import logging
import json

from functools import wraps
from datetime import datetime
from time import time

from flask import make_response, request, session, Response, redirect, abort as flask_abort

from app import storage as store, app
from auth.auth_context import get_authenticated_user
from auth.decorators import extract_namespace_repo_from_session, process_auth
from auth.permissions import (ReadRepositoryPermission, ModifyRepositoryPermission)
from data import database
from data.registry_model import registry_model
from data.registry_model.blobuploader import upload_blob, BlobUploadSettings, BlobUploadException
from data.registry_model.manifestbuilder import lookup_manifest_builder
from digest import checksums
from endpoints.v1 import v1_bp, check_v1_push_enabled
from endpoints.v1.index import ensure_namespace_enabled
from endpoints.decorators import anon_protect, check_region_blacklisted
from util.http import abort, exact_abort
from util.registry.replication import queue_storage_replication

logger = logging.getLogger(__name__)


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']
    repository_ref = registry_model.lookup_repository(namespace, repository)
    if repository_ref is not None:
      legacy_image = registry_model.get_legacy_image(repository_ref, image_id)
      if legacy_image is not None and legacy_image.uploading:
        abort(400, 'Image %(image_id)s is being uploaded, retry later', issue='upload-in-progress',
              image_id=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


@v1_bp.route('/images/<image_id>/layer', methods=['HEAD'])
@process_auth
@extract_namespace_repo_from_session
@ensure_namespace_enabled
@require_completion
@set_cache_headers
@anon_protect
def head_image_layer(namespace, repository, image_id, headers):
  permission = ReadRepositoryPermission(namespace, repository)
  repository_ref = registry_model.lookup_repository(namespace, repository, kind_filter='image')

  logger.debug('Checking repo permissions')
  if permission.can() or (repository_ref is not None and repository_ref.is_public):
    if repository_ref is None:
      abort(404)

    logger.debug('Looking up placement locations')
    legacy_image = registry_model.get_legacy_image(repository_ref, image_id, include_blob=True)
    if legacy_image is None:
      logger.debug('Could not find any blob placement locations')
      abort(404, 'Image %(image_id)s not found', issue='unknown-image', image_id=image_id)

    # Add the Accept-Ranges header if the storage engine supports resumable
    # downloads.
    extra_headers = {}
    if store.get_supports_resumable_downloads(legacy_image.blob.placements):
      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)


@v1_bp.route('/images/<image_id>/layer', methods=['GET'])
@process_auth
@extract_namespace_repo_from_session
@ensure_namespace_enabled
@require_completion
@set_cache_headers
@check_region_blacklisted()
@anon_protect
def get_image_layer(namespace, repository, image_id, headers):
  permission = ReadRepositoryPermission(namespace, repository)
  repository_ref = registry_model.lookup_repository(namespace, repository, kind_filter='image')

  logger.debug('Checking repo permissions')
  if permission.can() or (repository_ref is not None and repository_ref.is_public):
    if repository_ref is None:
      abort(404)

    legacy_image = registry_model.get_legacy_image(repository_ref, image_id, include_blob=True)
    if legacy_image is None:
      abort(404, 'Image %(image_id)s not found', issue='unknown-image', image_id=image_id)

    path = legacy_image.blob.storage_path

    try:
      logger.debug('Looking up the direct download URL for path: %s', path)
      direct_download_url = store.get_direct_download_url(legacy_image.blob.placements, path,
                                                          request.remote_addr)
      if direct_download_url:
        logger.debug('Returning direct download URL')
        resp = redirect(direct_download_url)
        return resp

      # Close the database handle here for this process before we send the long download.
      database.close_db_filter(None)
      logger.debug('Streaming layer data')
      return Response(store.stream_read(legacy_image.blob.placements, 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)


@v1_bp.route('/images/<image_id>/layer', methods=['PUT'])
@process_auth
@extract_namespace_repo_from_session
@check_v1_push_enabled()
@ensure_namespace_enabled
@anon_protect
def put_image_layer(namespace, repository, image_id):
  logger.debug('Checking repo permissions')
  permission = ModifyRepositoryPermission(namespace, repository)
  if not permission.can():
    abort(403)

  repository_ref = registry_model.lookup_repository(namespace, repository, kind_filter='image')
  if repository_ref is None:
    abort(403)

  logger.debug('Checking for image in manifest builder')
  builder = lookup_manifest_builder(repository_ref, session.get('manifest_builder'), store)
  if builder is None:
    abort(400)

  layer = builder.lookup_layer(image_id)
  if layer is None:
    abort(404)

  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']

  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)

  extra_handlers = []

  # 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 = bool(builder.get_layer_checksums(layer))
  if requires_tarsum:
    tmp, tmp_hndlr = store.temp_store_handler()
    extra_handlers.append(tmp_hndlr)

  # Add a handler which computes the simple Docker V1 checksum.
  h, sum_hndlr = checksums.simple_checksum_handler(layer.v1_metadata_string)
  extra_handlers.append(sum_hndlr)

  uploaded_blob = None
  try:
    with upload_blob(repository_ref, store, settings,
                     extra_blob_stream_handlers=extra_handlers) as manager:
      manager.upload_chunk(app.config, input_stream)
      uploaded_blob = manager.commit_to_blob(app.config)
  except BlobUploadException:
    logger.exception('Exception when writing image data')
    abort(520, 'Image %(image_id)s could not be written. Please try again.', image_id=image_id)

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

  try:
    if requires_tarsum:
      tmp.seek(0)
      csums.append(checksums.compute_tarsum(tmp, layer.v1_metadata_string))
      tmp.close()
  except (IOError, checksums.TarError) as exc:
    logger.debug('put_image_layer: Error when computing tarsum %s', exc)

  # If there was already a precomputed checksum, validate against it now.
  if builder.get_layer_checksums(layer):
    checksum = builder.get_layer_checksums(layer)[0]
    if not builder.validate_layer_checksum(layer, checksum):
      logger.debug('put_image_checksum: Wrong checksum. Given: %s and expected: %s', checksum,
                   builder.get_layer_checksums(layer))
      abort(400, 'Checksum mismatch for image: %(image_id)s', issue='checksum-mismatch',
            image_id=image_id)

  # Assign the blob to the layer in the manifest.
  if not builder.assign_layer_blob(layer, uploaded_blob, csums):
    abort(500, 'Something went wrong')

  # Send a job to the work queue to replicate the image layer.
  # TODO: move this into a better place.
  queue_storage_replication(namespace, uploaded_blob)

  return make_response('true', 200)


@v1_bp.route('/images/<image_id>/checksum', methods=['PUT'])
@process_auth
@extract_namespace_repo_from_session
@check_v1_push_enabled()
@ensure_namespace_enabled
@anon_protect
def put_image_checksum(namespace, repository, image_id):
  logger.debug('Checking repo permissions')
  permission = ModifyRepositoryPermission(namespace, repository)
  if not permission.can():
    abort(403)

  repository_ref = registry_model.lookup_repository(namespace, repository, kind_filter='image')
  if repository_ref is None:
    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')

  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)

  logger.debug('Checking for image in manifest builder')
  builder = lookup_manifest_builder(repository_ref, session.get('manifest_builder'), store)
  if builder is None:
    abort(400)

  layer = builder.lookup_layer(image_id)
  if layer is None:
    abort(404)

  if old_checksum:
    builder.save_precomputed_checksum(layer, checksum)
    return make_response('true', 200)

  if not builder.validate_layer_checksum(layer, checksum):
    logger.debug('put_image_checksum: Wrong checksum. Given: %s and expected: %s', checksum,
                 builder.get_layer_checksums(layer))
    abort(400, 'Checksum mismatch for image: %(image_id)s', issue='checksum-mismatch',
          image_id=image_id)

  return make_response('true', 200)


@v1_bp.route('/images/<image_id>/json', methods=['GET'])
@process_auth
@extract_namespace_repo_from_session
@ensure_namespace_enabled
@require_completion
@set_cache_headers
@anon_protect
def get_image_json(namespace, repository, image_id, headers):
  logger.debug('Checking repo permissions')
  permission = ReadRepositoryPermission(namespace, repository)
  repository_ref = registry_model.lookup_repository(namespace, repository, kind_filter='image')
  if not permission.can() and not (repository_ref is not None and repository_ref.is_public):
    abort(403)

  logger.debug('Looking up repo image')
  legacy_image = registry_model.get_legacy_image(repository_ref, image_id, include_blob=True)
  if legacy_image is None:
    flask_abort(404)

  size = legacy_image.blob.compressed_size
  if size is not None:
    # Note: X-Docker-Size is optional and we *can* end up with a NULL image_size,
    # so handle this case rather than failing.
    headers['X-Docker-Size'] = str(size)

  response = make_response(legacy_image.v1_metadata_string, 200)
  response.headers.extend(headers)
  return response


@v1_bp.route('/images/<image_id>/ancestry', methods=['GET'])
@process_auth
@extract_namespace_repo_from_session
@ensure_namespace_enabled
@require_completion
@set_cache_headers
@anon_protect
def get_image_ancestry(namespace, repository, image_id, headers):
  logger.debug('Checking repo permissions')
  permission = ReadRepositoryPermission(namespace, repository)
  repository_ref = registry_model.lookup_repository(namespace, repository, kind_filter='image')
  if not permission.can() and not (repository_ref is not None and repository_ref.is_public):
    abort(403)

  logger.debug('Looking up repo image')
  legacy_image = registry_model.get_legacy_image(repository_ref, image_id, include_parents=True)
  if legacy_image is None:
    abort(404, 'Image %(image_id)s not found', issue='unknown-image', image_id=image_id)

  # NOTE: We can not use jsonify here because we are returning a list not an object.
  ancestor_ids = ([legacy_image.docker_image_id] + 
                  [a.docker_image_id for a in legacy_image.parents])
  response = make_response(json.dumps(ancestor_ids), 200)
  response.headers.extend(headers)
  return response


@v1_bp.route('/images/<image_id>/json', methods=['PUT'])
@process_auth
@extract_namespace_repo_from_session
@check_v1_push_enabled()
@ensure_namespace_enabled
@anon_protect
def put_image_json(namespace, repository, image_id):
  logger.debug('Checking repo permissions')
  permission = ModifyRepositoryPermission(namespace, repository)
  if not permission.can():
    abort(403)

  repository_ref = registry_model.lookup_repository(namespace, repository, kind_filter='image')
  if repository_ref is None:
    abort(403)

  builder = lookup_manifest_builder(repository_ref, session.get('manifest_builder'), store)
  if builder is None:
    abort(400)

  logger.debug('Parsing image JSON')
  try:
    uploaded_metadata = request.data
    data = json.loads(uploaded_metadata.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)

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

  logger.debug('Looking up repo image')
  location_pref = store.preferred_locations[0]
  username = get_authenticated_user() and get_authenticated_user().username
  layer = builder.start_layer(image_id, uploaded_metadata, location_pref, username,
                              app.config['PUSH_TEMP_TAG_EXPIRATION_SEC'])
  if layer is None:
    abort(400, 'Image %(image_id)s has invalid metadata',
          issue='invalid-request', image_id=image_id)

  return make_response('true', 200)