from io import BytesIO

import structlog
from django.utils.translation import gettext_lazy as _
from openpyxl import Workbook

from vbv_lernwelt.core.models import User
from vbv_lernwelt.course.models import CourseSession
from vbv_lernwelt.course_session.services.export_attendance import (
    add_user_headers,
    make_export_filename,
    sanitize_sheet_name,
)
from vbv_lernwelt.dashboard.utils import create_person_list_with_roles

PERSONS_EXPORT_FILENAME = _("export_personen")

logger = structlog.get_logger(__name__)


def export_persons(
    user: User,
    course_session_ids: list[str],
    save_as_file: bool = False,
):
    if len(course_session_ids) == 0:
        return

    wb = Workbook()
    # remove the first sheet is just easier than keeping track of the active sheet
    wb.remove(wb.active)

    user_with_roles = create_person_list_with_roles(user, course_session_ids)
    course_sessions = CourseSession.objects.filter(id__in=course_session_ids)

    for cs in course_sessions:
        _create_sheet(
            wb,
            cs.title,
            cs.id,
            user_with_roles,
        )

    if save_as_file:
        wb.save(make_export_filename(PERSONS_EXPORT_FILENAME))
    else:
        output = BytesIO()
        wb.save(output)

        output.seek(0)
        return output.getvalue()


def _create_sheet(
    wb: Workbook,
    title: str,
    cs_id: int,
    user_with_roles,
):
    sheet = wb.create_sheet(title=sanitize_sheet_name(title))

    if len(user_with_roles) == 0:
        return sheet

    # headers
    # common user headers, Circle <title> <learningcontenttitle> bestanden,  Circle <title> <learningcontenttitle> Resultat, ...
    col_idx = add_user_headers(sheet)
    sheet.cell(row=1, column=col_idx, value=str(_("Telefon")))
    sheet.cell(row=1, column=col_idx + 1, value=str(_("Rolle")))

    _add_rows(sheet, user_with_roles, cs_id)

    return sheet


def _add_rows(
    sheet,
    users,
    course_session_id,
):
    idx_offset = 0

    for row_idx, user in enumerate(users, start=2):

        def get_user_cs_by_id(user_cs, cs_id):
            return next((cs for cs in user_cs if int(cs.get("id")) == cs_id), None)

        user_cs = get_user_cs_by_id(user["course_sessions"], course_session_id)

        if not user_cs:
            logger.warning(
                "User not found in course session",
                user_id=user["user_id"],
                course_session_id=course_session_id,
            )
            idx_offset += 1
            continue

        user_role = (user_cs.get("user_role"),)
        idx = row_idx - idx_offset

        sheet.cell(row=idx, column=1, value=user["first_name"])
        sheet.cell(row=idx, column=2, value=user["last_name"])
        sheet.cell(row=idx, column=3, value=user["email"])
        sheet.cell(row=idx, column=4, value=user.get("Lehrvertragsnummer", ""))
        sheet.cell(
            row=idx,
            column=5,
            value=user.get("phone", ""),
        )
        sheet.cell(row=idx, column=6, value=user_role[0])