"""
Common utilities for the course experience, including course outline.
"""

from django.utils import timezone
from opaque_keys.edx.keys import CourseKey

from lms.djangoapps.course_api.blocks.api import get_blocks
from lms.djangoapps.course_blocks.api import get_course_blocks
from openedx.core.djangoapps.content.course_overviews.models import CourseOverview
from openedx.core.lib.cache_utils import request_cached
from openedx.features.course_experience import RELATIVE_DATES_DISABLE_RESET_FLAG, RELATIVE_DATES_FLAG
from common.djangoapps.student.models import CourseEnrollment
from xmodule.modulestore.django import modulestore  # lint-amnesty, pylint: disable=wrong-import-order


@request_cached()
def get_course_outline_block_tree(request, course_id, user=None, allow_start_dates_in_future=False):  # lint-amnesty, pylint: disable=too-many-statements
    """
    Returns the root block of the course outline, with children as blocks.

    allow_start_dates_in_future (bool): When True, will allow blocks to be
            returned that can bypass the StartDateTransformer's filter to show
            blocks with start dates in the future.
    """

    assert user is None or user.is_authenticated

    def populate_children(block, all_blocks):
        """
        Replace each child id with the full block for the child.

        Given a block, replaces each id in its children array with the full
        representation of that child, which will be looked up by id in the
        passed all_blocks dict. Recursively do the same replacement for children
        of those children.
        """
        children = block.get('children', [])

        for i in range(len(children)):
            child_id = block['children'][i]
            child_detail = populate_children(all_blocks[child_id], all_blocks)
            block['children'][i] = child_detail

        return block

    def recurse_mark_scored(block):
        """
        Mark this block as 'scored' if any of its descendents are 'scored' (that is, 'has_score' and 'weight' > 0).
        """
        is_scored = block.get('has_score', False) and block.get('weight', 1) > 0
        # Use a list comprehension to force the recursion over all children, rather than just stopping
        # at the first child that is scored.
        children_scored = any(tuple(recurse_mark_scored(child) for child in block.get('children', [])))
        if is_scored or children_scored:
            block['scored'] = True
            return True
        else:
            block['scored'] = False
            return False

    def recurse_num_graded_problems(block):
        """
        Marks each block with the number of graded and scored leaf blocks below it as 'num_graded_problems'
        """
        is_scored = block.get('has_score') and block.get('weight', 1) > 0
        is_graded = block.get('graded')
        is_countable = block.get('type') not in ('lti', 'lti_consumer')
        is_graded_problem = is_scored and is_graded and is_countable

        num_graded_problems = 1 if is_graded_problem else 0
        num_graded_problems += sum(recurse_num_graded_problems(child) for child in block.get('children', []))

        block['num_graded_problems'] = num_graded_problems
        return num_graded_problems

    def recurse_mark_auth_denial(block):
        """
        Mark this block as 'scored' if any of its descendents are 'scored' (that is, 'has_score' and 'weight' > 0).
        """
        own_denial_reason = {block['authorization_denial_reason']} if 'authorization_denial_reason' in block else set()
        # Use a list comprehension to force the recursion over all children, rather than just stopping
        # at the first child that is scored.
        child_denial_reasons = own_denial_reason.union(
            *(recurse_mark_auth_denial(child) for child in block.get('children', []))
        )
        if child_denial_reasons:
            block['all_denial_reasons'] = child_denial_reasons
        return child_denial_reasons

    course_key = CourseKey.from_string(course_id)
    course_usage_key = modulestore().make_course_usage_key(course_key)

    all_blocks = get_blocks(
        request,
        course_usage_key,
        user=user,
        nav_depth=3,
        requested_fields=[
            'children',
            'contains_gated_content',
            'display_name',
            'due',
            'effort_activities',
            'effort_time',
            'format',
            'graded',
            'has_scheduled_content',
            'has_score',
            'show_gated_sections',
            'special_exam_info',
            'start',
            'type',
            'weight',
            'completion',
            'complete',
            'resume_block',
            'hide_from_toc',
            'icon_class',
        ],
        allow_start_dates_in_future=allow_start_dates_in_future,
    )

    course_outline_root_block = all_blocks['blocks'].get(all_blocks['root'], None)
    if course_outline_root_block:
        populate_children(course_outline_root_block, all_blocks['blocks'])
        recurse_mark_scored(course_outline_root_block)
        recurse_num_graded_problems(course_outline_root_block)
        recurse_mark_auth_denial(course_outline_root_block)
    return course_outline_root_block


def get_start_block(block):
    """
    Gets the deepest block to use as the starting block.
    """
    if not block.get('children'):
        return block

    first_child = block['children'][0]

    return get_start_block(first_child)


def dates_banner_should_display(course_key, user, allow_warning=False):
    """
    Return whether or not the reset banner should display,
    determined by whether or not a course has any past-due,
    incomplete sequentials and which enrollment mode is being
    dealt with for the current user and course.

    Args:
        course_key (CourseKey)
        user (User)
        allow_warning (bool): whether to ignore relative_dates_disable_reset_flag, in order to render
            warnings for past-due incomplete units.

    Returns:
        (missed_deadlines, missed_gated_content):
            missed_deadlines is True if the user has missed any graded content deadlines
            missed_gated_content is True if the first content that the user missed was gated content
    """
    if not RELATIVE_DATES_FLAG.is_enabled(course_key):
        return False, False

    if RELATIVE_DATES_DISABLE_RESET_FLAG.is_enabled(course_key) and not allow_warning:
        # The `missed_deadlines` value is ignored by `reset_course_deadlines` views. Instead, they check the value of
        # `missed_gated_content` to determine if learners can reset the deadlines by themselves.
        # We could have added this logic directly to `reset_self_paced_schedule`, but this function is used in other
        # places (e.g., when an enrollment mode is changed). We want this flag to affect only the use case when
        # learners try to reset their deadlines.
        return False, True

    course_overview = CourseOverview.objects.get(id=str(course_key))

    # Only display the banner for self-paced courses
    if not course_overview.self_paced:
        return False, False

    # Only display the banner for enrolled users
    if not CourseEnrollment.is_enrolled(user, course_key):
        return False, False

    # Don't display the banner if the course has ended
    if course_overview.has_ended():
        return False, False

    store = modulestore()
    course_usage_key = store.make_course_usage_key(course_key)
    block_data = get_course_blocks(user, course_usage_key, include_completion=True)
    for section_key in block_data.get_children(course_usage_key):
        for subsection_key in block_data.get_children(section_key):
            subsection_due_date = block_data.get_xblock_field(subsection_key, 'due', None)
            if (subsection_due_date and subsection_due_date < timezone.now() and
                    not is_block_structure_complete_for_assignments(block_data, subsection_key)):
                # Display the banner if the due date for an incomplete graded subsection has passed
                return True, block_data.get_xblock_field(subsection_key, 'contains_gated_content', False)

    # Don't display the banner if there were no missed deadlines
    return False, False


def is_block_structure_complete_for_assignments(block_data, block_key):
    """
    Considers a block complete only if all scored & graded leaf blocks are complete.

    This is different from the normal `complete` flag because children of the block that are informative (like
    readings or videos) do not count. We only care about actual homework content.
    """
    children = block_data.get_children(block_key)
    if children:
        return all(is_block_structure_complete_for_assignments(block_data, child_key) for child_key in children)

    category = block_data.get_xblock_field(block_key, 'category')
    if category in ('course', 'chapter', 'sequential', 'vertical'):
        # If there are no children for these "hierarchy" block types, just bail. This could be because the
        # content isn't available yet (start date in future) or we're too late and the block has hide_after_due
        # set. Or maybe a different transformer cut off content for whatever reason. Regardless of the cause - if the
        # user can't see this content and we continue, we might accidentally say this block is complete because it
        # isn't scored (which most hierarchy blocks wouldn't be).
        return False

    complete = block_data.get_xblock_field(block_key, 'complete', False)
    graded = block_data.get_xblock_field(block_key, 'graded', False)
    has_score = block_data.get_xblock_field(block_key, 'has_score', False)
    weight = block_data.get_xblock_field(block_key, 'weight', 1)
    scored = has_score and (weight is None or weight > 0)

    return complete or not graded or not scored