from sqlalchemy.orm import Session
from app.dao.task_dao import TaskDAO
from app.model.task_model import Task

class TaskService:
    def __init__(self, db_session: Session):
        self.task_dao = TaskDAO(db_session)

    def get_all_tasks(self):
        return self.task_dao.get_all()

    def get_task_by_id(self, task_id: int):
        task = self.task_dao.get_by_id(task_id)
        if not task:
            raise ValueError(f"Task with id {task_id} not found.")
        return task

    def create_new_task(self, title: str, description: str = None):
        if not title:
            raise ValueError("Title cannot be empty.")
        
        new_task = Task(title=title, description=description)
        return self.task_dao.create(new_task)

    def update_existing_task(self, task_id: int, title: str = None, description: str = None, done: bool = None):
        task = self.get_task_by_id(task_id) # 复用 get_task_by_id 方法，包含了查找不到的逻辑

        if title is not None:
            task.title = title
        if description is not None:
            task.description = description
        if done is not None:
            task.done = done
            
        return self.task_dao.update(task)

    def delete_task(self, task_id: int):
        task = self.get_task_by_id(task_id)
        self.task_dao.delete(task)
        return True