from __future__ import absolute_import, unicode_literals

import io
import logging
import os

from django.db import models

from common.utils import mkstemp

from .classes import KeyStub, SignatureVerification
from .exceptions import (
    DecryptionError, KeyDoesNotExist, KeyFetchingError, VerificationError
)
from .literals import KEY_TYPE_PUBLIC, KEY_TYPE_SECRET
from .runtime import gpg_backend
from .settings import setting_keyserver

logger = logging.getLogger(__name__)


class KeyManager(models.Manager):
    def _preload_keys(self, all_keys=False, key_fingerprint=None, key_id=None):
        # Preload keys
        if all_keys:
            logger.debug('preloading all keys')
            keys = self.values()
        elif key_fingerprint:
            logger.debug('preloading key fingerprint: %s', key_fingerprint)
            keys = self.filter(fingerprint=key_fingerprint).values()
            if not keys:
                logger.debug('key fingerprint %s not found', key_fingerprint)
                raise KeyDoesNotExist(
                    'Specified key for verification not found'
                )
        elif key_id:
            logger.debug('preloading key id: %s', key_id)
            keys = self.filter(fingerprint__endswith=key_id).values()
            if keys:
                logger.debug('key id %s impored', key_id)
            else:
                logger.debug('key id %s not found', key_id)
        else:
            keys = ()

        return keys

    def decrypt_file(self, file_object, all_keys=False, key_fingerprint=None, key_id=None):
        keys = self._preload_keys(
            all_keys=all_keys, key_fingerprint=key_fingerprint, key_id=key_id
        )

        decrypt_result = gpg_backend.decrypt_file(
            file_object=file_object, keys=keys
        )

        logger.debug('decrypt_result.status: %s', decrypt_result.status)

        if not decrypt_result.status or decrypt_result.status == 'no data was provided':
            raise DecryptionError('Unable to decrypt file')

        file_object.close()

        return io.BytesIO(decrypt_result.data)

    def private_keys(self):
        return self.filter(key_type=KEY_TYPE_SECRET)

    def public_keys(self):
        return self.filter(key_type=KEY_TYPE_PUBLIC)

    def receive_key(self, key_id):
        key_data = gpg_backend.recv_keys(
            keyserver=setting_keyserver.value, key_id=key_id
        )

        if not key_data:
            raise KeyFetchingError('No key found')
        else:
            return self.create(key_data=key_data)

    def search(self, query):
        key_data_list = gpg_backend.search_keys(
            keyserver=setting_keyserver.value, query=query
        )

        result = []
        for key_data in key_data_list:
            result.append(KeyStub(raw=key_data))

        return result

    def verify_file(self, file_object, signature_file=None, all_keys=False, key_fingerprint=None, key_id=None):
        keys = self._preload_keys(
            all_keys=all_keys, key_fingerprint=key_fingerprint, key_id=key_id
        )

        if signature_file:
            # Save the original data and invert the argument order
            # Signature first, file second
            temporary_file_object, temporary_filename = mkstemp()
            os.write(temporary_file_object, file_object.read())
            os.close(temporary_file_object)

            signature_file_buffer = io.BytesIO()
            signature_file_buffer.write(signature_file.read())
            signature_file_buffer.seek(0)
            signature_file.seek(0)
            verify_result = gpg_backend.verify_file(
                file_object=signature_file_buffer,
                data_filename=temporary_filename, keys=keys
            )
            signature_file_buffer.close()
            os.unlink(temporary_filename)
        else:
            verify_result = gpg_backend.verify_file(
                file_object=file_object, keys=keys
            )

        logger.debug('verify_result.status: %s', verify_result.status)

        if verify_result:
            # Signed and key present
            logger.debug('signed and key present')
            return SignatureVerification(verify_result.__dict__)
        elif verify_result.status == 'no public key' and not (key_fingerprint or all_keys or key_id):
            # Signed but key not present, retry with key fetch
            logger.debug('no public key')
            file_object.seek(0)
            return self.verify_file(file_object=file_object, signature_file=signature_file, key_id=verify_result.key_id)
        elif verify_result.key_id:
            # Signed, retried and key still not found
            logger.debug('signed, retried and key still not found')
            return SignatureVerification(verify_result.__dict__)
        else:
            logger.debug('file not signed')
            raise VerificationError('File not signed')