from contentstore.course_group_config import GroupConfiguration
from django.conf import settings
from course_modes.models import CourseMode
from django.core.management.base import BaseCommand, CommandError

from openedx.core.djangoapps.course_groups.cohorts import CourseCohort
from openedx.core.djangoapps.course_groups.models import (CourseUserGroup, CourseUserGroupPartitionGroup)
from openedx.core.djangoapps.verified_track_content.models import (
    MigrateVerifiedTrackCohortsSetting,
    VerifiedTrackCohortedCourse
)

from xmodule.modulestore import ModuleStoreEnum
from xmodule.modulestore.django import modulestore
from xmodule.partitions.partitions import ENROLLMENT_TRACK_PARTITION_ID
from xmodule.partitions.partitions_service import PartitionService


class Command(BaseCommand):
    """
    Migrates a course's xblock's group_access from Verified Track Cohorts to Enrollment Tracks
    """

    def handle(self, *args, **options):

        errors = []

        module_store = modulestore()

        print "Starting Swap from Auto Track Cohort Pilot command"

        verified_track_cohorts_setting = self._latest_settings()

        if not verified_track_cohorts_setting:
            raise CommandError("No MigrateVerifiedTrackCohortsSetting found")

        if not verified_track_cohorts_setting.enabled:
            raise CommandError("No enabled MigrateVerifiedTrackCohortsSetting found")

        old_course_key = verified_track_cohorts_setting.old_course_key
        rerun_course_key = verified_track_cohorts_setting.rerun_course_key
        audit_cohort_names = verified_track_cohorts_setting.get_audit_cohort_names()

        # Verify that the MigrateVerifiedTrackCohortsSetting has all required fields
        if not old_course_key:
            raise CommandError("No old_course_key set for MigrateVerifiedTrackCohortsSetting with ID: '%s'"
                               % verified_track_cohorts_setting.id)

        if not rerun_course_key:
            raise CommandError("No rerun_course_key set for MigrateVerifiedTrackCohortsSetting with ID: '%s'"
                               % verified_track_cohorts_setting.id)

        if not audit_cohort_names:
            raise CommandError("No audit_cohort_names set for MigrateVerifiedTrackCohortsSetting with ID: '%s'"
                               % verified_track_cohorts_setting.id)

        print "Running for MigrateVerifiedTrackCohortsSetting with old_course_key='%s' and rerun_course_key='%s'" % \
              (verified_track_cohorts_setting.old_course_key, verified_track_cohorts_setting.rerun_course_key)

        # Get the CourseUserGroup IDs for the audit course names from the old course
        audit_course_user_group_ids = CourseUserGroup.objects.filter(
            name__in=audit_cohort_names,
            course_id=old_course_key,
            group_type=CourseUserGroup.COHORT,
        ).values_list('id', flat=True)

        if not audit_course_user_group_ids:
            raise CommandError(
                "No Audit CourseUserGroup found for course_id='%s' with group_type='%s' for names='%s'"
                % (old_course_key, CourseUserGroup.COHORT, audit_cohort_names)
            )

        # Get all of the audit CourseCohorts from the above IDs that are RANDOM
        random_audit_course_user_group_ids = CourseCohort.objects.filter(
            course_user_group_id__in=audit_course_user_group_ids,
            assignment_type=CourseCohort.RANDOM
        ).values_list('course_user_group_id', flat=True)

        if not random_audit_course_user_group_ids:
            raise CommandError(
                "No Audit CourseCohorts found for course_user_group_ids='%s' with assignment_type='%s"
                % (audit_course_user_group_ids, CourseCohort.RANDOM)
            )

        # Get the CourseUserGroupPartitionGroup for the above IDs, these contain the partition IDs and group IDs
        # that are set for group_access inside of modulestore
        random_audit_course_user_group_partition_groups = list(CourseUserGroupPartitionGroup.objects.filter(
            course_user_group_id__in=random_audit_course_user_group_ids
        ))

        if not random_audit_course_user_group_partition_groups:
            raise CommandError(
                "No Audit CourseUserGroupPartitionGroup found for course_user_group_ids='%s'"
                % random_audit_course_user_group_ids
            )

        # Get the single VerifiedTrackCohortedCourse for the old course
        try:
            verified_track_cohorted_course = VerifiedTrackCohortedCourse.objects.get(course_key=old_course_key)
        except VerifiedTrackCohortedCourse.DoesNotExist:
            raise CommandError("No VerifiedTrackCohortedCourse found for course: '%s'" % old_course_key)

        if not verified_track_cohorted_course.enabled:
            raise CommandError("VerifiedTrackCohortedCourse not enabled for course: '%s'" % old_course_key)

        # Get the single CourseUserGroupPartitionGroup for the verified_track
        # based on the verified_track name for the old course
        try:
            verified_course_user_group = CourseUserGroup.objects.get(
                course_id=old_course_key,
                group_type=CourseUserGroup.COHORT,
                name=verified_track_cohorted_course.verified_cohort_name
            )
        except CourseUserGroup.DoesNotExist:
            raise CommandError(
                "No Verified CourseUserGroup found for course_id='%s' with group_type='%s' for names='%s'"
                % (old_course_key, CourseUserGroup.COHORT, verified_track_cohorted_course.verified_cohort_name)
            )

        try:
            verified_course_user_group_partition_group = CourseUserGroupPartitionGroup.objects.get(
                course_user_group_id=verified_course_user_group.id
            )
        except CourseUserGroupPartitionGroup.DoesNotExist:
            raise CommandError(
                "No Verified CourseUserGroupPartitionGroup found for course_user_group_ids='%s'"
                % random_audit_course_user_group_ids
            )

        # Verify the enrollment track CourseModes exist for the new course
        try:
            CourseMode.objects.get(
                course_id=rerun_course_key,
                mode_slug=CourseMode.AUDIT
            )
        except CourseMode.DoesNotExist:
            raise CommandError("Audit CourseMode is not defined for course: '%s'" % rerun_course_key)

        try:
            CourseMode.objects.get(
                course_id=rerun_course_key,
                mode_slug=CourseMode.VERIFIED
            )
        except CourseMode.DoesNotExist:
            raise CommandError("Verified CourseMode is not defined for course: '%s'" % rerun_course_key)

        items = module_store.get_items(rerun_course_key)
        if not items:
            raise CommandError("Items for Course with key '%s' not found." % rerun_course_key)

        items_to_update = []

        all_cohorted_track_group_ids = set()
        for audit_course_user_group_partition_group in random_audit_course_user_group_partition_groups:
            all_cohorted_track_group_ids.add(audit_course_user_group_partition_group.group_id)
            all_cohorted_track_group_ids.add(verified_course_user_group_partition_group.group_id)

        for item in items:
            # Verify that there exists group access for this xblock, otherwise skip these checks
            if item.group_access:
                set_audit_enrollment_track = False
                set_verified_enrollment_track = False

                # Check the partition and group IDs for the audit course groups, if they exist in
                # the xblock's access settings then set the audit track flag to true
                for audit_course_user_group_partition_group in random_audit_course_user_group_partition_groups:
                    audit_partition_group_access = item.group_access.get(
                        audit_course_user_group_partition_group.partition_id,
                        None
                    )
                    if (audit_partition_group_access
                            and audit_course_user_group_partition_group.group_id in audit_partition_group_access):
                        set_audit_enrollment_track = True

                # Check the partition and group IDs for the verified course group, if it exists in
                # the xblock's access settings then set the verified track flag to true
                verified_partition_group_access = item.group_access.get(
                    verified_course_user_group_partition_group.partition_id,
                    None
                )
                if (verified_partition_group_access
                        and verified_course_user_group_partition_group.group_id in verified_partition_group_access):
                    set_verified_enrollment_track = True

                # If the item has group_access that is not the
                # verified or audit group IDs then raise an error
                # This only needs to be checked for this partition_group once
                non_verified_track_access_groups = set(verified_partition_group_access) - all_cohorted_track_group_ids
                if non_verified_track_access_groups:
                    errors.append(
                        "Non audit/verified cohorted content group set for xblock, location '%s' with IDs '%s'"
                        % (item.location, non_verified_track_access_groups)
                    )

                # Add the enrollment track ids to a group access array
                enrollment_track_group_access = []
                if set_audit_enrollment_track:
                    enrollment_track_group_access.append(settings.COURSE_ENROLLMENT_MODES['audit'])
                if set_verified_enrollment_track:
                    enrollment_track_group_access.append(settings.COURSE_ENROLLMENT_MODES['verified'])

                # If there are no errors, and either the audit track, or verified
                #  track needed an update, set the access, update and publish
                if set_verified_enrollment_track or set_audit_enrollment_track:
                    # Sets whether or not an xblock has changes
                    has_changes = module_store.has_changes(item)

                    # Check that the xblock does not have changes and add it to be updated, otherwise add an error
                    if not has_changes:
                        item.group_access = {ENROLLMENT_TRACK_PARTITION_ID: enrollment_track_group_access}
                        items_to_update.append(item)
                    else:
                        errors.append("XBlock '%s' with location '%s' needs access changes, but is a draft"
                                      % (item.display_name, item.location))

        partitions_to_delete = random_audit_course_user_group_partition_groups
        partitions_to_delete.append(verified_course_user_group_partition_group)

        # If there are no errors iterate over and update all of the items that had the access changed
        if not errors:
            for item in items_to_update:
                module_store.update_item(item, ModuleStoreEnum.UserID.mgmt_command)
                module_store.publish(item.location, ModuleStoreEnum.UserID.mgmt_command)

        # Check if we should delete any partition groups if there are no errors.
        # If there are errors, none of the xblock items will have been updated,
        # so this section will throw errors for each partition in use
        if partitions_to_delete and not errors:
            partition_service = PartitionService(rerun_course_key)
            course = partition_service.get_course()
            for partition_to_delete in partitions_to_delete:
                # Get the user partition, and the index of that partition in the course
                partition = partition_service.get_user_partition(partition_to_delete.partition_id)
                if partition:
                    partition_index = course.user_partitions.index(partition)
                    group_id = int(partition_to_delete.group_id)

                    # Sanity check to verify that all of the groups being deleted are empty,
                    # since they should have been converted to use enrollment tracks instead.
                    # Taken from contentstore/views/course.py.remove_content_or_experiment_group
                    usages = GroupConfiguration.get_partitions_usage_info(module_store, course)
                    used = group_id in usages
                    if used:
                        errors.append("Content group '%s' is in use and cannot be deleted."
                                      % partition_to_delete.group_id)

                    # If there are not errors, proceed to update the course and user_partitions
                    if not errors:
                        # Remove the groups that match the group ID of the partition to be deleted
                        # Else if there are no match groups left, remove the user partition
                        matching_groups = [group for group in partition.groups if group.id == group_id]
                        if matching_groups:
                            group_index = partition.groups.index(matching_groups[0])
                            partition.groups.pop(group_index)
                            # Update the course user partition with the updated groups
                            if partition.groups:
                                course.user_partitions[partition_index] = partition
                            else:
                                course.user_partitions.pop(partition_index)
                        module_store.update_item(course, ModuleStoreEnum.UserID.mgmt_command)

        # If there are any errors, join them together and raise the CommandError
        if errors:
            raise CommandError(
                ("Error for MigrateVerifiedTrackCohortsSetting with ID='%s'\n" % verified_track_cohorts_setting.id) +
                "\t\n".join(errors)
            )

        print "Finished for MigrateVerifiedTrackCohortsSetting with ID='%s" % verified_track_cohorts_setting.id

    def _latest_settings(self):
        """
        Return the latest version of the MigrateVerifiedTrackCohortsSetting
        """
        return MigrateVerifiedTrackCohortsSetting.current()
