from typing import List, Optional
from datetime import datetime

from sqlalchemy.orm import Session
from sqlalchemy import and_, not_

from app.models.todo import Todo
from app.schemas.todo import TodoCreate, TodoUpdate


class CRUDTodo:
    """CRUD operations for Todo model."""

    def get(self, db: Session, todo_id: int) -> Optional[Todo]:
        """Get a single todo by ID."""
        return db.query(Todo).filter(Todo.id == todo_id).first()

    def get_multi(
        self,
        db: Session,
        *,
        skip: int = 0,
        limit: int = 100,
        category: Optional[str] = None,
        completed: Optional[bool] = None,
        overdue_only: bool = False,
    ) -> List[Todo]:
        """Get multiple todos with pagination and filtering."""
        query = db.query(Todo)

        filters = []
        if category:
            filters.append(Todo.category == category)
        if completed is not None:
            filters.append(Todo.completed == completed)
        if overdue_only:
            filters.append(and_(Todo.due_date < datetime.now(), not_(Todo.completed)))

        if filters:
            query = query.filter(and_(*filters))

        return query.offset(skip).limit(limit).all()

    def create(self, db: Session, *, obj_in: TodoCreate) -> Todo:
        """Create a new todo."""
        db_obj = Todo(
            title=obj_in.title,
            description=obj_in.description,
            completed=obj_in.completed,
            category=obj_in.category,
            due_date=obj_in.due_date,
        )
        db.add(db_obj)
        db.commit()
        db.refresh(db_obj)
        return db_obj

    def update(self, db: Session, *, db_obj: Todo, obj_in: TodoUpdate) -> Todo:
        """Update a todo."""
        update_data = obj_in.model_dump(exclude_unset=True)
        for field, value in update_data.items():
            setattr(db_obj, field, value)
        db.add(db_obj)
        db.commit()
        db.refresh(db_obj)
        return db_obj

    def remove(self, db: Session, *, todo_id: int) -> Optional[Todo]:
        """Delete a todo."""
        obj = db.query(Todo).get(todo_id)
        if obj:
            db.delete(obj)
            db.commit()
        return obj

    def get_by_category(self, db: Session, *, category: str) -> List[Todo]:
        """Get all todos by category."""
        return db.query(Todo).filter(Todo.category == category).all()

    def get_overdue(self, db: Session) -> List[Todo]:
        """Get all overdue todos."""
        return (
            db.query(Todo)
            .filter(and_(Todo.due_date < datetime.now(), not_(Todo.completed)))
            .all()
        )


todo = CRUDTodo()