from typing import Optional, Any
from sqlalchemy.orm import Session
from fastapi import BackgroundTasks
from app.models.AuditLogModel import AuditLog
from app.core.database.db_session import SessionLocal
import ulid

class AuditService:
    @staticmethod
    def log_change(
        db: Session,
        request_id: str,
        user_id: Optional[str],
        entity_type: str,
        entity_id: str,
        action: str,
        old_value: Optional[Any],
        new_value: Optional[Any],
        ip_address: str,
        user_agent: Optional[str]
    ) -> AuditLog:
        audit_id = str(ulid.ULID())
        log_entry = AuditLog(
            audit_id=audit_id,
            request_id=request_id,
            user_id=user_id,
            entity_type=entity_type,
            entity_id=entity_id,
            action=action,
            old_value=old_value,
            new_value=new_value,
            ip_address=ip_address,
            user_agent=user_agent
        )
        db.add(log_entry)
        db.commit()
        db.refresh(log_entry)
        return log_entry

    @classmethod
    def _log_change_task(
        cls,
        request_id: str,
        user_id: Optional[str],
        entity_type: str,
        entity_id: str,
        action: str,
        old_value: Optional[Any],
        new_value: Optional[Any],
        ip_address: str,
        user_agent: Optional[str]
    ) -> None:
        # Open fresh session for background thread
        db = SessionLocal()
        try:
            cls.log_change(
                db=db,
                request_id=request_id,
                user_id=user_id,
                entity_type=entity_type,
                entity_id=entity_id,
                action=action,
                old_value=old_value,
                new_value=new_value,
                ip_address=ip_address,
                user_agent=user_agent
            )
        finally:
            db.close()

    @classmethod
    def log_change_async(
        cls,
        background_tasks: BackgroundTasks,
        request_id: str,
        user_id: Optional[str],
        entity_type: str,
        entity_id: str,
        action: str,
        old_value: Optional[Any],
        new_value: Optional[Any],
        ip_address: str,
        user_agent: Optional[str]
    ) -> None:
        background_tasks.add_task(
            cls._log_change_task,
            request_id=request_id,
            user_id=user_id,
            entity_type=entity_type,
            entity_id=entity_id,
            action=action,
            old_value=old_value,
            new_value=new_value,
            ip_address=ip_address,
            user_agent=user_agent
        )

audit_service = AuditService()