import agent_util
import time
from datetime import datetime
import socket
import struct

def getNTPTime(host="pool.ntp.org", port=123):
    buf = 1024
    address = (host, port)
    msg = '\x1b' + 47 * '\0'

    TIME1970 = 2208988800 # 1970-01-01 00:00:00

    # connect to server
    try:
        client = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        client.settimeout(15)
        client.sendto(msg.encode(), address)
        msg, address = client.recvfrom(buf)

        t = struct.unpack("!12I", msg)[10]
        t -= TIME1970
        ## t = time.gmtime(t)
        ## t = datetime(year=t.tm_year, month=t.tm_mon, day=t.tm_mday, hour=t.tm_hour, minute=t.tm_min, second=t.tm_sec)
        return t
    except:
        return None

class NTPPlugin(agent_util.Plugin):
    textkey = "ntp"
    label = "NTP"

    @classmethod
    def get_metadata(self, config):
        status = agent_util.SUPPORTED
        msg = None

        metadata = {
            "ntp_diff": {
                "label": "Difference between machine and NTP time",
                "options": None,
                "status": status,
                "error_message": msg,
                "unit": "second"
            }
        }

        return metadata

    def check(self, textkey, data, config={}):
        if textkey == 'ntp_diff':
            host = config.get("ntp_host", "pool.ntp.org")
            port = int(config.get("ntp_port", 123))
            ntp_time = getNTPTime(host, port)
            local_time = time.mktime(datetime.now().timetuple())
            if not ntp_time:
                self.log.critical("Unable to get NTP time from %s:%s" % (host, port))
                return
            else:
                self.log.info("NTP: %s, local: %s" % (ntp_time, local_time))

            time_diff =  abs(local_time - ntp_time)
            if time_diff < 86400*365:
                # Return the value if it's less than a year out of sync
                return time_diff
            else:
                return None

        return 0