trainlight.py

from __future__ import division
from xml.etree import ElementTree
from datetime import datetime

import requests
import Adafruit_WS2801
import dateutil.parser
import sys


NEXTRIP_URL = "http://svc.metrotransit.org/NexTrip/56039"
PIXEL_COUNT = 25

# Specify a software SPI connection for Raspberry Pi on the following pins:
PIXEL_CLOCK = 18
PIXEL_DOUT = 23
pixels = Adafruit_WS2801.WS2801Pixels(PIXEL_COUNT, clk=PIXEL_CLOCK, do=PIXEL_DOUT)

# Alternatively specify a hardware SPI connection on /dev/spidev0.0:
#SPI_PORT = 0
#SPI_DEVICE = 0
#pixels = Adafruit_WS2801.WS2801Pixels(PIXEL_COUNT, spi=SPI.SpiDev(SPI_PORT, SPI_DEVICE))


def time_to_next_train():
    """Return the time to next train in seconds."""
    xml_resp = requests.get(NEXTRIP_URL)
    if xml_resp.status_code != 200:
        pass
    tree = ElementTree.fromstring(xml_resp.content)
    date_str = tree[0][3].text
    next_dep_date = dateutil.parser.parse(date_str)
    now_date = datetime.now()

    diff = next_dep_date - now_date
    diff_seconds = diff.total_seconds()

    print("Next Departure at: {}".format(next_dep_date))
    print("Seconds to next departure: {}".format(diff_seconds))

    return diff_seconds


def set_red():
    print("Setting color to red")
    set_pixels_rgb(255, 0, 0)
    pixels.show()


def set_green():
    print("Setting color to green")
    set_pixels_rgb(0, 255, 0)
    pixels.show()


def set_blue():
    print("Setting color to blue")
    set_pixels_rgb(0, 0, 255)
    pixels.show()


def set_pixels_rgb(r, g, b):
    """Library func is broken."""
    for i in range(PIXEL_COUNT):
        pixels.set_pixel_rgb(i, r, g, b)


def run():
    '''Main Entrypoint'''
    time = time_to_next_train()

    if time > 7 * 60:
        set_blue()
    elif time > 5 * 60:
        set_green()
    else:
        set_red()


if __name__ == '__main__':
    if len(sys.argv) > 1:
        pixels.clear()
        pixels.show()
    else:
        run()