from typing import Sequence, Optional
from sqlalchemy import select, desc, func
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import joinedload
from datetime import date, timedelta

from app.domain.models import Appointment


class AppointmentsRepository:
    def __init__(self, db: AsyncSession):
        self.db = db

    async def get_all(self, start_date: date | None = None, end_date: date | None = None) -> Sequence[Appointment]:
        stmt = (
            select(Appointment)
            .options(joinedload(Appointment.type))
            .options(joinedload(Appointment.patient))
            .options(joinedload(Appointment.doctor))
            .order_by(desc(Appointment.appointment_datetime))
        )
        if start_date:
            stmt = stmt.filter(Appointment.appointment_datetime >= start_date)
        if end_date:
            stmt = stmt.filter(Appointment.appointment_datetime <= end_date)
        result = await self.db.execute(stmt)
        return result.scalars().all()

    async def get_by_doctor_id(self, doctor_id: int, start_date: date | None = None, end_date: date | None = None) -> \
            Sequence[Appointment]:
        stmt = (
            select(Appointment)
            .options(joinedload(Appointment.type))
            .options(joinedload(Appointment.patient))
            .options(joinedload(Appointment.doctor))
            .filter_by(doctor_id=doctor_id)
            .order_by(desc(Appointment.appointment_datetime))
        )
        if start_date:
            stmt = stmt.filter(Appointment.appointment_datetime >= start_date)
        if end_date:
            stmt = stmt.filter(Appointment.appointment_datetime <= end_date)
        result = await self.db.execute(stmt)
        return result.scalars().all()

    async def get_reminders(self, current_date: date) -> Sequence[Appointment]:
        stmt = (
            select(Appointment)
            .options(joinedload(Appointment.type))
            .options(joinedload(Appointment.patient))
            .options(joinedload(Appointment.doctor))
            .filter(Appointment.days_until_the_next_appointment.is_not(None))
        )
        result = await self.db.execute(stmt)
        appointments = result.scalars().all()

        filtered_appointments = []
        for appointment in appointments:
            next_appointment_date = (appointment.appointment_datetime + timedelta(
                days=appointment.days_until_the_next_appointment)).date()
            days_until = appointment.days_until_the_next_appointment
            window_days = (
                7 if days_until <= 90 else
                14 if days_until <= 180 else
                30 if days_until <= 365 else
                60
            )
            window_start = next_appointment_date - timedelta(days=window_days)
            window_end = next_appointment_date + timedelta(days=window_days)
            if window_start <= current_date <= window_end:
                filtered_appointments.append(appointment)

        return filtered_appointments

    async def get_upcoming_by_doctor_id(self, doctor_id: int) -> Sequence[Appointment]:
        stmt = (
            select(Appointment)
            .options(joinedload(Appointment.type))
            .options(joinedload(Appointment.patient))
            .options(joinedload(Appointment.doctor))
            .filter_by(doctor_id=doctor_id)
            .filter(Appointment.appointment_datetime >= func.now())
            .order_by(Appointment.appointment_datetime)
            .limit(5)
        )
        result = await self.db.execute(stmt)
        return result.scalars().all()

    async def get_by_patient_id(self, patient_id: int, start_date: date | None = None, end_date: date | None = None) -> \
            Sequence[Appointment]:
        stmt = (
            select(Appointment)
            .options(joinedload(Appointment.type))
            .options(joinedload(Appointment.patient))
            .options(joinedload(Appointment.doctor))
            .filter_by(patient_id=patient_id)
            .order_by(desc(Appointment.appointment_datetime))
        )
        if start_date:
            stmt = stmt.filter(Appointment.appointment_datetime >= start_date)
        if end_date:
            stmt = stmt.filter(Appointment.appointment_datetime <= end_date)
        result = await self.db.execute(stmt)
        return result.scalars().all()

    async def get_by_id(self, appointment_id: int) -> Optional[Appointment]:
        stmt = (
            select(Appointment)
            .options(joinedload(Appointment.type))
            .options(joinedload(Appointment.patient))
            .options(joinedload(Appointment.doctor))
            .filter_by(id=appointment_id)
        )
        result = await self.db.execute(stmt)
        return result.scalars().first()

    async def create(self, appointment: Appointment) -> Appointment:
        self.db.add(appointment)
        await self.db.commit()
        await self.db.refresh(appointment)
        return appointment

    async def update(self, appointment: Appointment) -> Appointment:
        await self.db.merge(appointment)
        await self.db.commit()
        return appointment

    async def delete(self, appointment) -> Appointment:
        await self.db.delete(appointment)
        await self.db.commit()
        return appointment