from xmodule.modulestore.django import modulestore
from opaque_keys.edx.keys import CourseKey, UsageKey
from opaque_keys import InvalidKeyError

# Old style IDs -- note the lack of Course Run info in usage_id
# course_id = "edX/DemoX.1/2014"
# usage_id = "i4x://edX/DemoX.1/problem/466f474fa4d045a8b7bde1b911e095ca"

# New style IDs -- usage_id has full Course Run info
course_id = "course-v1:edX+DemoX+Demo_Course"
usage_id = "block-v1:edX+DemoX+Demo_Course+type@problem+block@d2e35c1d294b4ba0b3b1048615605d2a"

# Parse the Course ID.
try:
    # This will return a SlashSeparatedCourseKey (old) or CourseLocator (new)
    # Always use CourseKey.from_string() when parsing Course IDs.
    course_key = CourseKey.from_string(course_id)
except InvalidKeyError:
    # Do some error handling here -- this is just completely made up
    raise ValueError("Could not parse course_id {}".format(course_id))

# Parse the Usage ID
try:
    # This will return a Location (old) or BlockUsageLocator (new)
    # Always use UsageKey.from_string() when parsing Usage IDs.
    unmapped_usage_key = UsageKey.from_string(usage_id)

    # The map_into_course() call is not necessary for BlockUsageLocators, but
    # we do it to maintain compatibility with old style usage keys.
    usage_key = unmapped_usage_key.map_into_course(course_key)
except InvalidKeyError:
    # Do some error handling here -- this is just completely made up
    raise ValueError("Could not parse usage_id {}".format(usage_id))


ms = modulestore()

# Get a single CapaDescriptor (a Capa problem, like multiple choice).
# This object has all its XModule content fields, but not the user ones.
problem = ms.get_item(usage_key)

# Query the Modulestore for all sequentials in the Course.
sequences = ms.get_items(course_key, qualifiers={'category': 'sequential'})

# Get the root CourseDescriptor
course = ms.get_course(course_key)

# List of child usage keys (Locations/BlockUsageLocators) for the chapters.
course.children

# Iterate through the descriptors for those children instead:
for chapter in course.get_children():
    print chapter.location, chapter.display_name