import redis
import json

from util.dynamic import import_class
from datetime import timedelta


ONE_DAY = timedelta(days=1)


class BuildStatusRetrievalError(Exception):
  pass

class RedisBuildLogs(object):
  ERROR = 'error'
  COMMAND = 'command'
  PHASE = 'phase'

  def __init__(self, redis_host):
    self._redis = redis.StrictRedis(host=redis_host, socket_timeout=5)

  @staticmethod
  def _logs_key(build_id):
    return 'builds/%s/logs' % build_id

  def append_log_entry(self, build_id, log_obj):
    """
    Appends the serialized form of log_obj to the end of the log entry list
    and returns the new length of the list.
    """
    return self._redis.rpush(self._logs_key(build_id), json.dumps(log_obj))

  def append_log_message(self, build_id, log_message, log_type=None, log_data=None):
    """
    Wraps the message in an envelope and push it to the end of the log entry
    list and returns the index at which it was inserted.
    """
    log_obj = {
      'message': log_message
    }

    if log_type:
      log_obj['type'] = log_type

    if log_data:
      log_obj['data'] = log_data

    return self._redis.rpush(self._logs_key(build_id), json.dumps(log_obj)) - 1

  def get_log_entries(self, build_id, start_index):
    """ 
    Returns a tuple of the current length of the list and an iterable of the
    requested log entries.
    """
    try:
      llen = self._redis.llen(self._logs_key(build_id))
      log_entries = self._redis.lrange(self._logs_key(build_id), start_index, -1)
      return (llen, (json.loads(entry) for entry in log_entries))
    except redis.ConnectionError:
      raise BuildStatusRetrievalError('Cannot retrieve build logs')

  def expire_log_entries(self, build_id):
    """
    Sets the log entry to expire in 1 day.
    """
    self._redis.expire(self._logs_key(build_id), ONE_DAY)


  @staticmethod
  def _status_key(build_id):
    return 'builds/%s/status' % build_id

  def set_status(self, build_id, status_obj):
    """
    Sets the status key for this build to json serialized form of the supplied
    obj.
    """
    self._redis.set(self._status_key(build_id), json.dumps(status_obj))

  def get_status(self, build_id):
    """
    Loads the status information for the specified build id.
    """
    try:
      fetched = self._redis.get(self._status_key(build_id))
    except redis.ConnectionError:
      raise BuildStatusRetrievalError('Cannot retrieve build status')

    return json.loads(fetched) if fetched else None

  def check_health(self):
    try:
      return self._redis.ping() == True
    except redis.ConnectionError:
      return False


class BuildLogs(object):
  def __init__(self, app=None):
    self.app = app
    if app is not None:
      self.state = self.init_app(app)
    else:
      self.state = None

  def init_app(self, app):
    buildlogs_hostname = app.config.get('BUILDLOGS_REDIS_HOSTNAME')
    buildlogs_options = app.config.get('BUILDLOGS_OPTIONS', [])
    buildlogs_import = app.config.get('BUILDLOGS_MODULE_AND_CLASS', None)

    if buildlogs_import is None:
      klass = RedisBuildLogs
    else:
      klass = import_class(buildlogs_import[0], buildlogs_import[1])

    buildlogs = klass(buildlogs_hostname, *buildlogs_options)

    # register extension with app
    app.extensions = getattr(app, 'extensions', {})
    app.extensions['buildlogs'] = buildlogs
    return buildlogs

  def __getattr__(self, name):
    return getattr(self.state, name, None)