# Much code from https://github.com/vsergeev/python-periphery/blob/master/periphery/pwm.py
# Copyright (c) 2015-2016 vsergeev / Ivan (Vanya) A. Sergeev
# License: MIT

import os
import digitalio

try:
    from microcontroller.pin import pwmOuts
except ImportError:
    raise RuntimeError("No PWM outputs defined for this board")

class PWMError(IOError):
    """Base class for PWM errors."""
    pass


class PWMOut(object):
    # Sysfs paths
    _sysfs_path = "/sys/class/pwm/"
    _channel_path = "pwmchip{}"

    # Channel paths
    _export_path = "export"
    _unexport_path = "unexport"
    _pin_path = "pwm{}"

    # Pin attribute paths
    _pin_period_path = "period"
    _pin_duty_cycle_path = "duty_cycle"
    _pin_polarity_path = "polarity"
    _pin_enable_path = "enable"

    def __init__(self, pin, *, frequency=500, duty_cycle=0, variable_frequency=False):
        """Instantiate a PWM object and open the sysfs PWM corresponding to the
        specified channel and pin.

        Args:
            pin (Pin): CircuitPython Pin object to output to
            duty_cycle (int) : The fraction of each pulse which is high. 16-bit
            frequency (int) : target frequency in Hertz (32-bit)
            variable_frequency (bool) : True if the frequency will change over time

        Returns:
            PWMOut: PWMOut object.

        Raises:
            PWMError: if an I/O or OS error occurs.
            TypeError: if `channel` or `pin` types are invalid.
            ValueError: if PWM channel does not exist.

        """

        self._pwmpin = None
        self._open(pin, duty_cycle, frequency, variable_frequency)

    def __del__(self):
        self.close()

    def __enter__(self):
        return self

    def __exit__(self, t, value, traceback):
        self.close()

    def _open(self, pin, duty=0, freq=500, variable_frequency=False):
        self._channel = None
        for pwmpair in pwmOuts:
            if pwmpair[1] == pin:
                self._channel = pwmpair[0][0]
                self._pwmpin = pwmpair[0][1]

        self._pin = pin
        if self._channel is None:
            raise RuntimeError("No PWM channel found for this Pin")

        channel_path = os.path.join(self._sysfs_path, self._channel_path.format(self._channel))
        if not os.path.isdir(channel_path):
            raise ValueError("PWM channel does not exist, check that the required modules are loaded.")

        pin_path = os.path.join(channel_path, self._pin_path.format(self._pwmpin))
        try:
            with open(os.path.join(channel_path, self._unexport_path), "w") as f_unexport:
                f_unexport.write("%d\n" % self._pwmpin)
        except IOError as e:
            pass # not unusual, it doesnt already exist
        try:
            with open(os.path.join(channel_path, self._export_path), "w") as f_export:
                f_export.write("%d\n" % self._pwmpin)
        except IOError as e:
            raise PWMError(e.errno, "Exporting PWM pin: " + e.strerror)

        self._set_enabled(False)
        
        # Look up the period, for fast duty cycle updates
        self._period = self._get_period()

        self.duty_cycle = 0

        # set frequency
        self.frequency = freq
        # set duty
        self.duty_cycle = duty

        self._set_enabled(True)

    def close(self):
        """Close the sysfs PWM."""
        if self._channel is not None:
            self.duty_cycle = 0
            try:
                channel_path = os.path.join(self._sysfs_path, self._channel_path.format(self._channel))
                with open(os.path.join(channel_path, self._unexport_path), "w") as f_unexport:
                    f_unexport.write("%d\n" % self._pwmpin)
            except IOError as e:
                raise PWMError(e.errno, "Unexporting PWM pin: " + e.strerror)

        self._channel = None
        self._pwmpin = None

    def _write_pin_attr(self, attr, value):
        path = os.path.join(
            self._sysfs_path,
            self._channel_path.format(self._channel),
            self._pin_path.format(self._pwmpin),
            attr)

        with open(path, 'w') as f_attr:
            #print(value, path)
            f_attr.write(value + "\n")
            
    def _read_pin_attr(self, attr):
        path = os.path.join(
            self._sysfs_path,
            self._channel_path.format(self._channel),
            self._pin_path.format(self._pwmpin),
            attr)

        with open(path, 'r') as f_attr:
            return f_attr.read().strip()

    # Mutable properties

    def _get_period(self):
        try:
            period_ns = int(self._read_pin_attr(self._pin_period_path))
        except ValueError:
            raise PWMError(None, "Unknown period value: \"%s\"" % period_ns)

        # Convert period from nanoseconds to seconds
        period = period_ns / 1e9

        # Update our cached period
        self._period = period

        return period

    def _set_period(self, period):
        if not isinstance(period, (int, float)):
            raise TypeError("Invalid period type, should be int or float.")

        # Convert period from seconds to integer nanoseconds
        period_ns = int(period * 1e9)

        self._write_pin_attr(self._pin_period_path, "{}".format(period_ns))

        # Update our cached period
        self._period = float(period)

    """Get or set the PWM's output period in seconds.

    Raises:
        PWMError: if an I/O or OS error occurs.
        TypeError: if value type is not int or float.

    :type: int, float
    """

    def _get_duty_cycle(self):
        try:
            duty_cycle_ns = int(self._read_pin_attr(self._pin_duty_cycle_path))
        except ValueError:
            raise PWMError(None, "Unknown duty cycle value: \"%s\"" % duty_cycle_ns)

        # Convert duty cycle from nanoseconds to seconds
        duty_cycle = duty_cycle_ns / 1e9

        # Convert duty cycle to ratio from 0.0 to 1.0
        duty_cycle = duty_cycle / self._period

        # convert to 16-bit
        duty_cycle = int(duty_cycle * 65535)
        return duty_cycle

    def _set_duty_cycle(self, duty_cycle):
        if not isinstance(duty_cycle, (int, float)):
            raise TypeError("Invalid duty cycle type, should be int or float.")

        # convert from 16-bit
        duty_cycle /= 65535.0
        if not 0.0 <= duty_cycle <= 1.0:
            raise ValueError("Invalid duty cycle value, should be between 0.0 and 1.0.")

        # Convert duty cycle from ratio to seconds
        duty_cycle = duty_cycle * self._period

        # Convert duty cycle from seconds to integer nanoseconds
        duty_cycle_ns = int(duty_cycle * 1e9)

        self._write_pin_attr(self._pin_duty_cycle_path, "{}".format(duty_cycle_ns))

    duty_cycle = property(_get_duty_cycle, _set_duty_cycle)
    """Get or set the PWM's output duty cycle as a ratio from 0.0 to 1.0.

    Raises:
        PWMError: if an I/O or OS error occurs.
        TypeError: if value type is not int or float.
        ValueError: if value is out of bounds of 0.0 to 1.0.

    :type: int, float
    """

    def _get_frequency(self):
        return 1.0 / self._get_period()

    def _set_frequency(self, frequency):
        if not isinstance(frequency, (int, float)):
            raise TypeError("Invalid frequency type, should be int or float.")

        self._set_period(1.0 / frequency)

    frequency = property(_get_frequency, _set_frequency)
    """Get or set the PWM's output frequency in Hertz.

    Raises:
        PWMError: if an I/O or OS error occurs.
        TypeError: if value type is not int or float.

    :type: int, float
    """

    def _get_enabled(self):
        enabled = self._read_pin_attr(self._pin_enable_path)

        if enabled == "1":
            return True
        elif enabled == "0":
            return False

        raise PWMError(None, "Unknown enabled value: \"%s\"" % enabled)

    def _set_enabled(self, value):
        if not isinstance(value, bool):
            raise TypeError("Invalid enabled type, should be string.")

        self._write_pin_attr(self._pin_enable_path, "1" if value else "0")

    """Get or set the PWM's output enabled state.

    Raises:
        PWMError: if an I/O or OS error occurs.
        TypeError: if value type is not bool.

    :type: bool
    """

    # String representation

    def __str__(self):
        return "PWM%d, pin %s (freq=%f Hz, duty_cycle=%f%%)" % \
            (self._channel, self._pin, self.frequency, self.duty_cycle * 100,)