""" Swift storage driver.

    Uses: http://docs.openstack.org/developer/swift/overview_large_objects.html
"""
from swiftclient.client import Connection, ClientException
from storage.basestorage import BaseStorage
from util.registry.generatorfile import GeneratorFile
from urlparse import urlparse
from random import SystemRandom
from hashlib import sha1
from time import time
from collections import namedtuple
from util.registry import filelike

import copy
import hmac
import string
import logging
from uuid import uuid4

logger = logging.getLogger(__name__)

_PartUploadMetadata = namedtuple('_PartUploadMetadata', ['path', 'offset', 'length'])
_SEGMENTS_KEY = 'segments'
_SEGMENT_DIRECTORY = 'segments'
_MAXIMUM_SEGMENT_SIZE = 5000000000 # 5 GB

class SwiftStorage(BaseStorage):
  def __init__(self, swift_container, storage_path, auth_url, swift_user,
               swift_password, auth_version=None, os_options=None, ca_cert_path=None,
               temp_url_key=None):
    super(SwiftStorage, self).__init__()
    self._swift_container = swift_container
    self._storage_path = storage_path

    self._auth_url = auth_url
    self._ca_cert_path = ca_cert_path

    self._swift_user = swift_user
    self._swift_password = swift_password

    self._temp_url_key = temp_url_key

    try:
      self._auth_version = int(auth_version or '2')
    except ValueError:
      self._auth_version = 2

    self._os_options = os_options or {}

    self._initialized = False

  def _get_connection(self):
    return Connection(
        authurl=self._auth_url,
        cacert=self._ca_cert_path,

        user=self._swift_user,
        key=self._swift_password,

        auth_version=self._auth_version,
        os_options=self._os_options)

  def _get_relative_path(self, path):
    if path.startswith(self._storage_path):
      path = path[len(self._storage_path)]

    if path.endswith('/'):
      path = path[:-1]

    return path

  def _normalize_path(self, object_path=None):
    path = self._storage_path
    if not path.endswith('/'):
      path = path + '/'

    path = path + (object_path or '')

    # Openstack does not like paths starting with '/' and we always normalize
    # to remove trailing '/'
    if path.startswith('/'):
      path = path[1:]

    if path.endswith('/'):
      path = path[:-1]

    return path

  def _get_container(self, path):
    path = self._normalize_path(path)

    if path and not path.endswith('/'):
        path += '/'

    try:
       _, container = self._get_connection().get_container(
            container=self._swift_container,
            prefix=path, delimiter='/')
       return container
    except:
      logger.exception('Could not get container: %s', path)
      raise IOError('Unknown path: %s' % path)

  def _get_object(self, path, chunk_size=None):
    path = self._normalize_path(path)
    try:
      _, obj = self._get_connection().get_object(self._swift_container, path,
          resp_chunk_size=chunk_size)
      return obj
    except Exception:
      logger.exception('Could not get object: %s', path)
      raise IOError('Path %s not found' % path)

  def _put_object(self, path, content, chunk=None, content_type=None, content_encoding=None,
                  headers=None):
    path = self._normalize_path(path)
    headers = headers or {}

    if content_encoding is not None:
      headers['Content-Encoding'] = content_encoding

    try:
      self._get_connection().put_object(self._swift_container, path, content,
                                        chunk_size=chunk, content_type=content_type,
                                        headers=headers)
    except ClientException:
      # We re-raise client exception here so that validation of config during setup can see
      # the client exception messages.
      raise
    except Exception:
      logger.exception('Could not put object: %s', path)
      raise IOError("Could not put content: %s" % path)

  def _head_object(self, path):
    path = self._normalize_path(path)
    try:
      return self._get_connection().head_object(self._swift_container, path)
    except Exception:
      logger.exception('Could not head object: %s', path)
      return None

  def get_direct_download_url(self, object_path, expires_in=60, requires_cors=False):
    if requires_cors:
      return None

    # Reference: http://docs.openstack.org/juno/config-reference/content/object-storage-tempurl.html
    if not self._temp_url_key:
      return None

    # Retrieve the auth details for the connection.
    try:
      object_url_value, _ = self._get_connection().get_auth()
    except ClientException:
      logger.exception('Got client exception when trying to load Swift auth')
      return None

    object_url = urlparse(object_url_value)
    scheme = object_url.scheme
    path = object_url.path
    hostname = object_url.netloc

    if not path.endswith('/'):
      path = path + '/'

    object_path = self._normalize_path(object_path)

    # Generate the signed HMAC body.
    method = 'GET'
    expires = int(time() + expires_in)
    full_path = '%s%s/%s' % (path, self._swift_container, object_path)

    hmac_body = '%s\n%s\n%s' % (method, expires, full_path)
    sig = hmac.new(self._temp_url_key.encode('utf-8'), hmac_body.encode('utf-8'), sha1).hexdigest()

    surl = '{scheme}://{host}{full_path}?temp_url_sig={sig}&temp_url_expires={expires}'
    return surl.format(scheme=scheme, host=hostname, full_path=full_path, sig=sig, expires=expires)

  def validate(self, client):
    if self._temp_url_key:
      # Add a file to test direct download.
      self.put_content('dd_path', 'testing 3456')

      # Generate a direct download URL.
      dd_url = self.get_direct_download_url('dd_path')

      if not dd_url:
        self.remove('dd_path')
        raise Exception('Could not validate direct download URL; the token may be invalid.')

      # Try to retrieve the direct download URL.
      response = client.get(dd_url, timeout=2)

      # Remove the test file.
      self.remove('dd_path')

      if response.status_code != 200:
        logger.debug('Direct download failure: %s => %s with body %s', dd_url,
                     response.status_code, response.text)

        msg = 'Direct download URL failed with status code %s. Please check your temp-url-key.'
        raise Exception(msg % response.status_code)

  def get_content(self, path):
    return self._get_object(path)

  def put_content(self, path, content):
    self._put_object(path, content)

  def stream_read(self, path):
    for data in self._get_object(path, self.buffer_size):
      yield data

  def stream_read_file(self, path):
    return GeneratorFile(self.stream_read(path))

  def stream_write(self, path, fp, content_type=None, content_encoding=None):
    self._put_object(path, fp, self.buffer_size, content_type=content_type,
                     content_encoding=content_encoding)

  def list_directory(self, path=None):
    container = self._get_container(path)
    if not container:
      raise OSError('Unknown path: %s' % path)

    for entry in container:
      param = None
      if 'name' in entry:
        param = 'name'
      elif 'subdir' in entry:
        param = 'subdir'
      else:
        continue

      yield self._get_relative_path(entry[param])

  def exists(self, path):
    return bool(self._head_object(path))

  def remove(self, path):
    path = self._normalize_path(path)
    try:
      self._get_connection().delete_object(self._swift_container, path)
    except Exception:
      raise IOError('Cannot delete path: %s' % path)

  def _random_checksum(self, count):
    chars = string.ascii_uppercase + string.digits
    return ''.join(SystemRandom().choice(chars) for _ in range(count))

  def get_checksum(self, path):
    headers = self._head_object(path)
    if not headers:
      raise IOError('Cannot lookup path: %s' % path)

    return headers.get('etag', '')[1:-1][:7] or self._random_checksum(7)

  @staticmethod
  def _segment_list_from_metadata(storage_metadata):
    return [_PartUploadMetadata(*segment_args) for segment_args in storage_metadata[_SEGMENTS_KEY]]

  def initiate_chunked_upload(self):
    random_uuid = str(uuid4())

    metadata = {
      _SEGMENTS_KEY: [],
    }

    return random_uuid, metadata

  def stream_upload_chunk(self, uuid, offset, length, in_fp, storage_metadata):
    if length == 0:
      return 0, storage_metadata

    # Note: Swift limits segments to a maximum of 5GB, so we keep writing segments until we
    # are finished hitting the data limit.
    total_bytes_written = 0
    while True:
      bytes_written, storage_metadata = self._stream_upload_segment(uuid, offset, length, in_fp,
                                                                    storage_metadata)

      if length != filelike.READ_UNTIL_END:
        length = length - bytes_written

      offset = offset + bytes_written
      total_bytes_written = total_bytes_written + bytes_written
      if bytes_written == 0 or length <= 0:
        return total_bytes_written, storage_metadata

  def _stream_upload_segment(self, uuid, offset, length, in_fp, storage_metadata):
    updated_metadata = copy.deepcopy(storage_metadata)
    segment_count = len(updated_metadata[_SEGMENTS_KEY])
    segment_path = '%s/%s/%s' % (_SEGMENT_DIRECTORY, uuid, segment_count)

    # Track the number of bytes read and if an explicit length is specified, limit the
    # file stream to that length.
    if length == filelike.READ_UNTIL_END:
      length = _MAXIMUM_SEGMENT_SIZE
    else:
      length = min(_MAXIMUM_SEGMENT_SIZE, length)

    limiting_fp = filelike.LimitingStream(in_fp, length)

    # Write the segment to Swift.
    self.stream_write(segment_path, limiting_fp)

    # We are only going to track keys to which data was confirmed written.
    bytes_written = limiting_fp.tell()
    if bytes_written > 0:
      updated_metadata[_SEGMENTS_KEY].append(_PartUploadMetadata(segment_path, offset,
                                                                 bytes_written))

    return bytes_written, updated_metadata

  def complete_chunked_upload(self, uuid, final_path, storage_metadata):
    """ Complete the chunked upload and store the final results in the path indicated.
        Returns nothing.
    """
    # Finally, we write an empty file at the proper location with a X-Object-Manifest
    # header pointing to the prefix for the segments.
    segments_prefix_path = self._normalize_path('%s/%s/' % (_SEGMENT_DIRECTORY, uuid))
    contained_segments_prefix_path = '%s/%s' % (self._swift_container, segments_prefix_path)

    self._put_object(final_path, '', headers={'X-Object-Manifest': contained_segments_prefix_path})

  def cancel_chunked_upload(self, uuid, storage_metadata):
    """ Cancel the chunked upload and clean up any outstanding partially uploaded data.
        Returns nothing.
    """
    # Delete all the uploaded segments.
    for segment in SwiftStorage._segment_list_from_metadata(storage_metadata):
      self.remove(segment.path)