Build a simple Todo app with FastAPI

- Setup project structure with FastAPI, SQLAlchemy, and SQLite
- Create Todo model and database migrations
- Implement CRUD API endpoints
- Add error handling and validation
- Update README with documentation and examples

generated with BackendIM... (backend.im)

README.md

@@ -1,3 +1,143 @@
-# FastAPI Application
+# Simple Todo Application
 
-This is a FastAPI application bootstrapped by BackendIM, the AI-powered backend generation platform.
+A simple RESTful API for managing todos built with FastAPI, SQLAlchemy, and SQLite.
+
+## Features
+
+- Create, Read, Update, Delete todo items
+- Filter todos by completion status
+- Proper error handling and validation
+- API documentation via Swagger UI
+- SQLite database for persistence
+- Database migrations using Alembic
+
+## Project Structure
+
+```
+simpletodoapplication/
+├── alembic/               # Database migration scripts
+├── app/                   # Application package
+│   ├── api/               # API endpoints
+│   │   └── routers/       # API routers
+│   ├── core/              # Core functionality
+│   ├── db/                # Database session and connection
+│   ├── models/            # SQLAlchemy models
+│   └── schemas/           # Pydantic schemas
+├── alembic.ini            # Alembic configuration
+├── main.py                # Application entry point
+└── requirements.txt       # Project dependencies
+```
+
+## Setup
+
+1. Clone the repository:
+
+```bash
+git clone <repository-url>
+cd simpletodoapplication
+```
+
+2. Install dependencies:
+
+```bash
+pip install -r requirements.txt
+```
+
+3. Apply database migrations:
+
+```bash
+alembic upgrade head
+```
+
+4. Run the application:
+
+```bash
+uvicorn main:app --reload
+```
+
+The API server will be running at http://localhost:8000.
+
+## API Documentation
+
+Once the server is running, you can access the auto-generated API documentation:
+
+- Swagger UI: http://localhost:8000/docs
+- ReDoc: http://localhost:8000/redoc
+
+## API Endpoints
+
+- `GET /api/v1/todos`: Get all todos
+  - Query Parameters:
+    - `skip`: Number of items to skip (default: 0)
+    - `limit`: Maximum number of items to return (default: 100)
+    - `completed`: Filter by completion status (boolean, optional)
+
+- `POST /api/v1/todos`: Create a new todo
+  - Request Body:
+    - `title`: String (required)
+    - `description`: String (optional)
+    - `completed`: Boolean (default: false)
+
+- `GET /api/v1/todos/{todo_id}`: Get a specific todo by ID
+
+- `PUT /api/v1/todos/{todo_id}`: Update a todo
+  - Request Body (all fields optional):
+    - `title`: String
+    - `description`: String
+    - `completed`: Boolean
+
+- `DELETE /api/v1/todos/{todo_id}`: Delete a todo
+
+- `GET /health`: Health check endpoint
+
+## Example Requests
+
+### Create a Todo
+
+```bash
+curl -X 'POST' \
+  'http://localhost:8000/api/v1/todos/' \
+  -H 'accept: application/json' \
+  -H 'Content-Type: application/json' \
+  -d '{
+  "title": "Buy groceries",
+  "description": "Milk, eggs, bread",
+  "completed": false
+}'
+```
+
+### Get All Todos
+
+```bash
+curl -X 'GET' \
+  'http://localhost:8000/api/v1/todos/' \
+  -H 'accept: application/json'
+```
+
+### Get Only Completed Todos
+
+```bash
+curl -X 'GET' \
+  'http://localhost:8000/api/v1/todos/?completed=true' \
+  -H 'accept: application/json'
+```
+
+### Update a Todo
+
+```bash
+curl -X 'PUT' \
+  'http://localhost:8000/api/v1/todos/1' \
+  -H 'accept: application/json' \
+  -H 'Content-Type: application/json' \
+  -d '{
+  "completed": true
+}'
+```
+
+### Delete a Todo
+
+```bash
+curl -X 'DELETE' \
+  'http://localhost:8000/api/v1/todos/1' \
+  -H 'accept: application/json'
+```

alembic.ini

@@ -0,0 +1,85 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = alembic
+
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# timezone to use when rendering the date
+# within the migration file as well as the filename.
+# string value is passed to dateutil.tz.gettz()
+# leave blank for localtime
+# timezone =
+
+# max length of characters to apply to the
+# "slug" field
+# truncate_slug_length = 40
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+# set to 'true' to allow .pyc and .pyo files without
+# a source .py file to be detected as revisions in the
+# versions/ directory
+# sourceless = false
+
+# version location specification; this defaults
+# to alembic/versions.  When using multiple version
+# directories, initial revisions must be specified with --version-path
+# version_locations = %(here)s/bar %(here)s/bat alembic/versions
+
+# the output encoding used when revision files
+# are written from script.py.mako
+# output_encoding = utf-8
+
+sqlalchemy.url = sqlite:////app/storage/db/db.sqlite
+
+
+[post_write_hooks]
+# post_write_hooks defines scripts or Python functions that are run
+# on newly generated revision scripts.  See the documentation for further
+# detail and examples
+
+# format using "black" - use the console_scripts runner, against the "black" entrypoint
+# hooks=black
+# black.type=console_scripts
+# black.entrypoint=black
+# black.options=-l 79
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

alembic/env.py

@@ -0,0 +1,79 @@
+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+from app.db.session import Base
+from app.models.todo import Todo
+target_metadata = Base.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline():
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online():
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection, target_metadata=target_metadata
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

alembic/script.py.mako

@@ -0,0 +1,24 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+branch_labels = ${repr(branch_labels)}
+depends_on = ${repr(depends_on)}
+
+
+def upgrade():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}

alembic/versions/01_create_todos_table.py

@@ -0,0 +1,37 @@
+"""Create todos table
+
+Revision ID: 01_create_todos_table
+Revises: 
+Create Date: 2025-05-15
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '01_create_todos_table'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.create_table(
+        'todos',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('title', sa.String(), nullable=False),
+        sa.Column('description', sa.String(), nullable=True),
+        sa.Column('completed', sa.Boolean(), default=False),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('now()')),
+        sa.Column('updated_at', sa.DateTime(timezone=True), nullable=True),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_todos_id'), 'todos', ['id'], unique=False)
+    op.create_index(op.f('ix_todos_title'), 'todos', ['title'], unique=False)
+
+
+def downgrade():
+    op.drop_index(op.f('ix_todos_title'), table_name='todos')
+    op.drop_index(op.f('ix_todos_id'), table_name='todos')
+    op.drop_table('todos')

app/api/routers/todo.py

@@ -0,0 +1,81 @@
+from typing import List, Optional
+from fastapi import APIRouter, Depends, status, Query
+from sqlalchemy.orm import Session
+
+from app.core.exceptions import TodoNotFoundException
+from app.db.session import get_db
+from app.models.todo import Todo as TodoModel
+from app.schemas.todo import Todo, TodoCreate, TodoUpdate
+
+router = APIRouter(prefix="/todos", tags=["todos"])
+
+@router.get("/", response_model=List[Todo])
+def read_todos(
+    skip: int = 0,
+    limit: int = 100,
+    completed: Optional[bool] = None,
+    db: Session = Depends(get_db)
+):
+    """
+    Retrieve all todos with optional filtering by completion status.
+    """
+    query = db.query(TodoModel)
+    
+    # Filter by completion status if provided
+    if completed is not None:
+        query = query.filter(TodoModel.completed == completed)
+    
+    todos = query.offset(skip).limit(limit).all()
+    return todos
+
+@router.post("/", response_model=Todo, status_code=status.HTTP_201_CREATED)
+def create_todo(todo: TodoCreate, db: Session = Depends(get_db)):
+    """
+    Create a new todo item.
+    """
+    db_todo = TodoModel(**todo.dict())
+    db.add(db_todo)
+    db.commit()
+    db.refresh(db_todo)
+    return db_todo
+
+@router.get("/{todo_id}", response_model=Todo)
+def read_todo(todo_id: int, db: Session = Depends(get_db)):
+    """
+    Get a specific todo by ID.
+    """
+    db_todo = db.query(TodoModel).filter(TodoModel.id == todo_id).first()
+    if db_todo is None:
+        raise TodoNotFoundException(todo_id=todo_id)
+    return db_todo
+
+@router.put("/{todo_id}", response_model=Todo)
+def update_todo(todo_id: int, todo: TodoUpdate, db: Session = Depends(get_db)):
+    """
+    Update a todo item.
+    """
+    db_todo = db.query(TodoModel).filter(TodoModel.id == todo_id).first()
+    if db_todo is None:
+        raise TodoNotFoundException(todo_id=todo_id)
+    
+    # Update only the fields that are provided
+    update_data = todo.dict(exclude_unset=True)
+    for key, value in update_data.items():
+        setattr(db_todo, key, value)
+    
+    db.commit()
+    db.refresh(db_todo)
+    return db_todo
+
+@router.delete("/{todo_id}", status_code=status.HTTP_204_NO_CONTENT)
+def delete_todo(todo_id: int, db: Session = Depends(get_db)):
+    """
+    Delete a todo item.
+    """
+    db_todo = db.query(TodoModel).filter(TodoModel.id == todo_id).first()
+    if db_todo is None:
+        raise TodoNotFoundException(todo_id=todo_id)
+    
+    db.delete(db_todo)
+    db.commit()
+    return None

app/core/config.py

@@ -0,0 +1,26 @@
+import os
+from pathlib import Path
+from pydantic_settings import BaseSettings
+
+class Settings(BaseSettings):
+    # Project settings
+    PROJECT_NAME: str = "Todo API"
+    API_V1_STR: str = "/api/v1"
+    DEBUG: bool = True
+    
+    # Server settings
+    HOST: str = "0.0.0.0"
+    PORT: int = 8000
+    
+    # Database settings
+    DB_DIR: Path = Path("/app") / "storage" / "db"
+    DATABASE_URL: str = f"sqlite:///{DB_DIR}/db.sqlite"
+    
+    class Config:
+        env_file = ".env"
+        env_file_encoding = "utf-8"
+
+# Ensure DB directory exists
+Path(settings.DB_DIR).mkdir(parents=True, exist_ok=True)
+
+settings = Settings()

app/core/exceptions.py

@@ -0,0 +1,22 @@
+from fastapi import HTTPException, status
+
+class TodoNotFoundException(HTTPException):
+    def __init__(self, todo_id: int):
+        super().__init__(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Todo with ID {todo_id} not found",
+        )
+
+class ValidationError(HTTPException):
+    def __init__(self, detail: str):
+        super().__init__(
+            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+            detail=detail,
+        )
+
+class DatabaseError(HTTPException):
+    def __init__(self, detail: str = "Database error occurred"):
+        super().__init__(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            detail=detail,
+        )

app/core/middleware.py

@@ -0,0 +1,28 @@
+from fastapi import Request, status
+from fastapi.responses import JSONResponse
+from fastapi.exceptions import RequestValidationError
+from sqlalchemy.exc import SQLAlchemyError
+
+from app.core.exceptions import TodoNotFoundException, ValidationError, DatabaseError
+
+async def exception_handler(request: Request, exc: Exception):
+    if isinstance(exc, TodoNotFoundException):
+        return JSONResponse(
+            status_code=exc.status_code,
+            content={"detail": exc.detail},
+        )
+    elif isinstance(exc, RequestValidationError):
+        return JSONResponse(
+            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+            content={"detail": str(exc)},
+        )
+    elif isinstance(exc, SQLAlchemyError):
+        return JSONResponse(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            content={"detail": "Database error occurred"},
+        )
+    else:
+        return JSONResponse(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            content={"detail": "An unexpected error occurred"},
+        )

app/db/session.py

@@ -0,0 +1,29 @@
+from sqlalchemy import create_engine
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import sessionmaker
+from pathlib import Path
+
+from app.core.config import settings
+
+# Ensure the database directory exists
+settings.DB_DIR.mkdir(parents=True, exist_ok=True)
+
+# Create the SQLAlchemy engine
+engine = create_engine(
+    settings.DATABASE_URL,
+    connect_args={"check_same_thread": False}  # Only needed for SQLite
+)
+
+# Create session factory
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+# Create base class for models
+Base = declarative_base()
+
+# Dependency to get DB session
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()

app/models/__init__.py

@@ -0,0 +1 @@
+from app.models.todo import Todo

app/models/todo.py

@@ -0,0 +1,14 @@
+from sqlalchemy import Column, Integer, String, Boolean, DateTime
+from sqlalchemy.sql import func
+
+from app.db.session import Base
+
+class Todo(Base):
+    __tablename__ = "todos"
+
+    id = Column(Integer, primary_key=True, index=True)
+    title = Column(String, index=True)
+    description = Column(String, nullable=True)
+    completed = Column(Boolean, default=False)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now())

app/schemas/__init__.py

@@ -0,0 +1 @@
+from app.schemas.todo import Todo, TodoCreate, TodoUpdate, TodoInDB

app/schemas/todo.py

@@ -0,0 +1,28 @@
+from datetime import datetime
+from typing import Optional
+
+from pydantic import BaseModel, Field
+
+class TodoBase(BaseModel):
+    title: str = Field(..., min_length=1, max_length=100)
+    description: Optional[str] = Field(None, max_length=500)
+    completed: bool = False
+
+class TodoCreate(TodoBase):
+    pass
+
+class TodoUpdate(BaseModel):
+    title: Optional[str] = Field(None, min_length=1, max_length=100)
+    description: Optional[str] = Field(None, max_length=500)
+    completed: Optional[bool] = None
+
+class TodoInDB(TodoBase):
+    id: int
+    created_at: datetime
+    updated_at: Optional[datetime] = None
+
+    class Config:
+        orm_mode = True
+
+class Todo(TodoInDB):
+    pass

main.py

@@ -0,0 +1,61 @@
+import uvicorn
+from fastapi import FastAPI, Request, status
+from fastapi.exceptions import RequestValidationError
+from fastapi.responses import JSONResponse
+from pathlib import Path
+from sqlalchemy.exc import SQLAlchemyError
+
+from app.api.routers import todo
+from app.core.config import settings
+from app.core.exceptions import TodoNotFoundException, ValidationError, DatabaseError
+
+app = FastAPI(
+    title="Todo API",
+    description="A simple Todo API built with FastAPI",
+    version="0.1.0"
+)
+
+# Exception handlers
+@app.exception_handler(TodoNotFoundException)
+async def todo_not_found_exception_handler(request: Request, exc: TodoNotFoundException):
+    return JSONResponse(
+        status_code=exc.status_code,
+        content={"detail": exc.detail},
+    )
+
+@app.exception_handler(RequestValidationError)
+async def validation_exception_handler(request: Request, exc: RequestValidationError):
+    return JSONResponse(
+        status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+        content={"detail": str(exc)},
+    )
+
+@app.exception_handler(SQLAlchemyError)
+async def sqlalchemy_exception_handler(request: Request, exc: SQLAlchemyError):
+    return JSONResponse(
+        status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+        content={"detail": "Database error occurred"},
+    )
+
+@app.exception_handler(Exception)
+async def general_exception_handler(request: Request, exc: Exception):
+    return JSONResponse(
+        status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+        content={"detail": "An unexpected error occurred"},
+    )
+
+# Include routers
+app.include_router(todo.router, prefix="/api/v1")
+
+# Health check endpoint
+@app.get("/health", tags=["Health"])
+async def health_check():
+    return {"status": "healthy"}
+
+if __name__ == "__main__":
+    uvicorn.run(
+        "main:app",
+        host=settings.HOST,
+        port=settings.PORT,
+        reload=settings.DEBUG,
+    )

requirements.txt

@@ -0,0 +1,7 @@
+fastapi==0.110.0
+uvicorn==0.29.0
+sqlalchemy==2.0.25
+alembic==1.13.1
+pydantic==2.6.1
+python-dotenv==1.0.1
+ruff==0.3.0