import logging
import time

from landscape.log import format_delta, format_percent


class Timer(object):
"""
A timer keeps track of the number of seconds passed during it's
lifetime and since the last reset.
"""

def __init__(self, create_time=None):
self._create_time = create_time or time.time
self._creation_time = self._create_time()
self._last_time = self._creation_time

def time(self):
return self._create_time()

def since_start(self):
return self._create_time() - self._creation_time

def since_reset(self):
return self._create_time() - self._last_time

def reset(self):
self._last_time = self._create_time()


class Monitor(Timer):
"""
A monitor tracks the number of pings it received during it's
lifetime and since the last reset. The component being monitored
is responsible for calling C{ping()} everytime a monitored
activity occurs. It should register a reactor event that logs
statistics from this monitor every N seconds. Essentially,
monitors are just statistics checkers that components can use to
monitor themselves.
"""

def __init__(self, event_name, create_time=None):
super(Monitor, self).__init__(create_time=create_time)
self.event_name = event_name
self.count = 0
self.total_count = 0

def ping(self):
self.count += 1
self.total_count += 1

def reset(self):
super(Monitor, self).reset()
self.count = 0

def log(self):
logging.info("%d %s events occurred in the last %s.", self.count,
self.event_name, format_delta(self.since_reset()))
self.reset()


class BurstMonitor(Monitor):
"""
A burst monitor tracks the volume pings it receives. It goes into
warn mode when too many pings are received in a short period of
time.
"""

def __init__(self, repeat_interval, maximum_count, event_name,
create_time=None):
super(BurstMonitor, self).__init__(event_name, create_time=create_time)
self.repeat_interval = repeat_interval
self.maximum_count = maximum_count
self._last_times = []

def ping(self):
super(BurstMonitor, self).ping()
now = self.time()
self._last_times.append(now)
if (self._last_times[0] - now > self.repeat_interval
or len(self._last_times) > self.maximum_count+1):
self._last_times.pop(0)

def warn(self):
if not self._last_times:
return False
delta = self.time() - self._last_times[0]
return (delta < self.repeat_interval
and len(self._last_times) >= self.maximum_count+1)


class CoverageMonitor(Monitor):
"""
A coverage monitor tracks the volume of pings received since the
last reset. It has normal and warn states that are determined by
calculating the number of expected pings since the last reset. If
the actual number of pings falls below the minimum required
percent the monitor goes into warn mode. The component being
monitored should register a reactor event that logs statistics
from this monitor every N seconds.
"""

def __init__(self, repeat_interval, min_percent, event_name,
create_time=None):
super(CoverageMonitor, self).__init__(event_name,
create_time=create_time)
self.repeat_interval = repeat_interval
self.min_percent = min_percent

@property
def percent(self):
if not self.count and not self.expected_count:
return 1.0

elapsed_time = self.since_reset()
if not elapsed_time:
return 1.0

return self.count / float(self.expected_count)

@property
def expected_count(self):
return int(self.since_reset() / self.repeat_interval)

def log(self):
percent = 0.0
if self.percent and self.expected_count:
percent = self.percent * 100

log = logging.info
if self.warn():
log = logging.warning
log("%d of %d expected %s events (%s) occurred in the last %s.",
self.count, self.expected_count, self.event_name,
format_percent(percent), format_delta(self.since_reset()))

self.reset()

def warn(self):
if self.repeat_interval and self.min_percent:
if not self.expected_count:
return False
if self.percent < self.min_percent:
return True
return False


class FrequencyMonitor(Monitor):
"""
A frequency monitor tracks the number of pings received during a
fixed period of time. It has normal and warn states; a warn state
is triggered when the minimum expected pings were not received
during the specified interval. The component being monitored
should register a reactor event that checks the warn state of this
monitor every N seconds.
"""

def __init__(self, repeat_interval, min_frequency, event_name,
create_time=None):
super(FrequencyMonitor, self).__init__(event_name,
create_time=create_time)
self.repeat_interval = repeat_interval
self.min_frequency = min_frequency
self._last_count = self._create_time()

@property
def expected_count(self):
since_ping = self._create_time() - self._last_count
return since_ping // self.repeat_interval

def ping(self):
super(FrequencyMonitor, self).ping()
self._last_count = self._create_time()

def log(self):
if self.warn():
logging.warning("Only %d of %d minimum expected %s events "
"occurred in the last %s.", self.count,
self.expected_count, self.event_name,
format_delta(self.repeat_interval))
self.reset()

def warn(self):
if self.repeat_interval and self.min_frequency:
if (self._create_time() - self._last_count >= self.repeat_interval
and self.count < self.min_frequency):
return True
return False