import logging
import re

from flask import url_for, request, redirect, Response, abort as flask_abort

from app import storage, app, get_app_url, metric_queue, model_cache
from auth.registry_jwt_auth import process_registry_jwt_auth
from auth.permissions import ReadRepositoryPermission
from data import database
from data.registry_model import registry_model
from data.registry_model.blobuploader import (create_blob_upload, retrieve_blob_upload_manager,
                                              complete_when_uploaded, BlobUploadSettings,
                                              BlobUploadException, BlobTooLargeException,
                                              BlobRangeMismatchException)
from digest import digest_tools
from endpoints.decorators import anon_protect, parse_repository_name, check_region_blacklisted
from endpoints.v2 import v2_bp, require_repo_read, require_repo_write, get_input_stream
from endpoints.v2.errors import (
  BlobUnknown, BlobUploadInvalid, BlobUploadUnknown, Unsupported, NameUnknown, LayerTooLarge,
  InvalidRequest, BlobDownloadGeoBlocked)
from util.cache import cache_control
from util.names import parse_namespace_repository

logger = logging.getLogger(__name__)

BASE_BLOB_ROUTE = '/<repopath:repository>/blobs/<regex("{0}"):digest>'
BLOB_DIGEST_ROUTE = BASE_BLOB_ROUTE.format(digest_tools.DIGEST_PATTERN)
RANGE_HEADER_REGEX = re.compile(r'^bytes=([0-9]+)-([0-9]+)$')
BLOB_CONTENT_TYPE = 'application/octet-stream'


class _InvalidRangeHeader(Exception):
  pass


@v2_bp.route(BLOB_DIGEST_ROUTE, methods=['HEAD'])
@parse_repository_name()
@process_registry_jwt_auth(scopes=['pull'])
@require_repo_read
@anon_protect
@cache_control(max_age=31436000)
def check_blob_exists(namespace_name, repo_name, digest):
  # Find the blob.
  blob = registry_model.get_cached_repo_blob(model_cache, namespace_name, repo_name, digest)
  if blob is None:
    raise BlobUnknown()

  # Build the response headers.
  headers = {
    'Docker-Content-Digest': digest,
    'Content-Length': blob.compressed_size,
    'Content-Type': BLOB_CONTENT_TYPE,
  }

  # If our storage supports range requests, let the client know.
  if storage.get_supports_resumable_downloads(blob.placements):
    headers['Accept-Ranges'] = 'bytes'

  # Write the response to the client.
  return Response(headers=headers)


@v2_bp.route(BLOB_DIGEST_ROUTE, methods=['GET'])
@parse_repository_name()
@process_registry_jwt_auth(scopes=['pull'])
@require_repo_read
@anon_protect
@check_region_blacklisted(BlobDownloadGeoBlocked)
@cache_control(max_age=31536000)
def download_blob(namespace_name, repo_name, digest):
  # Find the blob.
  blob = registry_model.get_cached_repo_blob(model_cache, namespace_name, repo_name, digest)
  if blob is None:
    raise BlobUnknown()

  # Build the response headers.
  headers = {'Docker-Content-Digest': digest}

  # If our storage supports range requests, let the client know.
  if storage.get_supports_resumable_downloads(blob.placements):
    headers['Accept-Ranges'] = 'bytes'

  # Short-circuit by redirecting if the storage supports it.
  path = blob.storage_path
  logger.debug('Looking up the direct download URL for path: %s', path)
  direct_download_url = storage.get_direct_download_url(blob.placements, path, request.remote_addr)
  if direct_download_url:
    logger.debug('Returning direct download URL')
    resp = redirect(direct_download_url)
    resp.headers.extend(headers)
    return resp

  # Close the database connection before we stream the download.
  logger.debug('Closing database connection before streaming layer data')
  with database.CloseForLongOperation(app.config):
    # Stream the response to the client.
    return Response(
      storage.stream_read(blob.placements, path),
      headers=headers.update({
        'Content-Length': blob.compressed_size,
        'Content-Type': BLOB_CONTENT_TYPE,
      }),
    )


def _try_to_mount_blob(repository_ref, mount_blob_digest):
  """ Attempts to mount a blob requested by the user from another repository. """
  logger.debug('Got mount request for blob `%s` into `%s`', mount_blob_digest, repository_ref)
  from_repo = request.args.get('from', None)
  if from_repo is None:
    raise InvalidRequest

  # Ensure the user has access to the repository.
  logger.debug('Got mount request for blob `%s` under repository `%s` into `%s`',
               mount_blob_digest, from_repo, repository_ref)
  from_namespace, from_repo_name = parse_namespace_repository(from_repo,
                                                              app.config['LIBRARY_NAMESPACE'],
                                                              include_tag=False)

  from_repository_ref = registry_model.lookup_repository(from_namespace, from_repo_name)
  if from_repository_ref is None:
    logger.debug('Could not find from repo: `%s/%s`', from_namespace, from_repo_name)
    return None

  # First check permission.
  read_permission = ReadRepositoryPermission(from_namespace, from_repo_name).can()
  if not read_permission:
    # If no direct permission, check if the repostory is public.
    if not from_repository_ref.is_public:
      logger.debug('No permission to mount blob `%s` under repository `%s` into `%s`',
                   mount_blob_digest, from_repo, repository_ref)
      return None

  # Lookup if the mount blob's digest exists in the repository.
  mount_blob = registry_model.get_repo_blob_by_digest(from_repository_ref, mount_blob_digest)
  if mount_blob is None:
    logger.debug('Blob `%s` under repository `%s` not found', mount_blob_digest, from_repo)
    return None

  logger.debug('Mounting blob `%s` under repository `%s` into `%s`', mount_blob_digest,
               from_repo, repository_ref)

  # Mount the blob into the current repository and return that we've completed the operation.
  expiration_sec = app.config['PUSH_TEMP_TAG_EXPIRATION_SEC']
  mounted = registry_model.mount_blob_into_repository(mount_blob, repository_ref, expiration_sec)
  if not mounted:
    logger.debug('Could not mount blob `%s` under repository `%s` not found', mount_blob_digest,
                 from_repo)
    return

  # Return the response for the blob indicating that it was mounted, and including its content
  # digest.
  logger.debug('Mounted blob `%s` under repository `%s` into `%s`', mount_blob_digest,
               from_repo, repository_ref)

  namespace_name = repository_ref.namespace_name
  repo_name = repository_ref.name

  return Response(
    status=201,
    headers={
      'Docker-Content-Digest': mount_blob_digest,
      'Location':
        get_app_url() + url_for('v2.download_blob',
                                repository='%s/%s' % (namespace_name, repo_name),
                                digest=mount_blob_digest),
    },
  )


@v2_bp.route('/<repopath:repository>/blobs/uploads/', methods=['POST'])
@parse_repository_name()
@process_registry_jwt_auth(scopes=['pull', 'push'])
@require_repo_write
@anon_protect
def start_blob_upload(namespace_name, repo_name):
  repository_ref = registry_model.lookup_repository(namespace_name, repo_name)
  if repository_ref is None:
    raise NameUnknown()

  # Check for mounting of a blob from another repository.
  mount_blob_digest = request.args.get('mount', None)
  if mount_blob_digest is not None:
    response = _try_to_mount_blob(repository_ref, mount_blob_digest)
    if response is not None:
      return response

  # Begin the blob upload process.
  blob_uploader = create_blob_upload(repository_ref, storage, _upload_settings())
  if blob_uploader is None:
    logger.debug('Could not create a blob upload for `%s/%s`', namespace_name, repo_name)
    raise InvalidRequest()

  # Check if the blob will be uploaded now or in followup calls. If the `digest` is given, then
  # the upload will occur as a monolithic chunk in this call. Otherwise, we return a redirect
  # for the client to upload the chunks as distinct operations.
  digest = request.args.get('digest', None)
  if digest is None:
    # Short-circuit because the user will send the blob data in another request.
    return Response(
      status=202,
      headers={
        'Docker-Upload-UUID': blob_uploader.blob_upload_id,
        'Range': _render_range(0),
        'Location':
          get_app_url() + url_for('v2.upload_chunk',
                                  repository='%s/%s' % (namespace_name, repo_name),
                                  upload_uuid=blob_uploader.blob_upload_id)
      },
    )

  # Upload the data sent and commit it to a blob.
  with complete_when_uploaded(blob_uploader):
    _upload_chunk(blob_uploader, digest)

  # Write the response to the client.
  return Response(
    status=201,
    headers={
      'Docker-Content-Digest': digest,
      'Location':
        get_app_url() + url_for('v2.download_blob',
                                repository='%s/%s' % (namespace_name, repo_name),
                                digest=digest),
    },
  )


@v2_bp.route('/<repopath:repository>/blobs/uploads/<upload_uuid>', methods=['GET'])
@parse_repository_name()
@process_registry_jwt_auth(scopes=['pull'])
@require_repo_write
@anon_protect
def fetch_existing_upload(namespace_name, repo_name, upload_uuid):
  repository_ref = registry_model.lookup_repository(namespace_name, repo_name)
  if repository_ref is None:
    raise NameUnknown()

  uploader = retrieve_blob_upload_manager(repository_ref, upload_uuid, storage, _upload_settings())
  if uploader is None:
    raise BlobUploadUnknown()

  return Response(
    status=204,
    headers={
      'Docker-Upload-UUID': upload_uuid,
      'Range': _render_range(uploader.blob_upload.byte_count + 1),  # byte ranges are exclusive
    },
  )


@v2_bp.route('/<repopath:repository>/blobs/uploads/<upload_uuid>', methods=['PATCH'])
@parse_repository_name()
@process_registry_jwt_auth(scopes=['pull', 'push'])
@require_repo_write
@anon_protect
def upload_chunk(namespace_name, repo_name, upload_uuid):
  repository_ref = registry_model.lookup_repository(namespace_name, repo_name)
  if repository_ref is None:
    raise NameUnknown()

  uploader = retrieve_blob_upload_manager(repository_ref, upload_uuid, storage, _upload_settings())
  if uploader is None:
    raise BlobUploadUnknown()

  # Upload the chunk for the blob.
  _upload_chunk(uploader)

  # Write the response to the client.
  return Response(
    status=204,
    headers={
      'Location': _current_request_url(),
      'Range': _render_range(uploader.blob_upload.byte_count, with_bytes_prefix=False),
      'Docker-Upload-UUID': upload_uuid,
    },
  )


@v2_bp.route('/<repopath:repository>/blobs/uploads/<upload_uuid>', methods=['PUT'])
@parse_repository_name()
@process_registry_jwt_auth(scopes=['pull', 'push'])
@require_repo_write
@anon_protect
def monolithic_upload_or_last_chunk(namespace_name, repo_name, upload_uuid):
  # Ensure the digest is present before proceeding.
  digest = request.args.get('digest', None)
  if digest is None:
    raise BlobUploadInvalid(detail={'reason': 'Missing digest arg on monolithic upload'})

  # Find the upload.
  repository_ref = registry_model.lookup_repository(namespace_name, repo_name)
  if repository_ref is None:
    raise NameUnknown()

  uploader = retrieve_blob_upload_manager(repository_ref, upload_uuid, storage, _upload_settings())
  if uploader is None:
    raise BlobUploadUnknown()

  # Upload the chunk for the blob and commit it once complete.
  with complete_when_uploaded(uploader):
    _upload_chunk(uploader, digest)

  # Write the response to the client.
  return Response(status=201, headers={
    'Docker-Content-Digest': digest,
    'Location':
      get_app_url() + url_for('v2.download_blob',
                              repository='%s/%s' % (namespace_name, repo_name),
                              digest=digest),
    },
  )


@v2_bp.route('/<repopath:repository>/blobs/uploads/<upload_uuid>', methods=['DELETE'])
@parse_repository_name()
@process_registry_jwt_auth(scopes=['pull', 'push'])
@require_repo_write
@anon_protect
def cancel_upload(namespace_name, repo_name, upload_uuid):
  repository_ref = registry_model.lookup_repository(namespace_name, repo_name)
  if repository_ref is None:
    raise NameUnknown()

  uploader = retrieve_blob_upload_manager(repository_ref, upload_uuid, storage, _upload_settings())
  if uploader is None:
    raise BlobUploadUnknown()

  uploader.cancel_upload()
  return Response(status=204)


@v2_bp.route('/<repopath:repository>/blobs/<digest>', methods=['DELETE'])
@parse_repository_name()
@process_registry_jwt_auth(scopes=['pull', 'push'])
@require_repo_write
@anon_protect
def delete_digest(namespace_name, repo_name, upload_uuid):
  # We do not support deleting arbitrary digests, as they break repo images.
  raise Unsupported()


def _render_range(num_uploaded_bytes, with_bytes_prefix=True):
  """
  Returns a string formatted to be used in the Range header.
  """
  return '{0}0-{1}'.format('bytes=' if with_bytes_prefix else '', num_uploaded_bytes - 1)


def _current_request_url():
  return '{0}{1}{2}'.format(get_app_url(), request.script_root, request.path)


def _abort_range_not_satisfiable(valid_end, upload_uuid):
  """
  Writes a failure response for scenarios where the registry cannot function
  with the provided range.

  TODO(jzelinskie): Unify this with the V2RegistryException class.
  """
  flask_abort(
    Response(status=416, headers={
      'Location': _current_request_url(),
      'Range': '0-{0}'.format(valid_end),
      'Docker-Upload-UUID': upload_uuid}))


def _parse_range_header(range_header_text):
  """
  Parses the range header.

  Returns a tuple of the start offset and the length.
  If the parse fails, raises _InvalidRangeHeader.
  """
  found = RANGE_HEADER_REGEX.match(range_header_text)
  if found is None:
    raise _InvalidRangeHeader()

  start = int(found.group(1))
  length = int(found.group(2)) - start

  if length <= 0:
    raise _InvalidRangeHeader()

  return (start, length)


def _start_offset_and_length(range_header):
  """
  Returns a tuple of the start offset and the length.
  If the range header doesn't exist, defaults to (0, -1).
  If parsing fails, returns (None, None).
  """
  start_offset, length = 0, -1
  if range_header is not None:
    try:
      start_offset, length = _parse_range_header(range_header)
    except _InvalidRangeHeader:
      return None, None

  return start_offset, length


def _upload_settings():
  """ Returns the settings for instantiating a blob upload manager. """
  expiration_sec = app.config['PUSH_TEMP_TAG_EXPIRATION_SEC']
  settings = BlobUploadSettings(maximum_blob_size=app.config['MAXIMUM_LAYER_SIZE'],
                                bittorrent_piece_size=app.config['BITTORRENT_PIECE_SIZE'],
                                committed_blob_expiration=expiration_sec)
  return settings


def _upload_chunk(blob_uploader, commit_digest=None):
  """ Performs uploading of a chunk of data in the current request's stream, via the blob uploader
      given. If commit_digest is specified, the upload is committed to a blob once the stream's
      data has been read and stored.
  """
  start_offset, length = _start_offset_and_length(request.headers.get('range'))
  if None in {start_offset, length}:
    raise InvalidRequest()

  input_fp = get_input_stream(request)

  try:
    # Upload the data received.
    blob_uploader.upload_chunk(app.config, input_fp, start_offset, length, metric_queue)

    if commit_digest is not None:
      # Commit the upload to a blob.
      return blob_uploader.commit_to_blob(app.config, commit_digest)
  except BlobTooLargeException as ble:
    raise LayerTooLarge(uploaded=ble.uploaded, max_allowed=ble.max_allowed)
  except BlobRangeMismatchException:
    logger.exception('Exception when uploading blob to %s', blob_uploader.blob_upload_id)
    _abort_range_not_satisfiable(blob_uploader.blob_upload.byte_count,
                                 blob_uploader.blob_upload_id)
  except BlobUploadException:
    logger.exception('Exception when uploading blob to %s', blob_uploader.blob_upload_id)
    raise BlobUploadInvalid()