import urllib.request
import re
import sys
import os
import argparse
import filecmp

def main():
    parser = argparse.ArgumentParser(description='Check numeric values on a webpage against Nagios thresholds or check to see if the page(or part of it) changes.')

    parser.add_argument('-s', default=False, action='store_true',  help="Suppress printing value.")
    parser.add_argument('-u', metavar='URL', type=str, help="URL to extact value from.")
    parser.add_argument('-r', metavar='REGEX', type=str, help="Regex to match returned results. The plugin looks for the first capturing group in the match - regex must include grouping parentheses()")
    parser.add_argument('-f', metavar='FILE', type=str, help="File to store results to subsequently check against. Only used if -w and -c are not used. Default filename is results.txt", default="results.txt")
    parser.add_argument('-p', metavar='PERFDATA LABEL', type=str, help="Label to apply to performance data. Default label is 'value'. Peformance data only available if -w or -c are used", default="value")
    parser.add_argument('-w', metavar='WARNING THRESHOLD', type=str, help="Warning threshold to check the returned value against")
    parser.add_argument('-c', metavar='CRITICAL THRESHOLD', type=str, help="Critical threshold to check the returned value against")

    args = parser.parse_args()

    suppress=args.s
    url=args.u
    regex=args.r
    file=args.f
    warning=args.w
    critical=args.c
    perfdatalabel=args.p

    tmpFile = file + ".tmp"

    if not url:
        nagios_exit("url is required", check_status.UNKNOWN)
    
    if not regex:
         nagios_exit("regex is required", check_status.UNKNOWN)


    url_request=urllib.request.urlopen(url)
    data = url_request.read().decode("UTF-8")
  
    match = re.search(regex, str(data), re.DOTALL)

    if match:
        newValue = match.group(1)
        f = open(tmpFile, 'w+')
        f.write(newValue)
        f.flush()
        f.close
    else:
        nagios_exit("regex did not match: " + str(data), check_status.UNKNOWN)

    if not warning and not critical:
        if not os.path.exists(file):
            os.rename(tmpFile, file)
            nagios_exit("inital check", check_status.OK)

        filecmp.clear_cache()

        same = filecmp.cmp(file, tmpFile, shallow=False)

        if not same:
            os.remove(file)
            os.rename(tmpFile,file)
            if suppress:
                nagios_exit("value changed", check_status.CRITICAL)
            else:
                nagios_exit("value changed to: " + newValue, check_status.CRITICAL)
        else:
            if suppress:
                nagios_exit("Value remains the same", check_status.OK)
            else:
                nagios_exit("Value remains the same: " + newValue, check_status.OK)
    else:
        if critical:
            criticalRange = threshold_string_to_tuple(critical)
            nagios_exit(newValue, check_status.CRITICAL, perfdata=" | " +  perfdatalabel + "=" + str(newValue))
        if warning:
            warningRange = threshold_string_to_tuple(warning)
            nagios_exit(newValue, check_status.WARNING, perfdata=" | " +  perfdatalabel + "=" + str(newValue))

def check_alarm(value, rangeTuple):
    low = rangeTuple[0]
    high = rangeTuple[1]
    inclusive = rangeTuple[2]

    if inclusive:
        return float(value) >= low and float(value) <= high
    else:
        return float(value) < low or float(value) > high

def threshold_string_to_tuple(threshold_string):
    # Default values if not set
    low = 0
    high = float('inf') # ok even if we use integers otherwise
    inclusive = False

    if not threshold_string:
        threshold_string = "~:"
    
    if threshold_string[0] == "@":
        inclusive = True 
        threshold_string = threshold_string[1:]

    threshold_list = threshold_string.split(":")

    length = len(threshold_list)
    if length < 1 or length > 2:
        nagios_exit("Thresholds are composed of 1-2 arguments.", check_status.UNKNOWN)
    elif length == 1:
        try:
            high = float(threshold_list[0])
        except ValueError:
            nagios_exit(str(threshold_list[0]) + " could not be converted to a number", check_status.UNKNOWN)
    elif length == 2:
        if not threshold_list[0]:
            threshold_list[0] = "0"
        if (threshold_list[0] == "~" or threshold_list[0] == os.path.expanduser("~")):
            threshold_list[0] = "-inf"
        if not threshold_list[1]:
            threshold_list[1] = 'inf'
        try:
            low = float(threshold_list[0])
            high = float(threshold_list[1])
        except ValueError:
            nagios_exit("One of " + str(threshold_list) + " could not be converted to a number", check_status.UNKNOWN)
    if low > high:
        nagios_exit("The threshold minimum " + str(low) + " must be less than the maximum " + str(high), check_status.UNKNOWN)
    return low, high, inclusive

def nagios_exit(out, code, perfdata="", verbose_out=""):
    prefix = code_to_status(code)
    out = prefix + ": " + out
    out += perfdata
    print(out)
    exit(code)

class check_status():
    OK = 0
    WARNING = 1
    CRITICAL = 2
    UNKNOWN = 3

def code_to_status(return_code):
    if return_code < check_status.OK or return_code > check_status.UNKNOWN:
        return_code = check_status.UNKNOWN
    words = ["OK", "WARNING", "CRITICAL", "UNKNOWN"]
    return words[return_code]
if __name__ == "__main__":
    main()