#!/usr/bin/python

"""serial_capture.py

Captures the data from the input serial connection and writes each line out to file, prefixed with the timestamp for each line.

Author: Lee Crippen
10-07-2015
"""

import os, argparse, argparse_help, serial, datetime, sys

""" Main function sets up the args, parses them to make sure they're valid, then uses them """
def main():
    parser = argparse.ArgumentParser(description='Listen to input serial device and output with timestamps. Specifying the output directory will auto create files named with timestamp for each capture.',
                                     formatter_class=argparse.ArgumentDefaultsHelpFormatter)
    parser.add_argument('inDevice', help='Device from which to listen to serial data.', action='store')
    parser.add_argument('-r', help='Baud rate for the serial device.', type=int, nargs='?', default=57600, dest='rate')
    parser.add_argument('-lt', help='Time in ms to use between lines coming from the device.', type=float, nargs='?', default=3.968, dest='timePerLine')
    parser.add_argument('time', help='Amount of time in seconds to capture data.', action='store', type=float)
    parser.add_argument('outDirectory', help='Output directory in which to store data or none for stdout.', action='store', nargs='?', default=None, type=argparse_help.is_directory_writable)
    args = parser.parse_args()
    capture(args.inDevice, args.rate, args.time, args.outDirectory, args.timePerLine)

""" Capture function continuously pulls from serial device and writes to output for time duration """
def capture(inDevice, rate, time, outDir, timePerLine):

    f = sys.stdout
    if outDir != None:
        f = open(outDir + os.sep + 'serialOutput' + '_' + datetime.datetime.now().isoformat('_') + '.dat', 'wb')

    s = serial.Serial(inDevice, rate)
    s.flushInput()
    s.flushOutput()

    """ Throw out the first lines to account for serial connection driver garbage data """
    for x in xrange(50):
        get_line(s)

    currTime = startTime = datetime.datetime.now()
    endTime = currTime + datetime.timedelta(seconds=time)

    while True:
        secElapsed = float((currTime - startTime).total_seconds())
        f.write(str(secElapsed) + '\t' + get_line(s))
        currTime += datetime.timedelta(milliseconds=timePerLine)
        if currTime > endTime:
            break

    f.close()
    s.close()

""" Grab the next few bytes of data up until the newline """
def get_line(serialIn):
    line = str()
    while True:
        nextByte = serialIn.read()
        line += nextByte
        if nextByte == '\n':
            break
    return line

if __name__ == "__main__":
    main()