from __future__ import unicode_literals

from datetime import date
import logging
import uuid

from django.core.urlresolvers import reverse
from django.db import models
from django.utils.encoding import python_2_unicode_compatible
from django.utils.translation import ugettext_lazy as _

from model_utils.managers import InheritanceManager

from django_gpg.exceptions import DecryptionError, VerificationError
from django_gpg.models import Key
from documents.models import DocumentVersion

from .managers import EmbeddedSignatureManager, DetachedSignatureManager
from .runtime import storage_backend

logger = logging.getLogger(__name__)


def upload_to(*args, **kwargs):
    return unicode(uuid.uuid4())


@python_2_unicode_compatible
class SignatureBaseModel(models.Model):
    document_version = models.ForeignKey(
        DocumentVersion, editable=False, related_name='signatures',
        verbose_name=_('Document version')
    )
    # Basic fields
    date = models.DateField(
        blank=True, editable=False, null=True, verbose_name=_('Date signed')
    )
    key_id = models.CharField(max_length=40, verbose_name=_('Key ID'))
    # With proper key
    signature_id = models.CharField(
        blank=True, editable=False, null=True, max_length=64,
        verbose_name=_('Signature ID')
    )
    public_key_fingerprint = models.CharField(
        blank=True, editable=False, null=True, max_length=40, unique=True,
        verbose_name=_('Public key fingerprint')
    )

    objects = InheritanceManager()

    class Meta:
        verbose_name = _('Document version signature')
        verbose_name_plural = _('Document version signatures')

    def __str__(self):
        return self.signature_id or '{} - {}'.format(self.date, self.key_id)

    def get_absolute_url(self):
        return reverse(
            'document_signatures:document_version_signature_detail',
            args=(self.pk,)
        )

    @property
    def is_detached(self):
        return hasattr(self, 'signature_file')

    @property
    def is_embedded(self):
        return not hasattr(self, 'signature_file')


class EmbeddedSignature(SignatureBaseModel):
    objects = EmbeddedSignatureManager()

    class Meta:
        verbose_name = _('Document version embedded signature')
        verbose_name_plural = _('Document version embedded signatures')


class DetachedSignature(SignatureBaseModel):
    signature_file = models.FileField(
        blank=True, null=True, storage=storage_backend, upload_to=upload_to,
        verbose_name=_('Signature file')
    )

    objects = DetachedSignatureManager()

    class Meta:
        verbose_name = _('Document version detached signature')
        verbose_name_plural = _('Document version detached signatures')

    def delete(self, *args, **kwargs):
        self.signature_file.storage.delete(self.signature_file.name)
        super(DetachedSignature, self).delete(*args, **kwargs)