from __future__ import absolute_import

import logging

try:
    from cStringIO import StringIO
except ImportError:
    from StringIO import StringIO

from django.utils.translation import ugettext_lazy as _
from django.db.models.signals import post_save

from documents.models import Document, DocumentVersion
from navigation.api import register_links
from django_gpg.runtime import gpg
from django_gpg.exceptions import GPGDecryptionError
from acls.api import class_permissions

from .models import DocumentVersionSignature
from .permissions import (
    PERMISSION_DOCUMENT_VERIFY,
    PERMISSION_SIGNATURE_UPLOAD,
    PERMISSION_SIGNATURE_DOWNLOAD
)

logger = logging.getLogger(__name__)


def has_embedded_signature(context):
    return DocumentVersionSignature.objects.has_embedded_signature(context['object'])


def doesnt_have_detached_signature(context):
    return DocumentVersionSignature.objects.has_detached_signature(context['object']) == False


def document_pre_open_hook(descriptor):
    try:
        result = gpg.decrypt_file(descriptor, close_descriptor=False)
        # gpg return a string, turn it into a file like object
    except GPGDecryptionError:
        # At least return the original raw content
        descriptor.seek(0)
        return descriptor
    else:
        return StringIO(result.data)


def document_post_save(sender, instance, **kwargs):
    if kwargs.get('created', False):
        DocumentVersionSignature.objects.signature_state(instance.document)

document_signature_upload = {'text': _(u'upload signature'), 'view': 'document_signature_upload', 'args': 'object.pk', 'famfam': 'pencil_add', 'permissions': [PERMISSION_SIGNATURE_UPLOAD], 'conditional_disable': has_embedded_signature}
document_signature_download = {'text': _(u'download signature'), 'view': 'document_signature_download', 'args': 'object.pk', 'famfam': 'disk', 'permissions': [PERMISSION_SIGNATURE_DOWNLOAD], 'conditional_disable': doesnt_have_detached_signature}
document_verify = {'text': _(u'signatures'), 'view': 'document_verify', 'args': 'object.pk', 'famfam': 'text_signature', 'permissions': [PERMISSION_DOCUMENT_VERIFY]}

register_links(Document, [document_verify], menu_name='form_header')
register_links(['document_verify', 'document_signature_upload', 'document_signature_download'], [document_signature_upload, document_signature_download], menu_name='sidebar')

DocumentVersion.register_pre_open_hook(1, document_pre_open_hook)

post_save.connect(document_post_save, sender=DocumentVersion)

class_permissions(Document, [
    PERMISSION_DOCUMENT_VERIFY,
    PERMISSION_SIGNATURE_UPLOAD,
    PERMISSION_SIGNATURE_DOWNLOAD
])