# The MIT License (MIT)
#
# Copyright (c) 2018 Carter Nelson for Adafruit
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
"""
`analog_in`
==============================
AnalogIn for single-ended and
differential ADC readings.

* Author(s): Carter Nelson, adapted from MCP3xxx original by Brent Rubell
"""

# pylint: disable=bad-whitespace
_ADS1X15_DIFF_CHANNELS = {
    (0, 1): 0,
    (0, 3): 1,
    (1, 3): 2,
    (2, 3): 3
}
_ADS1X15_PGA_RANGE = {
    2/3: 6.144,
    1:   4.096,
    2:   2.048,
    4:   1.024,
    8:   0.512,
    16:  0.256
}
# pylint: enable=bad-whitespace

class AnalogIn():
    """AnalogIn Mock Implementation for ADC Reads."""

    def __init__(self, ads, positive_pin, negative_pin=None):
        """AnalogIn

        :param ads: The ads object.
        :param ~digitalio.DigitalInOut positive_pin: Required pin for single-ended.
        :param ~digitalio.DigitalInOut negative_pin: Optional pin for differential reads.
        """
        self._ads = ads
        self._pin_setting = positive_pin
        self._negative_pin = negative_pin
        self.is_differential = False
        if negative_pin is not None:
            pins = (self._pin_setting, self._negative_pin)
            if pins not in _ADS1X15_DIFF_CHANNELS:
                raise ValueError("Differential channels must be one of: {}"
                                 .format(list(_ADS1X15_DIFF_CHANNELS.keys())))
            self._pin_setting = _ADS1X15_DIFF_CHANNELS[pins]
            self.is_differential = True

    @property
    def value(self):
        """Returns the value of an ADC pin as an integer."""
        return self._ads.read(self._pin_setting,
                              is_differential=self.is_differential) << (16 - self._ads.bits)

    @property
    def voltage(self):
        """Returns the voltage from the ADC pin as a floating point value."""
        raw = self.value
        volts = raw * (_ADS1X15_PGA_RANGE[self._ads.gain] / (2**(self._ads.bits-1) - 1))
        return volts
