Parse further information from Stud.IP

[N-Coder]

• [ ] File creation date
• [ ] parse Course list from "Farbgruppierung"
  • this requires further requests to get information for all courses
• [ ] VirtualPath._known_tokens should also return file name and extension as separate fields
• [ ] provide file extension / MIME-type if not specified
• [ ] check length specified by StudIP

The optimal solution would be a generic method for generating listings of a certain group of objects and then querying further details about these objects (if they weren't included in the listing).

[N-Coder]

• [ ] with the globally managed model classes, one Course can exist within multiple Semesters, so some invariants the VirtualPath relies on no longer hold
• [ ] as _known_tokens uses the most specific known data, the path of a child VirtualPath may change in comparison to its parent (due to the above point and more specific values for children, e.g. creation time)
• [ ] path / known_data validation should be reenabled in VirtualPath, once changing known_data is fixed. InvalidVirtualPathException should be thrown and handled gracefully

Old checks that assume that one Course can only exist within one Semester:

if self._course:
    assert not self._semester or self._course.semester == self._semester, \
        "virtual path %s describes course %s of semester %s, " \
        "which doesn't match the semester of the virtual path %s" % \
        (self, self._course, self._course.semester, self._semester)
if self._file:
    assert not self._semester or self._file.semester == self._semester, \
        "virtual path %s describes file %s of semester %s, " \
        "which doesn't match the semester of the virtual path %s" % \
        (self, self._file, self._file.semester, self._semester)
    assert not self._course or self._file.course == self._course, \
        "virtual path %s describes file %s of course %s %s, " \
        "which doesn't match the course of the virtual path %s %s" % \
        (self, self._file, self._file.course, self._file.course.semester, self._course, self._course.semester)

New checks that ensure that known_data doesn't change:

if self.parent:
    assert self.partial_path.startswith(self.parent.partial_path), \
        "Path of child file %s doesn't start with the path of its parent %s. " \
        "Does your path format specification make sense?" % (self, self.parent)
    assert set(self._known_tokens.items()).issuperset(self.parent._known_tokens.items()), \
        "Known data of child file %s doesn't include all data of its parent %s. " \
        "Does your path format specification make sense? " \
        "Offending keys are:\n%s" % (self, self.parent, tabulate(
            ((key, self.parent._known_tokens.get(key, "unset"), self._known_tokens.get(key, "unset"))
             for key in set(chain(self._known_tokens.keys(), self.parent._known_tokens.keys()))),
            headers=["key", "parent value", "child value"], missingval="None"
        ))