Create simple inventory management app with FastAPI and SQLite

- Set up project structure with FastAPI
- Implement SQLAlchemy models for inventory items and categories
- Create database connection with SQLite
- Add CRUD operations for inventory management
- Implement API endpoints for categories, items, and inventory transactions
- Add health check endpoint
- Set up Alembic for database migrations
- Update README with documentation

README.md

@@ -1,3 +1,137 @@
-# FastAPI Application
+# Simple Inventory Management App
 
-This is a FastAPI application bootstrapped by BackendIM, the AI-powered backend generation platform.
+A REST API for managing inventory items built with FastAPI and SQLite.
+
+## Features
+
+- Category management (CRUD operations)
+- Item management with inventory tracking
+- Inventory transactions (stock in/out)
+- Search and filter functionality
+- Health check endpoint
+- API documentation via Swagger UI and ReDoc
+
+## Project Structure
+
+```
+simple-inventory-management-app/
+├── alembic/                  # Database migration files
+├── app/                      # Application code
+│   ├── api/                  # API endpoints
+│   │   └── v1/               # API version 1
+│   │       ├── endpoints/    # API route handlers
+│   │       └── api.py        # API router
+│   ├── core/                 # Core functionality
+│   │   └── config.py         # Application configuration
+│   ├── crud/                 # CRUD operations
+│   ├── db/                   # Database setup and session
+│   ├── models/               # SQLAlchemy models
+│   └── schemas/              # Pydantic schemas
+└── main.py                   # Application entry point
+```
+
+## Requirements
+
+- Python 3.8+
+- Dependencies listed in `requirements.txt`
+
+## Installation
+
+1. Clone the repository:
+
+```bash
+git clone <repository-url>
+cd simple-inventory-management-app
+```
+
+2. Create a virtual environment and activate it:
+
+```bash
+python -m venv venv
+source venv/bin/activate  # On Windows: venv\Scripts\activate
+```
+
+3. Install dependencies:
+
+```bash
+pip install -r requirements.txt
+```
+
+## Database Setup
+
+The application uses SQLite as the database. The database file will be created automatically in the `/app/storage/db/` directory.
+
+To initialize the database with the latest migrations:
+
+```bash
+alembic upgrade head
+```
+
+## Running the Application
+
+Start the application with:
+
+```bash
+uvicorn main:app --reload
+```
+
+The API will be available at http://localhost:8000
+
+## API Documentation
+
+- Swagger UI: http://localhost:8000/docs
+- ReDoc: http://localhost:8000/redoc
+
+## API Endpoints
+
+### Health Check
+
+- `GET /api/v1/health` - Check application health
+
+### Categories
+
+- `GET /api/v1/categories` - List all categories
+- `POST /api/v1/categories` - Create a new category
+- `GET /api/v1/categories/{category_id}` - Get a specific category
+- `PUT /api/v1/categories/{category_id}` - Update a category
+- `DELETE /api/v1/categories/{category_id}` - Delete a category
+
+### Items
+
+- `GET /api/v1/items` - List all items (with filtering options)
+- `POST /api/v1/items` - Create a new item
+- `GET /api/v1/items/{item_id}` - Get a specific item
+- `PUT /api/v1/items/{item_id}` - Update an item
+- `DELETE /api/v1/items/{item_id}` - Delete an item
+- `POST /api/v1/items/{item_id}/transactions` - Add inventory transaction
+- `GET /api/v1/items/{item_id}/transactions` - Get item transaction history
+
+## Environment Variables
+
+The application uses the following environment variables:
+
+None required for basic operation. The application uses default values that work out of the box.
+
+## Development
+
+### Running Tests
+
+```bash
+# To be implemented
+```
+
+### Running Linting
+
+```bash
+ruff check .
+```
+
+### Running Formatting
+
+```bash
+ruff format .
+```
+
+## License
+
+[MIT](LICENSE)

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
+
+# SQLite URL
+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/README

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

alembic/env.py

@@ -0,0 +1,84 @@
+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+# Import Base before defining target_metadata
+from app.db.base_model 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"},
+        render_as_batch=True,  # Required for SQLite
+    )
+
+    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:
+        is_sqlite = connection.dialect.name == 'sqlite'
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+            render_as_batch=is_sqlite,  # Required for SQLite
+        )
+
+        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/a1b2c3d4e5f6_initial_migration.py

@@ -0,0 +1,77 @@
+"""Initial migration
+
+Revision ID: a1b2c3d4e5f6
+Revises: 
+Create Date: 2023-11-10 12:00:00.000000
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = 'a1b2c3d4e5f6'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # Create categories table
+    op.create_table(
+        'categories',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('name', sa.String(), nullable=False),
+        sa.Column('description', sa.Text(), nullable=True),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_categories_id'), 'categories', ['id'], unique=False)
+    op.create_index(op.f('ix_categories_name'), 'categories', ['name'], unique=True)
+
+    # Create items table
+    op.create_table(
+        'items',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('name', sa.String(), nullable=False),
+        sa.Column('description', sa.Text(), nullable=True),
+        sa.Column('quantity', sa.Integer(), nullable=False, server_default='0'),
+        sa.Column('price', sa.Float(), nullable=True),
+        sa.Column('sku', sa.String(), nullable=True),
+        sa.Column('category_id', sa.Integer(), nullable=True),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=False),
+        sa.Column('updated_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=False),
+        sa.ForeignKeyConstraint(['category_id'], ['categories.id'], ),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_items_id'), 'items', ['id'], unique=False)
+    op.create_index(op.f('ix_items_name'), 'items', ['name'], unique=False)
+    op.create_index(op.f('ix_items_sku'), 'items', ['sku'], unique=True)
+
+    # Create inventory_transactions table
+    op.create_table(
+        'inventory_transactions',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('item_id', sa.Integer(), nullable=False),
+        sa.Column('quantity_change', sa.Integer(), nullable=False),
+        sa.Column('transaction_type', sa.String(), nullable=False),
+        sa.Column('notes', sa.Text(), nullable=True),
+        sa.Column('timestamp', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=False),
+        sa.ForeignKeyConstraint(['item_id'], ['items.id'], ),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_inventory_transactions_id'), 'inventory_transactions', ['id'], unique=False)
+
+
+def downgrade():
+    # Drop tables in reverse order to respect foreign key constraints
+    op.drop_index(op.f('ix_inventory_transactions_id'), table_name='inventory_transactions')
+    op.drop_table('inventory_transactions')
+    
+    op.drop_index(op.f('ix_items_sku'), table_name='items')
+    op.drop_index(op.f('ix_items_name'), table_name='items')
+    op.drop_index(op.f('ix_items_id'), table_name='items')
+    op.drop_table('items')
+    
+    op.drop_index(op.f('ix_categories_name'), table_name='categories')
+    op.drop_index(op.f('ix_categories_id'), table_name='categories')
+    op.drop_table('categories')

app/api/v1/api.py

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

app/api/v1/endpoints/__init__.py

@@ -0,0 +1 @@
+# Import endpoints modules here for easier importing

app/api/v1/endpoints/categories.py

@@ -0,0 +1,118 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from app import crud
+from app.db.session import get_db
+from app.schemas.category import Category, CategoryCreate, CategoryUpdate
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[Category])
+def read_categories(
+    db: Session = Depends(get_db),
+    skip: int = 0,
+    limit: int = 100,
+) -> Any:
+    """
+    Retrieve categories.
+    """
+    categories = crud.category.get_multi(db, skip=skip, limit=limit)
+    return categories
+
+
+@router.post("/", response_model=Category)
+def create_category(
+    *,
+    db: Session = Depends(get_db),
+    category_in: CategoryCreate,
+) -> Any:
+    """
+    Create new category.
+    """
+    category = crud.category.get_by_name(db, name=category_in.name)
+    if category:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Category with this name already exists",
+        )
+    category = crud.category.create(db, obj_in=category_in)
+    return category
+
+
+@router.get("/{category_id}", response_model=Category)
+def read_category(
+    *,
+    db: Session = Depends(get_db),
+    category_id: int,
+) -> Any:
+    """
+    Get category by ID.
+    """
+    category = crud.category.get(db, id=category_id)
+    if not category:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Category not found",
+        )
+    return category
+
+
+@router.put("/{category_id}", response_model=Category)
+def update_category(
+    *,
+    db: Session = Depends(get_db),
+    category_id: int,
+    category_in: CategoryUpdate,
+) -> Any:
+    """
+    Update a category.
+    """
+    category = crud.category.get(db, id=category_id)
+    if not category:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Category not found",
+        )
+    
+    # Check if updating name and if it already exists
+    if category_in.name and category_in.name != category.name:
+        existing_category = crud.category.get_by_name(db, name=category_in.name)
+        if existing_category:
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail="Category with this name already exists",
+            )
+    
+    category = crud.category.update(db, db_obj=category, obj_in=category_in)
+    return category
+
+
+@router.delete("/{category_id}", status_code=status.HTTP_204_NO_CONTENT, response_model=None)
+def delete_category(
+    *,
+    db: Session = Depends(get_db),
+    category_id: int,
+) -> None:
+    """
+    Delete a category.
+    """
+    category = crud.category.get(db, id=category_id)
+    if not category:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Category not found",
+        )
+    
+    # Check if category has items
+    items = crud.item.get_by_category(db, category_id=category_id)
+    if items:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Cannot delete category with associated items",
+        )
+    
+    crud.category.remove(db, id=category_id)
+    return None

app/api/v1/endpoints/health.py

@@ -0,0 +1,31 @@
+from typing import Dict
+
+from fastapi import APIRouter, Depends
+from sqlalchemy.orm import Session
+
+from app.db.session import get_db
+
+router = APIRouter()
+
+
+@router.get("/")
+def health_check(
+    db: Session = Depends(get_db),
+) -> Dict:
+    """
+    Perform health check of the application.
+    
+    Checks:
+    - Database connection
+    """
+    # Test database connection
+    db_status = "healthy"
+    try:
+        db.execute("SELECT 1")
+    except Exception:
+        db_status = "unhealthy"
+    
+    return {
+        "status": "healthy" if db_status == "healthy" else "unhealthy",
+        "database": db_status
+    }

app/api/v1/endpoints/items.py

@@ -0,0 +1,227 @@
+from typing import Any, List, Optional
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from app import crud
+from app.db.session import get_db
+from app.schemas.item import (
+    Item, ItemCreate, ItemUpdate, 
+    InventoryTransaction, InventoryTransactionCreate
+)
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[Item])
+def read_items(
+    db: Session = Depends(get_db),
+    skip: int = 0,
+    limit: int = 100,
+    category_id: Optional[int] = None,
+    search: Optional[str] = None,
+    low_stock: Optional[bool] = False,
+    low_stock_threshold: Optional[int] = 10,
+) -> Any:
+    """
+    Retrieve items with filtering options.
+    """
+    if category_id:
+        # Filter by category
+        items = crud.item.get_by_category(db, category_id=category_id, skip=skip, limit=limit)
+    elif search:
+        # Search by name or description
+        items = crud.item.search_items(db, query=search, skip=skip, limit=limit)
+    elif low_stock:
+        # Get low stock items
+        items = crud.item.get_low_stock_items(db, threshold=low_stock_threshold, skip=skip, limit=limit)
+    else:
+        # Get all items
+        items = crud.item.get_multi(db, skip=skip, limit=limit)
+    return items
+
+
+@router.post("/", response_model=Item)
+def create_item(
+    *,
+    db: Session = Depends(get_db),
+    item_in: ItemCreate,
+) -> Any:
+    """
+    Create new item.
+    """
+    # Check if SKU exists if provided
+    if item_in.sku:
+        existing_item = crud.item.get_by_sku(db, sku=item_in.sku)
+        if existing_item:
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail="Item with this SKU already exists",
+            )
+    
+    # Check if category exists if provided
+    if item_in.category_id:
+        category = crud.category.get(db, id=item_in.category_id)
+        if not category:
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail="Category not found",
+            )
+    
+    # Create item with transaction if initial quantity > 0
+    item = crud.item.create_with_transaction(db, obj_in=item_in)
+    return item
+
+
+@router.get("/{item_id}", response_model=Item)
+def read_item(
+    *,
+    db: Session = Depends(get_db),
+    item_id: int,
+) -> Any:
+    """
+    Get item by ID.
+    """
+    item = crud.item.get(db, id=item_id)
+    if not item:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Item not found",
+        )
+    return item
+
+
+@router.put("/{item_id}", response_model=Item)
+def update_item(
+    *,
+    db: Session = Depends(get_db),
+    item_id: int,
+    item_in: ItemUpdate,
+) -> Any:
+    """
+    Update an item.
+    """
+    item = crud.item.get(db, id=item_id)
+    if not item:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Item not found",
+        )
+    
+    # Check if SKU is being updated and if it already exists
+    if item_in.sku and item_in.sku != item.sku:
+        existing_item = crud.item.get_by_sku(db, sku=item_in.sku)
+        if existing_item:
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail="Item with this SKU already exists",
+            )
+    
+    # Check if category exists if being updated
+    if item_in.category_id and item_in.category_id != item.category_id:
+        category = crud.category.get(db, id=item_in.category_id)
+        if not category:
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail="Category not found",
+            )
+    
+    # If quantity is being updated, create a transaction
+    if item_in.quantity is not None and item_in.quantity != item.quantity:
+        quantity_change = item_in.quantity - item.quantity
+        if item.quantity + quantity_change < 0:
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail="Cannot reduce quantity below zero",
+            )
+        
+        # Update quantity with transaction
+        return crud.item.update_quantity(
+            db, 
+            db_obj=item, 
+            quantity_change=quantity_change, 
+            transaction_type="adjustment",
+            notes="Quantity updated via API"
+        )
+    else:
+        # Regular update without quantity change
+        return crud.item.update(db, db_obj=item, obj_in=item_in)
+
+
+@router.delete("/{item_id}", status_code=status.HTTP_204_NO_CONTENT, response_model=None)
+def delete_item(
+    *,
+    db: Session = Depends(get_db),
+    item_id: int,
+) -> None:
+    """
+    Delete an item.
+    """
+    item = crud.item.get(db, id=item_id)
+    if not item:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Item not found",
+        )
+    
+    crud.item.remove(db, id=item_id)
+    return None
+
+
+@router.post("/{item_id}/transactions", response_model=Item)
+def add_inventory_transaction(
+    *,
+    db: Session = Depends(get_db),
+    item_id: int,
+    transaction_in: InventoryTransactionCreate,
+) -> Any:
+    """
+    Add inventory transaction (stock in/out).
+    """
+    item = crud.item.get(db, id=item_id)
+    if not item:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Item not found",
+        )
+    
+    # Update item quantity with transaction
+    try:
+        updated_item = crud.item.update_quantity(
+            db, 
+            db_obj=item, 
+            quantity_change=transaction_in.quantity_change, 
+            transaction_type=transaction_in.transaction_type,
+            notes=transaction_in.notes
+        )
+        return updated_item
+    except ValueError as e:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=str(e),
+        )
+
+
+@router.get("/{item_id}/transactions", response_model=List[InventoryTransaction])
+def get_item_transactions(
+    *,
+    db: Session = Depends(get_db),
+    item_id: int,
+    skip: int = 0,
+    limit: int = 100,
+) -> Any:
+    """
+    Get transaction history for an item.
+    """
+    # Check if item exists
+    item = crud.item.get(db, id=item_id)
+    if not item:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Item not found",
+        )
+    
+    transactions = crud.inventory_transaction.get_by_item(
+        db, item_id=item_id, skip=skip, limit=limit
+    )
+    return transactions

app/core/config.py

@@ -0,0 +1,25 @@
+from pydantic_settings import BaseSettings
+from pathlib import Path
+from typing import List
+
+
+class Settings(BaseSettings):
+    API_V1_STR: str = "/api/v1"
+    PROJECT_NAME: str = "Simple Inventory Management App"
+    
+    # Database settings
+    DB_DIR: Path = Path("/app") / "storage" / "db"
+    SQLALCHEMY_DATABASE_URL: str = f"sqlite:///{DB_DIR}/db.sqlite"
+    
+    # CORS Settings
+    BACKEND_CORS_ORIGINS: List[str] = ["*"]
+
+    class Config:
+        env_file = ".env"
+        case_sensitive = True
+
+
+# Create DB directory if it doesn't exist
+Path("/app/storage/db").mkdir(parents=True, exist_ok=True)
+
+settings = Settings()

app/crud/__init__.py

@@ -0,0 +1,2 @@
+from app.crud.crud_category import category as category
+from app.crud.crud_item import item as item, inventory_transaction as inventory_transaction

app/crud/crud_category.py

@@ -0,0 +1,34 @@
+from typing import List, Optional
+
+from sqlalchemy.orm import Session
+
+from app.db.crud_base import CRUDBase
+from app.models.item import Category
+from app.schemas.category import CategoryCreate, CategoryUpdate
+
+
+class CRUDCategory(CRUDBase[Category, CategoryCreate, CategoryUpdate]):
+    """
+    CRUD operations for Category
+    """
+    def get_by_name(self, db: Session, *, name: str) -> Optional[Category]:
+        """
+        Get a category by name
+        """
+        return db.query(self.model).filter(self.model.name == name).first()
+    
+    def get_multi_with_items(
+        self, db: Session, *, skip: int = 0, limit: int = 100
+    ) -> List[Category]:
+        """
+        Get multiple categories with their associated items
+        """
+        return (
+            db.query(self.model)
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+
+
+category = CRUDCategory(Category)

app/crud/crud_item.py

@@ -0,0 +1,137 @@
+from typing import List, Optional
+
+from sqlalchemy.orm import Session
+
+from app.db.crud_base import CRUDBase
+from app.models.item import Item, InventoryTransaction
+from app.schemas.item import ItemCreate, ItemUpdate, InventoryTransactionCreate
+
+
+class CRUDItem(CRUDBase[Item, ItemCreate, ItemUpdate]):
+    """
+    CRUD operations for Item
+    """
+    def get_by_sku(self, db: Session, *, sku: str) -> Optional[Item]:
+        """
+        Get an item by SKU
+        """
+        return db.query(self.model).filter(self.model.sku == sku).first()
+    
+    def get_by_category(
+        self, db: Session, *, category_id: int, skip: int = 0, limit: int = 100
+    ) -> List[Item]:
+        """
+        Get items by category ID
+        """
+        return (
+            db.query(self.model)
+            .filter(self.model.category_id == category_id)
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+    
+    def search_items(
+        self, db: Session, *, query: str, skip: int = 0, limit: int = 100
+    ) -> List[Item]:
+        """
+        Search items by name or description
+        """
+        search_pattern = f"%{query}%"
+        return (
+            db.query(self.model)
+            .filter(
+                (self.model.name.ilike(search_pattern)) | 
+                (self.model.description.ilike(search_pattern))
+            )
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+    
+    def create_with_transaction(
+        self, db: Session, *, obj_in: ItemCreate
+    ) -> Item:
+        """
+        Create an item and record it as an inventory transaction if quantity > 0
+        """
+        # Create the item
+        db_obj = self.create(db, obj_in=obj_in)
+        
+        # If initial quantity > 0, create a transaction record
+        if db_obj.quantity > 0:
+            transaction = InventoryTransaction(
+                item_id=db_obj.id,
+                quantity_change=db_obj.quantity,
+                transaction_type="initial",
+                notes="Initial inventory"
+            )
+            db.add(transaction)
+            db.commit()
+        
+        return db_obj
+    
+    def update_quantity(
+        self, db: Session, *, db_obj: Item, quantity_change: int, transaction_type: str, notes: Optional[str] = None
+    ) -> Item:
+        """
+        Update item quantity and record the transaction
+        """
+        # Update item quantity
+        new_quantity = db_obj.quantity + quantity_change
+        if new_quantity < 0:
+            raise ValueError("Cannot reduce quantity below zero")
+        
+        db_obj.quantity = new_quantity
+        db.add(db_obj)
+        
+        # Create transaction record
+        transaction = InventoryTransaction(
+            item_id=db_obj.id,
+            quantity_change=quantity_change,
+            transaction_type=transaction_type,
+            notes=notes
+        )
+        db.add(transaction)
+        db.commit()
+        db.refresh(db_obj)
+        
+        return db_obj
+    
+    def get_low_stock_items(
+        self, db: Session, *, threshold: int = 10, skip: int = 0, limit: int = 100
+    ) -> List[Item]:
+        """
+        Get items with quantity below the specified threshold
+        """
+        return (
+            db.query(self.model)
+            .filter(self.model.quantity < threshold)
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+
+
+class CRUDInventoryTransaction(CRUDBase[InventoryTransaction, InventoryTransactionCreate, InventoryTransactionCreate]):
+    """
+    CRUD operations for InventoryTransaction
+    """
+    def get_by_item(
+        self, db: Session, *, item_id: int, skip: int = 0, limit: int = 100
+    ) -> List[InventoryTransaction]:
+        """
+        Get transactions for a specific item
+        """
+        return (
+            db.query(self.model)
+            .filter(self.model.item_id == item_id)
+            .order_by(self.model.timestamp.desc())
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+
+
+item = CRUDItem(Item)
+inventory_transaction = CRUDInventoryTransaction(InventoryTransaction)

app/db/base.py

@@ -0,0 +1,3 @@
+from sqlalchemy.ext.declarative import declarative_base
+
+Base = declarative_base()

app/db/crud_base.py

@@ -0,0 +1,79 @@
+from typing import Any, Dict, Generic, List, Optional, Type, TypeVar, Union
+
+from fastapi.encoders import jsonable_encoder
+from pydantic import BaseModel
+from sqlalchemy.orm import Session
+
+from app.db.base import Base
+
+ModelType = TypeVar("ModelType", bound=Base)
+CreateSchemaType = TypeVar("CreateSchemaType", bound=BaseModel)
+UpdateSchemaType = TypeVar("UpdateSchemaType", bound=BaseModel)
+
+
+class CRUDBase(Generic[ModelType, CreateSchemaType, UpdateSchemaType]):
+    """
+    CRUD base class with default methods for Create, Read, Update, Delete operations
+    """
+    def __init__(self, model: Type[ModelType]):
+        """
+        Initialize CRUD object with SQLAlchemy model
+        """
+        self.model = model
+
+    def get(self, db: Session, id: Any) -> Optional[ModelType]:
+        """
+        Get a single record by ID
+        """
+        return db.query(self.model).filter(self.model.id == id).first()
+
+    def get_multi(
+        self, db: Session, *, skip: int = 0, limit: int = 100
+    ) -> List[ModelType]:
+        """
+        Get multiple records with pagination
+        """
+        return db.query(self.model).offset(skip).limit(limit).all()
+
+    def create(self, db: Session, *, obj_in: CreateSchemaType) -> ModelType:
+        """
+        Create a new record
+        """
+        obj_in_data = jsonable_encoder(obj_in)
+        db_obj = self.model(**obj_in_data)
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+
+    def update(
+        self,
+        db: Session,
+        *,
+        db_obj: ModelType,
+        obj_in: Union[UpdateSchemaType, Dict[str, Any]]
+    ) -> ModelType:
+        """
+        Update a record
+        """
+        obj_data = jsonable_encoder(db_obj)
+        if isinstance(obj_in, dict):
+            update_data = obj_in
+        else:
+            update_data = obj_in.dict(exclude_unset=True)
+        for field in obj_data:
+            if field in update_data:
+                setattr(db_obj, field, update_data[field])
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+
+    def remove(self, db: Session, *, id: int) -> ModelType:
+        """
+        Delete a record
+        """
+        obj = db.query(self.model).get(id)
+        db.delete(obj)
+        db.commit()
+        return obj

app/db/session.py

@@ -0,0 +1,27 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+from app.core.config import settings
+
+# Create DB directory if it doesn't exist
+settings.DB_DIR.mkdir(parents=True, exist_ok=True)
+
+engine = create_engine(
+    settings.SQLALCHEMY_DATABASE_URL,
+    connect_args={"check_same_thread": False}  # Only needed for SQLite
+)
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+
+def get_db():
+    """
+    Dependency function to get a database session.
+    
+    Yields:
+        Session: SQLAlchemy session
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()

app/models/item.py

@@ -0,0 +1,56 @@
+from sqlalchemy import Column, Integer, String, Float, DateTime, ForeignKey, Text
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.db.base import Base
+
+
+class Category(Base):
+    """
+    Model for item categories in inventory
+    """
+    __tablename__ = "categories"
+
+    id = Column(Integer, primary_key=True, index=True)
+    name = Column(String, unique=True, index=True, nullable=False)
+    description = Column(Text, nullable=True)
+    
+    # Relationships
+    items = relationship("Item", back_populates="category")
+
+
+class Item(Base):
+    """
+    Model for inventory items
+    """
+    __tablename__ = "items"
+
+    id = Column(Integer, primary_key=True, index=True)
+    name = Column(String, index=True, nullable=False)
+    description = Column(Text, nullable=True)
+    quantity = Column(Integer, default=0, nullable=False)
+    price = Column(Float, nullable=True)
+    sku = Column(String, unique=True, index=True, nullable=True)
+    category_id = Column(Integer, ForeignKey("categories.id"), nullable=True)
+    created_at = Column(DateTime(timezone=True), server_default=func.now(), nullable=False)
+    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now(), nullable=False)
+    
+    # Relationships
+    category = relationship("Category", back_populates="items")
+
+
+class InventoryTransaction(Base):
+    """
+    Model for tracking inventory transactions (additions/removals)
+    """
+    __tablename__ = "inventory_transactions"
+
+    id = Column(Integer, primary_key=True, index=True)
+    item_id = Column(Integer, ForeignKey("items.id"), nullable=False)
+    quantity_change = Column(Integer, nullable=False)  # Positive for additions, negative for removals
+    transaction_type = Column(String, nullable=False)  # "addition", "removal", "adjustment"
+    notes = Column(Text, nullable=True)
+    timestamp = Column(DateTime(timezone=True), server_default=func.now(), nullable=False)
+    
+    # Relationships
+    item = relationship("Item")

app/schemas/category.py

@@ -0,0 +1,47 @@
+from pydantic import BaseModel, Field
+from typing import Optional, List, ForwardRef
+
+
+# Shared properties
+class CategoryBase(BaseModel):
+    name: str = Field(..., description="Category name", example="Electronics")
+    description: Optional[str] = Field(None, description="Category description", example="Electronic devices and accessories")
+
+
+# Properties to receive via API on creation
+class CategoryCreate(CategoryBase):
+    pass
+
+
+# Properties to receive via API on update
+class CategoryUpdate(BaseModel):
+    name: Optional[str] = Field(None, description="Category name", example="Electronics")
+    description: Optional[str] = Field(None, description="Category description", example="Electronic devices and accessories")
+
+
+# Properties shared by models stored in DB
+class CategoryInDBBase(CategoryBase):
+    id: int = Field(..., description="The unique identifier of the category")
+
+    class Config:
+        from_attributes = True
+
+
+# Properties to return to client
+class Category(CategoryInDBBase):
+    pass
+
+
+# Forward reference for Item
+Item = ForwardRef("Item")
+
+
+# Properties to return to client with relationships
+class CategoryWithItems(CategoryInDBBase):
+    items: List[Item] = Field([], description="Items in this category")
+
+
+# Import here to avoid circular import (moved down to fix linting)
+from app.schemas.item import Item  # noqa: E402
+
+CategoryWithItems.model_rebuild()  # Update forward references

app/schemas/item.py

@@ -0,0 +1,77 @@
+from pydantic import BaseModel, Field, field_validator
+from typing import Optional
+from datetime import datetime
+
+
+# Shared properties
+class ItemBase(BaseModel):
+    name: str = Field(..., description="Item name", example="Laptop")
+    description: Optional[str] = Field(None, description="Item description", example="High-performance laptop")
+    quantity: int = Field(0, description="Current quantity in stock", example=10, ge=0)
+    price: Optional[float] = Field(None, description="Item price", example=999.99, ge=0)
+    sku: Optional[str] = Field(None, description="Stock Keeping Unit", example="LAPTOP-001")
+    category_id: Optional[int] = Field(None, description="Category ID", example=1)
+
+
+# Properties to receive via API on creation
+class ItemCreate(ItemBase):
+    pass
+
+
+# Properties to receive via API on update
+class ItemUpdate(BaseModel):
+    name: Optional[str] = Field(None, description="Item name", example="Laptop")
+    description: Optional[str] = Field(None, description="Item description", example="High-performance laptop")
+    quantity: Optional[int] = Field(None, description="Current quantity in stock", example=10)
+    price: Optional[float] = Field(None, description="Item price", example=999.99)
+    sku: Optional[str] = Field(None, description="Stock Keeping Unit", example="LAPTOP-001")
+    category_id: Optional[int] = Field(None, description="Category ID", example=1)
+
+    @field_validator("quantity", "price")
+    @classmethod
+    def validate_non_negative(cls, v):
+        if v is not None and v < 0:
+            raise ValueError("Value cannot be negative")
+        return v
+
+
+# Properties shared by models stored in DB
+class ItemInDBBase(ItemBase):
+    id: int = Field(..., description="The unique identifier of the item")
+    created_at: datetime = Field(..., description="Item creation timestamp")
+    updated_at: datetime = Field(..., description="Item last update timestamp")
+
+    class Config:
+        from_attributes = True
+
+
+# Properties to return to client
+class Item(ItemInDBBase):
+    pass
+
+
+# Properties for transaction
+class InventoryTransactionBase(BaseModel):
+    item_id: int = Field(..., description="Item ID", example=1)
+    quantity_change: int = Field(..., description="Quantity change (positive for additions, negative for removals)", example=5)
+    transaction_type: str = Field(..., description="Transaction type", example="addition")
+    notes: Optional[str] = Field(None, description="Transaction notes", example="Received new shipment")
+
+
+# Properties to receive via API on creation
+class InventoryTransactionCreate(InventoryTransactionBase):
+    pass
+
+
+# Properties shared by models stored in DB
+class InventoryTransactionInDBBase(InventoryTransactionBase):
+    id: int = Field(..., description="The unique identifier of the transaction")
+    timestamp: datetime = Field(..., description="Transaction timestamp")
+
+    class Config:
+        from_attributes = True
+
+
+# Properties to return to client
+class InventoryTransaction(InventoryTransactionInDBBase):
+    pass

main.py

@@ -0,0 +1,46 @@
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+
+from app.api.v1.api import api_router
+from app.core.config import settings
+
+app = FastAPI(
+    title=settings.PROJECT_NAME,
+    openapi_url="/openapi.json",
+    docs_url="/docs",
+    redoc_url="/redoc",
+)
+
+# Set up CORS middleware
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+# Include the API router
+app.include_router(api_router, prefix=settings.API_V1_STR)
+
+@app.get("/")
+async def root():
+    """
+    Root endpoint that returns basic information about the API.
+    """
+    return {
+        "title": settings.PROJECT_NAME,
+        "docs": f"{settings.API_V1_STR}/docs",
+        "health": f"{settings.API_V1_STR}/health"
+    }
+
+@app.get("/health")
+async def health_check():
+    """
+    Health check endpoint to verify the API is functioning.
+    """
+    return {"status": "healthy"}
+
+if __name__ == "__main__":
+    import uvicorn
+    uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=True)

requirements.txt

@@ -0,0 +1,9 @@
+fastapi>=0.104.0
+uvicorn>=0.23.2
+sqlalchemy>=2.0.0
+alembic>=1.12.0
+pydantic>=2.4.2
+pydantic-settings>=2.0.3
+python-dotenv>=1.0.0
+ruff>=0.1.4
+pathlib>=1.0.1