import logging
import json

from flask import (make_response, request, session, Response, redirect,
                   Blueprint, abort as flask_abort)
from functools import wraps
from datetime import datetime
from time import time

from app import storage as store, image_diff_queue, app
from auth.auth import process_auth, extract_namespace_repo_from_session
from auth.auth_context import get_authenticated_user, get_grant_user_context
from util import checksums, changes
from util.http import abort, exact_abort
from auth.permissions import (ReadRepositoryPermission,
                              ModifyRepositoryPermission)
from data import model, database
from util import gzipstream


registry = Blueprint('registry', __name__)

logger = logging.getLogger(__name__)

class SocketReader(object):
  def __init__(self, fp):
    self._fp = fp
    self.handlers = []

  def add_handler(self, handler):
    self.handlers.append(handler)

  def read(self, n=-1):
    buf = self._fp.read(n)
    if not buf:
      return ''
    for handler in self.handlers:
      handler(buf)
    return buf

  def tell(self):
    raise IOError('Stream is not seekable.')


def image_is_uploading(repo_image):
  if repo_image is None:
    return False

  return repo_image.storage.uploading


def set_uploading_flag(repo_image, is_image_uploading):
  repo_image.storage.uploading = is_image_uploading
  repo_image.storage.save()


def require_completion(f):
  """This make sure that the image push correctly finished."""
  @wraps(f)
  def wrapper(namespace, repository, *args, **kwargs):
    image_id = kwargs['image_id']
    repo_image = model.get_repo_image_extended(namespace, repository, image_id)
    if image_is_uploading(repo_image):
      abort(400, 'Image %(image_id)s is being uploaded, retry later',
            issue='upload-in-progress', image_id=kwargs['image_id'])

    return f(namespace, repository, *args, **kwargs)
  return wrapper


def set_cache_headers(f):
  """Returns HTTP headers suitable for caching."""
  @wraps(f)
  def wrapper(*args, **kwargs):
    # Set TTL to 1 year by default
    ttl = 31536000
    expires = datetime.fromtimestamp(int(time()) + ttl)
    expires = expires.strftime('%a, %d %b %Y %H:%M:%S GMT')
    headers = {
      'Cache-Control': 'public, max-age={0}'.format(ttl),
      'Expires': expires,
      'Last-Modified': 'Thu, 01 Jan 1970 00:00:00 GMT',
    }
    if 'If-Modified-Since' in request.headers:
      response = make_response('Not modified', 304)
      response.headers.extend(headers)
      return response
    kwargs['headers'] = headers
    # Prevent the Cookie to be sent when the object is cacheable
    session.modified = False
    return f(*args, **kwargs)
  return wrapper


@registry.route('/images/<image_id>/layer', methods=['HEAD'])
@process_auth
@extract_namespace_repo_from_session
@require_completion
@set_cache_headers
def head_image_layer(namespace, repository, image_id, headers):
  permission = ReadRepositoryPermission(namespace, repository)

  logger.debug('Checking repo permissions')
  if permission.can() or model.repository_is_public(namespace, repository):
    logger.debug('Looking up repo image')
    repo_image = model.get_repo_image_extended(namespace, repository, image_id)
    if not repo_image:
      logger.debug('Image not found')
      abort(404, 'Image %(image_id)s not found', issue='unknown-image',
            image_id=image_id)

    extra_headers = {}

    # Add the Accept-Ranges header if the storage engine supports resumable
    # downloads.
    if store.get_supports_resumable_downloads(repo_image.storage.locations):
      logger.debug('Storage supports resumable downloads')
      extra_headers['Accept-Ranges'] = 'bytes'

    resp = make_response('')
    resp.headers.extend(headers)
    resp.headers.extend(extra_headers)
    return resp

  abort(403)


@registry.route('/images/<image_id>/layer', methods=['GET'])
@process_auth
@extract_namespace_repo_from_session
@require_completion
@set_cache_headers
def get_image_layer(namespace, repository, image_id, headers):
  permission = ReadRepositoryPermission(namespace, repository)

  logger.debug('Checking repo permissions')
  if permission.can() or model.repository_is_public(namespace, repository):
    logger.debug('Looking up repo image')
    repo_image = model.get_repo_image_extended(namespace, repository, image_id)
    if not repo_image:
      logger.debug('Image not found')
      abort(404, 'Image %(image_id)s not found', issue='unknown-image',
            image_id=image_id)

    logger.debug('Looking up the layer path')
    try:
      path = store.image_layer_path(repo_image.storage.uuid)

      logger.debug('Looking up the direct download URL')
      direct_download_url = store.get_direct_download_url(repo_image.storage.locations, path)

      if direct_download_url:
        logger.debug('Returning direct download URL')
        resp = redirect(direct_download_url)
        return resp

      logger.debug('Streaming layer data')

      # Close the database handle here for this process before we send the long download.
      database.close_db_filter(None)

      return Response(store.stream_read(repo_image.storage.locations, path), headers=headers)
    except (IOError, AttributeError):
      logger.exception('Image layer data not found')
      abort(404, 'Image %(image_id)s not found', issue='unknown-image',
            image_id=image_id)

  abort(403)


@registry.route('/images/<image_id>/layer', methods=['PUT'])
@process_auth
@extract_namespace_repo_from_session
def put_image_layer(namespace, repository, image_id):
  logger.debug('Checking repo permissions')
  permission = ModifyRepositoryPermission(namespace, repository)
  if not permission.can():
    abort(403)

  logger.debug('Retrieving image')
  repo_image = model.get_repo_image_extended(namespace, repository, image_id)
  try:
    logger.debug('Retrieving image data')
    uuid = repo_image.storage.uuid
    json_data = store.get_content(repo_image.storage.locations, store.image_json_path(uuid))
  except (IOError, AttributeError):
    logger.exception('Exception when retrieving image data')
    abort(404, 'Image %(image_id)s not found', issue='unknown-image',
          image_id=image_id)

  logger.debug('Retrieving image path info')
  layer_path = store.image_layer_path(uuid)

  if (store.exists(repo_image.storage.locations, layer_path) and not
      image_is_uploading(repo_image)):
    exact_abort(409, 'Image already exists')

  logger.debug('Storing layer data')

  input_stream = request.stream
  if request.headers.get('transfer-encoding') == 'chunked':
    # Careful, might work only with WSGI servers supporting chunked
    # encoding (Gunicorn)
    input_stream = request.environ['wsgi.input']

  # Create a socket reader to read the input stream containing the layer data.
  sr = SocketReader(input_stream)

  # Add a handler that copies the data into a temp file. This is used to calculate the tarsum,
  # which is only needed for older versions of Docker.
  requires_tarsum = session.get('checksum_format') == 'tarsum'
  if requires_tarsum:
    tmp, tmp_hndlr = store.temp_store_handler()
    sr.add_handler(tmp_hndlr)

  # Add a handler to compute the compressed and uncompressed sizes of the layer.
  size_info, size_hndlr = gzipstream.calculate_size_handler()
  sr.add_handler(size_hndlr)

  # Add a handler which computes the checksum.
  h, sum_hndlr = checksums.simple_checksum_handler(json_data)
  sr.add_handler(sum_hndlr)

  # Stream write the data to storage.
  with database.CloseForLongOperation(app.config):
    store.stream_write(repo_image.storage.locations, layer_path, sr)

  # Append the computed checksum.
  csums = []
  csums.append('sha256:{0}'.format(h.hexdigest()))

  try:
    # Save the size of the image.
    model.set_image_size(image_id, namespace, repository, size_info.compressed_size,
                         size_info.uncompressed_size)

    if requires_tarsum:
      tmp.seek(0)
      csums.append(checksums.compute_tarsum(tmp, json_data))
      tmp.close()

  except (IOError, checksums.TarError) as e:
    logger.debug('put_image_layer: Error when computing tarsum '
                 '{0}'.format(e))

  if repo_image.storage.checksum is None:
    # We don't have a checksum stored yet, that's fine skipping the check.
    # Not removing the mark though, image is not downloadable yet.
    session['checksum'] = csums
    return make_response('true', 200)

  checksum = repo_image.storage.checksum

  # We check if the checksums provided matches one the one we computed
  if checksum not in csums:
    logger.warning('put_image_layer: Wrong checksum')
    abort(400, 'Checksum mismatch; ignoring the layer for image %(image_id)s',
          issue='checksum-mismatch', image_id=image_id)

  # Checksum is ok, we remove the marker
  set_uploading_flag(repo_image, False)

  # The layer is ready for download, send a job to the work queue to
  # process it.
  logger.debug('Adding layer to diff queue')
  repo = model.get_repository(namespace, repository)
  image_diff_queue.put([repo.namespace_user.username, repository, image_id], json.dumps({
    'namespace_user_id': repo.namespace_user.id,
    'repository': repository,
    'image_id': image_id,
  }))

  return make_response('true', 200)


@registry.route('/images/<image_id>/checksum', methods=['PUT'])
@process_auth
@extract_namespace_repo_from_session
def put_image_checksum(namespace, repository, image_id):
  logger.debug('Checking repo permissions')
  permission = ModifyRepositoryPermission(namespace, repository)
  if not permission.can():
    abort(403)

  # Docker Version < 0.10 (tarsum+sha):
  old_checksum = request.headers.get('X-Docker-Checksum')

  # Docker Version >= 0.10 (sha):
  new_checksum = request.headers.get('X-Docker-Checksum-Payload')

  # Store whether we need to calculate the tarsum.
  if new_checksum:
    session['checksum_format'] = 'sha256'
  else:
    session['checksum_format'] = 'tarsum'

  checksum = new_checksum or old_checksum
  if not checksum:
    abort(400, "Missing checksum for image %(image_id)s", issue='missing-checksum',
          image_id=image_id)

  if not session.get('checksum'):
    abort(400, 'Checksum not found in Cookie for image %(image_id)s',
          issue='missing-checksum-cookie', image_id=image_id)

  logger.debug('Looking up repo image')
  repo_image = model.get_repo_image_extended(namespace, repository, image_id)
  if not repo_image or not repo_image.storage:
    abort(404, 'Image not found: %(image_id)s', issue='unknown-image', image_id=image_id)

  uuid = repo_image.storage.uuid

  logger.debug('Looking up repo layer data')
  if not store.exists(repo_image.storage.locations, store.image_json_path(uuid)):
    abort(404, 'Image not found: %(image_id)s', issue='unknown-image', image_id=image_id)

  logger.debug('Marking image path')
  if not image_is_uploading(repo_image):
    abort(409, 'Cannot set checksum for image %(image_id)s',
          issue='image-write-error', image_id=image_id)

  logger.debug('Storing image checksum')
  err = store_checksum(repo_image.storage, checksum)
  if err:
    abort(400, err)

  if checksum not in session.get('checksum', []):
    logger.debug('session checksums: %s' % session.get('checksum', []))
    logger.debug('client supplied checksum: %s' % checksum)
    logger.debug('put_image_checksum: Wrong checksum')
    abort(400, 'Checksum mismatch for image: %(image_id)s',
          issue='checksum-mismatch', image_id=image_id)

  # Checksum is ok, we remove the marker
  set_uploading_flag(repo_image, False)

  # The layer is ready for download, send a job to the work queue to
  # process it.
  logger.debug('Adding layer to diff queue')
  repo = model.get_repository(namespace, repository)
  image_diff_queue.put([repo.namespace_user.username, repository, image_id], json.dumps({
    'namespace_user_id': repo.namespace_user.id,
    'repository': repository,
    'image_id': image_id,
  }))

  return make_response('true', 200)


@registry.route('/images/<image_id>/json', methods=['GET'])
@process_auth
@extract_namespace_repo_from_session
@require_completion
@set_cache_headers
def get_image_json(namespace, repository, image_id, headers):
  logger.debug('Checking repo permissions')
  permission = ReadRepositoryPermission(namespace, repository)
  if not permission.can() and not model.repository_is_public(namespace,
                                                             repository):
    abort(403)

  logger.debug('Looking up repo image')
  repo_image = model.get_repo_image_extended(namespace, repository, image_id)

  logger.debug('Looking up repo layer data')
  try:
    uuid = repo_image.storage.uuid
    data = store.get_content(repo_image.storage.locations, store.image_json_path(uuid))
  except (IOError, AttributeError):
    flask_abort(404)

  logger.debug('Looking up repo layer size')
  size = repo_image.storage.image_size
  headers['X-Docker-Size'] = str(size)

  response = make_response(data, 200)
  response.headers.extend(headers)
  return response


@registry.route('/images/<image_id>/ancestry', methods=['GET'])
@process_auth
@extract_namespace_repo_from_session
@require_completion
@set_cache_headers
def get_image_ancestry(namespace, repository, image_id, headers):
  logger.debug('Checking repo permissions')
  permission = ReadRepositoryPermission(namespace, repository)
  if not permission.can() and not model.repository_is_public(namespace,
                                                             repository):
    abort(403)

  logger.debug('Looking up repo image')
  repo_image = model.get_repo_image_extended(namespace, repository, image_id)

  logger.debug('Looking up image data')
  try:
    uuid = repo_image.storage.uuid
    data = store.get_content(repo_image.storage.locations, store.image_ancestry_path(uuid))
  except (IOError, AttributeError):
    abort(404, 'Image %(image_id)s not found', issue='unknown-image',
          image_id=image_id)

  logger.debug('Converting to <-> from JSON')
  response = make_response(json.dumps(json.loads(data)), 200)
  response.headers.extend(headers)

  logger.debug('Done')
  return response


def generate_ancestry(image_id, uuid, locations, parent_id=None, parent_uuid=None,
                      parent_locations=None):
  if not parent_id:
    store.put_content(locations, store.image_ancestry_path(uuid), json.dumps([image_id]))
    return

  data = store.get_content(parent_locations, store.image_ancestry_path(parent_uuid))
  data = json.loads(data)
  data.insert(0, image_id)
  store.put_content(locations, store.image_ancestry_path(uuid), json.dumps(data))


def store_checksum(image_storage, checksum):
  checksum_parts = checksum.split(':')
  if len(checksum_parts) != 2:
    return 'Invalid checksum format'

  # We store the checksum
  image_storage.checksum = checksum
  image_storage.save()


@registry.route('/images/<image_id>/json', methods=['PUT'])
@process_auth
@extract_namespace_repo_from_session
def put_image_json(namespace, repository, image_id):
  logger.debug('Checking repo permissions')
  permission = ModifyRepositoryPermission(namespace, repository)
  if not permission.can():
    abort(403)

  logger.debug('Parsing image JSON')
  try:
    data = json.loads(request.data.decode('utf8'))
  except ValueError:
    pass

  if not data or not isinstance(data, dict):
    abort(400, 'Invalid JSON for image: %(image_id)s\nJSON: %(json)s',
          issue='invalid-request', image_id=image_id, json=request.data)

  if 'id' not in data:
    abort(400, 'Missing key `id` in JSON for image: %(image_id)s',
          issue='invalid-request', image_id=image_id)

  logger.debug('Looking up repo image')

  repo = model.get_repository(namespace, repository)
  if repo is None:
    abort(404, 'Repository does not exist: %(namespace)s/%(repository)s', issue='no-repo',
          namespace=namespace, repository=repository)

  repo_image = model.get_repo_image_extended(namespace, repository, image_id)
  if not repo_image:
    username = (get_authenticated_user() and get_authenticated_user().username or
                get_grant_user_context())
    logger.debug('Image not found, creating image with initiating user context: %s', username)
    repo_image = model.find_create_or_link_image(image_id, repo, username, {},
                                                 store.preferred_locations[0])

  # Create a temporary tag to prevent this image from getting garbage collected while the push
  # is in progress.
  model.create_temporary_hidden_tag(repo, repo_image, app.config['PUSH_TEMP_TAG_EXPIRATION_SEC'])

  uuid = repo_image.storage.uuid

  if image_id != data['id']:
    abort(400, 'JSON data contains invalid id for image: %(image_id)s',
          issue='invalid-request', image_id=image_id)

  parent_id = data.get('parent')

  parent_image = None
  if parent_id:
    logger.debug('Looking up parent image')
    parent_image = model.get_repo_image_extended(namespace, repository, parent_id)

  parent_uuid = parent_image and parent_image.storage.uuid
  parent_locations = parent_image and parent_image.storage.locations

  if parent_id:
    logger.debug('Looking up parent image data')

  if (parent_id and not
      store.exists(parent_locations, store.image_json_path(parent_uuid))):
    abort(400, 'Image %(image_id)s depends on non existing parent image %(parent_id)s',
          issue='invalid-request', image_id=image_id, parent_id=parent_id)

  logger.debug('Looking up image storage paths')
  json_path = store.image_json_path(uuid)

  logger.debug('Checking if image already exists')
  if (store.exists(repo_image.storage.locations, json_path) and not
      image_is_uploading(repo_image)):
    exact_abort(409, 'Image already exists')

  set_uploading_flag(repo_image, True)

  # If we reach that point, it means that this is a new image or a retry
  # on a failed push
  # save the metadata
  command_list = data.get('container_config', {}).get('Cmd', None)
  command = json.dumps(command_list) if command_list else None

  logger.debug('Setting image metadata')
  model.set_image_metadata(image_id, namespace, repository,
                           data.get('created'), data.get('comment'), command,
                           parent_image)

  logger.debug('Putting json path')
  store.put_content(repo_image.storage.locations, json_path, request.data)

  logger.debug('Generating image ancestry')

  try:
    generate_ancestry(image_id, uuid, repo_image.storage.locations, parent_id, parent_uuid,
                      parent_locations)
  except IOError as ioe:
    logger.debug('Error when generating ancestry: %s' % ioe.message)
    abort(404)

  logger.debug('Done')
  return make_response('true', 200)


def process_image_changes(namespace, repository, image_id):
  logger.debug('Generating diffs for image: %s' % image_id)

  repo_image = model.get_repo_image_extended(namespace, repository, image_id)
  if not repo_image:
    logger.warning('No image for id: %s', image_id)
    return None, None

  uuid = repo_image.storage.uuid

  image_diffs_path = store.image_file_diffs_path(uuid)
  image_trie_path = store.image_file_trie_path(uuid)

  if store.exists(repo_image.storage.locations, image_diffs_path):
    logger.debug('Diffs already exist for image: %s' % image_id)
    return image_trie_path, repo_image.storage.locations

  image = model.get_image_by_id(namespace, repository, image_id)
  parents = model.get_parent_images(namespace, repository, image)

  # Compute the diffs and fs for the parent first if necessary
  parent_trie_path = None
  if parents:
    parent_trie_path, parent_locations = process_image_changes(namespace, repository,
                                                               parents[-1].docker_image_id)

  # Read in the collapsed layer state of the filesystem for the parent
  parent_trie = changes.empty_fs()
  if parent_trie_path:
    parent_trie_bytes = store.get_content(parent_locations, parent_trie_path)
    parent_trie.frombytes(parent_trie_bytes)

  # Read in the file entries from the layer tar file
  layer_path = store.image_layer_path(uuid)
  with store.stream_read_file(image.storage.locations, layer_path) as layer_tar_stream:
    removed_files = set()
    layer_files = changes.files_and_dirs_from_tar(layer_tar_stream,
                                                  removed_files)

    new_metadata = changes.compute_new_diffs_and_fs(parent_trie, layer_files,
                                                    removed_files)
  (new_trie, added, changed, removed) = new_metadata

  # Write out the new trie
  store.put_content(image.storage.locations, image_trie_path, new_trie.tobytes())

  # Write out the diffs
  diffs = {}
  sections = ('added', 'changed', 'removed')
  for section, source_trie in zip(sections, new_metadata[1:]):
    diffs[section] = list(source_trie)
    diffs[section].sort()
  store.put_content(image.storage.locations, image_diffs_path, json.dumps(diffs, indent=2))

  return image_trie_path, image.storage.locations