refactor: move xmodule folder to root

- Moving xmodule folder to root as we're dissolving sub-projects of common folder in edx-platform
    - More info: https://openedx.atlassian.net/browse/BOM-2579
- -e common/lib/xmodule has been removed from the requirements as xmodule has itself become the part of edx-platform and not being installed through requirements
- The test files common/lib/xmodule/test_files/ have been removed as they are not being used anymore

xmodule/course_metadata_utils.py

@@ -0,0 +1,174 @@
+"""
+Simple utility functions that operate on course metadata.
+
+This is a place to put simple functions that operate on course metadata. It
+allows us to share code between the CourseBlock and CourseOverview
+classes, which both need these type of functions.
+"""
+
+
+from base64 import b32encode
+from datetime import datetime, timedelta
+from math import exp
+
+import dateutil.parser
+from pytz import utc
+
+DEFAULT_START_DATE = datetime(2030, 1, 1, tzinfo=utc)
+
+"""
+Default grading policy for a course run.
+"""
+DEFAULT_GRADING_POLICY = {
+    "GRADER": [
+        {
+            "type": "Homework",
+            "short_label": "HW",
+            "min_count": 12,
+            "drop_count": 2,
+            "weight": 0.15,
+        },
+        {
+            "type": "Lab",
+            "min_count": 12,
+            "drop_count": 2,
+            "weight": 0.15,
+        },
+        {
+            "type": "Midterm Exam",
+            "short_label": "Midterm",
+            "min_count": 1,
+            "drop_count": 0,
+            "weight": 0.3,
+        },
+        {
+            "type": "Final Exam",
+            "short_label": "Final",
+            "min_count": 1,
+            "drop_count": 0,
+            "weight": 0.4,
+        }
+    ],
+    "GRADE_CUTOFFS": {
+        "Pass": 0.5,
+    },
+}
+
+
+def clean_course_key(course_key, padding_char):
+    """
+    Encode a course's key into a unique, deterministic base32-encoded ID for
+    the course.
+
+    Arguments:
+        course_key (CourseKey): A course key.
+        padding_char (str): Character used for padding at end of the encoded
+            string. The standard value for this is '='.
+    """
+    encoded = b32encode(str(course_key).encode('utf8')).decode('utf8')
+    return "course_{}".format(
+        encoded.replace('=', padding_char)
+    )
+
+
+def number_for_course_location(location):
+    """
+    Given a course's block usage locator, returns the course's number.
+
+    This is a "number" in the sense of the "course numbers" that you see at
+    lots of universities. For example, given a course
+    "Intro to Computer Science" with the course key "edX/CS-101/2014", the
+    course number would be "CS-101"
+
+    Arguments:
+        location (BlockUsageLocator): The usage locator of the course in
+            question.
+    """
+    return location.course
+
+
+def has_course_started(start_date):
+    """
+    Given a course's start datetime, returns whether the current time's past it.
+
+    Arguments:
+        start_date (datetime): The start datetime of the course in question.
+    """
+    # TODO: This will throw if start_date is None... consider changing this behavior?
+    return datetime.now(utc) > start_date
+
+
+def has_course_ended(end_date):
+    """
+    Given a course's end datetime, returns whether
+        (a) it is not None, and
+        (b) the current time is past it.
+
+    Arguments:
+        end_date (datetime): The end datetime of the course in question.
+    """
+    return datetime.now(utc) > end_date if end_date is not None else False
+
+
+def course_starts_within(start_date, look_ahead_days):
+    """
+    Given a course's start datetime and look ahead days, returns True if
+    course's start date falls within look ahead days otherwise False
+
+    Arguments:
+        start_date (datetime): The start datetime of the course in question.
+        look_ahead_days (int): number of days to see in future for course start date.
+    """
+    return datetime.now(utc) + timedelta(days=look_ahead_days) > start_date
+
+
+def course_start_date_is_default(start, advertised_start):
+    """
+    Returns whether a course's start date hasn't yet been set.
+
+    Arguments:
+        start (datetime): The start datetime of the course in question.
+        advertised_start (str): The advertised start date of the course
+            in question.
+    """
+    return advertised_start is None and start == DEFAULT_START_DATE
+
+
+def sorting_score(start, advertised_start, announcement):
+    """
+    Returns a tuple that can be used to sort the courses according
+    to how "new" they are. The "newness" score is computed using a
+    heuristic that takes into account the announcement and
+    (advertised) start dates of the course if available.
+
+    The lower the number the "newer" the course.
+    """
+    # Make courses that have an announcement date have a lower
+    # score than courses than don't, older courses should have a
+    # higher score.
+    announcement, start, now = sorting_dates(start, advertised_start, announcement)
+    scale = 300.0  # about a year
+    if announcement:
+        days = (now - announcement).days
+        score = -exp(-days / scale)
+    else:
+        days = (now - start).days
+        score = exp(days / scale)
+    return score
+
+
+def sorting_dates(start, advertised_start, announcement):
+    """
+    Utility function to get datetime objects for dates used to
+    compute the is_new flag and the sorting_score.
+    """
+    try:
+        start = dateutil.parser.parse(advertised_start)
+        if start.tzinfo is None:
+            start = start.replace(tzinfo=utc)
+    except (TypeError, ValueError, AttributeError):
+        start = start  # lint-amnesty, pylint: disable=self-assigning-variable
+
+    now = datetime.now(utc)
+
+    return announcement, start, now