"""\
ArduinoProtocol.py : abstract class to manage serial communication with an Arduino sketch.

Copyright (c) 2015-2017, Garth Zeglin.  All rights reserved. Licensed under the terms
of the BSD 3-clause license.

"""

#================================================================
from __future__ import print_function
import time

# This requires a pySerial installation.
#  Package details: https://pypi.python.org/pypi/pyserial,
#  Documentation: http://pythonhosted.org/pyserial/
import serial

#================================================================
class ArduinoProtocol(object):
    """Abstract class to manage a serial connection to an Arduino sketch.

    This class is sufficient to send and receive structured data messages as
    line-delimited text, but is more useful as a parent class for an
    application-specific class which manages the specific data types in the
    stream.

    :param port: the name of the serial port device
    :param verbose: flag to increase console output
    :param debug: flag to print raw inputs on console
    :param rate: serial baud rate
    :param kwargs: collect any unused keyword arguments
    """
    
    def __init__(self, port=None, verbose=False, debug=False, rate=115200, **kwargs ):
        # initialize the protocol state
        self.output = None  #: Output port object (usually same as input).
        self.input  = None  #: Input port object (usually same as output).

        self.messages_received = 0 #: Count of total lines received.
        self.messages_sent     = 0 #: Count of total lines sent.

        self._verbose    = verbose
        self._debug      = debug
        self._portname   = port
        self._port       = None
        self._start_time = 0.0
        self._rate       = rate
        return

    def fileno(self):
        """Return the file descriptor for the input port, useful for blocking on available input with select."""
        return self.input.fileno()
        
    def is_connected(self):
        """Return true if the serial port device is open."""
        return self._port is not None
    
    def set_serial_port_name(self, name):
        """Set the name of the serial port device."""
        self._portname = name
        return
    
    def open_serial_port(self):
        """Open the serial connection to the Arduino and initialize communications."""

        # open the serial port, which should also reset the Arduino
        self._port = serial.Serial( self._portname, self._rate, timeout=5 )
        if self._verbose:
            print("Opened serial port named", self._port.name)

        # initialize timer to allow waiting briefly for the Arduino to finish booting
        self._start_time = time.time()

        # save separate copies of the file object; this will ease simulation using other sources
        self.output = self._port
        self.input  = self._port
        return

    def is_startup_delay_complete(self):
        """Check whether the boot time interval has completed after opening the serial port."""
        return time.time() > self._start_time + 2.0

    def flush_serial_input(self):
        """Clear the input buffer."""
        if self.input is not None:
            self.input.flushInput()

    def close_serial_port(self):
        """Shut down the serial connection to the Arduino, after which this object may no longer be used."""
        self._port.close()
        self._port = None
        return

    def message_received(self, tokens):
        """Method called whenever a new message is received from the Arduino.
        The default implentation is null but this may be overridden in
        subclasses as a hook for this event.

        :param tokens: list of strings representing whitespace-delimited tokens in received message
        """
        pass
    
    def wait_for_message(self):
        """Wait for a line of input from the Arduino 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 one line of input, blocking if no data is available
        line = self._port.readline().rstrip()
            
        if line:
            self.messages_received += 1
            elements = line.split()
            if self._debug:
                print("Received: '%s'" % line)
            self.message_received(elements)
        return

    def send_message_string(self, string):
        """Issue a message string to the Arduino.

        :param string: message as single string without terminating newline
        """
        if self.output is None:
            print("Port not open for output.")
        else:
            if self._debug:
                print("Sending: '%s'" % string)
            self.output.write( string+'\n')
            self.messages_sent += 1
        return

    def send_message(self, tokens):
        """Issue a message to the Arduino sketch.

        :param tokens: message as list of values
        """
        string = " ".join([str(elem) for elem in tokens])
        return self.send_message_string(string)
        
#================================================================