#!/usr/bin/env python3
#
# spotprices
#
# Copyright (C) 2021
# Paul E. Jones <paulej@packetizer.com>
#
# This program will connect to Packetizer's Precious Metal Spot Prices Service
# and display the current spot prices.
#

import json
import urllib.request

# Define the URL for querying precious metal spot prices
SPOT_METAL_PRICES = "https://services.packetizer.com/spotprices/?f=json"

def create_error_string(error_string):
    """
    Common routine to print errors
    """
    return "An error occurred trying to get spot prices: {}".format(error_string)

def get_spot_prices(url):
    """
    Routine to query the precious metal spot prices from the given URL.  If
    the error string has a zero-length, then the results can be found
    in the returned spot_prices dictionary
    """
    error_string = ""
    spot_prices = {}
    try:
        resource = urllib.request.urlopen(url)
        if resource.status == 200:
            spot_prices = json.loads(resource.read())
        else:
            error_string = create_error_string("Unexpected HTTP response is {}".format(resource.status.code))
    except urllib.error.URLError as error:
        error_string = create_error_string("{}".format(str(error)))
        spot_prices = {}
    except json.JSONDecodeError:
        error_string = create_error_string("could not parse JSON response")
        spot_prices = {}
    except Exception as error:
        error_string = create_error_string("{}".format(str(error)))
        spot_prices = {}

    return spot_prices, error_string

def main():
    """
    Main routine
    """
    spot_prices, error_string = get_spot_prices(SPOT_METAL_PRICES)
    if len(error_string) > 0:
        print(error_string)
    elif len(spot_prices) >= 3:
        print("Gold: {}".format(spot_prices["gold"]))
        print("Silver: {}".format(spot_prices["silver"]))
        print("Platinum: {}".format(spot_prices["platinum"]))
    else:
        print("Could not get spot metal prices")

if __name__ == "__main__":
    main()