Alexa skill handler for Cambridge bin collection query

lambda_function.py

# Set environment variable BIN_CALENDAR_URL to the specific ical calendar for your postcode
# https://refusecalendarapi.azurewebsites.net/calendar/ical/<id> where <id> can be found
# interactively using https://www.cambridge.gov.uk/check-when-your-bin-will-be-emptied

from urllib2 import urlopen
from datetime import datetime, timedelta
import os
from ask_sdk_core.skill_builder import SkillBuilder
from ask_sdk_core.dispatch_components import (
    AbstractRequestHandler, AbstractExceptionHandler,
    AbstractRequestInterceptor, AbstractResponseInterceptor)
from ask_sdk_core.utils import is_request_type, is_intent_name
from ask_sdk_core.handler_input import HandlerInput

from ask_sdk_model.ui import SimpleCard
from ask_sdk_model import Response

# Quick and dirty ical parsing to find the next occurrence of each 
# type of collection. This avoids needing the full ical library
# which relies on strftime format strings that don't work on all
# platforms.

def get_next_dates(url):
    # We're only interested in dates from today onwards. Set our threshold to
    # this time yesterday so that the "all-day" (midnight) timestamp for
    # today shows as in the future
    threshold = datetime.now() - timedelta(1)
    ical = urlopen(url).read().decode('iso-8859-1')
    earliest = {}
    current_date = None
    current_item = None
    for line in ical.splitlines():
        if line.startswith("BEGIN:VEVENT"):
            current_date = None
            current_item = None
        elif line.startswith("END:VEVENT"):
            if current_date != None and current_item != None:
                if current_date < threshold:
                    pass
                elif earliest.has_key(current_item):
                    if current_date < earliest[current_item]:
                        earliest[current_item] = current_date
                else:
                    earliest[current_item] = current_date
        elif line.startswith("DTSTART;VALUE=DATE:"):
            current_date = datetime.strptime(line.split(":")[1], "%Y%m%d")
        elif line.startswith("SUMMARY:"):
            current_item = line.split(":")[1]
    return earliest

sb = SkillBuilder()

class BinDateIntentHandler(AbstractRequestHandler):
    """Handler for BinDateIntent."""
    def can_handle(self, handler_input):
        # type: (HandlerInput) -> bool
        return is_intent_name("BinDateIntent")(handler_input)

    def handle(self, handler_input):
        # type: (HandlerInput) -> Response
        try:
            dates = get_next_dates(os.environ["BIN_CALENDAR_URL"])
            slots = handler_input.request_envelope.request.intent.slots
            if "BinColor" in slots:
                color = slots["BinColor"].value
                if color in ["green", "black", "blue"]:
                    item = color.title() + " Bin Collection"
                    if item in dates:
                        # Construct the response
                        resp = "The next " + item + " is "
                        if datetime.now().date() == dates[item].date():
                            resp = resp + "today"
                        elif (datetime.now() + timedelta(1)).date() == dates[item].date():
                            resp = resp + "tomorrow"
                        else:
                            delta_days = (dates[item].date() - datetime.now().date()).days
                            if delta_days < 7:
                                resp = resp + "this coming "
                            else:
                                resp = resp + "on "
                            resp = resp + dates[item].strftime("%A, %B") + " "
                            d = dates[item].strftime("%d").lstrip("0")
                            resp = resp + d
                            if d in ["1", "21", "31"]: resp = resp + "st"
                            if d in ["2", "22"]: resp = resp + "nd"
                            if d in ["3", "23"]: resp = resp + "rd"
                        handler_input.response_builder.speak(resp)
                    else:
                        handler_input.response_builder.speak("Sorry, I can't find the date for the " + item + " in the collection calendar.")
                else:
                    handler_input.response_builder.speak("Sorry, I don't think that there are any " + color + " bin collections.")
            else:
                handler_input.response_builder.speak("Please specify which bin colour you'd like the schedule for.")
        except:
            handler_input.response_builder.speak("Sorry, something went wrong fetching the bin collection calendar.")
        return handler_input.response_builder.response

sb.add_request_handler(BinDateIntentHandler())

# Handler name that is used on AWS lambda
lambda_handler = sb.lambda_handler()