''' Purpose: provide weather forecast by accessing US Weather Service web service

    Usage:   user provides a zipcode

    Output:  current forecast for that zipcode
'''

# get url access capability from cs 1112 module
import url 

# define weather.gov base query
# https - s = secure website
WEATHER_GOV_QUERY = "https://forecast.weather.gov/zipcity.php?inputstring="

# forecast delimiters -- these will help us locate where the forecast is -- between the front_delimiter
# and end_delimiter
FRONT_DELIMITER = "<div class=\"col-sm-10 forecast-text\">"   # text that precedes forecast
REAR_DELIMITER  = "</div>"                                    # text that follows forecast

# delimiter lengths
LENGTH_FRONT_DELIMITER = len( FRONT_DELIMITER )    # we need the length of the front delimiter
                                                   # b/c the forecast starts RIGHT AFTER the front_delimiter
                                                   # not where the front_delimiter starts
LENGTH_REAR_DELIMITER  = len( REAR_DELIMITER )

# get zipcode of interest
reply = input( "Enter zipcode: " )
zipcode = reply.strip()                         # clean-up response: clean whitespaces

# specify complete query
query_link = WEATHER_GOV_QUERY + zipcode    # get the complete link to that zip code on the National Weather
                                            # Service website

# get response from weather.gov
page = url.get_contents( query_link )     # get_contents() is a function within the url module
                                          # gives it a string that is a link for a website
                                          # then gives us back the content of the website
# print( page )

# to get the forecast, we need to find it within the page

# start by finding the forecast delimiters
front_index = page.find( FRONT_DELIMITER )     # at what index does the FRONT_DELIMITER start in the string page?
                                               # for strings, we use find() to get the index of the argument

rear_index  = page.find( REAR_DELIMITER, front_index )
# find the index at which the END_DELIMITER starts
# second parameter -- find the REAR_DELIMITER starting from the front_index

# print( front_index, rear_index )   # print where the FRONT_DELIMITER starts, where the REAR_DELIMITER starts
                                     # after the index of the FRONT_DELIMITER

# (mis)try to use those index delimiters to pick off the forecast
# want a slice from page where the forecast starts
forecast = page[ front_index : rear_index ]
# includes from front_index and up to but not including rear_index
# but if we start at front_index, we also include the FRONT_DELIMITER string --> we want the index
# AFTER the FRONT_DELIMITER --> so we add the LENGTH of the FRONT_DELIMITER
# if the front_index is 2, and the front_delimiter has length 5 --> the forecast actually starts at index 7
# since that is after the entire front_delimiter string
# so we add 2 and 5 = 7 --> 7 is the index where the forecast starts

print( forecast )  # this version, since it only starts at front_index, also includes the FRONT_DELIMITER

print()


# get the indices for the front and rear of the forecast
forecast_start = front_index + LENGTH_FRONT_DELIMITER

forecast_rear  = rear_index

# ready to get and print the forecast
forecast = page[ forecast_start : forecast_rear ]

# print the forecast
print( forecast )