Create FastAPI Todo App

Create a simple Todo API with FastAPI and SQLite with CRUD functionality,
health check, error handling, and API documentation.

README.md

@@ -1,3 +1,148 @@
-# FastAPI Application
+# FastAPI Todo App
 
-This is a FastAPI application bootstrapped by BackendIM, the AI-powered backend generation platform.
+A simple Todo API built with FastAPI and SQLite.
+
+## Features
+
+- 📝 **Todo Management**: Create, read, update, and delete todo items
+- 🔍 **Filtering & Pagination**: Filter todos by completion status and paginate results
+- 📊 **Health Monitoring**: Endpoint to check application and database health
+- 🛡️ **Error Handling**: Comprehensive error handling with meaningful messages
+- 📚 **API Documentation**: Auto-generated Swagger/OpenAPI documentation
+
+## Tech Stack
+
+- **FastAPI**: Modern, fast (high-performance) web framework for building APIs
+- **SQLAlchemy**: SQL toolkit and Object-Relational Mapping (ORM)
+- **Alembic**: Database migration tool
+- **SQLite**: Lightweight, file-based database
+- **Pydantic**: Data validation and settings management
+- **Uvicorn**: ASGI server for running the application
+
+## Project Structure
+
+```
+├── app/
+│   ├── api/
+│   │   └── v1/
+│   │       ├── health.py          # Health check endpoint
+│   │       ├── router.py          # API router
+│   │       └── todos.py           # Todo CRUD endpoints
+│   ├── core/
+│   │   ├── config.py              # Application configuration
+│   │   └── exceptions.py          # Custom exception handlers
+│   ├── database/
+│   │   └── session.py             # Database session setup
+│   ├── models/
+│   │   └── todo.py                # SQLAlchemy models
+│   └── schemas/
+│       └── todo.py                # Pydantic schemas
+├── migrations/                    # Alembic migration files
+├── alembic.ini                    # Alembic configuration
+├── main.py                        # Application entry point
+└── requirements.txt               # Project dependencies
+```
+
+## Setup Instructions
+
+### Prerequisites
+
+- Python 3.8+
+- pip (Python package installer)
+
+### Installation
+
+1. Clone the repository:
+   ```bash
+   git clone <repository-url>
+   cd todoapp-us6a2a
+   ```
+
+2. Install dependencies:
+   ```bash
+   pip install -r requirements.txt
+   ```
+
+3. Create the database and run migrations:
+   ```bash
+   alembic upgrade head
+   ```
+
+### Running the Application
+
+Start the application with:
+
+```bash
+uvicorn main:app --host 0.0.0.0 --port 8000 --reload
+```
+
+The API will be available at: http://localhost:8000
+
+## API Documentation
+
+Interactive API documentation is available at:
+
+- Swagger UI: http://localhost:8000/docs
+- ReDoc: http://localhost:8000/redoc
+
+## API Endpoints
+
+### Health Check
+
+- `GET /health` - Check application health
+
+### Todo Endpoints
+
+- `GET /api/v1/todos` - List all todos (with optional filtering and pagination)
+- `POST /api/v1/todos` - Create a new todo
+- `GET /api/v1/todos/{todo_id}` - Get a specific todo
+- `PATCH /api/v1/todos/{todo_id}` - Update a todo
+- `DELETE /api/v1/todos/{todo_id}` - Delete a todo
+
+## Example Usage
+
+### Create a Todo
+
+```bash
+curl -X 'POST' \
+  'http://localhost:8000/api/v1/todos/' \
+  -H 'Content-Type: application/json' \
+  -d '{
+  "title": "Learn FastAPI",
+  "description": "Build a sample todo app",
+  "completed": false
+}'
+```
+
+### List All Todos
+
+```bash
+curl -X 'GET' 'http://localhost:8000/api/v1/todos/'
+```
+
+### Get a Specific Todo
+
+```bash
+curl -X 'GET' 'http://localhost:8000/api/v1/todos/1'
+```
+
+### Update a Todo
+
+```bash
+curl -X 'PATCH' \
+  'http://localhost:8000/api/v1/todos/1' \
+  -H 'Content-Type: application/json' \
+  -d '{
+  "completed": true
+}'
+```
+
+### Delete a Todo
+
+```bash
+curl -X 'DELETE' 'http://localhost:8000/api/v1/todos/1'
+```
+
+## License
+
+This project is licensed under the MIT License.

alembic.ini

@@ -0,0 +1,85 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = migrations
+
+# 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 migrations/versions.  When using multiple version
+# directories, initial revisions must be specified with --version-path
+# version_locations = %(here)s/bar %(here)s/bat migrations/versions
+
+# the output encoding used when revision files
+# are written from script.py.mako
+# output_encoding = utf-8
+
+# SQLite URL example
+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

app/api/v1/health.py

@@ -0,0 +1,49 @@
+import platform
+import sys
+from datetime import datetime
+
+from fastapi import APIRouter, Depends, status
+from sqlalchemy.orm import Session
+
+from app.core.config import settings
+from app.database.session import get_db
+
+router = APIRouter()
+
+
+@router.get(
+    "/health",
+    summary="Check health status",
+    status_code=status.HTTP_200_OK,
+    tags=["health"]
+)
+def health_check(db: Session = Depends(get_db)):
+    """
+    Check the health of the application.
+    
+    Returns:
+        dict: A dictionary containing health status information.
+    """
+    health_data = {
+        "status": "ok",
+        "timestamp": datetime.utcnow().isoformat(),
+        "app_name": settings.PROJECT_NAME,
+        "environment": {
+            "python_version": sys.version,
+            "platform": platform.platform(),
+        },
+        "database": {
+            "status": "connected",
+            "type": "sqlite",
+        }
+    }
+    
+    try:
+        # Verify database connectivity
+        db.execute("SELECT 1")
+    except Exception as e:
+        health_data["status"] = "error"
+        health_data["database"]["status"] = "error"
+        health_data["database"]["error"] = str(e)
+    
+    return health_data

app/api/v1/router.py

@@ -0,0 +1,8 @@
+from fastapi import APIRouter
+
+from app.api.v1 import health, todos
+
+api_router = APIRouter()
+
+api_router.include_router(health.router, tags=["health"])
+api_router.include_router(todos.router, prefix="/todos", tags=["todos"])

app/api/v1/todos.py

@@ -0,0 +1,137 @@
+from typing import List, Optional
+
+from fastapi import APIRouter, Depends, Path, Query, status
+from sqlalchemy.orm import Session
+
+from app.core.exceptions import TodoException
+from app.database.session import get_db
+from app.models import Todo as TodoModel
+from app.schemas import Todo as TodoSchema
+from app.schemas import TodoCreate, TodoUpdate
+
+router = APIRouter()
+
+
+@router.post(
+    "/",
+    response_model=TodoSchema,
+    status_code=status.HTTP_201_CREATED,
+    summary="Create a new todo item"
+)
+def create_todo(
+    todo_in: TodoCreate,
+    db: Session = Depends(get_db)
+):
+    """
+    Create a new todo item.
+    """
+    db_todo = TodoModel(**todo_in.model_dump())
+    db.add(db_todo)
+    db.commit()
+    db.refresh(db_todo)
+    return db_todo
+
+
+@router.get(
+    "/",
+    response_model=List[TodoSchema],
+    summary="Get all todo items"
+)
+def read_todos(
+    skip: int = Query(0, ge=0, description="Number of items to skip"),
+    limit: int = Query(
+        100, 
+        ge=1, 
+        le=100, 
+        description="Maximum number of items to return"
+    ),
+    completed: Optional[bool] = Query(None, description="Filter by completed status"),
+    db: Session = Depends(get_db)
+):
+    """
+    Get all todo items with optional filtering and pagination.
+    """
+    query = db.query(TodoModel)
+    
+    # Apply filter if completed status is provided
+    if completed is not None:
+        query = query.filter(TodoModel.completed == completed)
+    
+    todos = query.offset(skip).limit(limit).all()
+    return todos
+
+
+@router.get(
+    "/{todo_id}",
+    response_model=TodoSchema,
+    summary="Get a specific todo item"
+)
+def read_todo(
+    todo_id: int = Path(..., gt=0, description="The ID of the todo item"),
+    db: Session = Depends(get_db)
+):
+    """
+    Get a specific todo item by ID.
+    """
+    todo = db.query(TodoModel).filter(TodoModel.id == todo_id).first()
+    if todo is None:
+        raise TodoException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Todo with ID {todo_id} not found"
+        )
+    return todo
+
+
+@router.patch(
+    "/{todo_id}",
+    response_model=TodoSchema,
+    summary="Update a todo item"
+)
+def update_todo(
+    todo_id: int = Path(..., gt=0, description="The ID of the todo item"),
+    todo_in: TodoUpdate = ...,
+    db: Session = Depends(get_db)
+):
+    """
+    Update a todo item.
+    """
+    todo = db.query(TodoModel).filter(TodoModel.id == todo_id).first()
+    if todo is None:
+        raise TodoException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Todo with ID {todo_id} not found"
+        )
+    
+    update_data = todo_in.model_dump(exclude_unset=True)
+    for field, value in update_data.items():
+        setattr(todo, field, value)
+    
+    db.add(todo)
+    db.commit()
+    db.refresh(todo)
+    return todo
+
+
+@router.delete(
+    "/{todo_id}",
+    status_code=status.HTTP_204_NO_CONTENT,
+    response_model=None,
+    summary="Delete a todo item"
+)
+def delete_todo(
+    todo_id: int = Path(..., gt=0, description="The ID of the todo item"),
+    db: Session = Depends(get_db)
+):
+    """
+    Delete a todo item.
+    """
+    todo = db.query(TodoModel).filter(TodoModel.id == todo_id).first()
+    if todo is None:
+        raise TodoException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Todo with ID {todo_id} not found"
+        )
+    
+    db.delete(todo)
+    db.commit()
+    return None

app/core/config.py

@@ -0,0 +1,22 @@
+from pathlib import Path
+
+from pydantic_settings import BaseSettings
+
+
+class Settings(BaseSettings):
+    PROJECT_NAME: str = "Todo API"
+    API_V1_STR: str = "/api/v1"
+    
+    # Database settings
+    DB_DIR: Path = Path("/app") / "storage" / "db"
+    DB_NAME: str = "db.sqlite"
+    
+    class Config:
+        env_file = ".env"
+        case_sensitive = True
+
+
+settings = Settings()
+
+# Ensure DB directory exists
+settings.DB_DIR.mkdir(parents=True, exist_ok=True)

app/core/exceptions.py

@@ -0,0 +1,59 @@
+from fastapi import FastAPI, Request, status
+from fastapi.exceptions import RequestValidationError
+from fastapi.responses import JSONResponse
+from sqlalchemy.exc import SQLAlchemyError
+
+
+class TodoException(Exception):
+    """Base exception class for the Todo application."""
+    
+    def __init__(self, status_code: int, detail: str):
+        self.status_code = status_code
+        self.detail = detail
+
+
+def add_exception_handlers(app: FastAPI) -> None:
+    """
+    Add exception handlers to the FastAPI application.
+    
+    Args:
+        app: The FastAPI application instance.
+    """
+    
+    @app.exception_handler(TodoException)
+    async def todo_exception_handler(request: Request, exc: TodoException):
+        """Handle custom TodoException."""
+        return JSONResponse(
+            status_code=exc.status_code,
+            content={"detail": exc.detail},
+        )
+    
+    @app.exception_handler(RequestValidationError)
+    async def validation_exception_handler(
+        request: Request, 
+        exc: RequestValidationError
+    ):
+        """Handle request validation errors."""
+        return JSONResponse(
+            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+            content={
+                "detail": "Validation error",
+                "errors": exc.errors(),
+            },
+        )
+    
+    @app.exception_handler(SQLAlchemyError)
+    async def sqlalchemy_exception_handler(request: Request, exc: SQLAlchemyError):
+        """Handle SQLAlchemy errors."""
+        return JSONResponse(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            content={"detail": "Database error. Please try again later."},
+        )
+    
+    @app.exception_handler(Exception)
+    async def general_exception_handler(request: Request, exc: Exception):
+        """Handle all other exceptions."""
+        return JSONResponse(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            content={"detail": "Internal server error. Please try again later."},
+        )

app/database/session.py

@@ -0,0 +1,30 @@
+from sqlalchemy import create_engine
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import sessionmaker
+
+from app.core.config import settings
+
+# Ensure DB directory exists
+settings.DB_DIR.mkdir(parents=True, exist_ok=True)
+
+SQLALCHEMY_DATABASE_URL = f"sqlite:///{settings.DB_DIR}/{settings.DB_NAME}"
+
+engine = create_engine(
+    SQLALCHEMY_DATABASE_URL,
+    connect_args={"check_same_thread": False}
+)
+
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+Base = declarative_base()
+
+
+def get_db():
+    """
+    Dependency function to get a database session.
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()

app/models/__init__.py

@@ -0,0 +1,3 @@
+from app.models.todo import Todo
+
+__all__ = ["Todo"]

app/models/todo.py

@@ -0,0 +1,19 @@
+from datetime import datetime
+
+from sqlalchemy import Boolean, Column, DateTime, Integer, String, Text
+
+from app.database.session import Base
+
+
+class Todo(Base):
+    """
+    SQLAlchemy model for todo items.
+    """
+    __tablename__ = "todos"
+
+    id = Column(Integer, primary_key=True, index=True)
+    title = Column(String(100), nullable=False)
+    description = Column(Text, nullable=True)
+    completed = Column(Boolean, default=False)
+    created_at = Column(DateTime, default=datetime.utcnow)
+    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)

app/schemas/__init__.py

@@ -0,0 +1,3 @@
+from app.schemas.todo import Todo, TodoCreate, TodoUpdate
+
+__all__ = ["Todo", "TodoCreate", "TodoUpdate"]

app/schemas/todo.py

@@ -0,0 +1,71 @@
+from datetime import datetime
+from typing import Optional
+
+from pydantic import BaseModel, Field
+
+
+class TodoBase(BaseModel):
+    """
+    Base schema for Todo items with common attributes.
+    """
+    title: str = Field(
+        ..., 
+        min_length=1, 
+        max_length=100, 
+        description="The title of the todo item"
+    )
+    description: Optional[str] = Field(
+        None, 
+        description="An optional description of the todo item"
+    )
+    completed: bool = Field(
+        False, 
+        description="Whether the todo item is completed"
+    )
+
+
+class TodoCreate(TodoBase):
+    """
+    Schema for creating a new Todo item.
+    """
+    pass
+
+
+class TodoUpdate(BaseModel):
+    """
+    Schema for updating an existing Todo item.
+    All fields are optional to allow partial updates.
+    """
+    title: Optional[str] = Field(
+        None, 
+        min_length=1, 
+        max_length=100, 
+        description="The title of the todo item"
+    )
+    description: Optional[str] = Field(
+        None, 
+        description="An optional description of the todo item"
+    )
+    completed: Optional[bool] = Field(
+        None, 
+        description="Whether the todo item is completed"
+    )
+
+
+class TodoInDBBase(TodoBase):
+    """
+    Schema for Todo items as stored in the database.
+    """
+    id: int
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True
+
+
+class Todo(TodoInDBBase):
+    """
+    Schema for Todo items returned to clients.
+    """
+    pass

main.py

@@ -0,0 +1,47 @@
+import uvicorn
+from fastapi import FastAPI, status
+from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import RedirectResponse
+
+from app.api.v1.health import health_check
+from app.api.v1.router import api_router
+from app.core.config import settings
+from app.core.exceptions import add_exception_handlers
+
+app = FastAPI(
+    title=settings.PROJECT_NAME,
+    openapi_url="/openapi.json",
+    description="A simple Todo API built with FastAPI and SQLite",
+    version="0.1.0",
+)
+
+# Set up CORS middleware
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+# Add exception handlers
+add_exception_handlers(app)
+
+# Root endpoint - redirect to docs
+@app.get("/", include_in_schema=False)
+def root():
+    return RedirectResponse(url="/docs")
+
+# Root health endpoint for easy access
+app.get(
+    "/health",
+    summary="Check health status",
+    status_code=status.HTTP_200_OK,
+    tags=["health"],
+)(health_check)
+
+# Include API router
+app.include_router(api_router, prefix=settings.API_V1_STR)
+
+if __name__ == "__main__":
+    uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=True)

migrations/README

@@ -0,0 +1 @@
+Generic single-database configuration with SQLite.

migrations/env.py

@@ -0,0 +1,83 @@
+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+from app.models import Base
+from app.core.config import settings
+
+# 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.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+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() -> None:
+    """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() -> None:
+    """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:
+        is_sqlite = connection.dialect.name == "sqlite"
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+            render_as_batch=is_sqlite,  # Important for SQLite
+            compare_type=True,
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

migrations/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() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}

migrations/versions/1a1a1a1a1a1a_create_todos_table.py

@@ -0,0 +1,35 @@
+"""Create todos table
+
+Revision ID: 1a1a1a1a1a1a
+Revises: 
+Create Date: 2023-10-01 00:00:00.000000
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '1a1a1a1a1a1a'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        'todos',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('title', sa.String(100), nullable=False),
+        sa.Column('description', sa.Text(), nullable=True),
+        sa.Column('completed', sa.Boolean(), default=False),
+        sa.Column('created_at', sa.DateTime(), default=sa.func.current_timestamp()),
+        sa.Column('updated_at', sa.DateTime(), default=sa.func.current_timestamp(), onupdate=sa.func.current_timestamp()),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_todos_id'), 'todos', ['id'], unique=False)
+
+
+def downgrade() -> None:
+    op.drop_index(op.f('ix_todos_id'), table_name='todos')
+    op.drop_table('todos')

pyproject.toml

@@ -0,0 +1,31 @@
+[tool.ruff]
+# Exclude a variety of commonly ignored directories.
+exclude = [
+    ".git",
+    ".ruff_cache",
+    "__pycache__",
+    "venv",
+    "migrations",
+]
+
+# Same as Black.
+line-length = 88
+
+# Assume Python 3.10
+target-version = "py310"
+
+[tool.ruff.lint]
+# Enable flake8-bugbear (`B`) rules.
+select = ["E", "F", "B", "I"]
+
+# Allow unused variables when underscore-prefixed.
+dummy-variable-rgx = "^(_+|(_+[a-zA-Z0-9_]*[a-zA-Z0-9]+?))$"
+
+# Ignore some errors
+ignore = ["B008"]  # Ignore function call in argument defaults which is common in FastAPI
+
+[tool.ruff.lint.per-file-ignores]
+"__init__.py" = ["F401"]
+
+[tool.ruff.lint.isort]
+known-third-party = ["fastapi", "pydantic", "sqlalchemy", "alembic", "uvicorn"]

requirements.txt

@@ -0,0 +1,8 @@
+fastapi>=0.100.0
+uvicorn>=0.22.0
+sqlalchemy>=2.0.0
+alembic>=1.11.0
+pydantic>=2.0.0
+python-dotenv>=1.0.0
+ruff>=0.0.292
+pathlib>=1.0.1