import datetime
import logging
import time

from functools import wraps
from Queue import Queue, Full

from flask import g, request


logger = logging.getLogger(__name__)

# Buckets for the API response times.
API_RESPONSE_TIME_BUCKETS = [.01, .025, .05, .1, .25, .5, 1.0, 2.5, 5.0]


class MetricQueue(object):
  """ Object to which various metrics are written, for distribution to metrics collection
      system(s) such Prometheus.
  """
  def __init__(self, prom):
    # Define the various exported metrics.
    self.resp_time = prom.create_histogram('response_time', 'HTTP response time in seconds',
                                           labelnames=['endpoint'],
                                           buckets=API_RESPONSE_TIME_BUCKETS)
    self.resp_code = prom.create_counter('response_code', 'HTTP response code',
                                         labelnames=['endpoint', 'code'])
    self.non_200 = prom.create_counter('response_non200', 'Non-200 HTTP response codes',
                                       labelnames=['endpoint'])
    self.multipart_upload_start = prom.create_counter('multipart_upload_start',
                                                      'Multipart upload startse')
    self.multipart_upload_end = prom.create_counter('self._metric_queue.multipart_upload_end',
                                                    'Multipart upload ends.', labelnames=['type'])
    self.build_capacity_shortage = prom.create_gauge('build_capacity_shortage',
                                                     'Build capacity shortage.')
    self.percent_building = prom.create_gauge('build_percent_building', 'Percent building.')
    self.build_counter = prom.create_counter('builds', 'Number of builds', labelnames=['name'])
    self.ephemeral_build_workers = prom.create_counter('ephemeral_build_workers',
      'Number of started ephemeral build workers', labelnames=['name', 'build_uuid'])
    self.ephemeral_build_worker_failure = prom.create_counter('ephemeral_build_worker_failure',
      'Number of failed-to-start ephemeral build workers', labelnames=['build_uuid'])

    self.work_queue_running = prom.create_gauge('work_queue_running', 'Running items in a queue',
                                                labelnames=['queue_name'])
    self.work_queue_available = prom.create_gauge('work_queue_available',
                                                  'Available items in a queue',
                                                  labelnames=['queue_name'])

    # Deprecated: Define an in-memory queue for reporting metrics to CloudWatch or another
    # provider.
    self._queue = None

  def enable_deprecated(self, maxsize=10000):
    self._queue = Queue(maxsize)

  def put_deprecated(self, name, value, **kwargs):
    if self._queue is None:
      logger.debug('No metric queue %s %s %s', name, value, kwargs)
      return

    try:
      kwargs.setdefault('timestamp', datetime.datetime.now())
      kwargs.setdefault('dimensions', {})
      self._queue.put_nowait((name, value, kwargs))
    except Full:
      logger.error('Metric queue full')

  def get_deprecated(self):
    return self._queue.get()

  def get_nowait_deprecated(self):
    return self._queue.get_nowait()


def time_decorator(name, metric_queue):
  """ Decorates an endpoint method to have its request time logged to the metrics queue. """
  after = _time_after_request(name, metric_queue)
  def decorator(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
      _time_before_request()
      rv = func(*args, **kwargs)
      after(rv)
      return rv
    return wrapper
  return decorator


def time_blueprint(bp, metric_queue):
  """ Decorates a blueprint to have its request time logged to the metrics queue. """
  bp.before_request(_time_before_request)
  bp.after_request(_time_after_request(bp.name, metric_queue))


def _time_before_request():
  g._request_start_time = time.time()


def _time_after_request(name, metric_queue):
  def f(r):
    start = getattr(g, '_request_start_time', None)
    if start is None:
      return r

    dur = time.time() - start
    dims = {'endpoint': request.endpoint}

    metric_queue.put_deprecated('ResponseTime', dur, dimensions=dims, unit='Seconds')
    metric_queue.put_deprecated('ResponseCode', r.status_code, dimensions=dims)

    metric_queue.resp_time.Observe(dur, labelvalues=[request.endpoint])
    metric_queue.resp_code.Inc(labelvalues=[request.endpoint, r.status_code])

    if r.status_code >= 500:
      metric_queue.put_deprecated('5XXResponse', 1, dimensions={'name': name})
    elif r.status_code < 200 or r.status_code >= 300:
      metric_queue.put_deprecated('Non200Response', 1, dimensions={'name': name})
      metric_queue.non_200.Inc(labelvalues=[request.endpoint])

    return r
  return f