import typing
from datetime import datetime
from io import BytesIO
from itertools import groupby

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

from vbv_lernwelt.course.models import CourseSessionUser
from vbv_lernwelt.course_session.models import CourseSessionAttendanceCourse

logger = structlog.get_logger(__name__)

ATTENDANCE_EXPORT_FILENAME = _("export_anwesenheit")


def export_attendance(
    course_session_ids: list[str],
    save_as_file: bool = False,
    circle_ids: list[int] = None,
):
    wb = Workbook()

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

    attendance_courses = CourseSessionAttendanceCourse.objects.filter(
        course_session_id__in=course_session_ids
    ).order_by("course_session", "due_date")

    grouped_cs_users = get_ordered_csus_by_course_session(course_session_ids)

    # create dict with course_session_title as key and list of attendance_courses as value. Easier to access in the loop
    grouped_attendance_course = {
        key: list(group)
        for key, group in groupby(
            sorted(attendance_courses, key=lambda x: x.course_session.title),
            key=lambda x: x.course_session.title,
        )
    }

    # create a sheet for each course_session
    for course_session, cs_users in grouped_cs_users.items():
        logger.debug(
            "export_attendance_for_course_session",
            data={
                "course_session": course_session,
            },
            label="attendance_export",
        )
        _create_sheet(
            wb,
            course_session,
            cs_users,
            grouped_attendance_course[course_session],
            circle_ids,
        )

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

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


def _create_sheet(
    wb: Workbook,
    title: str,
    users: list[CourseSessionUser],
    attendance_courses: list[CourseSessionAttendanceCourse],
    circle_ids: typing.Optional[list[int]],
):
    sheet = wb.create_sheet(title=sanitize_sheet_name(title))

    if len(users) == 0:
        return sheet

    # headers
    # common user headers..., <attendance_course> <date>, status <attendance_course>, ..
    col_idx = add_user_headers(sheet)

    sheet.cell(row=1, column=col_idx, value=str(_("Optionale Anwesenheit")))
    col_idx += 1

    attendance_data = {}

    for course in attendance_courses:
        circle = course.get_circle()
        if circle_ids and circle.id not in circle_ids:
            continue

        presence_str = str(_("Anwesenheit"))  # f-strings are not picked up by gettext

        sheet.cell(
            row=1,
            column=col_idx,
            value=f"{presence_str} {circle.title} {course.due_date.start.strftime('%d.%m.%Y')}",
        )
        user_dict_map = {d["user_id"]: d for d in course.attendance_user_list}
        attendance_data[circle.title] = user_dict_map

        col_idx += 1

    # add rows with user data
    _add_rows(sheet, users, attendance_data)

    return sheet


def _add_rows(sheet, users: list[CourseSessionUser], attendance_data):
    for row_idx, user in enumerate(users, start=2):
        col_idx = add_user_export_data(sheet, user, row_idx)

        optional_attendance_text = (
            str(_("Ja")) if user.optional_attendance else str(_("Nein"))
        )
        sheet.cell(row=row_idx, column=col_idx, value=optional_attendance_text)
        col_idx += 1

        for key, user_dict_map in attendance_data.items():
            user_dict = user_dict_map.get(str(user.user.id), {})
            status = user_dict.get("status", "") if user_dict else ""
            status_text = (
                str(_("Anwesend")) if status == "PRESENT" else str(_("Nicht anwesend"))
            )
            sheet.cell(row=row_idx, column=col_idx, value=status_text)
            col_idx += 1


def add_user_headers(sheet):
    sheet.cell(row=1, column=1, value=str(_("Vorname")))
    sheet.cell(row=1, column=2, value=str(_("Nachname")))
    sheet.cell(row=1, column=3, value=str(_("Email")))
    sheet.cell(row=1, column=4, value=str(_("Lehrvertragsnummer")))

    return 5  # return the next column index


def add_user_export_data(sheet, user: CourseSessionUser, row_idx: int) -> int:
    sheet.cell(row=row_idx, column=1, value=user.user.first_name)
    sheet.cell(row=row_idx, column=2, value=user.user.last_name)
    sheet.cell(row=row_idx, column=3, value=user.user.email)
    sheet.cell(
        row=row_idx,
        column=4,
        value=user.user.additional_json_data.get("Lehrvertragsnummer", ""),
    )

    return 5  # return the next column index


def get_ordered_csus_by_course_session(course_session_ids: list[str]):
    csus = CourseSessionUser.objects.filter(
        course_session_id__in=course_session_ids, role=CourseSessionUser.Role.MEMBER
    ).order_by("course_session", "user__last_name", "user__first_name")
    return group_by_session_title(
        sorted(csus, key=lambda x: x.course_session.title),
    )


def group_by_session_title(items):
    return {
        key: list(group)
        for key, group in groupby(
            sorted(items, key=lambda x: x.course_session.title),
            key=lambda x: x.course_session.title,
        )
    }


def make_export_filename(name: str):
    today_date = datetime.today().strftime("%Y-%m-%d")
    return f"{name}_{today_date}.xlsx"


def sanitize_sheet_name(text, default_name="DefaultSheet"):
    if text is None:
        return default_name

    prohibited_chars = ["\\", "/", "*", "?", ":", "[", "]"]
    for char in prohibited_chars:
        text = text.replace(char, "")

    text = text.strip("'")

    text = text[:31]

    if len(text) == 0:
        return default_name

    return text