"""In-memory translation session store with 24h TTL."""

import uuid
from datetime import datetime, timezone, timedelta
from typing import Any

from backend.models import TranslationSession


class SessionStore:
    """Thread-safe-ish in-memory dict for translation sessions.

    Each session is keyed by a UUID and has a 24-hour TTL.
    Expired sessions are lazily cleaned on access.
    """

    def __init__(self, ttl_hours: int = 24):
        self._store: dict[str, dict[str, Any]] = {}
        self.ttl_hours = ttl_hours

    def create(self, session_data: TranslationSession) -> str:
        session_id = uuid.uuid4().hex[:16]
        self._store[session_id] = {
            "data": session_data.model_dump(),
            "created_at": datetime.now(timezone.utc),
            "updated_at": datetime.now(timezone.utc),
        }
        return session_id

    def get(self, session_id: str) -> TranslationSession | None:
        entry = self._store.get(session_id)
        if entry is None:
            return None
        # Check TTL
        now = datetime.now(timezone.utc)
        age = now - entry["updated_at"]
        if age > timedelta(hours=self.ttl_hours):
            del self._store[session_id]
            return None
        # Touch (refresh TTL)
        entry["updated_at"] = now
        return TranslationSession(**entry["data"])

    def update(self, session_id: str, data: dict[str, Any]) -> TranslationSession | None:
        entry = self._store.get(session_id)
        if entry is None:
            return None
        entry["data"].update(data)
        entry["updated_at"] = datetime.now(timezone.utc)
        return TranslationSession(**entry["data"])

    def delete(self, session_id: str) -> bool:
        if session_id in self._store:
            del self._store[session_id]
            return True
        return False

    def cleanup_expired(self):
        """Remove all expired sessions."""
        now = datetime.now(timezone.utc)
        expired_keys = [
            k for k, v in self._store.items()
            if (now - v["updated_at"]) > timedelta(hours=self.ttl_hours)
        ]
        for k in expired_keys:
            del self._store[k]


# Singleton instance
session_store = SessionStore(ttl_hours=24)