from __future__ import annotations

from datetime import datetime, timedelta
from uuid import uuid4

from fastapi import Request, Response
from sqlalchemy import delete, select

from app.core.config import settings
from app.db.engine import get_session
from app.db.models import Session


SESSION_COOKIE_NAME = "session_id"


def _now_utc() -> datetime:
    return datetime.utcnow()


def create_session(user_id: int, request: Request) -> str:
    session_id = uuid4().hex
    expires_at = _now_utc() + timedelta(minutes=settings.session_expiry_minutes)
    db = get_session()
    try:
        record = Session(
            id=session_id,
            user_id=user_id,
            expires_at=expires_at,
            ip=request.client.host if request.client else "",
            user_agent=request.headers.get("User-Agent", ""),
        )
        db.add(record)
        db.commit()
    finally:
        db.close()
    return session_id


def delete_session(session_id: str) -> None:
    db = get_session()
    try:
        db.execute(delete(Session).where(Session.id == session_id))
        db.commit()
    finally:
        db.close()


def set_session_cookie(response: Response, session_id: str) -> None:
    response.set_cookie(
        SESSION_COOKIE_NAME,
        session_id,
        httponly=True,
        samesite="lax",
        max_age=settings.session_expiry_minutes * 60,
    )


def clear_session_cookie(response: Response) -> None:
    response.delete_cookie(SESSION_COOKIE_NAME)


def get_current_user(request: Request) -> User | None:
    if hasattr(request.state, "user"):
        return request.state.user

    session_id = request.cookies.get(SESSION_COOKIE_NAME)
    if not session_id:
        request.state.user = None
        return None

    db = get_session()
    try:
        record = db.scalar(select(Session).where(Session.id == session_id))
        if not record:
            request.state.user = None
            return None
        if record.expires_at <= _now_utc():
            db.execute(delete(Session).where(Session.id == session_id))
            db.commit()
            request.state.user = None
            return None
        user = db.get(User, record.user_id)
        if not user or not user.is_active:
            request.state.user = None
            return None
        request.state.user = user
        return user
    finally:
        db.close()