instrument.timetrace_dt()
        return np.linspace(0, dt*npts, npts, endpoint=False)



class _Keysight_344xxA(KeysightErrorQueueMixin, VisaInstrument):
    """
    Instrument class for Keysight 34460A, 34461A, 34465A and 34470A
    multimeters.

    The driver currently only supports using the instrument as a voltmeter
    for DC measurements.

    This driver makes use of submodules for implementing different
    subsystems of the instrument.

    Attributes:
        model: The model number of the instrument
        NPLC_list: A list of the available Power Line Cycle settings
        ranges: A list of the available voltage ranges
    """

    def __init__(self, name: str, address: str, silent: bool = False,
                 **kwargs: Any):
        """
        Create an instance of the instrument.

        Args:
            name: Name used by QCoDeS. Appears in the DataSet
            address: Visa-resolvable instrument address.
            silent: If True, the connect_message of the instrument
                is supressed. Default: False
        """

        super().__init__(name, address, terminator='\n', **kwargs)

        idn = self.IDN.get()
        self.model = idn['model']

        self.is_34465A_34470A = self.model in ['34465A', '34470A']

        ####################################
        # Instrument specifications

        options = self._options()
        self.has_DIG = self.is_34465A_34470A and (
            'DIG' in options
            or LooseVersion('A.03') <= LooseVersion(idn['firmware'])
        )
        # Note that the firmware version check is still needed because
        # ``_options`` (the ``*OPT?`` command) returns 'DIG' option for
        # firmware 3.0 only if it has been purchased before
        self.has_MEM = self.is_34465A_34470A and 'MEM' in options

        PLCs = {'34410A': [0.006, 0.02, 0.06, 0.2, 1, 2, 10, 100],
                '34460A': [0.02, 0.2, 1, 10, 100],
                '34461A': [0.02, 0.2, 1, 10, 100],
                '34465A': [0.02, 0.06, 0.2, 1, 10, 100],
                '34470A': [0.02, 0.06, 0.2, 1, 10, 100]
                }
        if self.has_DIG:
            PLCs['34465A'] = [0.001, 0.002, 0.006] + PLCs['34465A']
            PLCs['34470A'] = [0.001, 0.002, 0.006] + PLCs['34470A']

        ranges = {'34410A': [10**n for n in range(3, 10)],  # 100 to 1 G
                  '34460A': [10**n for n in range(-3, 9)],  # 1 m to 100 M
                  '34461A': [10**n for n in range(-3, 9)],  # 1 m to 100 M
                  '34465A': [10**n for n in range(-3, 10)],  # 1 m to 1 G
                  '34470A': [10**n for n in range(-3, 10)],  # 1 m to 1 G
                  }

        # The resolution factor order matches the order of PLCs
        res_factors = {'34410A': [30e-6, 15e-5, 6e-6, 3e-6, 1.5e-6, 0.7e-6,
                                  0.3e-6, 0.2e-6, 0.1e-6, 0.03e-6],
                       '34460A': [300e-6, 100e-6, 30e-6, 10e-6, 3e-6],
                       '34461A': [100e-6, 10e-6, 3e-6, 1e-6, 0.3e-6],
                       '34465A': [3e-6, 1.5e-6, 0.7e-6, 0.3e-6, 0.1e-6,
                                  0.03e-6],
                       '34470A': [1e-6, 0.5e-6, 0.3e-6, 0.1e-6, 0.03e-6,
                                  0.01e-6]
                       }
        if self.has_DIG:
            res_factors['34465A'] = [30e-6, 15e-6, 6e-6] + res_factors['34465A']
            res_factors['34470A'] = [30e-6, 10e-6, 3e-6] + res_factors['34470A']

        self._resolution_factors = res_factors[self.model]
        self.ranges = ranges[self.model]
        self.NPLC_list = PLCs[self.model]

        ####################################
        # PARAMETERS

        # this is the "master" parameter that determines whether the DMM is
        # a voltmeter, an ampmeter, etc.
        self.add_parameter('sense_function',
                           label="Instrument sense function",
                           get_cmd="SENSe:FUNCtion?",
                           set_cmd="SENSe:FUNCtion {}",
                           val_mapping={"DC Voltage": '"VOLT"',
                                        "AC Voltage": '"VOLT:AC"',
                                        "DC Current": '"CURR"',
                                        "AC Current": '"CURR:AC"',
                                        "2 Wire Resistance": '"RES"',
                                        "4 Wire Resistance": '"FRES"'})

        self.add_parameter('line_frequency',
                           get_cmd='SYSTem:LFRequency?',
                           get_parser=int,
                           set_cmd=False,
                           label='Line Frequency',
                           unit='Hz',
                           docstring=('The frequency of the power line where '
                                      'the instrument is plugged')
                           )

        self.add_parameter('NPLC',
                           get_cmd='SENSe:VOLTage:DC:NPLC?',
                           get_parser=float,
                           set_cmd=self._set_NPLC,
                           vals=vals.Enum(*self.NPLC_list),
                           label='Integration time',
                           unit='NPLC',
                           docstring=textwrap.dedent("""\
            Sets the integration time in number of power line cycles (PLC)
            for DC voltage and ratio measurements. Integration time is the
            period that the instrument's analog-to-digital (A/D) converter
            samples the input signal for a measurement. A longer integration
            time gives better measurement resolution but slower measurement
            speed.

            Only integration times of 1, 10, or 100 PLC provide normal mode
            (line frequency noise) rejection.

            Setting the integration time also sets the measurement
            resolution."""))

        self.add_parameter('range',
                           get_cmd='SENSe:VOLTage:DC:RANGe?',
                           get_parser=float,
                           set_cmd='SENSe:VOLTage:DC:RANGe {:f}',
                           vals=vals.Enum(*self.ranges))

        self.add_parameter('resolution',
                           get_cmd='SENSe:VOLTage:DC:RESolution?',
                           get_parser=float,
                           set_cmd=self._set_resolution,
                           label='Resolution',
                           unit='V',
                           vals=vals.MultiType(
                               vals.Numbers(0),
                               vals.Enum('MIN', 'MAX', 'DEF')),
                           docstring=textwrap.dedent("""\
            Selects the measurement resolution for DC voltage and ratio
            measurements. The resolution is specified in the same units as the
            selected measurement function, not in number of digits.

            You can also specify MIN (best resolution) or MAX (worst
            resolution).

            To achieve normal mode (line frequency noise) rejection,
            use a resolution that corresponds to an integration time that is
            an integral number of power line cycles.

            Refer to "Resolution Table" or "Range, Resolution and NPLC"
            sections of the instrument's manual for the available ranges for
            the resolution values."""))

        self.add_parameter('autorange',
                           label='Autorange',
                           set_cmd='SENSe:VOLTage:DC:RANGe:AUTO {}',
                           get_cmd='SENSe:VOLTage:DC:RANGe:AUTO?',
                           val_mapping={'ON': 1, 'OFF': 0},
                           vals=vals.Enum('ON', 'OFF'))

        self.add_parameter('autozero',
                           label='Autozero',
                           set_cmd='SENSe:VOLTage:DC:ZERO:AUTO {}',
                           get_cmd='SENSe:VOLTage:DC:ZERO:AUTO?',
                           val_mapping={'ON': 1, 'OFF': 0, 'ONCE': 'ONCE'},
                           vals=vals.Enum('ON', 'OFF', 'ONCE'),
                           docstring=textwrap.dedent("""\
            Disables or enables the autozero mode for DC voltage and ratio
            measurements.

            ON:   the DMM internally measures the offset following each
                  measurement. It then subtracts that measurement from the
                  preceding reading. This prevents offset voltages present on
                  the DMM’s input circuitry from affecting measurement
                  accuracy.
            OFF:  the instrument uses the last measured zero measurement and
                  subtracts it from each measurement. It takes a new zero
                  measurement each time you change the function, range or
                  integration time.
            ONCE: the instrument takes one zero measurement and sets
                  autozero OFF. The zero measurement taken is used for all
                  subsequent measurements until the next change to the
                  function, range or integration time. If the specified
                  integration time is less than 1 PLC, the zero measurement
                  is taken at 1 PLC to optimize noise rejection. Subsequent
                  measurements are taken at the specified fast (< 1 PLC)
                  integration time."""))

        ####################################
        # Aperture parameters

        if self.is_34465A_34470A:
            # Define the extreme aperture time values for the 34465A and 34470A
            utility_freq = self.line_frequency()
            if utility_freq == 50:
                apt_times = {'34465A': [0.3e-3, 2],
                            '34470A': [0.3e-3, 2]}
            elif utility_freq == 60:
                apt_times = {'34465A': [0.3e-3, 1.67],
                            '34470A': [0.3e-3, 1.67]}
            if self.has_DIG:
                apt_times['34465A'][0] = 20e-6
                apt_times['34470A'][0] = 20e-6

            self.add_parameter('aperture_mode',
                               label='Aperture mode',
                               set_cmd='SENSe:VOLTage:DC:APERture:ENABled {}',
                               get_cmd='SENSe:VOLTage:DC:APERture:ENABled?',
                               val_mapping={'ON': 1, 'OFF': 0},
                               vals=vals.Enum('ON', 'OFF'),
                               docstring=textwrap.dedent("""\
                Enables the setting of integration time in seconds (called
                aperture time) for DC voltage measurements. If aperture time
                mode is disabled (default), the integration time is set in PLC
                (power-line cycles)."""))

            self.add_parameter('aperture_time',
                               label='Aperture time',
                               set_cmd=self._set_apt_time,
                               get_cmd='SENSe:VOLTage:DC:APERture?',
                               get_parser=float,
                               vals=vals.Numbers(*apt_times[self.model]),
                               docstring=textwrap.dedent("""\
                Specifies the integration time in seconds (called aperture
                time) with 2 µs resolution for DC voltage measurements.

                Use this command for precise control of the DMM's
                integration time. Use `NPLC` for better power-line noise
                rejection characteristics (NPLC > 1).

                Setting the aperture time automatically enables the aperture
                mode."""))

        ####################################
        # Submodules

        self.add_submodule('display', Display(self, 'display'))
        self.add_submodule('trigger', Trigger(self, 'trigger'))
        self.add_submodule('sample', Sample(self, 'sample'))

        ####################################
        # Measurement Parameters
        # snapshot_get is disabled for each of these to prevent rapid mode
        # changes on initialization or snapshot update, however the cached
        # (last read) value will still be stored in the snapshot.

        self.add_parameter('volt',
                           get_cmd=partial(self._get_parameter, "DC Voltage"),
                           label='Voltage',
                           unit='V',
                           snapshot_get=False)

        self.add_parameter('curr',
                           get_cmd=partial(self._get_parameter, "DC Current"),
                           label='Current',
                           unit='A',
                           snapshot_get=False)

        self.add_parameter('ac_volt',
                           get_cmd=partial(self._get_parameter, "AC Voltage"),
                           label='AC Voltage',
                           unit='V',
                           snapshot_get=False)

        self.add_parameter('ac_curr',
                           get_cmd=partial(self._get_parameter, "AC Current"),
                           label='AC Current',
                           unit='A',
                           snapshot_get=False)

        self.add_parameter('res',
                           get_cmd=partial(self._get_parameter,
                                           "2 Wire Resistance"),
                           label='Resistance',
                           unit='Ohms',
                           snapshot_get=False)

        self.add_parameter('four_wire_res',
                           get_cmd=partial(self._get_parameter,
                                           "4 Wire Resistance"),
                           label='Resistance',
                           unit='Ohms',
                           snapshot_get=False)

        #####################################
        # Time trace parameters

        self.add_parameter('timetrace_npts',
                           label='Time trace number of points',
                           initial_value=500,
                           get_cmd=None,
                           set_cmd=None,
                           vals=vals.Ints(1))

        self.add_parameter('timetrace_dt',
                           label='Time trace time interval',
                           unit='s',
                           initial_value=1e-1,
                           get_cmd=None,
                           set_cmd=None,
                           vals=vals.Numbers(0))

        self.add_parameter('time_axis',
                           label='Time',
                           unit='s',
                           snapshot_value=False,
                           vals=vals.Arrays(shape=(self.timetrace_npts,)),
                           parameter_class=TimeAxis)

        self.add_parameter('timetrace',
                           vals=vals.Arrays(shape=(self.timetrace_npts,)),
                           setpoints=(self.time_axis,),
                           parameter_class=TimeTrace)

        ####################################
        # Connect message

        if not silent:
            self.connect_message()

    def init_measurement(self) -> None:
        """
        Change the state of the triggering system from "idle" to
        "wait-for-trigger", and clear the previous set of measurements from
        reading memory.

        This method is an "overlapped" command. This means that after
        executing it, you can send other commands that do not affect the
        measurements.

        Storing measurements in reading memory with this method is faster than
        sending measurements to the instrument's output buffer using
        `read` method ("READ?" command) (provided you do not `fetch`,
        "FETCh?" command, until done).
        """
        self.write('INIT')

    def reset(self) -> None:
        """
        Reset the instrument to factory defaults. Also updates the snapshot to
        reflect the new (default) values of parameters.
        """
        self.write('*RST')
        # before we can update the snapshot, the reset must complete
        self.ask('*OPC?')
        self.snapshot(update=True)

    def abort_measurement(self) -> None:
        """
        Abort a measurement in progress, returning the instrument to the
        trigger idle state.
        """
        self.write('ABORt')

    def _licenses(self) -> Sequence[str]:
        """
        Return extra licenses purchased with the DMM. The 34410A does not have
        optional modules, hence always returns an empty tuple.
        """
        if self.model != '34410A':
            licenses_raw = self.ask('SYST:LIC:CAT?')
            licenses_list = [x.strip('"') for x in licenses_raw.split(',')]
            return licenses_list
        return tuple()

    def _options(self) -> Tuple[str, ...]:
        """
        Return enabled options of the DMM returned by ``*OPT?`` command.
        The 34410A model does not have options, hence always returns
        an empty tuple.

        Note that for firmware version 3.0, output of ```*OPT?`` will contain
        the ``DIG`` option only if it has been purchased before, although
        the option itself is enabled by default in the firmware version 3.0.
        """
        if self.model != '34410A':
            options_raw = self.ask('*OPT?')
            options_list = [opt for opt in options_raw.split(',') if opt != '0']
            return tuple(options_list)
        return tuple()

    def _get_parameter(self, sense_function: str = "DC Voltage") -> float:
        """
        Measure the parameter given by sense_function. In case of overload i.e.
        when instrument throws +/-9.9e37, it is converted to +/-inf.

        Args:
            sense_function: The parameter to measure. Valid values are those
                accepted by the sense_function parameter.

        Returns:
            The float value of the parameter.
        """
        with self.sense_function.set_to(sense_function):
            with self.sample.count.set_to(1):
                response = self.ask('READ?')

        if float(response) >= 9.9e37:
            return np.inf
        elif float(response) <= -9.9e37:
            return -np.inf

        return float(response)

    def fetch(self) -> np.ndarray:
        """
        Waits for measurements to complete and copies all available
        measurements to the instrument's output buffer. The readings remain
        in reading memory.

        This query does not erase measurements from the reading memory. You
        can call this method multiple times to retrieve the same data.

        Returns:
            a 1D numpy array of all measured values that are currently in the
            reading memory
        """
        raw_vals: str = self.ask('FETCH?')
        return _raw_vals_to_array(raw_vals)

    def read(self) -> np.ndarray:
        """
        Starts a new set of measurements, waits for all measurements to
        complete, and transfers all available measurements.

        This method is similar to calling :meth:`init_measurement` followed
        immediately by :meth:`fetch`.

        Returns:
            a 1D numpy array of all measured values
        """
        raw_vals: str = self.ask('READ?')
        return _raw_vals_to_array(raw_vals)

    def _set_apt_time(self, value: float) -> None:
        self.write(f'SENSe:VOLTage:DC:APERture {value:f}')

        # setting aperture time switches aperture mode ON
        self.aperture_mode.get()

    def _set_NPLC(self, value: float) -> None:
        self.write(f'SENSe:VOLTage:DC:NPLC {value:f}')

        # resolution settings change with NPLC
        self.resolution.get()

        # setting NPLC switches off aperture mode
        if self.is_34465A_34470A:
            self.aperture_mode.get()

    def _set_range(self, value: float) -> None:
        self.write(f'SENSe:VOLTage:DC:RANGe {value:f}')

        # resolution settings change with range
        self.resolution.get()

    def _set_resolution(self, value: float) -> None:
        rang = self.range.get()

        # convert both value*range and the resolution factors
        # to strings with few digits, so we avoid floating point
        # rounding errors.
        res_fac_strs = [f'{(v * rang):.1e}' for v in self._resolution_factors]
        if f'{value:.1e}' not in res_fac_strs:
            raise ValueError(
                f'Resolution setting {value:.1e}'
                f'({value} at range {rang}) does not exist. '
                f'Possible values are {res_fac_strs}')

        self.write(f'VOLT:DC:RES {value:.1e}')

        # NPLC settings change with resolution
        self.NPLC.get()

    def autorange_once(self) -> None:
        """
        Performs immediate autorange and then turns autoranging off.

        The value of the `range` parameter is also updated.
        """
        self.write('SENSe:VOLTage:DC:RANGe:AUTO ONCE')
        self.range.get()

    def increase_range(
        self,
        range_value: Optional[float] = None,
        increase_by: int = 1
    ) -> None:
        """
        Increases the voltage range by a certain amount with default of 1.
        If limit is reached, the max range is used.

        Args:
            range_value: The desired voltage range needed.  Expressed by power
                of 10^x range from -3 to 10
            increase_by: How much to increase range by, default behavior
                 is by a step of one.

        """
        if increase_by < 1:
            raise ValueError("The steps must be increasing in value")

        if range_value is not None:
            current_range = range_value
        else:
            current_range = self.range.get()

        index = bisect_left(self.ranges, current_range)  # binary search
        if index + increase_by < len(self.ranges):
            self.range(self.ranges[index + increase_by])
        else:
            self.range(self.ranges[-1])

    def decrease_range(
        self,
        range_value: Optional[float] = None,
        decrease_by: int = -1
    ) -> None:
        """
        Decrease the voltage range by a certain amount with default of -1.
        If limit is reached, the min range is used.

        Args:
            range_value: The desired voltage range needed.  Expressed by power
                of 10^x range from -3 to 10
            decrease_by: How much to decrease range by, default behavior
                 is by a step of one.

        """
        if decrease_by > -1:
            raise ValueError("The steps must be decreasing in value")

        if range_value is not None:
            current_range = range_value
        else:
            current_range = self.range.get()

        index = bisect_left(self.ranges, current_range)  # binary search
        if index + decrease_by > -1:
            self.range(self.ranges[index + decrease_by])
        else:
            self.range(self.ranges[0])


def _raw_vals_to_array(raw_vals: str) -> np.ndarray:
    """
    Helper function that converts comma-delimited string of floating-point
    values to a numpy 1D array of them. Most data retrieval command of these
    instruments return data in this format.In case of overload i.e.
        when instrument throws +/-9.9e37, it is converted to +/-inf.

    Args:
        raw_vals: comma-delimited string of floating-point values

    Returns:
        numpy 1D array of data
    """
    result_array = np.fromstring(raw_vals, dtype=float, sep=",")
    result_array[result_array >= 9.9e37] = np.inf
    result_array[result_array <= -9.9e37] = -np.inf
    return result_array
