from __future__ import annotations

from datetime import date, timedelta
from decimal import Decimal

from ..extensions import db
from ..models import Expense, ReportLog, User
from .mail import MailService
from .settings import get_bool_setting


def _range_for_frequency(frequency: str, today: date):
    if frequency == 'daily':
        start = today - timedelta(days=1)
        label = start.isoformat()
    elif frequency == 'weekly':
        start = today - timedelta(days=7)
        label = f'{start.isoformat()}..{today.isoformat()}'
    else:
        start = date(today.year, today.month, 1)
        label = f'{today.year}-{today.month:02d}'
    return start, today, label


def send_due_reports(today: date | None = None) -> int:
    if not get_bool_setting('reports_enabled', True):
        return 0
    today = today or date.today()
    sent = 0
    users = User.query.filter(User.report_frequency.in_(['daily', 'weekly', 'monthly'])).all()
    for user in users:
        start, end, label = _range_for_frequency(user.report_frequency, today)
        if ReportLog.query.filter_by(user_id=user.id, frequency=user.report_frequency, period_label=label).first():
            continue
        q = Expense.query.filter_by(user_id=user.id, is_deleted=False).filter(Expense.purchase_date >= start, Expense.purchase_date <= end)
        rows = q.order_by(Expense.purchase_date.desc()).all()
        total = sum((expense.amount for expense in rows), Decimal('0.00'))
        MailService().send_template(user.email, f'Expense report {label}', 'expense_report', user=user, period_label=label, total=total, currency=user.default_currency, expenses=rows[:10])
        db.session.add(ReportLog(user_id=user.id, frequency=user.report_frequency, period_label=label))
        sent += 1
    db.session.commit()
    return sent