from typing import List, Optional
from sqlalchemy.orm import Session

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


def get_todo(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_todos(db: Session, skip: int = 0, limit: int = 100) -> List[Todo]:
    """
    Get multiple todos with pagination
    """
    return db.query(Todo).offset(skip).limit(limit).all()


def create_todo(db: Session, todo: TodoCreate) -> Todo:
    """
    Create a new todo
    """
    db_todo = Todo(
        title=todo.title,
        description=todo.description,
        completed=todo.completed
    )
    db.add(db_todo)
    db.commit()
    db.refresh(db_todo)
    return db_todo


def update_todo(db: Session, todo_id: int, todo_update: TodoUpdate) -> Optional[Todo]:
    """
    Update an existing todo
    """
    db_todo = get_todo(db, todo_id)
    if db_todo is None:
        return None

    update_data = todo_update.dict(exclude_unset=True)
    for key, value in update_data.items():
        setattr(db_todo, key, value)

    db.add(db_todo)
    db.commit()
    db.refresh(db_todo)
    return db_todo


def delete_todo(db: Session, todo_id: int) -> bool:
    """
    Delete a todo by ID
    """
    db_todo = get_todo(db, todo_id)
    if db_todo is None:
        return False

    db.delete(db_todo)
    db.commit()
    return True