"""Encapsulating a pySerial object as a transport class.

Copyright (c) 2015-2018, Garth Zeglin.  All rights reserved. Licensed under the terms
of the BSD 3-clause license.
"""
# Enable basic compatibility features to work with either Python 2 or 3.
from __future__ import print_function, absolute_import, unicode_literals

# Standard library modules.
import os, sys, time, argparse, select, logging

# This requires a pySerial installation.
import serial
import serial.tools.list_ports

# Import modules from the course library.
import ase.base

#================================================================
[docs]class SerialTransport(ase.base.Transport):
    """Manage a serial port as a bidirectional transport which passes along received
    data to a Protocol object, and can pass along write requests to the
    underlying port.

    :param protocol: object to received streamed data and generate messages
    :param portname: string naming the serial device
    :param rate: standard integer baud rate for communication. Default is 57600.
    """

    def __init__(self, protocol, portname, rate = 57600):
        self.protocol = protocol
        self._portname   = portname
        self._baud_rate  = rate

        # configure logging
        self.logger = logging.getLogger(__name__) #: logging object for controlling or capturing an event log
        self.logger.setLevel(logging.DEBUG)
        return

[docs]    def open(self):
        """Open the serial port and initialize communications."""

        # open the serial port, which should also reset the Arduino
        self._port = serial.Serial(self._portname, self._baud_rate, timeout=5 )
        self.logger.debug("Opened serial port named %s", self._port.name)

        # pass this transport object to the protocol object
        self.protocol.connection_made(self)
        return

[docs]    def close(self):
        """Shut down the serial connection to the Arduino, after which this object may no longer be used."""
        self.logger.debug("Closing serial port named %s", self._port.name)
        self._port.close()
        self._port = None
        self.protocol.connection_lost()        
        return

[docs]    def write(self, data):
        self._port.write(data)

[docs]    def fileno(self):
        # N.B. Windows does not support file descriptors for serial ports.
        return self._port.fileno()

[docs]    def flush(self):
        self._port.flush()

[docs]    def flush_input(self):
        self._port.reset_input_buffer()
        
[docs]    def wait_for_data(self):
        """Wait for at least one character of input from the serial port and process it,
        updating status variables.  This will block if data is not ready; if
        using in an event-driven system, it is important to check the port for
        available data prior to calling.
        """

        # read as much input as available, blocking if no data is available
        data = self._port.read(max(1, self._port.in_waiting))
        self.protocol.data_received(data)
        return

#================================================================
[docs]def print_serial_port_list():
    print("Available serial ports:")
    for p in serial.tools.list_ports.comports():
        print(" ", p.device)

#================================================================