Create Calculator API with FastAPI and SQLAlchemy

- Setup FastAPI project structure
- Add database models for calculations
- Create API endpoints for basic math operations
- Add health endpoint
- Configure SQLite and Alembic for database management
- Update README with usage instructions

generated with BackendIM... (backend.im)

README.md

@@ -1,3 +1,100 @@
-# FastAPI Application
+# Calculator API
 
-This is a FastAPI application bootstrapped by BackendIM, the AI-powered backend generation platform.
+A simple calculator API built with FastAPI and SQLAlchemy that performs basic arithmetic operations and stores calculation history.
+
+## Features
+
+- Basic arithmetic operations (add, subtract, multiply, divide)
+- Square root calculation
+- Calculation history storage in SQLite database
+- Health check endpoint
+
+## API Endpoints
+
+### Calculator Operations
+
+- `POST /api/v1/calculator/` - Perform a calculation
+- `GET /api/v1/calculator/history` - Get calculation history
+- `GET /api/v1/calculator/{calculation_id}` - Get a specific calculation
+
+### Health Check
+
+- `GET /api/v1/health` - API health status
+
+## Installation
+
+```bash
+# Clone the repository
+git clone <repository-url>
+
+# Install dependencies
+pip install -r requirements.txt
+
+# Run migrations
+alembic upgrade head
+
+# Start the API
+uvicorn main:app --reload
+```
+
+## Environment Variables
+
+Create a `.env` file in the root directory with the following variables:
+
+```
+# No environment variables required for basic setup
+```
+
+## API Documentation
+
+Once the API is running, you can access the API documentation at:
+
+- Swagger UI: `http://localhost:8000/docs`
+- ReDoc: `http://localhost:8000/redoc`
+
+## Example Usage
+
+### Perform Addition
+
+```json
+POST /api/v1/calculator/
+{
+  "operation": "add",
+  "first_number": 5,
+  "second_number": 3
+}
+```
+
+Response:
+```json
+{
+  "id": 1,
+  "operation": "add",
+  "first_number": 5,
+  "second_number": 3,
+  "result": 8,
+  "created_at": "2025-05-13T12:00:00.000Z"
+}
+```
+
+### Perform Square Root
+
+```json
+POST /api/v1/calculator/
+{
+  "operation": "square_root",
+  "first_number": 16
+}
+```
+
+Response:
+```json
+{
+  "id": 2,
+  "operation": "square_root",
+  "first_number": 16,
+  "second_number": null,
+  "result": 4,
+  "created_at": "2025-05-13T12:01:00.000Z"
+}
+```

alembic.ini

@@ -0,0 +1,106 @@
+# 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
+
+# sys.path path, will be prepended to sys.path if present.
+# defaults to the current working directory.
+prepend_sys_path = .
+
+# timezone to use when rendering the date within the migration file
+# as well as the filename.
+# If specified, requires the python-dateutil library that can be
+# installed by adding `alembic[tz]` to the pip requirements
+# 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.
+# The path separator used here should be the separator specified by "version_path_separator" below.
+# version_locations = %(here)s/bar:%(here)s/bat:alembic/versions
+
+# version path separator; As mentioned above, this is the character used to split
+# version_locations. The default within new alembic.ini files is "os", which uses os.pathsep.
+# If this key is omitted entirely, it falls back to the legacy behavior of splitting on spaces and/or commas.
+# Valid values for version_path_separator are:
+#
+# version_path_separator = :
+# version_path_separator = ;
+# version_path_separator = space
+version_path_separator = os  # Use os.pathsep. Default configuration used for new projects.
+
+# set to 'true' to search source files recursively
+# in each "version_locations" directory
+# new in Alembic version 1.10
+# recursive_version_locations = false
+
+# 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 REVISION_SCRIPT_FILENAME
+
+# 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/README

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

alembic/env.py

@@ -0,0 +1,77 @@
+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.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+from app.db.base import Base
+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:
+        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() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}

alembic/versions/001_initial_setup.py

@@ -0,0 +1,38 @@
+"""initial setup
+
+Revision ID: 001
+Revises: 
+Create Date: 2025-05-13
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '001'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # Create calculation table
+    op.create_table(
+        'calculation',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('operation', sa.String(), nullable=False),
+        sa.Column('first_number', sa.Float(), nullable=False),
+        sa.Column('second_number', sa.Float(), nullable=True),
+        sa.Column('result', sa.Float(), nullable=False),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('CURRENT_TIMESTAMP'), nullable=False),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_calculation_id'), 'calculation', ['id'], unique=False)
+    op.create_index(op.f('ix_calculation_operation'), 'calculation', ['operation'], unique=False)
+
+
+def downgrade() -> None:
+    op.drop_index(op.f('ix_calculation_operation'), table_name='calculation')
+    op.drop_index(op.f('ix_calculation_id'), table_name='calculation')
+    op.drop_table('calculation')

app/api/endpoints/calculator.py

@@ -0,0 +1,76 @@
+import math
+from typing import List
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from app.db.session import get_db
+from app.schemas.calculation import CalculationCreate, CalculationResponse
+from app.crud import calculation
+
+router = APIRouter()
+
+def perform_calculation(calc: CalculationCreate) -> float:
+    """Perform the calculation based on the operation and numbers provided."""
+    if calc.operation == "add":
+        if calc.second_number is None:
+            raise HTTPException(status_code=400, detail="Second number is required for addition")
+        return calc.first_number + calc.second_number
+    
+    elif calc.operation == "subtract":
+        if calc.second_number is None:
+            raise HTTPException(status_code=400, detail="Second number is required for subtraction")
+        return calc.first_number - calc.second_number
+    
+    elif calc.operation == "multiply":
+        if calc.second_number is None:
+            raise HTTPException(status_code=400, detail="Second number is required for multiplication")
+        return calc.first_number * calc.second_number
+    
+    elif calc.operation == "divide":
+        if calc.second_number is None:
+            raise HTTPException(status_code=400, detail="Second number is required for division")
+        if calc.second_number == 0:
+            raise HTTPException(status_code=400, detail="Cannot divide by zero")
+        return calc.first_number / calc.second_number
+    
+    elif calc.operation == "square_root":
+        if calc.first_number < 0:
+            raise HTTPException(status_code=400, detail="Cannot calculate square root of a negative number")
+        return math.sqrt(calc.first_number)
+    
+    else:
+        raise HTTPException(
+            status_code=400, 
+            detail="Invalid operation. Supported operations: add, subtract, multiply, divide, square_root"
+        )
+
+@router.post("/", response_model=CalculationResponse)
+def calculate(calc: CalculationCreate, db: Session = Depends(get_db)):
+    """
+    Perform a calculation and store it in the database.
+    
+    - **operation**: add, subtract, multiply, divide, or square_root
+    - **first_number**: First operand
+    - **second_number**: Second operand (not required for square_root)
+    """
+    result = perform_calculation(calc)
+    db_calc = calculation.create_calculation(db=db, calc=calc, result=result)
+    return db_calc
+
+@router.get("/history", response_model=List[CalculationResponse])
+def get_calculation_history(skip: int = 0, limit: int = 100, db: Session = Depends(get_db)):
+    """
+    Retrieve calculation history.
+    """
+    calcs = calculation.get_calculations(db, skip=skip, limit=limit)
+    return calcs
+
+@router.get("/{calculation_id}", response_model=CalculationResponse)
+def get_calculation_by_id(calculation_id: int, db: Session = Depends(get_db)):
+    """
+    Retrieve a specific calculation by ID.
+    """
+    db_calc = calculation.get_calculation(db, calculation_id=calculation_id)
+    if db_calc is None:
+        raise HTTPException(status_code=404, detail="Calculation not found")
+    return db_calc

app/api/endpoints/health.py

@@ -0,0 +1,25 @@
+from fastapi import APIRouter, Depends
+from sqlalchemy.orm import Session
+from app.db.session import get_db
+
+router = APIRouter()
+
+@router.get("/health")
+def health_check(db: Session = Depends(get_db)):
+    """
+    Health check endpoint for the API.
+    Returns status of the API and database connectivity.
+    """
+    # Check database connection
+    try:
+        # Execute a simple query to verify database connectivity
+        db.execute("SELECT 1")
+        db_status = "healthy"
+    except Exception as e:
+        db_status = f"unhealthy: {str(e)}"
+    
+    return {
+        "status": "healthy",
+        "database": db_status,
+        "version": "1.0.0"
+    }

app/api/router.py

@@ -0,0 +1,6 @@
+from fastapi import APIRouter
+from app.api.endpoints import calculator, health
+
+router = APIRouter()
+router.include_router(calculator.router, prefix="/calculator", tags=["calculator"])
+router.include_router(health.router, tags=["health"])

app/core/config.py

@@ -0,0 +1,17 @@
+from pathlib import Path
+from pydantic_settings import BaseSettings
+
+class Settings(BaseSettings):
+    API_V1_STR: str = "/api/v1"
+    PROJECT_NAME: str = "Calculator API"
+    
+    # Database settings
+    DB_DIR = Path("/app") / "storage" / "db"
+    DB_DIR.mkdir(parents=True, exist_ok=True)
+    DATABASE_URL: str = f"sqlite:///{DB_DIR}/db.sqlite"
+    
+    class Config:
+        env_file = ".env"
+        case_sensitive = True
+
+settings = Settings()

app/crud/calculation.py

@@ -0,0 +1,21 @@
+from sqlalchemy.orm import Session
+from app.models.calculation import Calculation
+from app.schemas.calculation import CalculationCreate
+
+def create_calculation(db: Session, calc: CalculationCreate, result: float) -> Calculation:
+    db_calculation = Calculation(
+        operation=calc.operation,
+        first_number=calc.first_number,
+        second_number=calc.second_number,
+        result=result
+    )
+    db.add(db_calculation)
+    db.commit()
+    db.refresh(db_calculation)
+    return db_calculation
+
+def get_calculations(db: Session, skip: int = 0, limit: int = 100):
+    return db.query(Calculation).order_by(Calculation.created_at.desc()).offset(skip).limit(limit).all()
+
+def get_calculation(db: Session, calculation_id: int):
+    return db.query(Calculation).filter(Calculation.id == calculation_id).first()

app/db/base.py

@@ -0,0 +1,2 @@
+from app.db.base_class import Base
+from app.models.calculation import Calculation

app/db/base_class.py

@@ -0,0 +1,11 @@
+from typing import Any
+from sqlalchemy.ext.declarative import as_declarative, declared_attr
+
+@as_declarative()
+class Base:
+    id: Any
+    __name__: str
+    
+    @declared_attr
+    def __tablename__(cls) -> str:
+        return cls.__name__.lower()

app/db/session.py

@@ -0,0 +1,22 @@
+from pathlib import Path
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+# Create DB directory
+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)
+
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()

app/models/calculation.py

@@ -0,0 +1,11 @@
+from sqlalchemy import Column, Integer, String, Float, DateTime
+from sqlalchemy.sql import func
+from app.db.base_class import Base
+
+class Calculation(Base):
+    id = Column(Integer, primary_key=True, index=True)
+    operation = Column(String, index=True)
+    first_number = Column(Float)
+    second_number = Column(Float, nullable=True)
+    result = Column(Float)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())

app/schemas/calculation.py

@@ -0,0 +1,19 @@
+from datetime import datetime
+from typing import Optional
+from pydantic import BaseModel, Field
+
+class CalculationBase(BaseModel):
+    operation: str = Field(..., description="Mathematical operation: add, subtract, multiply, divide, or square_root")
+    first_number: float = Field(..., description="First operand")
+    second_number: Optional[float] = Field(None, description="Second operand (not required for square_root)")
+
+class CalculationCreate(CalculationBase):
+    pass
+
+class CalculationResponse(CalculationBase):
+    id: int
+    result: float
+    created_at: datetime
+
+    class Config:
+        orm_mode = True

main.py

@@ -0,0 +1,14 @@
+import uvicorn
+from fastapi import FastAPI
+from app.api.router import router as api_router
+from app.core.config import settings
+
+app = FastAPI(
+    title=settings.PROJECT_NAME,
+    openapi_url=f"{settings.API_V1_STR}/openapi.json",
+)
+
+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)

requirements.txt

@@ -0,0 +1,7 @@
+fastapi==0.110.1
+uvicorn==0.29.0
+sqlalchemy==2.0.29
+pydantic==2.6.4
+alembic==1.13.1
+ruff==0.3.2
+python-dotenv==1.0.1