from django.core.management.base import BaseCommand, CommandError  # noqa
from django.db import transaction
from django.core.exceptions import ObjectDoesNotExist
from django.db.models import Q
from django.db.models.functions import Length

from course.models import FlowPageVisit, FlowPageBulkFeedback


def convert_flow_page_visit(stderr, fpv):
    course = fpv.flow_session.course

    from course.content import (
        get_course_repo, get_flow_desc,
        get_flow_page_desc, instantiate_flow_page)
    repo = get_course_repo(course)
    flow_id = fpv.flow_session.flow_id
    commit_sha = course.active_git_commit_sha.encode()
    try:
        flow_desc = get_flow_desc(repo, course,
                flow_id, commit_sha, tolerate_tabs=True)
    except ObjectDoesNotExist:
        stderr.write("warning: no flow yaml file found for '%s' in '%s'"
                % (flow_id, course.identifier))
        return

    try:
        page_desc = get_flow_page_desc(
                fpv.flow_session.flow_id, flow_desc,
                fpv.page_data.group_id, fpv.page_data.page_id)
    except ObjectDoesNotExist:
        stderr.write(f"warning: flow page visit {fpv.id}: no page yaml desc "
                "found for "
                f"'{flow_id}:{fpv.page_data.group_id}/{fpv.page_data.page_id}' "
                f"in '{course.identifier}'")
        return

    page = instantiate_flow_page(
            location="flow '%s', group, '%s', page '%s'"
            % (flow_id,
                fpv.page_data.group_id, fpv.page_data.page_id),
            repo=repo, page_desc=page_desc,
            commit_sha=commit_sha)

    from course.page.base import PageContext
    pctx = PageContext(
            course=course,
            repo=repo,
            commit_sha=commit_sha,
            flow_session=fpv.flow_session,
            page_uri=None)

    from course.page.upload import FileUploadQuestion
    from course.page.code import CodeQuestion

    if isinstance(page, FileUploadQuestion):
        content, mime_type = page.get_content_from_answer_data(
                fpv.answer)

        from django.core.files.base import ContentFile
        answer_data = page.file_to_answer_data(
                pctx, ContentFile(content), mime_type)
        fpv.answer = answer_data
        fpv.save()

        return True

    elif isinstance(page, CodeQuestion):
        code = page.get_code_from_answer_data(fpv.answer)
        answer_data = page.code_to_answer_data(pctx, code)
        fpv.answer = answer_data
        fpv.save()

        return True
    else:
        return False

    assert False


def convert_flow_page_visits(stdout, stderr):
    fpv_pk_qset = (FlowPageVisit
            .objects
            .annotate(answer_len=Length("answer"))
            .filter(
                Q(answer__contains="base64_data")
                | (
                    # code questions with long answer_data
                    Q(answer__contains="answer")
                    & Q(answer_len__gte=128))
                )
            .values("pk"))

    fpv_pk_qset_iterator = iter(fpv_pk_qset)

    quit = False
    total_count = 0
    while not quit:
        with transaction.atomic():
            for i in range(200):
                try:
                    fpv_pk = next(fpv_pk_qset_iterator)
                except StopIteration:
                    quit = True
                    break
                fpv = (FlowPageVisit
                        .objects
                        .select_related(
                            "flow_session",
                            "flow_session__course",
                            "flow_session__participation",
                            "flow_session__participation__user",
                            "page_data")
                        .get(pk=fpv_pk["pk"]))
                if convert_flow_page_visit(stderr, fpv):
                    total_count += 1

        stdout.write("converted %d page visits..." % total_count)

    stdout.write("done with visits!")


def convert_bulk_feedback(stdout, stderr):
    from course.models import BULK_FEEDBACK_FILENAME_KEY, update_bulk_feedback
    fbf_pk_qset = (FlowPageBulkFeedback
            .objects
            .annotate(bf_len=Length("bulk_feedback"))
            .filter(
                ~Q(bulk_feedback__contains=BULK_FEEDBACK_FILENAME_KEY)
                & Q(bf_len__gte=256))
            .values("pk"))

    fbf_pk_qset_iterator = iter(fbf_pk_qset)

    quit = False
    total_count = 0
    while not quit:
        with transaction.atomic():
            for i in range(200):
                try:
                    fbf_pk = next(fbf_pk_qset_iterator)
                except StopIteration:
                    quit = True
                    break
                fbf = (FlowPageBulkFeedback
                        .objects
                        .select_related(
                            "page_data",
                            "page_data__flow_session",
                            "page_data__flow_session__participation",
                            "page_data__flow_session__participation__user")
                        .get(pk=fbf_pk["pk"]))

                update_bulk_feedback(fbf.page_data, fbf.grade, fbf.bulk_feedback)
                total_count += 1

        stdout.write("converted %d items of bulk feedback..." % total_count)

    stdout.write("done with bulk feedback!")


class Command(BaseCommand):
    help = (
            "Migrates bulk data (e.g. file upload submissions) out of the database "
            "and into the storage given by RELATE_BULK_STORAGE. This command may "
            "safely be interrupted and will pick up where it left off.")

    def handle(self, *args, **options):
        convert_bulk_feedback(self.stdout, self.stderr)
        convert_flow_page_visits(self.stdout, self.stderr)

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