"""
Simple utility functions that operate on block metadata.

This is a place to put simple functions that operate on block metadata. It
allows us to share code between the XModuleMixin and CourseOverview and
BlockStructure.
"""

from datetime import datetime
from logging import getLogger
from markupsafe import Markup

from dateutil.tz import tzlocal

logger = getLogger(__name__)  # pylint: disable=invalid-name


def url_name_for_block(block):
    """
    Given a block, returns the block's URL name.

    Arguments:
        block (XModuleMixin|CourseOverview|BlockStructureBlockData):
            Block that is being accessed
    """
    return block.location.block_id


def display_name_with_default(block):
    """
    Calculates the display name for a block.

    Default to the display_name if it isn't None, else fall back to creating
    a name based on the URL.

    Unlike the rest of this module's functions, this function takes an entire
    course block/overview as a parameter. This is because a few test cases
    (specifically, {Text|Image|Video}AnnotationModuleTestCase.test_student_view)
    create scenarios where course.display_name is not None but course.location
    is None, which causes calling course.url_name to fail. So, although we'd
    like to just pass course.display_name and course.url_name as arguments to
    this function, we can't do so without breaking those tests.

    Note: This method no longer escapes as it once did, so the caller must
    ensure it is properly escaped where necessary.

    Arguments:
        block (XModuleMixin|CourseOverview|BlockStructureBlockData):
            Block that is being accessed
    """
    return (
        block.display_name if block.display_name is not None
        else url_name_for_block(block).replace('_', ' ')
    )


def display_name_with_default_escaped(block):
    """
    DEPRECATED: use display_name_with_default

    Calculates the display name for a block with some HTML escaping.
    This follows the same logic as display_name_with_default, with
    the addition of the escaping.

    Here is an example of how to move away from this method in Mako html:
        Before:
        <span class="course-name">${course.display_name_with_default_escaped}</span>

        After:
        <span class="course-name">${course.display_name_with_default | h}</span>
    If the context is Javascript in Mako, you'll need to follow other best practices.

    Note: Switch to display_name_with_default, and ensure the caller
    properly escapes where necessary.

    Note: This newly introduced method should not be used.  It was only
    introduced to enable a quick search/replace and the ability to slowly
    migrate and test switching to display_name_with_default, which is no
    longer escaped.

    Arguments:
        block (XModuleMixin|CourseOverview|BlockStructureBlockData):
            Block that is being accessed
    """
    # This escaping is incomplete.  However, rather than switching this to use
    # markupsafe.striptags() and fixing issues, better to put that energy toward
    # migrating away from this method altogether.
    return Markup(display_name_with_default(block)).striptags()


def get_datetime_field(xblock, name, default):
    """
    This method was moved from BlockStructureBlockData because some of the datetime
    that was cached from previous version of dateutil does not live here. This will
    be use as share code for reusability and Wack-a-mole situation of the same bug.

    Creates a new datetime object to avoid issues occurring due to upgrading
    python-datetuil version from 2.4.0
    More info: https://openedx.atlassian.net/browse/BOM-2245
    """
    field = getattr(xblock, name, default)
    if isinstance(field, datetime):
        if isinstance(field.tzinfo, tzlocal) and not hasattr(field.tzinfo, '_hasdst'):
            return datetime(
                year=field.year, month=field.month, day=field.day,
                hour=field.hour, minute=field.minute, second=field.second,
                tzinfo=tzlocal()
            )
    return field