from datetime import datetime

from scheduler.database import storage
from scheduler.manager.validator import (
    validate_employee_can_join_shift,
    validate_user_has_not_worked_more_than_five_days,
    validate_user_has_not_worked_same_day,
)

SHIFTS = ("morning", "afternoon", "evening")
DAYS = ("sunday", "monday", "tuesday", "wednesday", "thursday", "friday", "saturday")
MAX_EMPLOYEES_PER_SHIFT = 2


def _value(value):
    return value.value if hasattr(value, "value") else value


def _count_shift_employees(connection, day_of_week, shift, company_id=None):
    count = storage.count_shift_employees(
        connection, _value(day_of_week), _value(shift), company_id
    )
    if isinstance(count, dict):
        return count.get("cnt", count.get("employee_count", 0))
    return count


def _is_shift_full(connection, day_of_week, shift, company_id=None):
    return (
        _count_shift_employees(connection, day_of_week, shift, company_id)
        >= MAX_EMPLOYEES_PER_SHIFT
    )


def _get_user_company_id(connection, user_id):
    return storage.get_user_company_id(connection, user_id)


def _get_company_employee_ids(connection, company_id):
    return storage.get_company_employee_ids(connection, company_id)


def _get_shift_preferences(connection, user_id, day_of_week):
    row = storage.get_weekly_preferences(connection, user_id, _value(day_of_week))
    if row is None:
        return list(SHIFTS)
    return [row["first"], row["second"], row["third"]]


def _get_next_day(current_day):
    day = _value(current_day)
    if day not in DAYS:
        return None
    return DAYS[(DAYS.index(day) + 1) % len(DAYS)]


def _assign_shift(connection, user_id, day_of_week, shift, company_id=None):
    company_id = (
        company_id
        if company_id is not None
        else _get_user_company_id(connection, user_id)
    )
    if _is_shift_full(connection, day_of_week, shift, company_id):
        return None
    if not validate_employee_can_join_shift(
        connection, user_id, _value(day_of_week), _value(shift)
    ):
        return None
    return storage.add_schedule(
        connection,
        user_id,
        datetime.now(),
        _value(day_of_week),
        None,
        _value(shift),
    )


def detect_preferred_shift_conflict(connection, user_id, day_of_week, preferred_shift):
    company_id = _get_user_company_id(connection, user_id)
    return (
        _is_shift_full(connection, day_of_week, preferred_shift, company_id)
        or not validate_user_has_not_worked_same_day(
            connection, user_id, _value(day_of_week)
        )
        or not validate_user_has_not_worked_more_than_five_days(connection, user_id)
    )


def resolve_conflict_same_day(connection, user_id, day_of_week):
    for shift in SHIFTS:
        schedule = _assign_shift(connection, user_id, day_of_week, shift)
        if schedule is not None:
            return schedule
    return None


def resolve_conflict_next_day(connection, user_id, current_day):
    next_day = _get_next_day(current_day)
    if next_day is None:
        return None

    for shift in _get_shift_preferences(connection, user_id, next_day):
        schedule = _assign_shift(connection, user_id, next_day, shift)
        if schedule is not None:
            return schedule
    return None


def resolve_missing_second_employee(connection, company_id, day_of_week, shift):
    if (
        _count_shift_employees(connection, day_of_week, shift, company_id)
        >= MAX_EMPLOYEES_PER_SHIFT
    ):
        return None

    for user_id in _get_company_employee_ids(connection, company_id):
        schedule = _assign_shift(connection, user_id, day_of_week, shift, company_id)
        if schedule is not None:
            return schedule
    return None