import hashlib
import math
import logging

from requests.exceptions import RequestException

logger = logging.getLogger(__name__)

class Avatar(object):
  def __init__(self, app=None):
    self.app = app
    self.state = self._init_app(app)

  def _init_app(self, app):
    return AVATAR_CLASSES[app.config.get('AVATAR_KIND', 'Gravatar')](
      app.config['PREFERRED_URL_SCHEME'], app.config['AVATAR_COLORS'], app.config['HTTPCLIENT'])

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


class BaseAvatar(object):
  """ Base class for all avatar implementations. """
  def __init__(self, preferred_url_scheme, colors, http_client):
    self.preferred_url_scheme = preferred_url_scheme
    self.colors = colors
    self.http_client = http_client

  def get_mail_html(self, name, email_or_id, size=16, kind='user'):
    """ Returns the full HTML and CSS for viewing the avatar of the given name and email address,
        with an optional size.
    """
    data = self.get_data(name, email_or_id, kind)
    url = self._get_url(data['hash'], size) if kind != 'team' else None
    font_size = size - 6

    if url is not None:
      # Try to load the gravatar. If we get a non-404 response, then we use it in place of
      # the CSS avatar.
      try:
        response = self.http_client.get(url, timeout=5)
        if response.status_code == 200:
          return """<img src="%s" width="%s" height="%s" alt="%s"
                         style="vertical-align: middle;">""" % (url, size, size, kind)
      except RequestException:
        logger.exception('Could not retrieve avatar for user %s', name)

    radius = '50%' if kind == 'team' else '0%'
    letter = '&Omega;' if kind == 'team' and data['name'] == 'owners' else data['name'].upper()[0]

    return """
      <span style="width: %spx; height: %spx; background-color: %s; font-size: %spx;
                   line-height: %spx; margin-left: 2px; margin-right: 2px; display: inline-block;
                   vertical-align: middle; text-align: center; color: white; border-radius: %s">
        %s
      </span>
""" % (size, size, data['color'], font_size, size, radius, letter)

  def get_data_for_user(self, user):
    return self.get_data(user.username, user.email, 'robot' if user.robot else 'user')

  def get_data_for_team(self, team):
    return self.get_data(team.name, team.name, 'team')

  def get_data_for_org(self, org):
    return self.get_data(org.username, org.email, 'org')

  def get_data(self, name, email_or_id, kind='user'):
    """ Computes and returns the full data block for the avatar:
        {
          'name': name,
          'hash': The gravatar hash, if any.
          'color': The color for the avatar
        }
    """
    colors = self.colors
    hash_value = hashlib.md5(email_or_id.strip().lower()).hexdigest()

    byte_count = int(math.ceil(math.log(len(colors), 16)))
    byte_data = hash_value[0:byte_count]
    hash_color = colors[int(byte_data, 16) % len(colors)]

    return {
      'name': name,
      'hash': hash_value,
      'color': hash_color,
      'kind': kind
    }

  def _get_url(self, hash_value, size):
    """ Returns the URL for displaying the overlay avatar. """
    return None


class GravatarAvatar(BaseAvatar):
  """ Avatar system that uses gravatar for generating avatars. """
  def _get_url(self, hash_value, size=16):
    return '%s://www.gravatar.com/avatar/%s?d=404&size=%s' % (self.preferred_url_scheme,
                                                              hash_value, size)

class LocalAvatar(BaseAvatar):
  """ Avatar system that uses the local system for generating avatars. """
  pass

AVATAR_CLASSES = {
  'gravatar': GravatarAvatar,
  'local': LocalAvatar
}