text: # -*- coding: utf-8 -*-
  
  from __future__ import division, print_function
  
  __copyright__ = "Copyright (C) 2014 Andreas Kloeckner"
  
  __license__ = """
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
  
  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.
  
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  THE SOFTWARE.
  """
  
  import re
  import datetime
  import six
  import sys
  
  from django.core.exceptions import ObjectDoesNotExist
  from django.utils.html import escape
  from django.utils.translation import (
          ugettext_lazy as _, ugettext, string_concat)
  
  from course.content import get_repo_blob
  from relate.utils import Struct
  
  
  # {{{ validation tools
  
  class ValidationError(RuntimeError):
      pass
  
  
  ID_RE = re.compile(r"^[\w]+$")
  
  
  def validate_identifier(ctx, location, s, warning_only=False):
      if not ID_RE.match(s):
  
          if warning_only:
              msg = (string_concat(
                          _("invalid identifier"),
                          " '%(string)s'")
                      % {'location': location, 'string': s})
  
              ctx.add_warning(location, msg)
          else:
              msg = (string_concat(
                          "%(location)s: ",
                          _("invalid identifier"),
                          " '%(string)s'")
                      % {'location': location, 'string': s})
  
              raise ValidationError(msg)
  
  
  def validate_role(location, role):
      from course.constants import participation_role
  
      if role not in [
              participation_role.instructor,
              participation_role.teaching_assistant,
              participation_role.student,
              participation_role.unenrolled,
              ]:
          raise ValidationError(
                  string_concat("%(location)s: ",
                      _("invalid role '%(role)s'"))
                  % {'location': location, 'role': role})
  
  
  def validate_facility(ctx, location, facility):
      from django.conf import settings
      facilities = getattr(settings, "RELATE_FACILITIES", None)
      if facilities is None:
          return
  
      if facility not in facilities:
          ctx.add_warning(location, _(
              "Name of facility not recognized: '%(fac_name)s'. "
              "Known facility names: '%(known_fac_names)s'")
              % {
                  "fac_name": facility,
                  "known_fac_names": ", ".join(facilities),
                  })
  
  
  def validate_struct(ctx, location, obj, required_attrs, allowed_attrs):
      """
      :arg required_attrs: an attribute validation list (see below)
      :arg allowed_attrs: an attribute validation list (see below)
  
      An attribute validation list is a list of elements, where each element is
      either a string (the name of the attribute), in which case the type of each
      attribute is not checked, or a tuple *(name, type)*, where type is valid
      as a second argument to :func:`isinstance`.
      """
  
      if not isinstance(obj, Struct):
          raise ValidationError(
                  "%s: not a key-value map" % location)
  
      present_attrs = set(name for name in dir(obj) if not name.startswith("_"))
  
      for required, attr_list in [
              (True, required_attrs),
              (False, allowed_attrs),
              ]:
          for attr_rec in attr_list:
              if isinstance(attr_rec, tuple):
                  attr, allowed_types = attr_rec
              else:
                  attr = attr_rec
                  allowed_types = None
  
              if attr not in present_attrs:
                  if required:
                      raise ValidationError(
                              string_concat("%(location)s: ",
                                  _("attribute '%(attr)s' missing"))
                              % {'location': location, 'attr': attr})
              else:
                  present_attrs.remove(attr)
                  val = getattr(obj, attr)
  
                  is_markup = False
                  if allowed_types == "markup":
                      allowed_types = str
                      is_markup = True
  
                  if allowed_types == str:
                      # Love you, too, Python 2.
                      allowed_types = six.string_types
  
                  if not isinstance(val, allowed_types):
                      raise ValidationError(
                              string_concat("%(location)s: ",
                                  _("attribute '%(attr)s' has "
                                      "wrong type: got '%(name)s', "
                                      "expected '%(allowed)s'"))
                              % {
                                  'location': location,
                                  'attr': attr,
                                  'name': type(val).__name__,
                                  'allowed': escape(str(allowed_types))})
  
                  if is_markup:
                      validate_markup(ctx, "%s: attribute %s" % (location, attr), val)
  
      if present_attrs:
          raise ValidationError(
                  string_concat("%(location)s: ",
                      _("extraneous attribute(s) '%(attr)s'"))
                  % {'location': location, 'attr': ",".join(present_attrs)})
  
  
  datespec_types = (datetime.date, six.string_types, datetime.datetime)
  
  # }}}
  
  
  class ValidationWarning(object):
      def __init__(self, location, text):
          self.location = location
          self.text = text
  
  
  class ValidationContext(object):
      """
      .. attribute:: repo
      .. attribute:: commit_sha
      .. attribute:: course
  
          A :class:`course.models.Course` instance, or *None*, if no database
          is currently available.
      """
  
      def __init__(self, repo, commit_sha, course=None):
          self.repo = repo
          self.commit_sha = commit_sha
          self.course = course
  
          self.warnings = []
  
      def encounter_datespec(self, location, datespec):
          from course.content import parse_date_spec
          parse_date_spec(self.course, datespec, vctx=self, location=location)
  
      def add_warning(self, *args, **kwargs):
          self.warnings.append(ValidationWarning(*args, **kwargs))
  
  
  # {{{ course page validation
  
  def validate_markup(ctx, location, markup_str):
      def reverse_func(*args, **kwargs):
          pass
  
      from course.content import markup_to_html
      try:
          markup_to_html(
                  course=None,
                  repo=ctx.repo,
                  commit_sha=ctx.commit_sha,
                  text=markup_str,
                  reverse_func=reverse_func,
                  validate_only=True)
      except:
          from traceback import print_exc
          print_exc()
  
          tp, e, _ = sys.exc_info()
  
          raise ValidationError(
                  "%(location)s: %(err_type)s: %(err_str)s" % {
                      'location': location,
                      "err_type": tp.__name__,
                      "err_str": str(e)})
  
  
  def validate_chunk_rule(ctx, location, chunk_rule):
      validate_struct(
              ctx,
              location,
              chunk_rule,
              required_attrs=[
                  ("weight", int),
                  ],
              allowed_attrs=[
                  ("if_after", datespec_types),
                  ("if_before", datespec_types),
                  ("if_in_facility", str),
                  ("if_has_role", list),
  
                  ("start", datespec_types),
                  ("end", datespec_types),
                  ("roles", list),
  
                  ("shown", bool),
              ])
  
      if hasattr(chunk_rule, "if_after"):
          ctx.encounter_datespec(location, chunk_rule.if_after)
  
      if hasattr(chunk_rule, "if_before"):
          ctx.encounter_datespec(location, chunk_rule.if_before)
  
      if hasattr(chunk_rule, "if_has_role"):
          for role in chunk_rule.if_has_role:
              validate_role(location, role)
  
      if hasattr(chunk_rule, "if_in_facility"):
          validate_facility(ctx, location, chunk_rule.if_in_facility)
  
      # {{{ deprecated
  
      if hasattr(chunk_rule, "start"):
          ctx.add_warning(location, _("Uses deprecated 'start' attribute--"
                  "use 'if_after' instead"))
  
          ctx.encounter_datespec(location, chunk_rule.start)
  
      if hasattr(chunk_rule, "end"):
          ctx.add_warning(location, _("Uses deprecated 'end' attribute--"
                  "use 'if_before' instead"))
  
          ctx.encounter_datespec(location, chunk_rule.end)
  
      if hasattr(chunk_rule, "roles"):
          ctx.add_warning(location, _("Uses deprecated 'roles' attribute--"
                  "use 'if_has_role' instead"))
  
          for role in chunk_rule.roles:
              validate_role(location, role)
  
      # }}}
  
  
  def validate_chunk(ctx, location, chunk):
      validate_struct(
              ctx,
              location,
              chunk,
              required_attrs=[
                  ("title", str),
                  ("id", str),
                  ("rules", list),
                  ("content", "markup"),
                  ],
              allowed_attrs=[]
              )
  
      for i, rule in enumerate(chunk.rules):
          validate_chunk_rule(ctx,
                  "%s, rule %d" % (location, i+1),
                  rule)
  
  
  def validate_course_desc_struct(ctx, location, course_desc):
      validate_struct(
              ctx,
              location,
              course_desc,
              required_attrs=[
                  ("chunks", list),
                  ],
              allowed_attrs=[
                  ("grade_summary_code", str),
  
                  ("name", str),
                  ("number", str),
                  ("run", str),
                  ]
              )
  
      if hasattr(course_desc, "name"):
          ctx.add_warning(location, _("'name' is deprecated. "
              "This information is now kept in the database."))
      if hasattr(course_desc, "number"):
          ctx.add_warning(location, _("'number' is deprecated. "
              "This information is now kept in the database."))
      if hasattr(course_desc, "run"):
          ctx.add_warning(location, _("'run' is deprecated. "
              "This information is now kept in the database."))
  
      for i, chunk in enumerate(course_desc.chunks):
          validate_chunk(ctx,
                  "%s, chunk %d ('%s')"
                  % (location, i+1, getattr(chunk, "id", None)),
                  chunk)
  
      # {{{ check chunk id uniqueness
  
      chunk_ids = set()
  
      for chunk in course_desc.chunks:
          if chunk.id in chunk_ids:
              raise ValidationError(
                      string_concat(
                          "%(location)s: ",
                          _("chunk id '%(chunkid)s' not unique"))
                      % {'location': location, 'chunkid': chunk.id})
  
          chunk_ids.add(chunk.id)
  
      # }}}
  
  # }}}
  
  
  # {{{ flow validation
  
  def validate_flow_page(ctx, location, page_desc):
      if not hasattr(page_desc, "id"):
          raise ValidationError(
                  string_concat(
                      "%s: ",
                      ugettext("flow page has no ID"))
                  % location)
  
      validate_identifier(ctx, location, page_desc.id)
  
      from course.content import get_flow_page_class
      try:
          class_ = get_flow_page_class(ctx.repo, page_desc.type, ctx.commit_sha)
          class_(ctx, location, page_desc)
      except ValidationError:
          raise
      except:
          tp, e, __ = sys.exc_info()
  
          from traceback import format_exc
          raise ValidationError(
                  string_concat(
                      "%(location)s: ",
                      _("could not instantiate flow page"),
                      ": %(err_type)s: "
                      "%(err_str)s<br><pre>%(format_exc)s</pre>")
                  % {
                      'location': location,
                      "err_type": tp.__name__,
                      "err_str": str(e),
                      'format_exc': format_exc()})
  
  
  def validate_flow_group(ctx, location, grp):
      validate_struct(
              ctx,
              location,
              grp,
              required_attrs=[
                  ("id", str),
                  ("pages", list),
                  ],
              allowed_attrs=[
                  ("shuffle", bool),
                  ("max_page_count", int),
                  ]
              )
  
      for i, page_desc in enumerate(grp.pages):
          validate_flow_page(
                  ctx,
                  "%s, page %d ('%s')"
                  % (location, i+1, getattr(page_desc, "id", None)),
                  page_desc)
  
      if len(grp.pages) == 0:
          raise ValidationError(
                  string_concat(
                      "%(location)s, ",
                      _("group '%(group_id)s': group is empty"))
                  % {'location': location, 'group_id': grp.id})
  
      if hasattr(grp, "max_page_count") and grp.max_page_count <= 0:
          raise ValidationError(
                  string_concat(
                      "%(location)s, ",
                      _("group '%(group_id)s': "
                          "max_page_count is not positive"))
                  % {'location': location, 'group_id': grp.id})
  
      # {{{ check page id uniqueness
  
      page_ids = set()
  
      for page_desc in grp.pages:
          if page_desc.id in page_ids:
              raise ValidationError(
                      string_concat(
                          "%(location)s: ",
                          _("page id '%(page_desc_id)s' not unique"))
                      % {'location': location, 'page_desc_id': page_desc.id})
  
          page_ids.add(page_desc.id)
  
      # }}}
  
      validate_identifier(ctx, location, grp.id)
  
  
  # {{{ flow access rules
  
  def validate_session_start_rule(ctx, location, nrule, tags):
      validate_struct(
              ctx, location, nrule,
              required_attrs=[],
              allowed_attrs=[
                  ("if_after", datespec_types),
                  ("if_before", datespec_types),
                  ("if_has_role", list),
                  ("if_in_facility", str),
                  ("if_has_in_progress_session", bool),
                  ("if_has_session_tagged", (six.string_types, type(None))),
                  ("if_has_fewer_sessions_than", int),
                  ("if_has_fewer_tagged_sessions_than", int),
                  ("tag_session", (six.string_types, type(None))),
                  ("may_start_new_session", bool),
                  ("may_list_existing_sessions", bool),
                  ]
              )
  
      if hasattr(nrule, "if_after"):
          ctx.encounter_datespec(location, nrule.if_after)
      if hasattr(nrule, "if_before"):
          ctx.encounter_datespec(location, nrule.if_before)
      if hasattr(nrule, "if_has_role"):
          for j, role in enumerate(nrule.if_has_role):
              validate_role(
                      "%s, role %d" % (location, j+1),
                      role)
  
      if hasattr(nrule, "if_in_facility"):
          validate_facility(ctx, location, nrule.if_in_facility)
  
      if hasattr(nrule, "if_has_session_tagged"):
          if nrule.if_has_session_tagged is not None:
              validate_identifier(ctx, "%s: if_has_session_tagged" % location,
                      nrule.if_has_session_tagged)
  
      if not hasattr(nrule, "may_start_new_session"):
          ctx.add_warning(
                  location+", rules",
                  _("attribute 'may_start_new_session' is not present"))
      if not hasattr(nrule, "may_list_existing_sessions"):
          ctx.add_warning(
                  location+", rules",
                  _("attribute 'may_list_existing_sessions' is not present"))
  
      if hasattr(nrule, "tag_session"):
          if nrule.tag_session is not None:
              validate_identifier(ctx, "%s: tag_session" % location,
                      nrule.tag_session,
                      warning_only=True)
  
          if not (nrule.tag_session is None or nrule.tag_session in tags):
              raise ValidationError(
                      string_concat(
                          "%(location)s: ",
                          _("invalid tag '%(tag)s'"))
                      % {'location': location, 'tag': nrule.tag_session})
  
  
  def validate_session_access_rule(ctx, location, arule, tags):
      validate_struct(
              ctx, location, arule,
              required_attrs=[
                  ("permissions", list),
                  ],
              allowed_attrs=[
                  ("if_after", datespec_types),
                  ("if_before", datespec_types),
                  ("if_has_role", list),
                  ("if_in_facility", str),
                  ("if_has_tag", (six.string_types, type(None))),
                  ("if_in_progress", bool),
                  ("if_completed_before", datespec_types),
                  ("if_expiration_mode", str),
                  ("if_session_duration_shorter_than_minutes", (int, float)),
                  ("message", datespec_types),
                  ]
              )
  
      if hasattr(arule, "if_after"):
          ctx.encounter_datespec(location, arule.if_after)
      if hasattr(arule, "if_before"):
          ctx.encounter_datespec(location, arule.if_before)
      if hasattr(arule, "if_completed_before"):
          ctx.encounter_datespec(location, arule.if_completed_before)
  
      if hasattr(arule, "if_has_role"):
          for j, role in enumerate(arule.if_has_role):
              validate_role(
                      "%s, role %d" % (location, j+1),
                      role)
  
      if hasattr(arule, "if_in_facility"):
          validate_facility(ctx, location, arule.if_in_facility)
  
      if hasattr(arule, "if_has_tag"):
          if not (arule.if_has_tag is None or arule.if_has_tag in tags):
              raise ValidationError(
                      string_concat(
                          "%(location)s: ",
                          _("invalid tag '%(tag)s'"))
                      % {'location': location, 'tag': arule.if_has_tag})
  
      if hasattr(arule, "if_expiration_mode"):
          from course.constants import FLOW_SESSION_EXPIRATION_MODE_CHOICES
          if arule.if_expiration_mode not in dict(
                  FLOW_SESSION_EXPIRATION_MODE_CHOICES):
              raise ValidationError(
                      string_concat("%(location)s: ",
                          _("invalid expiration mode '%(expiremode)s'"))
                      % {
                          'location': location,
                          'expiremode': arule.if_expiration_mode})
  
      for j, perm in enumerate(arule.permissions):
          validate_flow_permission(
                  ctx,
                  "%s, permission %d" % (location, j+1),
                  perm)
  
  
  def validate_session_grading_rule(ctx, location, grule, tags, grade_identifier):
      """
      :returns: whether the rule only applies conditionally
      """
  
      validate_struct(
              ctx, location, grule,
              required_attrs=[
                  ],
              allowed_attrs=[
                  ("if_has_role", list),
                  ("if_has_tag", (six.string_types, type(None))),
                  ("if_completed_before", datespec_types),
  
                  ("credit_percent", (int, float)),
                  ("use_last_activity_as_completion_time", bool),
                  ("due", datespec_types),
                  ("generates_grade", bool),
                  ("description", str),
  
                  # legacy
                  ("grade_identifier", (type(None), str)),
                  ("grade_aggregation_strategy", str),
                  ]
              )
  
      if hasattr(grule, "grade_identifier"):
          raise ValidationError(
                  string_concat("%(location)s: ",
                      _("'grade_identifier' attribute found. "
                          "This attribute is no longer allowed here "
                          "and should be moved upward into the 'rules' "
                          "block."))
                  % {"location": location})
  
      if hasattr(grule, "grade_aggregation_strategy"):
          raise ValidationError(
                  string_concat("%(location)s: ",
                      _("'grade_aggregation_strategy' attribute found. "
                          "This attribute is no longer allowed here "
                          "and should be moved upward into the 'rules' "
                          "block."))
                  % {"location": location})
  
      has_conditionals = False
  
      if hasattr(grule, "if_completed_before"):
          ctx.encounter_datespec(location, grule.if_completed_before)
          has_conditionals = True
  
      if hasattr(grule, "if_has_role"):
          for j, role in enumerate(grule.if_has_role):
              validate_role(
                      "%s, role %d" % (location, j+1),
                      role)
          has_conditionals = True
  
      if hasattr(grule, "if_has_tag"):
          if not (grule.if_has_tag is None or grule.if_has_tag in tags):
              raise ValidationError(
                      string_concat(
                          "%(locatioin)s: ",
                          _("invalid tag '%(tag)s'"))
                      % {'location': location, 'tag': grule.if_has_tag})
          has_conditionals = True
  
      if hasattr(grule, "due"):
          ctx.encounter_datespec(location, grule.due)
  
      if (getattr(grule, "generates_grade", True)
              and grade_identifier is None):
          raise ValidationError(
                  string_concat("%(location)s: ",
                      _("'generates_grade' is true, but no 'grade_identifier'"
                          "is given."))
                  % {"location": location})
  
      return has_conditionals
  
  
  def validate_flow_rules(ctx, location, rules):
      validate_struct(
              ctx,
              location + ", rules",
              rules,
              required_attrs=[
                  ("access", list),
                  ],
              allowed_attrs=[
                  # may not start with an underscore
                  ("start", list),
                  ("grading", list),
                  ("tags", list),
  
                  ("grade_identifier", (type(None), str)),
                  ("grade_aggregation_strategy", str),
                  ]
              )
  
      if not hasattr(rules, "grade_identifier"):
          raise ValidationError(
                  string_concat("%(location)s: ",
                      _("'rules' block does not have a grade_identifier "
                          "attribute. This attribute needs to be moved out of "
                          "the lower-level 'grading' rules block and into "
                          "the 'rules' block itself."))
                  % {'location': location})
  
      tags = getattr(rules, "tags", [])
  
      for i, tag in enumerate(tags):
          validate_identifier(ctx, "%s: tag %d" % (location, i+1), tag)
  
      # {{{ validate new-session rules
  
      if hasattr(rules, "start"):
          for i, nrule in enumerate(rules.start):
              validate_session_start_rule(
                      ctx, "%s, rules/start %d" % (location,  i+1),
                      nrule, tags)
  
      # }}}
  
      # {{{ validate access rules
  
      for i, arule in enumerate(rules.access):
          validate_session_access_rule(
                  ctx,
                  location="%s, rules/access #%d"
                  % (location,  i+1), arule=arule, tags=tags)
  
      # }}}
  
      # {{{ grade_id
  
      if rules.grade_identifier:
          validate_identifier(ctx, "%s: grade_identifier" % location,
                  rules.grade_identifier)
          if not hasattr(rules, "grade_aggregation_strategy"):
              raise ValidationError(
                      string_concat("%(location)s: ",
                          _("grading rule that have a grade "
                              "identifier (%(type)s: %(identifier)s) "
                              "must have a grade_aggregation_strategy"))
                      % {
                          'location': location,
                          'type': type(rules.grade_identifier),
                          'identifier': rules.grade_identifier})
  
      from course.constants import GRADE_AGGREGATION_STRATEGY_CHOICES
      if (
              hasattr(rules, "grade_aggregation_strategy")
              and
              rules.grade_aggregation_strategy not in
              dict(GRADE_AGGREGATION_STRATEGY_CHOICES)):
          raise ValidationError(
                  string_concat("%s: ",
                      _("invalid grade aggregation strategy"))
                  % location)
  
      # }}}
  
      # {{{ validate grading rules
  
      if not hasattr(rules, "grading"):
          if rules.grade_identifier is not None:
              raise ValidationError(
                      string_concat("%(location)s: ",
                          _("'grading' block is required if grade_identifier "
                              "is not null/None.")
                          % {'location': location}))
  
      else:
          has_conditionals = None
  
          if len(rules.grading) == 0:
              raise ValidationError(
                      string_concat(
                          "%s, ",
                          _("rules/grading: "
                              "may not be an empty list"))
                      % location)
  
          for i, grule in enumerate(rules.grading):
              has_conditionals = validate_session_grading_rule(
                      ctx,
                      location="%s, rules/grading #%d"
                      % (location,  i+1), grule=grule, tags=tags,
                      grade_identifier=rules.grade_identifier)
  
          if has_conditionals:
              raise ValidationError(
                      string_concat(
                          "%s, ",
                          _("rules/grading: "
                              "last grading rule must be unconditional"))
                      % location)
  
      # }}}
  
  
  def validate_flow_permission(ctx, location, permission):
      from course.constants import FLOW_PERMISSION_CHOICES
      if permission == "modify":
          ctx.add_warning(location, _("Uses deprecated 'modify' permission--"
                  "replace by 'submit_answer' and 'end_session'"))
          return
  
      if permission == "see_answer":
          ctx.add_warning(location,
                  _("Uses deprecated 'see_answer' permission--"
                  "replace by 'see_answer_after_submission'"))
          return
  
      if permission not in dict(FLOW_PERMISSION_CHOICES):
          raise ValidationError(
                  string_concat("%(location)s: ",
                      _("invalid flow permission '%(permission)s'"))
                  % {'location': location, 'permission': permission})
  
  # }}}
  
  
  def validate_flow_desc(ctx, location, flow_desc):
      validate_struct(
              ctx,
              location,
              flow_desc,
              required_attrs=[
                  ("title", str),
                  ("description", "markup"),
                  ],
              allowed_attrs=[
                  ("completion_text", "markup"),
                  ("rules", Struct),
                  ("groups", list),
                  ("pages", list),
                  ("notify_on_submit", list),
                  ]
              )
  
      if hasattr(flow_desc, "rules"):
          validate_flow_rules(ctx, location, flow_desc.rules)
  
      # {{{ check for presence of 'groups' or 'pages'
  
      if (
              (not hasattr(flow_desc, "groups") and not hasattr(flow_desc, "pages"))
              or
              (hasattr(flow_desc, "groups") and hasattr(flow_desc, "pages"))):
          raise ValidationError(
                  string_concat("%(location)s: ",
                      _("must have either 'groups' or 'pages'"))
                  % {'location': location})
  
      # }}}
  
      if hasattr(flow_desc, "pages"):
          from course.content import normalize_flow_desc
          flow_desc = normalize_flow_desc(flow_desc)
  
          assert not hasattr(flow_desc, "pages")
          assert hasattr(flow_desc, "groups")
  
      # {{{ check for non-emptiness
  
      flow_has_page = False
      for i, grp in enumerate(flow_desc.groups):
          group_has_page = False
  
          for page in grp.pages:
              group_has_page = flow_has_page = True
              break
  
          if not group_has_page:
              raise ValidationError(
                      string_concat(
                          "%(location)s, ",
                          _("group %(group_index)d ('%(group_id)d'): "
                              "no pages found"))
                      % {
                          'location': location,
                          'group_index': i+1,
                          'group_id': grp.id})
  
      if not flow_has_page:
          raise ValidationError(_("%s: no pages found")
                  % location)
  
      # }}}
  
      # {{{ check group id uniqueness
  
      group_ids = set()
  
      for grp in flow_desc.groups:
          if grp.id in group_ids:
              raise ValidationError(
                      string_concat("%(location)s: ",
                          _("group id '%(group_id)s' not unique"))
                      % {'location': location, 'group_id': grp.id})
  
          group_ids.add(grp.id)
  
      # }}}
  
      for i, grp in enumerate(flow_desc.groups):
          validate_flow_group(ctx, "%s, group %d ('%s')"
                  % (location, i+1, grp.id),
                  grp)
  
      validate_markup(ctx, location, flow_desc.description)
      if hasattr(flow_desc, "completion_text"):
          validate_markup(ctx, location, flow_desc.completion_text)
  
      if hasattr(flow_desc, "notify_on_submit"):
          for i, item in enumerate(flow_desc.notify_on_submit):
              if not isinstance(item, six.string_types):
                  raise ValidationError(
                          "%s, notify_on_submit: item %d is not a string"
                          % (location, i+1))
  
  # }}}
  
  
  # {{{ calendar validation
  
  def validate_calendar_desc_struct(ctx, location, events_desc):
      validate_struct(
              ctx,
              location,
              events_desc,
              required_attrs=[
                  ],
              allowed_attrs=[
                  ("event_kinds", Struct),
                  ("events", Struct),
                  ]
              )
  
      # FIXME could do more here
  
  # }}}
  
  
  def get_yaml_from_repo_safely(repo, full_name, commit_sha):
      from course.content import get_yaml_from_repo
      try:
          return get_yaml_from_repo(
                  repo=repo, full_name=full_name, commit_sha=commit_sha,
                  cached=False)
      except:
          from traceback import print_exc
          print_exc()
  
          tp, e, _ = sys.exc_info()
  
          raise ValidationError(
                  "%(fullname)s: %(err_type)s: %(err_str)s" % {
                      'fullname': full_name,
                      "err_type": tp.__name__,
                      "err_str": six.text_type(e)})
  
  
  def check_attributes_yml(vctx, repo, path, tree):
      try:
          _, attr_blob_sha = tree[".attributes.yml"]
      except KeyError:
          # no .attributes.yml here
          pass
      else:
          from relate.utils import dict_to_struct
          from yaml import load as load_yaml
  
          att_yml = dict_to_struct(load_yaml(repo[attr_blob_sha].data))
  
          loc = path + "/" + ".attributes.yml"
          validate_struct(
                  vctx, loc, att_yml,
                  required_attrs=[],
                  allowed_attrs=[
                      ("public", list),
                      ("in_exam", list),
                  ])
  
          for access_kind in ["public", "in_exam"]:
              if hasattr(att_yml, access_kind):
                  for i, l in enumerate(att_yml.public):
                      if not isinstance(l, six.string_types):
                          raise ValidationError(
                                  "%s: entry %d in '%s' is not a string"
                                  % (loc, i+1, access_kind))
  
      import stat
      for entry in tree.items():
          if stat.S_ISDIR(entry.mode):
              _, blob_sha = tree[entry.path]
              subtree = repo[blob_sha]
              check_attributes_yml(
                      vctx, repo,
                      path+"/"+entry.path.decode("utf-8"), subtree)
  
  
  # {{{ check whether flow grade identifiers were changed in sketchy ways
  
  def check_grade_identifier_link(
          vctx, location, course, flow_id, flow_grade_identifier):
  
      from course.models import GradingOpportunity
      for bad_gopp in (
              GradingOpportunity.objects
              .filter(
                  course=course,
                  identifier=flow_grade_identifier)
              .exclude(flow_id=flow_id)):
          # 0 or 1 trips through this loop because of uniqueness
  
          raise ValidationError(
                  _(
                      "{location}: existing grading opportunity with identifier "
                      "'{grade_identifier}' refers to flow '{other_flow_id}', however "
                      "flow code in this flow ('{new_flow_id}') specifies the same "
                      "grade identifier. "
                      "(Have you renamed the flow? If so, edit the grading "
                      "opportunity to match.)")
                  .format(
                      location=location,
                      grade_identifier=flow_grade_identifier,
                      other_flow_id=bad_gopp.flow_id,
                      new_flow_id=flow_id,
                      new_grade_identifier=flow_grade_identifier))
  
  # }}}
  
  
  # {{{ check whether page types were changed
  
  def check_for_page_type_changes(vctx, location, course, flow_id, flow_desc):
      from course.content import normalize_flow_desc
      n_flow_desc = normalize_flow_desc(flow_desc)
  
      from course.models import FlowPageData
      for grp in n_flow_desc.groups:
          for page_desc in grp.pages:
              fpd_with_mismatched_page_types = list(
                      FlowPageData.objects
                      .filter(
                          flow_session__course=course,
                          flow_session__flow_id=flow_id,
                          group_id=grp.id,
                          page_id=page_desc.id)
                      .exclude(page_type=None)
                      .exclude(page_type=page_desc.type)
                      [0:1])
  
              if fpd_with_mismatched_page_types:
                  mismatched_fpd, = fpd_with_mismatched_page_types
                  raise ValidationError(
                          _("%(loc)s, group '%(group)s', page '%(page)s': "
                              "page type ('%(type_new)s') differs from "
                              "type used in database ('%(type_old)s')")
                          % {"loc": location, "group": grp.id,
                              "page": page_desc.id,
                              "type_new": page_desc.type,
                              "type_old": mismatched_fpd.page_type})
  
  # }}}
  
  
  def validate_course_content(repo, course_file, events_file,
          validate_sha, course=None):
      course_desc = get_yaml_from_repo_safely(repo, course_file,
              commit_sha=validate_sha)
  
      vctx = ValidationContext(
              repo=repo,
              commit_sha=validate_sha,
              course=course)
  
      validate_course_desc_struct(vctx, course_file, course_desc)
  
      try:
          from course.content import get_yaml_from_repo
          events_desc = get_yaml_from_repo(repo, events_file,
                  commit_sha=validate_sha, cached=False)
      except ObjectDoesNotExist:
          if events_file != "events.yml":
              vctx.add_warning(
                      _("Events file"),
                      _("Your course repository does not have an events "
                          "file named '%s'.")
                      % events_file)
          else:
              # That's OK--no calendar info.
              pass
      else:
          validate_calendar_desc_struct(vctx, events_file, events_desc)
  
      check_attributes_yml(
              vctx, repo, "", get_repo_blob(repo, "", validate_sha))
  
      try:
          flows_tree = get_repo_blob(repo, "media", validate_sha)
      except ObjectDoesNotExist:
          # That's great--no media directory.
          pass
      else:
          vctx.add_warning(
                  'media/', _(
                      "Your course repository has a 'media/' directory. "
                      "Linking to media files using 'media:' is discouraged. "
                      "Use the 'repo:' and 'repocur:' linkng schemes instead."))
  
      try:
          flows_tree = get_repo_blob(repo, "flows", validate_sha)
      except ObjectDoesNotExist:
          # That's OK--no flows yet.
          pass
      else:
          used_grade_identifiers = set()
  
          for entry in flows_tree.items():
              entry_path = entry.path.decode("utf-8")
              if not entry_path.endswith(".yml"):
                  continue
  
              from course.constants import FLOW_ID_REGEX
              flow_id = entry_path[:-4]
              match = re.match("^"+FLOW_ID_REGEX+"$", flow_id)
              if match is None:
                  raise ValidationError(
                          string_concat("%s: ",
                              _("invalid flow name. "
                                  "Flow names may only contain (roman) "
                                  "letters, numbers, "
                                  "dashes and underscores."))
                          % entry_path)
  
              location = "flows/%s" % entry_path
              flow_desc = get_yaml_from_repo_safely(repo, location,
                      commit_sha=validate_sha)
  
              validate_flow_desc(vctx, location, flow_desc)
  
              # {{{ check grade_identifier
  
              flow_grade_identifier = None
              if hasattr(flow_desc, "rules"):
                  flow_grade_identifier = getattr(
                          flow_desc.rules, "grade_identifier", None)
  
              if (
                      flow_grade_identifier is not None
                      and
                      set([flow_grade_identifier]) & used_grade_identifiers):
                  raise ValidationError(
                          string_concat("%s: ",
                                        _("flow uses the same grade_identifier "
                                          "as another flow"))
                          % location)
  
              used_grade_identifiers.add(flow_grade_identifier)
  
              if (course is not None
                      and flow_grade_identifier is not None):
                  check_grade_identifier_link(
                          vctx, location, course, flow_id, flow_grade_identifier)
  
              # }}}
  
              if course is not None:
                  check_for_page_type_changes(
                          vctx, location, course, flow_id, flow_desc)
  
      return vctx.warnings
  
  
  # {{{ validation script support
  
  class FileSystemFakeRepo(object):
      def __init__(self, root):
          self.root = root
  
      def controldir(self):
          return self.root
  
      def __getitem__(self, sha):
          return sha
  
      def __str__(self):
          return "<FAKEREPO:%s>" % self.root
  
      def decode(self):
          return self
  
      @property
      def tree(self):
          return FileSystemFakeRepoTree(self.root)
  
  
  class FileSystemFakeRepoTreeEntry(object):
      def __init__(self, path, mode):
          self.path = path
          self.mode = mode
  
  
  class FileSystemFakeRepoTree(object):
      def __init__(self, root):
          self.root = root
  
      def __getitem__(self, name):
          from os.path import join, isdir, exists
          name = join(self.root, name)
  
          if not exists(name):
              raise KeyError(name)
  
          # returns mode, "sha"
          if isdir(name):
              return None, FileSystemFakeRepoTree(name)
          else:
              return None, FileSystemFakeRepoFile(name)
  
      def items(self):
          import os
          return [
                  FileSystemFakeRepoTreeEntry(
                      path=n,
                      mode=os.stat(os.path.join(self.root, n)).st_mode)
                  for n in os.listdir(self.root)]
  
  
  class FileSystemFakeRepoFile(object):
      def __init__(self, name):
          self.name = name
  
      @property
      def data(self):
          with open(self.name, "rb") as inf:
              return inf.read()
  
  
  def validate_course_on_filesystem_script_entrypoint():
      from django.conf import settings
      settings.configure(DEBUG=True)
  
      import django
      django.setup()
  
      import os
      import argparse
      parser = argparse.ArgumentParser(description='Process some integers.')
      parser.add_argument("--course-file", default="course.yml")
      parser.add_argument("--events-file", default="events.yml")
      parser.add_argument('root', default=os.getcwd())
  
      args = parser.parse_args()
  
      fake_repo = FileSystemFakeRepo(args.root)
      warnings = validate_course_content(
              fake_repo,
              args.course_file, args.events_file,
              validate_sha=fake_repo, course=None)
  
      if warnings:
          print(_("WARNINGS: "))
          for w in warnings:
              print("***", w.location, w.text)
  
  # }}}
  
  # vim: foldmethod=marker
  