from datetime import date
from sqlalchemy import select, func, Subquery, cast
from sqlalchemy.dialects.postgresql import TIMESTAMP
from models import PaymentRecord, Expense
from services.base import BaseService
from services.statistics.common import generate_date_range


class ExpensesStatisticsService(BaseService):
    date_from: date
    date_to: date

    def _get_expenses_sub(self, model, date_column, amount_column) -> Subquery:
        all_dates = generate_date_range(self.date_from, self.date_to, ["expenses"])

        expenses = (
            select(
                func.sum(getattr(model, amount_column)).label("expenses"),
                cast(getattr(model, date_column), TIMESTAMP(timezone=False)).label("date"),
            )
            .group_by("date")
            .subquery()
        )

        expenses_with_gaps_filled = (
            select(
                all_dates.c.date,
                (all_dates.c.expenses + func.coalesce(expenses.c.expenses, 0)).label("expenses"),
            )
            .join(expenses, all_dates.c.date == expenses.c.date, isouter=True)
            .order_by(all_dates.c.date)
            .subquery()
        )
        return expenses_with_gaps_filled

    def _apply_expenses(self, deals_by_dates: Subquery, expenses_subquery: Subquery):
        return (
            select(
                deals_by_dates.c.date,
                deals_by_dates.c.deals_count,
                deals_by_dates.c.revenue,
                (func.coalesce(deals_by_dates.c.profit, 0) - func.coalesce(expenses_subquery.c.expenses, 0)).label(
                    "profit"),
                (deals_by_dates.c.expenses + expenses_subquery.c.expenses).label("expenses"),
            )
            .join(expenses_subquery, expenses_subquery.c.date == deals_by_dates.c.date)
        )

    def apply_expenses(self, date_from: date, date_to: date, deals_by_dates: Subquery):
        self.date_from, self.date_to = date_from, date_to

        # Apply salary expenses
        salary_expenses = self._get_expenses_sub(PaymentRecord, "start_date", "amount")
        deals_by_dates = self._apply_expenses(deals_by_dates, salary_expenses)

        # Apply additional expenses
        additional_expenses = self._get_expenses_sub(Expense, "spent_date", "amount")
        deals_by_dates = self._apply_expenses(deals_by_dates, additional_expenses)

        return deals_by_dates