Create Calculator API with FastAPI

Implemented:
- Basic arithmetic operations (add, subtract, multiply, divide)
- Input validation
- SQLite database with SQLAlchemy
- Alembic migrations
- Health endpoint

generated with BackendIM... (backend.im)

README.md

@@ -1,3 +1,43 @@
-# FastAPI Application
+# Calculator API
 
-This is a FastAPI application bootstrapped by BackendIM, the AI-powered backend generation platform.
+This is a FastAPI-based calculator API that provides basic arithmetic operations.
+
+## Features
+
+- Basic arithmetic operations: addition, subtraction, multiplication, division
+- Input validation
+- Results stored in SQLite database
+- Health check endpoint
+- OpenAPI documentation
+
+## API Endpoints
+
+- `GET /health`: Health check endpoint
+- `POST /api/add`: Add two numbers
+- `POST /api/subtract`: Subtract second number from first number
+- `POST /api/multiply`: Multiply two numbers
+- `POST /api/divide`: Divide first number by second number
+
+## Setup and Running
+
+1. Install dependencies:
+   ```
+   pip install -r requirements.txt
+   ```
+
+2. Run the application:
+   ```
+   uvicorn main:app --reload
+   ```
+
+3. Access the API documentation:
+   - Swagger UI: http://localhost:8000/docs
+   - ReDoc: http://localhost:8000/redoc
+
+## Database
+
+The application uses SQLite as the database, storing calculation history. The database file is located at `/app/storage/db/db.sqlite`.
+
+## Migrations
+
+Database migrations are managed with Alembic.

alembic.ini

@@ -0,0 +1,84 @@
+# 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 +1,83 @@
+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+import sys
+import os
+sys.path.append(os.path.dirname(os.path.dirname(__file__)))
+
+from main import Base
+
+# 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
+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/d29a9efb00af_initial_migration.py

@@ -0,0 +1,36 @@
+"""Initial migration
+
+Revision ID: d29a9efb00af
+Revises: 
+Create Date: 2025-05-14 00:00:00.000000
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = 'd29a9efb00af'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.create_table('calculations',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('operation', sa.String(), nullable=False),
+        sa.Column('num1', sa.Float(), nullable=False),
+        sa.Column('num2', sa.Float(), nullable=True),
+        sa.Column('result', sa.Float(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_calculations_id'), 'calculations', ['id'], unique=False)
+    op.create_index(op.f('ix_calculations_operation'), 'calculations', ['operation'], unique=False)
+
+
+def downgrade():
+    op.drop_index(op.f('ix_calculations_operation'), table_name='calculations')
+    op.drop_index(op.f('ix_calculations_id'), table_name='calculations')
+    op.drop_table('calculations')

main.py

@@ -0,0 +1,165 @@
+from fastapi import FastAPI, HTTPException, Depends
+from fastapi.responses import JSONResponse
+from pydantic import BaseModel, Field
+from typing import Optional
+from pathlib import Path
+from sqlalchemy import create_engine, Column, Integer, Float, String, DateTime
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import sessionmaker, Session
+import datetime
+
+app = FastAPI(
+    title="Calculator API",
+    description="A simple calculator API with basic operations",
+    version="1.0.0"
+)
+
+# Database setup
+DB_DIR = Path("/app") / "storage" / "db"
+DB_DIR.mkdir(parents=True, exist_ok=True)
+
+SQLALCHEMY_DATABASE_URL = f"sqlite:///{DB_DIR}/db.sqlite"
+
+engine = create_engine(
+    SQLALCHEMY_DATABASE_URL,
+    connect_args={"check_same_thread": False}
+)
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+Base = declarative_base()
+
+# Database models
+class Calculation(Base):
+    __tablename__ = "calculations"
+
+    id = Column(Integer, primary_key=True, index=True)
+    operation = Column(String, index=True)
+    num1 = Column(Float)
+    num2 = Column(Float, nullable=True)
+    result = Column(Float)
+    created_at = Column(DateTime, default=datetime.datetime.utcnow)
+
+# Create tables
+Base.metadata.create_all(bind=engine)
+
+# Dependency
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+# Input models
+class CalculationBase(BaseModel):
+    num1: float = Field(..., description="First number")
+    num2: float = Field(..., description="Second number")
+
+class CalculationResponse(BaseModel):
+    result: float = Field(..., description="Result of the calculation")
+    operation: str = Field(..., description="Operation performed")
+    num1: float = Field(..., description="First number")
+    num2: float = Field(..., description="Second number")
+
+    class Config:
+        orm_mode = True
+
+# Health check endpoint
+@app.get("/health", tags=["Health"])
+async def health():
+    return {"status": "healthy"}
+
+# Calculator endpoints
+@app.post("/api/add", response_model=CalculationResponse, tags=["Calculator"])
+async def add(data: CalculationBase, db: Session = Depends(get_db)):
+    result = data.num1 + data.num2
+    
+    # Save to database
+    db_calc = Calculation(
+        operation="add",
+        num1=data.num1,
+        num2=data.num2,
+        result=result
+    )
+    db.add(db_calc)
+    db.commit()
+    db.refresh(db_calc)
+    
+    return {
+        "result": result,
+        "operation": "add",
+        "num1": data.num1,
+        "num2": data.num2
+    }
+
+@app.post("/api/subtract", response_model=CalculationResponse, tags=["Calculator"])
+async def subtract(data: CalculationBase, db: Session = Depends(get_db)):
+    result = data.num1 - data.num2
+    
+    # Save to database
+    db_calc = Calculation(
+        operation="subtract",
+        num1=data.num1,
+        num2=data.num2,
+        result=result
+    )
+    db.add(db_calc)
+    db.commit()
+    db.refresh(db_calc)
+    
+    return {
+        "result": result,
+        "operation": "subtract",
+        "num1": data.num1,
+        "num2": data.num2
+    }
+
+@app.post("/api/multiply", response_model=CalculationResponse, tags=["Calculator"])
+async def multiply(data: CalculationBase, db: Session = Depends(get_db)):
+    result = data.num1 * data.num2
+    
+    # Save to database
+    db_calc = Calculation(
+        operation="multiply",
+        num1=data.num1,
+        num2=data.num2,
+        result=result
+    )
+    db.add(db_calc)
+    db.commit()
+    db.refresh(db_calc)
+    
+    return {
+        "result": result,
+        "operation": "multiply",
+        "num1": data.num1,
+        "num2": data.num2
+    }
+
+@app.post("/api/divide", response_model=CalculationResponse, tags=["Calculator"])
+async def divide(data: CalculationBase, db: Session = Depends(get_db)):
+    if data.num2 == 0:
+        raise HTTPException(status_code=400, detail="Cannot divide by zero")
+    
+    result = data.num1 / data.num2
+    
+    # Save to database
+    db_calc = Calculation(
+        operation="divide",
+        num1=data.num1,
+        num2=data.num2,
+        result=result
+    )
+    db.add(db_calc)
+    db.commit()
+    db.refresh(db_calc)
+    
+    return {
+        "result": result,
+        "operation": "divide",
+        "num1": data.num1,
+        "num2": data.num2
+    }
+
+if __name__ == "__main__":
+    import uvicorn
+    uvicorn.run(app, host="0.0.0.0", port=8000)

requirements.txt

@@ -0,0 +1,6 @@
+fastapi>=0.68.0
+uvicorn>=0.15.0
+sqlalchemy>=1.4.23
+pydantic>=1.8.2
+alembic>=1.7.1
+ruff>=0.0.171