from django.db import models
from django.core.urlresolvers import reverse
from django.core.exceptions import ImproperlyConfigured
from django.utils.translation import ugettext as _

from django.contrib.contenttypes import generic
from django.contrib.contenttypes.models import ContentType
from django.contrib.auth.models import User

try:
    from django.utils import timezone
    now = timezone.now
except ImportError:
    from datetime import datetime
    now = datetime.now

from actstream import settings as actstream_settings
from actstream.signals import action
from actstream.actions import action_handler
from actstream.managers import FollowManager


class Follow(models.Model):
    """
    Lets a user follow the activities of any specific actor
    """
    user = models.ForeignKey(User)

    content_type = models.ForeignKey(ContentType)
    object_id = models.CharField(max_length=255)
    follow_object = generic.GenericForeignKey()
    actor_only = models.BooleanField("Only follow actions where the object is "
        "the target.", default=True)
    started = models.DateTimeField(default=now)
    objects = FollowManager()

    class Meta:
        unique_together = ('user', 'content_type', 'object_id')

    def __unicode__(self):
        return u'%s -> %s' % (self.user, self.follow_object)


class Action(models.Model):
    """
    Action model describing the actor acting out a verb (on an optional
    target).
    Nomenclature based on http://activitystrea.ms/specs/atom/1.0/

    Generalized Format::

        <actor> <verb> <time>
        <actor> <verb> <target> <time>
        <actor> <verb> <action_object> <target> <time>

    Examples::

        <justquick> <reached level 60> <1 minute ago>
        <brosner> <commented on> <pinax/pinax> <2 hours ago>
        <washingtontimes> <started follow> <justquick> <8 minutes ago>
        <mitsuhiko> <closed> <issue 70> on <mitsuhiko/flask> <about 2 hours ago>

    Unicode Representation::

        justquick reached level 60 1 minute ago
        mitsuhiko closed issue 70 on mitsuhiko/flask 3 hours ago

    HTML Representation::

        <a href="http://oebfare.com/">brosner</a> commented on <a href="http://github.com/pinax/pinax">pinax/pinax</a> 2 hours ago

    """
    actor_content_type = models.ForeignKey(ContentType, related_name='actor')
    actor_object_id = models.CharField(max_length=255)
    actor = generic.GenericForeignKey('actor_content_type', 'actor_object_id')

    verb = models.CharField(max_length=255)
    description = models.TextField(blank=True, null=True)

    target_content_type = models.ForeignKey(ContentType, related_name='target',
        blank=True, null=True)
    target_object_id = models.CharField(max_length=255, blank=True, null=True)
    target = generic.GenericForeignKey('target_content_type',
        'target_object_id')

    action_object_content_type = models.ForeignKey(ContentType,
        related_name='action_object', blank=True, null=True)
    action_object_object_id = models.CharField(max_length=255, blank=True,
        null=True)
    action_object = generic.GenericForeignKey('action_object_content_type',
        'action_object_object_id')

    timestamp = models.DateTimeField(default=now)

    public = models.BooleanField(default=True)

    objects = actstream_settings.get_action_manager()

    class Meta:
        ordering = ('-timestamp', )

    def __unicode__(self):
        ctx = {
            'actor': self.actor,
            'verb': self.verb,
            'action_object': self.action_object,
            'target': self.target,
            'timesince': self.timesince()
        }
        if self.target:
            if self.action_object:
                return _('%(actor)s %(verb)s %(action_object)s on %(target)s %(timesince)s ago') % ctx
            return _('%(actor)s %(verb)s %(target)s %(timesince)s ago') % ctx
        if self.action_object:
            return _('%(actor)s %(verb)s %(action_object)s %(timesince)s ago') % ctx
        return _('%(actor)s %(verb)s %(timesince)s ago') % ctx

    def actor_url(self):
        """
        Returns the URL to the ``actstream_actor`` view for the current actor.
        """
        return reverse('actstream_actor', None,
                       (self.actor_content_type.pk, self.actor_object_id))

    def target_url(self):
        """
        Returns the URL to the ``actstream_actor`` view for the current target.
        """
        return reverse('actstream_actor', None,
                       (self.target_content_type.pk, self.target_object_id))

    def action_object_url(self):
        """
        Returns the URL to the ``actstream_action_object`` view for the current action object
        """
        return reverse('actstream_actor', None,
            (self.action_object_content_type.pk, self.action_object_object_id))

    def timesince(self, now=None):
        """
        Shortcut for the ``django.utils.timesince.timesince`` function of the
        current timestamp.
        """
        from django.utils.timesince import timesince as timesince_
        return timesince_(self.timestamp, now)

    @models.permalink
    def get_absolute_url(self):
        return ('actstream.views.detail', [self.pk])


# convenient accessors
actor_stream = Action.objects.actor
action_object_stream = Action.objects.action_object
target_stream = Action.objects.target
user_stream = Action.objects.user
model_stream = Action.objects.model_actions
followers = Follow.objects.followers
following = Follow.objects.following


def setup_generic_relations():
    """
    Set up GenericRelations for actionable models.
    """
    for model in actstream_settings.get_models().values():
        if not model:
            continue
        for field in ('actor', 'target', 'action_object'):
            attr = '%s_actions' % field
            if isinstance(getattr(model, attr, None),
                          generic.ReverseGenericRelatedObjectsDescriptor):
                break
            generic.GenericRelation(Action,
                content_type_field='%s_content_type' % field,
                object_id_field='%s_object_id' % field,
                related_name='actions_with_%s_%s_as_%s' % (
                    model._meta.app_label, model._meta.module_name, field),
            ).contribute_to_class(model, attr)

            # @@@ I'm not entirely sure why this works
            setattr(Action, 'actions_with_%s_%s_as_%s' % (
                model._meta.app_label, model._meta.module_name, field), None)


setup_generic_relations()


if actstream_settings.USE_JSONFIELD:
    try:
        from jsonfield.fields import JSONField
    except ImportError:
        raise ImproperlyConfigured('You must have django-jsonfield installed '
                                'if you wish to use a JSONField on your actions')
    JSONField(blank=True, null=True).contribute_to_class(Action, 'data')

# connect the signal
action.connect(action_handler, dispatch_uid='actstream.models')
