Implement Small Business Inventory Management System

This commit includes:
- Project structure setup with FastAPI and SQLite
- Database models and schemas for inventory management
- CRUD operations for all entities
- API endpoints for product, category, supplier, and inventory management
- User authentication with JWT tokens
- Initial database migration
- Comprehensive README with setup instructions

README.md

@@ -1,3 +1,161 @@
-# FastAPI Application
+# Small Business Inventory Management System
 
-This is a FastAPI application bootstrapped by BackendIM, the AI-powered backend generation platform.
+A comprehensive inventory management system designed for small businesses built with FastAPI and SQLite.
+
+## Features
+
+- **Product Management**: Create, update, and track products with SKU, barcode, price, cost, and more
+- **Category Organization**: Organize products into categories for easier management
+- **Supplier Management**: Track product suppliers with contact information
+- **Inventory Tracking**: Monitor stock levels across your business
+- **Transaction History**: Keep a complete history of inventory movements (purchases, sales, returns, etc.)
+- **Low Stock Alerts**: Easily identify products that need to be reordered
+- **User Authentication**: Secure API with JWT-based authentication and role-based permissions
+
+## Installation
+
+### Prerequisites
+
+- Python 3.8 or higher
+- pip (Python package manager)
+
+### Setup
+
+1. Clone the repository:
+
+```bash
+git clone <repository-url>
+cd small-business-inventory-management-system
+```
+
+2. Create a virtual environment:
+
+```bash
+python -m venv venv
+source venv/bin/activate  # On Windows: venv\Scripts\activate
+```
+
+3. Install dependencies:
+
+```bash
+pip install -r requirements.txt
+```
+
+4. Set up environment variables:
+
+```bash
+# For development
+export SECRET_KEY="your-super-secret-key-here"  # On Windows: set SECRET_KEY=your-super-secret-key-here
+```
+
+5. Run database migrations:
+
+```bash
+alembic upgrade head
+```
+
+6. Create a superuser:
+
+```bash
+python -m app.initial_data  # Script not included in this version, create manually via API
+```
+
+## Running the Application
+
+Start the server with:
+
+```bash
+uvicorn main:app --reload --host 0.0.0.0 --port 8000
+```
+
+The API will be available at http://localhost:8000/
+
+API documentation is available at:
+- Swagger UI: http://localhost:8000/docs
+- ReDoc: http://localhost:8000/redoc
+
+## API Endpoints
+
+### Authentication
+
+- `POST /api/v1/login/access-token` - Get access token (login)
+- `POST /api/v1/login/test-token` - Test token validity
+
+### Users
+
+- `GET /api/v1/users/` - List users (admin only)
+- `POST /api/v1/users/` - Create user (admin only)
+- `GET /api/v1/users/me` - Get current user
+- `PUT /api/v1/users/me` - Update current user
+- `GET /api/v1/users/{user_id}` - Get user by ID
+- `PUT /api/v1/users/{user_id}` - Update user by ID (admin only)
+
+### Categories
+
+- `GET /api/v1/categories/` - List categories
+- `POST /api/v1/categories/` - Create category
+- `GET /api/v1/categories/{id}` - Get category by ID
+- `PUT /api/v1/categories/{id}` - Update category
+- `DELETE /api/v1/categories/{id}` - Delete category
+
+### Suppliers
+
+- `GET /api/v1/suppliers/` - List suppliers
+- `POST /api/v1/suppliers/` - Create supplier
+- `GET /api/v1/suppliers/{id}` - Get supplier by ID
+- `PUT /api/v1/suppliers/{id}` - Update supplier
+- `DELETE /api/v1/suppliers/{id}` - Delete supplier
+
+### Products
+
+- `GET /api/v1/products/` - List products (with optional filtering)
+- `POST /api/v1/products/` - Create product
+- `GET /api/v1/products/{id}` - Get product by ID
+- `GET /api/v1/products/sku/{sku}` - Get product by SKU
+- `GET /api/v1/products/barcode/{barcode}` - Get product by barcode
+- `PUT /api/v1/products/{id}` - Update product
+- `DELETE /api/v1/products/{id}` - Delete product
+
+### Inventory
+
+- `GET /api/v1/inventory/` - List inventory items
+- `GET /api/v1/inventory/product/{product_id}` - Get inventory by product ID
+- `GET /api/v1/inventory/low-stock` - Get products with low stock
+- `GET /api/v1/inventory/summary` - Get inventory summary
+- `PUT /api/v1/inventory/adjust/{product_id}` - Adjust inventory for a product
+
+### Inventory Transactions
+
+- `POST /api/v1/inventory/transactions/` - Create inventory transaction
+- `GET /api/v1/inventory/transactions/` - List transactions (with optional filtering)
+- `GET /api/v1/inventory/transactions/{transaction_id}` - Get transaction by ID
+
+## Environment Variables
+
+The application uses the following environment variables:
+
+- `SECRET_KEY` - Secret key for JWT token generation and validation (default: "your-secret-key-here-replace-in-production")
+- `ACCESS_TOKEN_EXPIRE_MINUTES` - JWT token expiration time in minutes (default: 30)
+
+## Database Structure
+
+The application uses SQLite as the database, stored in `/app/storage/db/db.sqlite`. The database schema includes:
+
+- **User**: Authentication and system users
+- **Category**: Product categories
+- **Supplier**: Product suppliers
+- **Product**: Product information
+- **Inventory**: Current stock levels
+- **InventoryTransaction**: History of inventory movements
+
+## Contributing
+
+1. Fork the repository
+2. Create a feature branch: `git checkout -b feature-name`
+3. Commit your changes: `git commit -am 'Add some feature'`
+4. Push to the branch: `git push origin feature-name`
+5. Submit a pull request
+
+## License
+
+This project is licensed under the MIT License - see the LICENSE file for details.

alembic.ini

@@ -0,0 +1,106 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = migrations
+
+# template used to generate migration file names; The default value is %%(rev)s_%%(slug)s
+# Uncomment the line below if you want the files to be prepended with date and time
+# see https://alembic.sqlalchemy.org/en/latest/tutorial.html#editing-the-ini-file
+# for all available tokens
+# file_template = %%(year)d_%%(month).2d_%%(day).2d_%%(hour).2d%%(minute).2d-%%(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 migrations/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:migrations/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.
+
+# 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 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

app/__init__.py

@@ -0,0 +1 @@
+# app package initialization

app/api/__init__.py

@@ -0,0 +1 @@
+# api package initialization

app/api/deps.py

@@ -0,0 +1,60 @@
+from typing import Generator
+
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from jose import jwt
+from pydantic import ValidationError
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.core.config import settings
+from app.db.session import SessionLocal
+
+reusable_oauth2 = OAuth2PasswordBearer(
+    tokenUrl=f"{settings.API_V1_STR}/login/access-token"
+)
+
+
+def get_db() -> Generator:
+    try:
+        db = SessionLocal()
+        yield db
+    finally:
+        db.close()
+
+
+def get_current_user(
+    db: Session = Depends(get_db), token: str = Depends(reusable_oauth2)
+) -> models.User:
+    try:
+        payload = jwt.decode(
+            token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM]
+        )
+        token_data = schemas.TokenPayload(**payload)
+    except (jwt.JWTError, ValidationError):
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Could not validate credentials",
+        )
+    user = crud.user.get(db, id=token_data.sub)
+    if not user:
+        raise HTTPException(status_code=404, detail="User not found")
+    return user
+
+
+def get_current_active_user(
+    current_user: models.User = Depends(get_current_user),
+) -> models.User:
+    if not crud.user.is_active(current_user):
+        raise HTTPException(status_code=400, detail="Inactive user")
+    return current_user
+
+
+def get_current_active_superuser(
+    current_user: models.User = Depends(get_current_user),
+) -> models.User:
+    if not crud.user.is_superuser(current_user):
+        raise HTTPException(
+            status_code=400, detail="The user doesn't have enough privileges"
+        )
+    return current_user

app/api/v1/__init__.py

@@ -0,0 +1 @@
+# api v1 package initialization

app/api/v1/api.py

@@ -0,0 +1,12 @@
+from fastapi import APIRouter
+
+from app.api.v1.endpoints import login, users, products, categories, suppliers, inventory
+
+api_router = APIRouter()
+
+api_router.include_router(login.router, tags=["Authentication"])
+api_router.include_router(users.router, prefix="/users", tags=["Users"])
+api_router.include_router(products.router, prefix="/products", tags=["Products"])
+api_router.include_router(categories.router, prefix="/categories", tags=["Categories"])
+api_router.include_router(suppliers.router, prefix="/suppliers", tags=["Suppliers"])
+api_router.include_router(inventory.router, prefix="/inventory", tags=["Inventory"])

app/api/v1/endpoints/__init__.py

@@ -0,0 +1 @@
+# API endpoints initialization

app/api/v1/endpoints/categories.py

@@ -0,0 +1,112 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.Category])
+def read_categories(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve categories.
+    """
+    categories = crud.category.get_multi(db, skip=skip, limit=limit)
+    return categories
+
+
+@router.post("/", response_model=schemas.Category)
+def create_category(
+    *,
+    db: Session = Depends(deps.get_db),
+    category_in: schemas.CategoryCreate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new category.
+    """
+    category = crud.category.get_by_name(db, name=category_in.name)
+    if category:
+        raise HTTPException(
+            status_code=400,
+            detail="The category with this name already exists in the system.",
+        )
+    category = crud.category.create(db, obj_in=category_in)
+    return category
+
+
+@router.get("/{id}", response_model=schemas.Category)
+def read_category(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get category by ID.
+    """
+    category = crud.category.get(db, id=id)
+    if not category:
+        raise HTTPException(status_code=404, detail="Category not found")
+    return category
+
+
+@router.put("/{id}", response_model=schemas.Category)
+def update_category(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    category_in: schemas.CategoryUpdate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update a category.
+    """
+    category = crud.category.get(db, id=id)
+    if not category:
+        raise HTTPException(status_code=404, detail="Category not found")
+    
+    # Check if the updated name conflicts with an existing category
+    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=400,
+                detail="The category with this name already exists in the system.",
+            )
+    
+    category = crud.category.update(db, db_obj=category, obj_in=category_in)
+    return category
+
+
+@router.delete("/{id}", status_code=204, response_model=None)
+def delete_category(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Delete a category.
+    """
+    category = crud.category.get(db, id=id)
+    if not category:
+        raise HTTPException(status_code=404, detail="Category not found")
+    
+    # Check if the category has products
+    if category.products:
+        raise HTTPException(
+            status_code=400,
+            detail="Cannot delete category with associated products. Reassign or delete the products first.",
+        )
+    
+    crud.category.remove(db, id=id)
+    return None

app/api/v1/endpoints/inventory.py

@@ -0,0 +1,200 @@
+from typing import Any, List, Optional
+from datetime import datetime
+
+from fastapi import APIRouter, Depends, HTTPException, Body
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.Inventory])
+def read_inventories(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    location: Optional[str] = None,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve inventory items with optional filtering by location.
+    """
+    if location:
+        inventories = crud.inventory.get_by_location(db, location=location, skip=skip, limit=limit)
+    else:
+        inventories = crud.inventory.get_multi(db, skip=skip, limit=limit)
+    return inventories
+
+
+@router.get("/product/{product_id}", response_model=schemas.Inventory)
+def read_inventory_by_product(
+    *,
+    db: Session = Depends(deps.get_db),
+    product_id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get inventory by product ID.
+    """
+    inventory = crud.inventory.get_by_product_id(db, product_id=product_id)
+    if not inventory:
+        raise HTTPException(status_code=404, detail="Inventory not found for this product")
+    return inventory
+
+
+@router.get("/low-stock", response_model=schemas.InventorySummaryList)
+def read_low_stock(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get products with inventory below minimum stock level.
+    """
+    low_stock_items = crud.inventory.get_low_stock(db, skip=skip, limit=limit)
+    return {"inventories": low_stock_items}
+
+
+@router.get("/summary", response_model=schemas.InventorySummaryList)
+def read_inventory_summary(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get inventory summary for all products.
+    """
+    summary = crud.inventory.get_inventory_summary(db, skip=skip, limit=limit)
+    return {"inventories": summary}
+
+
+@router.put("/adjust/{product_id}", response_model=schemas.Inventory)
+def adjust_inventory(
+    *,
+    db: Session = Depends(deps.get_db),
+    product_id: int,
+    quantity_change: int = Body(..., description="Amount to add or subtract from inventory"),
+    location: Optional[str] = Body(None, description="Location of the inventory"),
+    notes: Optional[str] = Body(None, description="Notes about the adjustment"),
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Adjust inventory quantity for a product.
+    Positive values increase stock, negative values decrease stock.
+    """
+    # Verify the product exists
+    product = crud.product.get(db, id=product_id)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    
+    # Update inventory and create transaction record
+    result = crud.inventory.update_stock(
+        db=db,
+        product_id=product_id,
+        quantity_change=quantity_change,
+        user_id=current_user.id,
+        transaction_type="adjustment",
+        notes=notes
+    )
+    
+    # Update location if provided
+    if location and location != result["inventory"].location:
+        inventory_update = schemas.InventoryUpdate(
+            product_id=product_id,
+            quantity=result["inventory"].quantity,
+            location=location
+        )
+        inventory = crud.inventory.update(db, db_obj=result["inventory"], obj_in=inventory_update)
+        return inventory
+    
+    return result["inventory"]
+
+
+@router.post("/transactions/", response_model=schemas.InventoryTransaction)
+def create_inventory_transaction(
+    *,
+    db: Session = Depends(deps.get_db),
+    transaction_in: schemas.InventoryTransactionCreate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create a new inventory transaction and update inventory accordingly.
+    """
+    # Verify the product exists
+    product = crud.product.get(db, id=transaction_in.product_id)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    
+    # Validate transaction type
+    valid_types = ["purchase", "sale", "adjustment", "return", "transfer"]
+    if transaction_in.transaction_type not in valid_types:
+        raise HTTPException(
+            status_code=400,
+            detail=f"Invalid transaction type. Must be one of: {', '.join(valid_types)}"
+        )
+    
+    # Update inventory and create transaction record
+    result = crud.inventory.update_stock(
+        db=db,
+        product_id=transaction_in.product_id,
+        quantity_change=transaction_in.quantity,
+        user_id=current_user.id,
+        transaction_type=transaction_in.transaction_type,
+        reference=transaction_in.reference,
+        unit_price=transaction_in.unit_price,
+        notes=transaction_in.notes
+    )
+    
+    return result["transaction"]
+
+
+@router.get("/transactions/", response_model=List[schemas.InventoryTransaction])
+def read_inventory_transactions(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    product_id: Optional[int] = None,
+    transaction_type: Optional[str] = None,
+    start_date: Optional[datetime] = None,
+    end_date: Optional[datetime] = None,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve inventory transactions with optional filtering.
+    """
+    if product_id:
+        transactions = crud.inventory_transaction.get_by_product_id(
+            db, product_id=product_id, skip=skip, limit=limit
+        )
+    elif transaction_type:
+        transactions = crud.inventory_transaction.get_by_type(
+            db, transaction_type=transaction_type, skip=skip, limit=limit
+        )
+    elif start_date and end_date:
+        transactions = crud.inventory_transaction.get_by_date_range(
+            db, start_date=start_date, end_date=end_date, skip=skip, limit=limit
+        )
+    else:
+        transactions = crud.inventory_transaction.get_multi(db, skip=skip, limit=limit)
+    
+    return transactions
+
+
+@router.get("/transactions/{transaction_id}", response_model=schemas.InventoryTransaction)
+def read_inventory_transaction(
+    *,
+    db: Session = Depends(deps.get_db),
+    transaction_id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get inventory transaction by ID.
+    """
+    transaction = crud.inventory_transaction.get(db, id=transaction_id)
+    if not transaction:
+        raise HTTPException(status_code=404, detail="Transaction not found")
+    return transaction

app/api/v1/endpoints/login.py

@@ -0,0 +1,44 @@
+from datetime import timedelta
+from typing import Any
+
+from fastapi import APIRouter, Depends, HTTPException
+from fastapi.security import OAuth2PasswordRequestForm
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+from app.core import security
+from app.core.config import settings
+
+router = APIRouter()
+
+
+@router.post("/login/access-token", response_model=schemas.Token)
+def login_access_token(
+    db: Session = Depends(deps.get_db), form_data: OAuth2PasswordRequestForm = Depends()
+) -> Any:
+    """
+    OAuth2 compatible token login, get an access token for future requests
+    """
+    user = crud.user.authenticate(
+        db, email=form_data.username, password=form_data.password
+    )
+    if not user:
+        raise HTTPException(status_code=400, detail="Incorrect email or password")
+    elif not crud.user.is_active(user):
+        raise HTTPException(status_code=400, detail="Inactive user")
+    access_token_expires = timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
+    return {
+        "access_token": security.create_access_token(
+            user.id, expires_delta=access_token_expires
+        ),
+        "token_type": "bearer",
+    }
+
+
+@router.post("/login/test-token", response_model=schemas.User)
+def test_token(current_user: models.User = Depends(deps.get_current_user)) -> Any:
+    """
+    Test access token
+    """
+    return current_user

app/api/v1/endpoints/products.py

@@ -0,0 +1,221 @@
+from typing import Any, List, Optional
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.Product])
+def read_products(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    name: Optional[str] = None,
+    category_id: Optional[int] = None,
+    supplier_id: Optional[int] = None,
+    active_only: bool = False,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve products with optional filtering.
+    """
+    if name:
+        products = crud.product.get_by_name(db, name=name)
+    elif category_id:
+        products = crud.product.get_by_category_id(db, category_id=category_id, skip=skip, limit=limit)
+    elif supplier_id:
+        products = crud.product.get_by_supplier_id(db, supplier_id=supplier_id, skip=skip, limit=limit)
+    elif active_only:
+        products = crud.product.get_active(db, skip=skip, limit=limit)
+    else:
+        products = crud.product.get_multi(db, skip=skip, limit=limit)
+    return products
+
+
+@router.post("/", response_model=schemas.Product)
+def create_product(
+    *,
+    db: Session = Depends(deps.get_db),
+    product_in: schemas.ProductCreate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new product.
+    """
+    # Check if SKU exists
+    product = crud.product.get_by_sku(db, sku=product_in.sku)
+    if product:
+        raise HTTPException(
+            status_code=400,
+            detail="A product with this SKU already exists in the system.",
+        )
+    
+    # Check if barcode exists (if provided)
+    if product_in.barcode:
+        product = crud.product.get_by_barcode(db, barcode=product_in.barcode)
+        if product:
+            raise HTTPException(
+                status_code=400,
+                detail="A product with this barcode already exists in the system.",
+            )
+    
+    # Validate category_id if provided
+    if product_in.category_id:
+        category = crud.category.get(db, id=product_in.category_id)
+        if not category:
+            raise HTTPException(
+                status_code=404,
+                detail=f"Category with ID {product_in.category_id} not found",
+            )
+    
+    # Validate supplier_id if provided
+    if product_in.supplier_id:
+        supplier = crud.supplier.get(db, id=product_in.supplier_id)
+        if not supplier:
+            raise HTTPException(
+                status_code=404,
+                detail=f"Supplier with ID {product_in.supplier_id} not found",
+            )
+    
+    product = crud.product.create(db, obj_in=product_in)
+    
+    # Create initial inventory record with 0 quantity
+    inventory_in = schemas.InventoryCreate(
+        product_id=product.id,
+        quantity=0,
+        location=None
+    )
+    crud.inventory.create(db, obj_in=inventory_in)
+    
+    return product
+
+
+@router.get("/{id}", response_model=schemas.Product)
+def read_product(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get product by ID.
+    """
+    product = crud.product.get(db, id=id)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    return product
+
+
+@router.get("/sku/{sku}", response_model=schemas.Product)
+def read_product_by_sku(
+    *,
+    db: Session = Depends(deps.get_db),
+    sku: str,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get product by SKU.
+    """
+    product = crud.product.get_by_sku(db, sku=sku)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    return product
+
+
+@router.get("/barcode/{barcode}", response_model=schemas.Product)
+def read_product_by_barcode(
+    *,
+    db: Session = Depends(deps.get_db),
+    barcode: str,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get product by barcode.
+    """
+    product = crud.product.get_by_barcode(db, barcode=barcode)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    return product
+
+
+@router.put("/{id}", response_model=schemas.Product)
+def update_product(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    product_in: schemas.ProductUpdate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update a product.
+    """
+    product = crud.product.get(db, id=id)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    
+    # Check if SKU exists and is different from current product
+    if product_in.sku and product_in.sku != product.sku:
+        existing_product = crud.product.get_by_sku(db, sku=product_in.sku)
+        if existing_product:
+            raise HTTPException(
+                status_code=400,
+                detail="A product with this SKU already exists in the system.",
+            )
+    
+    # Check if barcode exists and is different from current product
+    if product_in.barcode and product_in.barcode != product.barcode:
+        existing_product = crud.product.get_by_barcode(db, barcode=product_in.barcode)
+        if existing_product:
+            raise HTTPException(
+                status_code=400,
+                detail="A product with this barcode already exists in the system.",
+            )
+    
+    # Validate category_id if provided
+    if product_in.category_id and product_in.category_id != product.category_id:
+        category = crud.category.get(db, id=product_in.category_id)
+        if not category:
+            raise HTTPException(
+                status_code=404,
+                detail=f"Category with ID {product_in.category_id} not found",
+            )
+    
+    # Validate supplier_id if provided
+    if product_in.supplier_id and product_in.supplier_id != product.supplier_id:
+        supplier = crud.supplier.get(db, id=product_in.supplier_id)
+        if not supplier:
+            raise HTTPException(
+                status_code=404,
+                detail=f"Supplier with ID {product_in.supplier_id} not found",
+            )
+    
+    product = crud.product.update(db, db_obj=product, obj_in=product_in)
+    return product
+
+
+@router.delete("/{id}", status_code=204, response_model=None)
+def delete_product(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Delete a product.
+    """
+    product = crud.product.get(db, id=id)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    
+    # First, delete associated inventory records
+    inventory = crud.inventory.get_by_product_id(db, product_id=id)
+    if inventory:
+        db.delete(inventory)
+        db.commit()
+    
+    crud.product.remove(db, id=id)
+    return None

app/api/v1/endpoints/suppliers.py

@@ -0,0 +1,96 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.Supplier])
+def read_suppliers(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve suppliers.
+    """
+    suppliers = crud.supplier.get_multi(db, skip=skip, limit=limit)
+    return suppliers
+
+
+@router.post("/", response_model=schemas.Supplier)
+def create_supplier(
+    *,
+    db: Session = Depends(deps.get_db),
+    supplier_in: schemas.SupplierCreate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new supplier.
+    """
+    supplier = crud.supplier.create(db, obj_in=supplier_in)
+    return supplier
+
+
+@router.get("/{id}", response_model=schemas.Supplier)
+def read_supplier(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get supplier by ID.
+    """
+    supplier = crud.supplier.get(db, id=id)
+    if not supplier:
+        raise HTTPException(status_code=404, detail="Supplier not found")
+    return supplier
+
+
+@router.put("/{id}", response_model=schemas.Supplier)
+def update_supplier(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    supplier_in: schemas.SupplierUpdate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update a supplier.
+    """
+    supplier = crud.supplier.get(db, id=id)
+    if not supplier:
+        raise HTTPException(status_code=404, detail="Supplier not found")
+    supplier = crud.supplier.update(db, db_obj=supplier, obj_in=supplier_in)
+    return supplier
+
+
+@router.delete("/{id}", status_code=204, response_model=None)
+def delete_supplier(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Delete a supplier.
+    """
+    supplier = crud.supplier.get(db, id=id)
+    if not supplier:
+        raise HTTPException(status_code=404, detail="Supplier not found")
+    
+    # Check if the supplier has products
+    if supplier.products:
+        raise HTTPException(
+            status_code=400,
+            detail="Cannot delete supplier with associated products. Reassign or delete the products first.",
+        )
+    
+    crud.supplier.remove(db, id=id)
+    return None

app/api/v1/endpoints/users.py

@@ -0,0 +1,120 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Body, Depends, HTTPException
+from fastapi.encoders import jsonable_encoder
+from pydantic import EmailStr
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.User])
+def read_users(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Retrieve users.
+    """
+    users = crud.user.get_multi(db, skip=skip, limit=limit)
+    return users
+
+
+@router.post("/", response_model=schemas.User)
+def create_user(
+    *,
+    db: Session = Depends(deps.get_db),
+    user_in: schemas.UserCreate,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Create new user.
+    """
+    user = crud.user.get_by_email(db, email=user_in.email)
+    if user:
+        raise HTTPException(
+            status_code=400,
+            detail="The user with this email already exists in the system.",
+        )
+    user = crud.user.create(db, obj_in=user_in)
+    return user
+
+
+@router.get("/me", response_model=schemas.User)
+def read_user_me(
+    db: Session = Depends(deps.get_db),
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get current user.
+    """
+    return current_user
+
+
+@router.put("/me", response_model=schemas.User)
+def update_user_me(
+    *,
+    db: Session = Depends(deps.get_db),
+    password: str = Body(None),
+    full_name: str = Body(None),
+    email: EmailStr = Body(None),
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update own user.
+    """
+    current_user_data = jsonable_encoder(current_user)
+    user_in = schemas.UserUpdate(**current_user_data)
+    if password is not None:
+        user_in.password = password
+    if full_name is not None:
+        user_in.full_name = full_name
+    if email is not None:
+        user_in.email = email
+    user = crud.user.update(db, db_obj=current_user, obj_in=user_in)
+    return user
+
+
+@router.get("/{user_id}", response_model=schemas.User)
+def read_user_by_id(
+    user_id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+    db: Session = Depends(deps.get_db),
+) -> Any:
+    """
+    Get a specific user by id.
+    """
+    user = crud.user.get(db, id=user_id)
+    if user == current_user:
+        return user
+    if not crud.user.is_superuser(current_user):
+        raise HTTPException(
+            status_code=400, detail="The user doesn't have enough privileges"
+        )
+    return user
+
+
+@router.put("/{user_id}", response_model=schemas.User)
+def update_user(
+    *,
+    db: Session = Depends(deps.get_db),
+    user_id: int,
+    user_in: schemas.UserUpdate,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Update a user.
+    """
+    user = crud.user.get(db, id=user_id)
+    if not user:
+        raise HTTPException(
+            status_code=404,
+            detail="The user with this username does not exist in the system",
+        )
+    user = crud.user.update(db, db_obj=user, obj_in=user_in)
+    return user

app/core/__init__.py

@@ -0,0 +1 @@
+# core package initialization

app/core/config.py

@@ -0,0 +1,27 @@
+import os
+from pathlib import Path
+from typing import List
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+class Settings(BaseSettings):
+    API_V1_STR: str = "/api/v1"
+    PROJECT_NAME: str = "Small Business Inventory Management System"
+    VERSION: str = "0.1.0"
+    
+    # Security
+    SECRET_KEY: str = os.environ.get("SECRET_KEY", "your-secret-key-here-replace-in-production")
+    ALGORITHM: str = "HS256"
+    ACCESS_TOKEN_EXPIRE_MINUTES: int = 30
+    
+    # Database
+    DB_DIR: Path = Path("/app") / "storage" / "db"
+    
+    # CORS
+    BACKEND_CORS_ORIGINS: List[str] = ["*"]
+    
+    model_config = SettingsConfigDict(case_sensitive=True)
+
+settings = Settings()
+
+# Ensure DB directory exists
+settings.DB_DIR.mkdir(parents=True, exist_ok=True)

app/core/security.py

@@ -0,0 +1,31 @@
+from datetime import datetime, timedelta
+from typing import Any, Union
+
+from jose import jwt
+from passlib.context import CryptContext
+
+from app.core.config import settings
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+
+def create_access_token(
+    subject: Union[str, Any], expires_delta: timedelta = None
+) -> str:
+    if expires_delta:
+        expire = datetime.utcnow() + expires_delta
+    else:
+        expire = datetime.utcnow() + timedelta(
+            minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES
+        )
+    to_encode = {"exp": expire, "sub": str(subject)}
+    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
+    return encoded_jwt
+
+
+def verify_password(plain_password: str, hashed_password: str) -> bool:
+    return pwd_context.verify(plain_password, hashed_password)
+
+
+def get_password_hash(password: str) -> str:
+    return pwd_context.hash(password)

app/crud/__init__.py

@@ -0,0 +1,5 @@
+from .crud_user import user as user
+from .crud_category import category as category
+from .crud_supplier import supplier as supplier
+from .crud_product import product as product
+from .crud_inventory import inventory as inventory, inventory_transaction as inventory_transaction

app/crud/base.py

@@ -0,0 +1,66 @@
+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]):
+    def __init__(self, model: Type[ModelType]):
+        """
+        CRUD object with default methods to Create, Read, Update, Delete (CRUD).
+
+        **Parameters**
+
+        * `model`: A SQLAlchemy model class
+        * `schema`: A Pydantic model (schema) class
+        """
+        self.model = model
+
+    def get(self, db: Session, id: Any) -> Optional[ModelType]:
+        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]:
+        return db.query(self.model).offset(skip).limit(limit).all()
+
+    def create(self, db: Session, *, obj_in: CreateSchemaType) -> ModelType:
+        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:
+        obj_data = jsonable_encoder(db_obj)
+        if isinstance(obj_in, dict):
+            update_data = obj_in
+        else:
+            update_data = obj_in.model_dump(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:
+        obj = db.query(self.model).get(id)
+        db.delete(obj)
+        db.commit()
+        return obj

app/crud/crud_category.py

@@ -0,0 +1,20 @@
+from typing import List, Optional
+
+from sqlalchemy.orm import Session
+
+from app.crud.base import CRUDBase
+from app.models.category import Category
+from app.schemas.category import CategoryCreate, CategoryUpdate
+
+
+class CRUDCategory(CRUDBase[Category, CategoryCreate, CategoryUpdate]):
+    def get_by_name(self, db: Session, *, name: str) -> Optional[Category]:
+        return db.query(Category).filter(Category.name == name).first()
+
+    def get_multi_by_ids(
+        self, db: Session, *, ids: List[int], skip: int = 0, limit: int = 100
+    ) -> List[Category]:
+        return db.query(Category).filter(Category.id.in_(ids)).offset(skip).limit(limit).all()
+
+
+category = CRUDCategory(Category)

app/crud/crud_inventory.py

@@ -0,0 +1,172 @@
+from typing import List, Optional, Dict, Any
+from datetime import datetime
+
+from sqlalchemy.orm import Session
+
+from app.crud.base import CRUDBase
+from app.models.inventory import Inventory, InventoryTransaction
+from app.models.product import Product
+from app.schemas.inventory import (
+    InventoryCreate, InventoryUpdate,
+    InventoryTransactionCreate, InventoryTransactionUpdate
+)
+
+
+class CRUDInventory(CRUDBase[Inventory, InventoryCreate, InventoryUpdate]):
+    def get_by_product_id(self, db: Session, *, product_id: int) -> Optional[Inventory]:
+        return db.query(Inventory).filter(Inventory.product_id == product_id).first()
+    
+    def get_by_location(
+        self, db: Session, *, location: str, skip: int = 0, limit: int = 100
+    ) -> List[Inventory]:
+        return db.query(Inventory).filter(Inventory.location == location).offset(skip).limit(limit).all()
+    
+    def get_low_stock(self, db: Session, *, skip: int = 0, limit: int = 100) -> List[Dict[str, Any]]:
+        """Get products where inventory is below minimum stock level."""
+        query = (
+            db.query(
+                Inventory, 
+                Product.name, 
+                Product.sku, 
+                Product.min_stock_level
+            )
+            .join(Product)
+            .filter(Inventory.quantity <= Product.min_stock_level)
+            .offset(skip)
+            .limit(limit)
+        )
+        
+        result = []
+        for inventory, name, sku, min_stock_level in query.all():
+            result.append({
+                "product_id": inventory.product_id,
+                "product_name": name,
+                "sku": sku,
+                "current_stock": inventory.quantity,
+                "min_stock_level": min_stock_level,
+                "is_low_stock": True
+            })
+        
+        return result
+    
+    def get_inventory_summary(self, db: Session, *, skip: int = 0, limit: int = 100) -> List[Dict[str, Any]]:
+        """Get inventory summary for all products."""
+        query = (
+            db.query(
+                Inventory, 
+                Product.name, 
+                Product.sku, 
+                Product.min_stock_level
+            )
+            .join(Product)
+            .offset(skip)
+            .limit(limit)
+        )
+        
+        result = []
+        for inventory, name, sku, min_stock_level in query.all():
+            result.append({
+                "product_id": inventory.product_id,
+                "product_name": name,
+                "sku": sku,
+                "current_stock": inventory.quantity,
+                "min_stock_level": min_stock_level,
+                "is_low_stock": inventory.quantity <= min_stock_level
+            })
+        
+        return result
+    
+    def update_stock(
+        self, db: Session, *, product_id: int, quantity_change: int, user_id: Optional[int] = None,
+        transaction_type: str = "adjustment", reference: Optional[str] = None,
+        unit_price: Optional[float] = None, notes: Optional[str] = None
+    ) -> Dict[str, Any]:
+        """Update stock level and create a transaction record."""
+        inventory = self.get_by_product_id(db=db, product_id=product_id)
+        
+        if not inventory:
+            # Create new inventory record if it doesn't exist
+            inventory_in = InventoryCreate(
+                product_id=product_id,
+                quantity=quantity_change if quantity_change > 0 else 0,  # Don't allow negative initial stock
+                last_counted_at=datetime.now()
+            )
+            inventory = super().create(db=db, obj_in=inventory_in)
+        else:
+            # Update existing inventory
+            new_quantity = inventory.quantity + quantity_change
+            if new_quantity < 0:
+                new_quantity = 0  # Don't allow negative stock
+            
+            inventory_in = InventoryUpdate(
+                product_id=product_id,
+                quantity=new_quantity,
+                last_counted_at=datetime.now()
+            )
+            inventory = super().update(db=db, db_obj=inventory, obj_in=inventory_in)
+        
+        # Create transaction record
+        transaction = InventoryTransaction(
+            product_id=product_id,
+            quantity=quantity_change,
+            transaction_type=transaction_type,
+            reference=reference,
+            unit_price=unit_price,
+            notes=notes,
+            transaction_date=datetime.now(),
+            user_id=user_id
+        )
+        db.add(transaction)
+        db.commit()
+        db.refresh(transaction)
+        
+        return {
+            "inventory": inventory,
+            "transaction": transaction
+        }
+
+
+class CRUDInventoryTransaction(CRUDBase[InventoryTransaction, InventoryTransactionCreate, InventoryTransactionUpdate]):
+    def get_by_product_id(
+        self, db: Session, *, product_id: int, skip: int = 0, limit: int = 100
+    ) -> List[InventoryTransaction]:
+        return (
+            db.query(InventoryTransaction)
+            .filter(InventoryTransaction.product_id == product_id)
+            .order_by(InventoryTransaction.transaction_date.desc())
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+    
+    def get_by_type(
+        self, db: Session, *, transaction_type: str, skip: int = 0, limit: int = 100
+    ) -> List[InventoryTransaction]:
+        return (
+            db.query(InventoryTransaction)
+            .filter(InventoryTransaction.transaction_type == transaction_type)
+            .order_by(InventoryTransaction.transaction_date.desc())
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+    
+    def get_by_date_range(
+        self, db: Session, *, start_date: datetime, end_date: datetime, 
+        skip: int = 0, limit: int = 100
+    ) -> List[InventoryTransaction]:
+        return (
+            db.query(InventoryTransaction)
+            .filter(
+                InventoryTransaction.transaction_date >= start_date,
+                InventoryTransaction.transaction_date <= end_date
+            )
+            .order_by(InventoryTransaction.transaction_date.desc())
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+
+
+inventory = CRUDInventory(Inventory)
+inventory_transaction = CRUDInventoryTransaction(InventoryTransaction)

app/crud/crud_product.py

@@ -0,0 +1,36 @@
+from typing import List, Optional
+
+from sqlalchemy.orm import Session
+
+from app.crud.base import CRUDBase
+from app.models.product import Product
+from app.schemas.product import ProductCreate, ProductUpdate
+
+
+class CRUDProduct(CRUDBase[Product, ProductCreate, ProductUpdate]):
+    def get_by_sku(self, db: Session, *, sku: str) -> Optional[Product]:
+        return db.query(Product).filter(Product.sku == sku).first()
+    
+    def get_by_barcode(self, db: Session, *, barcode: str) -> Optional[Product]:
+        return db.query(Product).filter(Product.barcode == barcode).first()
+    
+    def get_by_name(self, db: Session, *, name: str) -> List[Product]:
+        return db.query(Product).filter(Product.name.ilike(f"%{name}%")).all()
+    
+    def get_by_category_id(
+        self, db: Session, *, category_id: int, skip: int = 0, limit: int = 100
+    ) -> List[Product]:
+        return db.query(Product).filter(Product.category_id == category_id).offset(skip).limit(limit).all()
+    
+    def get_by_supplier_id(
+        self, db: Session, *, supplier_id: int, skip: int = 0, limit: int = 100
+    ) -> List[Product]:
+        return db.query(Product).filter(Product.supplier_id == supplier_id).offset(skip).limit(limit).all()
+    
+    def get_active(
+        self, db: Session, *, skip: int = 0, limit: int = 100
+    ) -> List[Product]:
+        return db.query(Product).filter(Product.is_active).offset(skip).limit(limit).all()
+
+
+product = CRUDProduct(Product)

app/crud/crud_supplier.py

@@ -0,0 +1,20 @@
+from typing import List, Optional
+
+from sqlalchemy.orm import Session
+
+from app.crud.base import CRUDBase
+from app.models.supplier import Supplier
+from app.schemas.supplier import SupplierCreate, SupplierUpdate
+
+
+class CRUDSupplier(CRUDBase[Supplier, SupplierCreate, SupplierUpdate]):
+    def get_by_name(self, db: Session, *, name: str) -> Optional[Supplier]:
+        return db.query(Supplier).filter(Supplier.name == name).first()
+
+    def get_multi_by_ids(
+        self, db: Session, *, ids: List[int], skip: int = 0, limit: int = 100
+    ) -> List[Supplier]:
+        return db.query(Supplier).filter(Supplier.id.in_(ids)).offset(skip).limit(limit).all()
+
+
+supplier = CRUDSupplier(Supplier)

app/crud/crud_user.py

@@ -0,0 +1,56 @@
+from typing import Any, Dict, Optional, Union
+
+from sqlalchemy.orm import Session
+
+from app.core.security import get_password_hash, verify_password
+from app.crud.base import CRUDBase
+from app.models.user import User
+from app.schemas.user import UserCreate, UserUpdate
+
+
+class CRUDUser(CRUDBase[User, UserCreate, UserUpdate]):
+    def get_by_email(self, db: Session, *, email: str) -> Optional[User]:
+        return db.query(User).filter(User.email == email).first()
+
+    def create(self, db: Session, *, obj_in: UserCreate) -> User:
+        db_obj = User(
+            email=obj_in.email,
+            hashed_password=get_password_hash(obj_in.password),
+            full_name=obj_in.full_name,
+            is_superuser=obj_in.is_superuser,
+            is_active=obj_in.is_active
+        )
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+
+    def update(
+        self, db: Session, *, db_obj: User, obj_in: Union[UserUpdate, Dict[str, Any]]
+    ) -> User:
+        if isinstance(obj_in, dict):
+            update_data = obj_in
+        else:
+            update_data = obj_in.model_dump(exclude_unset=True)
+        if update_data.get("password"):
+            hashed_password = get_password_hash(update_data["password"])
+            del update_data["password"]
+            update_data["hashed_password"] = hashed_password
+        return super().update(db, db_obj=db_obj, obj_in=update_data)
+
+    def authenticate(self, db: Session, *, email: str, password: str) -> Optional[User]:
+        user = self.get_by_email(db, email=email)
+        if not user:
+            return None
+        if not verify_password(password, user.hashed_password):
+            return None
+        return user
+
+    def is_active(self, user: User) -> bool:
+        return user.is_active
+
+    def is_superuser(self, user: User) -> bool:
+        return user.is_superuser
+
+
+user = CRUDUser(User)

app/db/__init__.py

@@ -0,0 +1 @@
+# db package initialization

app/db/base.py

@@ -0,0 +1,6 @@
+# Import all models here for Alembic to discover
+from sqlalchemy.ext.declarative import declarative_base
+
+Base = declarative_base()
+
+# Import all models so Alembic can discover them

app/db/base_class.py

@@ -0,0 +1,19 @@
+from sqlalchemy.ext.declarative import declared_attr
+from sqlalchemy import Column, Integer, DateTime
+from sqlalchemy.sql import func
+
+
+
+class BaseClass:
+    """
+    Base class for all SQLAlchemy models.
+    Provides common attributes like id and created_at/updated_at timestamps.
+    """
+    id = Column(Integer, primary_key=True, index=True)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now())
+
+    # Generate __tablename__ automatically
+    @declared_attr
+    def __tablename__(cls) -> str:
+        return cls.__name__.lower()

app/db/session.py

@@ -0,0 +1,26 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+from app.core.config import settings
+
+# Ensure directory exists
+settings.DB_DIR.mkdir(parents=True, exist_ok=True)
+
+SQLALCHEMY_DATABASE_URL = f"sqlite:///{settings.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():
+    """
+    Dependency function to get a DB session.
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()

app/models/__init__.py

@@ -0,0 +1 @@
+# models package initialization

app/models/category.py

@@ -0,0 +1,16 @@
+from sqlalchemy import Column, String, Text
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import BaseClass
+from app.db.base import Base
+
+
+class Category(Base, BaseClass):
+    """
+    Category model for product categorization.
+    """
+    name = Column(String(255), unique=True, index=True, nullable=False)
+    description = Column(Text, nullable=True)
+    
+    # Relationships
+    products = relationship("Product", back_populates="category")

app/models/inventory.py

@@ -0,0 +1,41 @@
+from sqlalchemy import Column, Integer, String, ForeignKey, Float, DateTime, Text
+from sqlalchemy.sql import func
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import BaseClass
+from app.db.base import Base
+
+
+class Inventory(Base, BaseClass):
+    """
+    Inventory model for tracking stock levels of products.
+    """
+    product_id = Column(Integer, ForeignKey("product.id"), nullable=False)
+    quantity = Column(Integer, nullable=False, default=0)
+    location = Column(String(255), nullable=True)
+    last_counted_at = Column(DateTime(timezone=True), nullable=True)
+    
+    # Relationships
+    product = relationship("Product", back_populates="inventory_items")
+
+
+class InventoryTransaction(Base, BaseClass):
+    """
+    Inventory Transaction model for tracking stock movements.
+    """
+    TRANSACTION_TYPES = ["purchase", "sale", "adjustment", "return", "transfer"]
+    
+    product_id = Column(Integer, ForeignKey("product.id"), nullable=False)
+    quantity = Column(Integer, nullable=False)
+    transaction_type = Column(String(50), nullable=False)  # purchase, sale, adjustment, return, transfer
+    reference = Column(String(255), nullable=True)  # Order number, invoice number, etc.
+    unit_price = Column(Float, nullable=True)
+    notes = Column(Text, nullable=True)
+    transaction_date = Column(DateTime(timezone=True), server_default=func.now())
+    
+    # Optional user who performed the transaction
+    user_id = Column(Integer, ForeignKey("user.id"), nullable=True)
+    
+    # Relationships
+    product = relationship("Product")
+    user = relationship("User")

app/models/product.py

@@ -0,0 +1,30 @@
+from sqlalchemy import Column, String, Text, Integer, Float, ForeignKey, Boolean
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import BaseClass
+from app.db.base import Base
+
+
+class Product(Base, BaseClass):
+    """
+    Product model for inventory items.
+    """
+    name = Column(String(255), index=True, nullable=False)
+    description = Column(Text, nullable=True)
+    sku = Column(String(50), unique=True, index=True, nullable=False)
+    barcode = Column(String(100), unique=True, index=True, nullable=True)
+    price = Column(Float, nullable=False, default=0.0)
+    cost = Column(Float, nullable=False, default=0.0)
+    
+    # Stock management
+    min_stock_level = Column(Integer, nullable=False, default=0)
+    is_active = Column(Boolean, default=True)
+    
+    # Foreign keys
+    category_id = Column(Integer, ForeignKey("category.id"), nullable=True)
+    supplier_id = Column(Integer, ForeignKey("supplier.id"), nullable=True)
+    
+    # Relationships
+    category = relationship("Category", back_populates="products")
+    supplier = relationship("Supplier", back_populates="products")
+    inventory_items = relationship("Inventory", back_populates="product")

app/models/supplier.py

@@ -0,0 +1,21 @@
+from sqlalchemy import Column, String, Text
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import BaseClass
+from app.db.base import Base
+
+
+class Supplier(Base, BaseClass):
+    """
+    Supplier model for managing product suppliers.
+    """
+    name = Column(String(255), index=True, nullable=False)
+    contact_name = Column(String(255), nullable=True)
+    email = Column(String(255), nullable=True)
+    phone = Column(String(50), nullable=True)
+    address = Column(Text, nullable=True)
+    website = Column(String(255), nullable=True)
+    notes = Column(Text, nullable=True)
+    
+    # Relationships
+    products = relationship("Product", back_populates="supplier")

app/models/user.py

@@ -0,0 +1,19 @@
+from sqlalchemy import Boolean, Column, String
+
+from app.db.base_class import BaseClass
+from app.db.base import Base
+
+
+class User(Base, BaseClass):
+    """
+    User model for authentication and authorization.
+    """
+    email = Column(String, unique=True, index=True, nullable=False)
+    full_name = Column(String, index=True)
+    hashed_password = Column(String, nullable=False)
+    is_active = Column(Boolean, default=True)
+    is_superuser = Column(Boolean, default=False)
+    
+    # Relationships
+    # When we create inventory transactions, we can link them to users
+    # transactions = relationship("InventoryTransaction", back_populates="user")

app/schemas/__init__.py

@@ -0,0 +1,12 @@
+from .token import Token as Token, TokenPayload as TokenPayload
+from .user import User as User, UserCreate as UserCreate, UserInDB as UserInDB, UserUpdate as UserUpdate
+from .category import Category as Category, CategoryCreate as CategoryCreate, CategoryUpdate as CategoryUpdate
+from .supplier import Supplier as Supplier, SupplierCreate as SupplierCreate, SupplierUpdate as SupplierUpdate
+from .product import Product as Product, ProductCreate as ProductCreate, ProductUpdate as ProductUpdate
+from .inventory import (
+    Inventory as Inventory, InventoryCreate as InventoryCreate, InventoryUpdate as InventoryUpdate,
+    InventoryTransaction as InventoryTransaction, 
+    InventoryTransactionCreate as InventoryTransactionCreate, 
+    InventoryTransactionUpdate as InventoryTransactionUpdate,
+    InventorySummary as InventorySummary, InventorySummaryList as InventorySummaryList
+)

app/schemas/category.py

@@ -0,0 +1,37 @@
+from typing import Optional
+from pydantic import BaseModel
+
+
+# Shared properties
+class CategoryBase(BaseModel):
+    name: Optional[str] = None
+    description: Optional[str] = None
+
+
+# Properties to receive on category creation
+class CategoryCreate(CategoryBase):
+    name: str
+
+
+# Properties to receive on category update
+class CategoryUpdate(CategoryBase):
+    pass
+
+
+# Properties shared by models in DB
+class CategoryInDBBase(CategoryBase):
+    id: int
+    name: str
+
+    class Config:
+        from_attributes = True
+
+
+# Properties to return to client
+class Category(CategoryInDBBase):
+    pass
+
+
+# Properties properties stored in DB
+class CategoryInDB(CategoryInDBBase):
+    pass

app/schemas/inventory.py

@@ -0,0 +1,98 @@
+from typing import Optional, List
+from datetime import datetime
+from pydantic import BaseModel
+
+
+# Shared properties for Inventory
+class InventoryBase(BaseModel):
+    product_id: int
+    quantity: int = 0
+    location: Optional[str] = None
+    last_counted_at: Optional[datetime] = None
+
+
+# Properties to receive on inventory creation
+class InventoryCreate(InventoryBase):
+    pass
+
+
+# Properties to receive on inventory update
+class InventoryUpdate(InventoryBase):
+    product_id: Optional[int] = None
+
+
+# Properties shared by models in DB
+class InventoryInDBBase(InventoryBase):
+    id: int
+    product_id: int
+
+    class Config:
+        from_attributes = True
+
+
+# Properties to return to client
+class Inventory(InventoryInDBBase):
+    pass
+
+
+# Properties properties stored in DB
+class InventoryInDB(InventoryInDBBase):
+    pass
+
+
+# Shared properties for InventoryTransaction
+class InventoryTransactionBase(BaseModel):
+    product_id: int
+    quantity: int
+    transaction_type: str  # purchase, sale, adjustment, return, transfer
+    reference: Optional[str] = None
+    unit_price: Optional[float] = None
+    notes: Optional[str] = None
+    transaction_date: Optional[datetime] = None
+    user_id: Optional[int] = None
+
+
+# Properties to receive on inventory transaction creation
+class InventoryTransactionCreate(InventoryTransactionBase):
+    pass
+
+
+# Properties to receive on inventory transaction update
+class InventoryTransactionUpdate(InventoryTransactionBase):
+    product_id: Optional[int] = None
+    quantity: Optional[int] = None
+    transaction_type: Optional[str] = None
+
+
+# Properties shared by models in DB
+class InventoryTransactionInDBBase(InventoryTransactionBase):
+    id: int
+    transaction_date: datetime
+
+    class Config:
+        from_attributes = True
+
+
+# Properties to return to client
+class InventoryTransaction(InventoryTransactionInDBBase):
+    pass
+
+
+# Properties properties stored in DB
+class InventoryTransactionInDB(InventoryTransactionInDBBase):
+    pass
+
+
+# Inventory summary for a product
+class InventorySummary(BaseModel):
+    product_id: int
+    product_name: str
+    sku: str
+    current_stock: int
+    min_stock_level: int
+    is_low_stock: bool
+
+
+# List of inventory summaries
+class InventorySummaryList(BaseModel):
+    inventories: List[InventorySummary]

app/schemas/product.py

@@ -0,0 +1,47 @@
+from typing import Optional
+from pydantic import BaseModel
+
+
+# Shared properties
+class ProductBase(BaseModel):
+    name: Optional[str] = None
+    description: Optional[str] = None
+    sku: Optional[str] = None
+    barcode: Optional[str] = None
+    price: Optional[float] = 0.0
+    cost: Optional[float] = 0.0
+    min_stock_level: Optional[int] = 0
+    is_active: Optional[bool] = True
+    category_id: Optional[int] = None
+    supplier_id: Optional[int] = None
+
+
+# Properties to receive on product creation
+class ProductCreate(ProductBase):
+    name: str
+    sku: str
+
+
+# Properties to receive on product update
+class ProductUpdate(ProductBase):
+    pass
+
+
+# Properties shared by models in DB
+class ProductInDBBase(ProductBase):
+    id: int
+    name: str
+    sku: str
+
+    class Config:
+        from_attributes = True
+
+
+# Properties to return to client
+class Product(ProductInDBBase):
+    pass
+
+
+# Properties properties stored in DB
+class ProductInDB(ProductInDBBase):
+    pass

app/schemas/supplier.py

@@ -0,0 +1,42 @@
+from typing import Optional
+from pydantic import BaseModel, EmailStr
+
+
+# Shared properties
+class SupplierBase(BaseModel):
+    name: Optional[str] = None
+    contact_name: Optional[str] = None
+    email: Optional[EmailStr] = None
+    phone: Optional[str] = None
+    address: Optional[str] = None
+    website: Optional[str] = None
+    notes: Optional[str] = None
+
+
+# Properties to receive on supplier creation
+class SupplierCreate(SupplierBase):
+    name: str
+
+
+# Properties to receive on supplier update
+class SupplierUpdate(SupplierBase):
+    pass
+
+
+# Properties shared by models in DB
+class SupplierInDBBase(SupplierBase):
+    id: int
+    name: str
+
+    class Config:
+        from_attributes = True
+
+
+# Properties to return to client
+class Supplier(SupplierInDBBase):
+    pass
+
+
+# Properties properties stored in DB
+class SupplierInDB(SupplierInDBBase):
+    pass

app/schemas/token.py

@@ -0,0 +1,11 @@
+from typing import Optional
+from pydantic import BaseModel
+
+
+class Token(BaseModel):
+    access_token: str
+    token_type: str
+
+
+class TokenPayload(BaseModel):
+    sub: Optional[int] = None

app/schemas/user.py

@@ -0,0 +1,38 @@
+from typing import Optional
+from pydantic import BaseModel, EmailStr
+
+
+# Shared properties
+class UserBase(BaseModel):
+    email: Optional[EmailStr] = None
+    is_active: Optional[bool] = True
+    is_superuser: bool = False
+    full_name: Optional[str] = None
+
+
+# Properties to receive via API on creation
+class UserCreate(UserBase):
+    email: EmailStr
+    password: str
+
+
+# Properties to receive via API on update
+class UserUpdate(UserBase):
+    password: Optional[str] = None
+
+
+class UserInDBBase(UserBase):
+    id: Optional[int] = None
+
+    class Config:
+        from_attributes = True
+
+
+# Additional properties to return via API
+class User(UserInDBBase):
+    pass
+
+
+# Additional properties stored in DB
+class UserInDB(UserInDBBase):
+    hashed_password: str

main.py

@@ -0,0 +1,49 @@
+import uvicorn
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+from starlette.responses import JSONResponse
+
+from app.api.v1.api import api_router
+from app.core.config import settings
+
+app = FastAPI(
+    title=settings.PROJECT_NAME,
+    openapi_url="/openapi.json",
+    version=settings.VERSION
+)
+
+# Set up CORS middleware
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+# Include API router
+app.include_router(api_router, prefix=settings.API_V1_STR)
+
+@app.get("/", tags=["Root"])
+async def root():
+    """
+    Root endpoint that returns basic service information.
+    """
+    return JSONResponse({
+        "name": settings.PROJECT_NAME,
+        "version": settings.VERSION,
+        "documentation": "/docs",
+        "health_check": "/health"
+    })
+
+@app.get("/health", tags=["Health"])
+async def health_check():
+    """
+    Health check endpoint.
+    """
+    return JSONResponse({
+        "status": "healthy"
+    })
+
+if __name__ == "__main__":
+    uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=True)

migrations/__init__.py

@@ -0,0 +1 @@
+# migrations package

migrations/env.py

@@ -0,0 +1,92 @@
+import sys
+from logging.config import fileConfig
+from pathlib import Path
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+# Add the app directory to the Python path so we can import our models
+sys.path.append(str(Path(__file__).resolve().parents[1]))
+
+# 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)
+
+# Import all models for Alembic to detect
+from app.db.base import Base  # noqa: E402
+from app.models.user import User  # noqa: E402, F401
+from app.models.product import Product  # noqa: E402, F401
+from app.models.category import Category  # noqa: E402, F401
+from app.models.supplier import Supplier  # noqa: E402, F401
+from app.models.inventory import Inventory, InventoryTransaction  # noqa: E402, F401
+
+# 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  # Use batch mode for SQLite
+        )
+
+        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 +1,26 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}

migrations/versions/01_initial_setup.py

@@ -0,0 +1,156 @@
+"""Initial setup
+
+Revision ID: 01_initial_setup
+Revises: 
+Create Date: 2023-11-22
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = '01_initial_setup'
+down_revision: Union[str, None] = None
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Create user table
+    op.create_table(
+        'user',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('email', sa.String(), nullable=False),
+        sa.Column('full_name', sa.String(), nullable=True),
+        sa.Column('hashed_password', sa.String(), nullable=False),
+        sa.Column('is_active', sa.Boolean(), nullable=True),
+        sa.Column('is_superuser', sa.Boolean(), nullable=True),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.Column('updated_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_user_email'), 'user', ['email'], unique=True)
+    op.create_index(op.f('ix_user_full_name'), 'user', ['full_name'], unique=False)
+    op.create_index(op.f('ix_user_id'), 'user', ['id'], unique=False)
+
+    # Create category table
+    op.create_table(
+        'category',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('name', sa.String(length=255), nullable=False),
+        sa.Column('description', sa.Text(), nullable=True),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.Column('updated_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_category_id'), 'category', ['id'], unique=False)
+    op.create_index(op.f('ix_category_name'), 'category', ['name'], unique=True)
+
+    # Create supplier table
+    op.create_table(
+        'supplier',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('name', sa.String(length=255), nullable=False),
+        sa.Column('contact_name', sa.String(length=255), nullable=True),
+        sa.Column('email', sa.String(length=255), nullable=True),
+        sa.Column('phone', sa.String(length=50), nullable=True),
+        sa.Column('address', sa.Text(), nullable=True),
+        sa.Column('website', sa.String(length=255), nullable=True),
+        sa.Column('notes', sa.Text(), nullable=True),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.Column('updated_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_supplier_id'), 'supplier', ['id'], unique=False)
+    op.create_index(op.f('ix_supplier_name'), 'supplier', ['name'], unique=False)
+
+    # Create product table
+    op.create_table(
+        'product',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('name', sa.String(length=255), nullable=False),
+        sa.Column('description', sa.Text(), nullable=True),
+        sa.Column('sku', sa.String(length=50), nullable=False),
+        sa.Column('barcode', sa.String(length=100), nullable=True),
+        sa.Column('price', sa.Float(), nullable=False, default=0.0),
+        sa.Column('cost', sa.Float(), nullable=False, default=0.0),
+        sa.Column('min_stock_level', sa.Integer(), nullable=False, default=0),
+        sa.Column('is_active', sa.Boolean(), nullable=True),
+        sa.Column('category_id', sa.Integer(), nullable=True),
+        sa.Column('supplier_id', sa.Integer(), nullable=True),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.Column('updated_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.ForeignKeyConstraint(['category_id'], ['category.id'], ),
+        sa.ForeignKeyConstraint(['supplier_id'], ['supplier.id'], ),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_product_barcode'), 'product', ['barcode'], unique=True)
+    op.create_index(op.f('ix_product_id'), 'product', ['id'], unique=False)
+    op.create_index(op.f('ix_product_name'), 'product', ['name'], unique=False)
+    op.create_index(op.f('ix_product_sku'), 'product', ['sku'], unique=True)
+
+    # Create inventory table
+    op.create_table(
+        'inventory',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('product_id', sa.Integer(), nullable=False),
+        sa.Column('quantity', sa.Integer(), nullable=False, default=0),
+        sa.Column('location', sa.String(length=255), nullable=True),
+        sa.Column('last_counted_at', sa.DateTime(timezone=True), nullable=True),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.Column('updated_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.ForeignKeyConstraint(['product_id'], ['product.id'], ),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_inventory_id'), 'inventory', ['id'], unique=False)
+
+    # Create inventory_transaction table
+    op.create_table(
+        'inventory_transaction',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('product_id', sa.Integer(), nullable=False),
+        sa.Column('quantity', sa.Integer(), nullable=False),
+        sa.Column('transaction_type', sa.String(length=50), nullable=False),
+        sa.Column('reference', sa.String(length=255), nullable=True),
+        sa.Column('unit_price', sa.Float(), nullable=True),
+        sa.Column('notes', sa.Text(), nullable=True),
+        sa.Column('transaction_date', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.Column('user_id', sa.Integer(), nullable=True),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.Column('updated_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
+        sa.ForeignKeyConstraint(['product_id'], ['product.id'], ),
+        sa.ForeignKeyConstraint(['user_id'], ['user.id'], ),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_inventory_transaction_id'), 'inventory_transaction', ['id'], unique=False)
+
+
+def downgrade() -> None:
+    # Drop tables in reverse order
+    op.drop_index(op.f('ix_inventory_transaction_id'), table_name='inventory_transaction')
+    op.drop_table('inventory_transaction')
+    
+    op.drop_index(op.f('ix_inventory_id'), table_name='inventory')
+    op.drop_table('inventory')
+    
+    op.drop_index(op.f('ix_product_sku'), table_name='product')
+    op.drop_index(op.f('ix_product_name'), table_name='product')
+    op.drop_index(op.f('ix_product_id'), table_name='product')
+    op.drop_index(op.f('ix_product_barcode'), table_name='product')
+    op.drop_table('product')
+    
+    op.drop_index(op.f('ix_supplier_name'), table_name='supplier')
+    op.drop_index(op.f('ix_supplier_id'), table_name='supplier')
+    op.drop_table('supplier')
+    
+    op.drop_index(op.f('ix_category_name'), table_name='category')
+    op.drop_index(op.f('ix_category_id'), table_name='category')
+    op.drop_table('category')
+    
+    op.drop_index(op.f('ix_user_id'), table_name='user')
+    op.drop_index(op.f('ix_user_full_name'), table_name='user')
+    op.drop_index(op.f('ix_user_email'), table_name='user')
+    op.drop_table('user')

requirements.txt

@@ -0,0 +1,11 @@
+fastapi>=0.104.0
+uvicorn>=0.23.2
+sqlalchemy>=2.0.23
+alembic>=1.12.1
+pydantic>=2.4.2
+pydantic-settings>=2.0.3
+python-jose[cryptography]>=3.3.0
+passlib[bcrypt]>=1.7.4
+python-multipart>=0.0.6
+ruff>=0.1.3
+pytest>=7.4.3