"""
Higher order functions built on the BlockStructureManager to interact with a django cache.
"""
from django.core.cache import cache
from xmodule.modulestore.django import modulestore

from .manager import BlockStructureManager


def get_course_in_cache(course_key):
    """
    A higher order function implemented on top of the
    block_structure.get_collected function that returns the block
    structure in the cache for the given course_key.

    Returns:
        BlockStructureBlockData - The collected block structure,
            starting at root_block_usage_key.
    """
    return get_block_structure_manager(course_key).get_collected()


def update_course_in_cache(course_key):
    """
    A higher order function implemented on top of the
    block_structure.updated_collected function that updates the block
    structure in the cache for the given course_key.
    """
    return get_block_structure_manager(course_key).update_collected_if_needed()


def clear_course_from_cache(course_key):
    """
    A higher order function implemented on top of the
    block_structure.clear_block_cache function that clears the block
    structure from the cache for the given course_key.

    Note: See Note in get_course_blocks. Even after MA-1604 is
    implemented, this implementation should still be valid since the
    entire block structure of the course is cached, even though
    arbitrary access to an intermediate block will be supported.
    """
    get_block_structure_manager(course_key).clear()


def get_block_structure_manager(course_key):
    """
    Returns the manager for managing Block Structures for the given course.
    """
    store = modulestore()
    course_usage_key = store.make_course_usage_key(course_key)
    return BlockStructureManager(course_usage_key, store, get_cache())


def get_cache():
    """
    Returns the storage for caching Block Structures.
    """
    return cache
