# 1 — Data Engineer (data) — models.py

**Malli:** `qwen-coder`

## System Prompt

```
You are a database architect specializing in SQLAlchemy and relational databases.

YOUR RESPONSIBILITIES:
1. Design normalized database schemas with proper column types and constraints
2. Define SQLAlchemy models with __tablename__, primary keys, indexes, and relationships
3. Set up engine, SessionLocal, and Base in the same file (models.py or database.py)
4. Use String(length) not bare String for SQLite compatibility
5. Add nullable=False for required fields, unique=True where appropriate
6. Use Column(Integer, primary_key=True, index=True) for IDs

ALWAYS INCLUDE:
- from sqlalchemy import create_engine, Column, Integer, String
- from sqlalchemy.ext.declarative import declarative_base
- from sqlalchemy.orm import sessionmaker
- DATABASE_URL, engine, SessionLocal, Base
```

## Syöte

```
You are a database architect specializing in SQLAlchemy and relational databases.

YOUR RESPONSIBILITIES:
1. Design normalized database schemas with proper column types and constraints
2. Define SQLAlchemy models with __tablename__, primary keys, indexes, and relationships
3. Set up engine, SessionLocal, and Base in the same file (models.py or database.py)
4. Use String(length) not bare String for SQLite compatibility
5. Add nullable=False for required fields, unique=True where appropriate
6. Use Column(Integer, primary_key=True, index=True) for IDs

ALWAYS INCLUDE:
- from sqlalchemy import create_engine, Column, Integer, String
- from sqlalchemy.ext.declarative import declarative_base
- from sqlalchemy.orm import sessionmaker
- DATABASE_URL, engine, SessionLocal, Base

EXAMPLE of models.py (for a different project, adapt to this one):
```
from sqlalchemy import create_engine, Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

DATABASE_URL = "sqlite:///./app.db"
engine = create_engine(DATABASE_URL, connect_args={"check_same_thread": False})
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
Base = declarative_base()

class Item(Base):
    __tablename__ = "items"
    id = Column(Integer, primary_key=True, index=True)
    name = Column(String(100), nullable=False)
    description = Column(String(500))
```

PROJECT REQUIREMENTS (from product owner):
1. **PROJECT NAME:** Todo-sovellus

2. **GOAL:** A simple task manager for individuals to keep track of their daily tasks and manage them efficiently.

3. **CORE FEATURES:**
   - Create new todos with title, description, due date.
   - Read/View all todos or a single todo by ID.
   - Update existing todos (title, description, status).
   - Delete completed or unnecessary todos.
   - Filter todos by status (e.g., pending, completed).

4. **DATA MODEL:**
   - Todo
     - id (integer, primary key)
     - title (string)
     - description (text)
     - due_date (date)
     - status (enum: 'pending', 'completed')

5. **API ENDPOINTS:**
   - GET /todos: Retrieve all todos.
   - GET /todos/{id}: Retrieve a single todo by ID.
   - POST /todos: Create a new todo.
   - PUT /todos/{id}: Update an existing todo.
   - DELETE /todos/{id}: Delete a todo.

6. **CONSTRAINTS:**
   - Must use SQLite as the database.
   - No authentication required for accessing endpoints.
   - Implement unit tests and integration tests to ensure functionality.

NOW write "models.py" for THIS project: Todo-sovellus FastAPI + SQLite, CRUD-endpointit ja testit
Define the SQLAlchemy model based on the project description. Always include:
- engine with check_same_thread=False for SQLite
- SessionLocal with autocommit=False
- Base = declarative_base()
- Model class with __tablename__, primary key, and fields
Adapt to the project requirements. Import from already written files. Write ONLY the code, no explanations.
```

## Tulos

```
from sqlalchemy import create_engine, Column, Integer, String, Date, Enum
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

DATABASE_URL = "sqlite:///./todo.db"
engine = create_engine(DATABASE_URL, connect_args={"check_same_thread": False})
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
Base = declarative_base()

class Todo(Base):
    __tablename__ = "todos"
    id = Column(Integer, primary_key=True, index=True)
    title = Column(String(100), nullable=False)
    description = Column(String(500))
    due_date = Column(Date, nullable=False)
    status = Column(Enum('pending', 'completed'), default='pending')
```