"""
The public API for certificates.
"""


import logging
from datetime import datetime

import six
from pytz import UTC

from lms.djangoapps.certificates.models import CertificateStatuses, CertificateWhitelist
from openedx.core.djangoapps.certificates.config import waffle
from student.models import CourseEnrollment

log = logging.getLogger(__name__)

SWITCHES = waffle.waffle()


def auto_certificate_generation_enabled():
    return SWITCHES.is_enabled(waffle.AUTO_CERTIFICATE_GENERATION)


def _enabled_and_instructor_paced(course):
    if auto_certificate_generation_enabled():
        return not course.self_paced
    return False


def certificates_viewable_for_course(course):
    """
    Returns True if certificates are viewable for any student enrolled in the course, False otherwise.
    """
    if course.self_paced:
        return True
    if (
        course.certificates_display_behavior in ('early_with_info', 'early_no_info')
        or course.certificates_show_before_end
    ):
        return True
    if (
        course.certificate_available_date
        and course.certificate_available_date <= datetime.now(UTC)
    ):
        return True
    if (
        course.certificate_available_date is None
        and course.has_ended()
    ):
        return True
    return False


def is_certificate_valid(certificate):
    """
    Returns True if the student has a valid, verified certificate for this course, False otherwise.
    """
    return CourseEnrollment.is_enrolled_as_verified(certificate.user, certificate.course_id) and certificate.is_valid()


def can_show_certificate_message(course, student, course_grade, certificates_enabled_for_course):
    is_whitelisted = CertificateWhitelist.objects.filter(user=student, course_id=course.id, whitelist=True).exists()
    auto_cert_gen_enabled = auto_certificate_generation_enabled()
    has_active_enrollment = CourseEnrollment.is_enrolled(student, course.id)
    certificates_are_viewable = certificates_viewable_for_course(course)

    # Adding a temporary logging for EDUCATOR-2017.
    if six.text_type(course.id) == u'course-v1:RITx+PM9004x+3T2017':
        log.info(
            (
                u'can_show_certificate_message called with:'
                u'course:%s, student: %s, course grade: %s,'
                u'certificates_enabled_for_course: %s, certificates_viewable_for_course: %s, auto_cert_gen_enabled: %s,'
                u'has_active_enrollment: %s, passed: %s, is_whitelisted: %s'
            ),
            course.id,
            student.username,
            course_grade,
            certificates_enabled_for_course,
            certificates_are_viewable,
            auto_cert_gen_enabled,
            has_active_enrollment,
            course_grade.passed,
            is_whitelisted
        )
    if not (
        (auto_cert_gen_enabled or certificates_enabled_for_course) and
        has_active_enrollment and
        certificates_are_viewable and
        (course_grade.passed or is_whitelisted)
    ):
        return False
    return True


def can_show_certificate_available_date_field(course):
    return _enabled_and_instructor_paced(course)


def _course_uses_available_date(course):
    return can_show_certificate_available_date_field(course) and course.certificate_available_date


def available_date_for_certificate(course, certificate):
    if _course_uses_available_date(course):
        return course.certificate_available_date
    return certificate.modified_date


def display_date_for_certificate(course, certificate):
    if _course_uses_available_date(course) and course.certificate_available_date < datetime.now(UTC):
        return course.certificate_available_date
    return certificate.modified_date


def is_valid_pdf_certificate(cert_data):
    return cert_data.cert_status == CertificateStatuses.downloadable and cert_data.download_url