Implement Small Business Inventory Management System

This commit implements a comprehensive inventory management system for small businesses using FastAPI and SQLAlchemy. Features include:
- Product and category management
- Inventory tracking across multiple locations
- Supplier management
- Purchase management
- Transaction tracking for inventory movements
- Complete API documentation

generated with BackendIM... (backend.im)

README.md

@@ -1,3 +1,131 @@
-# 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 API built with FastAPI and SQLAlchemy for small businesses. This API provides functionality to manage products, inventory, suppliers, and purchases.
+
+## Features
+
+- **Product Management**: CRUD operations for products and categories
+- **Inventory Management**: Track inventory levels across multiple locations
+- **Supplier Management**: Manage suppliers and their contact information
+- **Purchase Management**: Create and track purchase orders
+- **Transaction Tracking**: Record and track inventory movements (sales, purchases, transfers, adjustments)
+- **Stock Alerts**: Monitor low-stock items
+
+## Tech Stack
+
+- **FastAPI**: High-performance web framework for building APIs
+- **SQLAlchemy**: SQL toolkit and ORM
+- **Pydantic**: Data validation and settings management
+- **Alembic**: Database migration tool
+- **SQLite**: Lightweight database
+
+## Getting Started
+
+### Prerequisites
+
+- Python 3.8+
+- pip
+
+### Installation
+
+1. Clone the repository
+```bash
+git clone <repository-url>
+cd smallbusinessinventorymanagementsystem
+```
+
+2. Install dependencies
+```bash
+pip install -r requirements.txt
+```
+
+3. Run the application
+```bash
+uvicorn main:app --reload
+```
+
+4. Access the API documentation at http://localhost:8000/docs
+
+## API Endpoints
+
+The API is organized around the following main resources:
+
+### Products & Categories
+
+- `GET /api/v1/products/`: List all products
+- `POST /api/v1/products/`: Create a new product
+- `GET /api/v1/products/{product_id}`: Get product details
+- `PUT /api/v1/products/{product_id}`: Update a product
+- `DELETE /api/v1/products/{product_id}`: Delete a product
+
+- `GET /api/v1/categories/`: List all categories
+- `POST /api/v1/categories/`: Create a new category
+- `GET /api/v1/categories/{category_id}`: Get category details
+- `PUT /api/v1/categories/{category_id}`: Update a category
+- `DELETE /api/v1/categories/{category_id}`: Delete a category
+
+### Inventory Management
+
+- `GET /api/v1/inventory/`: List inventory items
+- `POST /api/v1/inventory/`: Create inventory item
+- `GET /api/v1/inventory/{item_id}`: Get inventory item details
+- `PUT /api/v1/inventory/{item_id}`: Update inventory item
+- `DELETE /api/v1/inventory/{item_id}`: Delete inventory item
+
+- `GET /api/v1/locations/`: List all locations
+- `POST /api/v1/locations/`: Create a new location
+- `GET /api/v1/locations/{location_id}`: Get location details
+- `PUT /api/v1/locations/{location_id}`: Update a location
+- `DELETE /api/v1/locations/{location_id}`: Delete a location
+
+- `GET /api/v1/inventory-transactions/`: List inventory transactions
+- `POST /api/v1/inventory-transactions/`: Create inventory transaction
+- `GET /api/v1/inventory-transactions/{transaction_id}`: Get transaction details
+
+### Suppliers & Purchases
+
+- `GET /api/v1/suppliers/`: List all suppliers
+- `POST /api/v1/suppliers/`: Create a new supplier
+- `GET /api/v1/suppliers/{supplier_id}`: Get supplier details
+- `PUT /api/v1/suppliers/{supplier_id}`: Update a supplier
+- `DELETE /api/v1/suppliers/{supplier_id}`: Delete a supplier
+
+- `GET /api/v1/purchases/`: List all purchases
+- `POST /api/v1/purchases/`: Create a new purchase
+- `GET /api/v1/purchases/{purchase_id}`: Get purchase details
+- `PUT /api/v1/purchases/{purchase_id}`: Update a purchase
+- `DELETE /api/v1/purchases/{purchase_id}`: Delete a purchase
+- `POST /api/v1/purchases/{purchase_id}/receive`: Receive purchase into inventory
+
+### System
+
+- `GET /health`: Check API health status
+
+## Database Schema
+
+The system uses the following main data models:
+
+- **Product**: Base product information (name, SKU, price, etc.)
+- **Category**: Product categories
+- **Location**: Inventory storage locations (warehouses, stores)
+- **InventoryItem**: Product stock at a specific location
+- **InventoryTransaction**: Record of inventory movements
+- **Supplier**: Supplier information
+- **Purchase**: Purchase orders from suppliers
+
+## Development
+
+### Database Migrations
+
+The project uses Alembic for database migrations:
+
+```bash
+# Generate a new migration
+alembic revision -m "description"
+
+# Run migrations
+alembic upgrade head
+
+# Rollback migration
+alembic downgrade -1
+```

alembic.ini

@@ -0,0 +1,84 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = migrations
+
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# timezone to use when rendering the date
+# within the migration file as well as the filename.
+# string value is passed to dateutil.tz.gettz()
+# leave blank for localtime
+# timezone =
+
+# max length of characters to apply to the
+# "slug" field
+# truncate_slug_length = 40
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+# set to 'true' to allow .pyc and .pyo files without
+# a source .py file to be detected as revisions in the
+# versions/ directory
+# sourceless = false
+
+# version location specification; this defaults
+# to ${script_location}/versions.  When using multiple version
+# directories, initial revisions must be specified with --version-path
+# version_locations = %(here)s/bar %(here)s/bat ${script_location}/versions
+
+# the output encoding used when revision files
+# are written from script.py.mako
+# output_encoding = utf-8
+
+sqlalchemy.url = sqlite:///app/storage/db/db.sqlite
+
+[post_write_hooks]
+# post_write_hooks defines scripts or Python functions that are run
+# on newly generated revision scripts.  See the documentation for further
+# detail and examples
+
+# format using "black" - use the console_scripts runner, against the "black" entrypoint
+# hooks=black
+# black.type=console_scripts
+# black.entrypoint=black
+# black.options=-l 79
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

app/api/deps.py

@@ -0,0 +1,53 @@
+from typing import Generator
+from fastapi import Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from app.db.session import get_db
+from app.models.product import Product, Category
+from app.models.inventory import InventoryItem, Location
+from app.models.supplier import Supplier, Purchase
+
+# Common dependencies
+def get_product(db: Session = Depends(get_db), product_id: int = None):
+    if product_id:
+        product = db.query(Product).filter(Product.id == product_id).first()
+        if not product:
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail=f"Product with ID {product_id} not found"
+            )
+        return product
+    return None
+
+def get_category(db: Session = Depends(get_db), category_id: int = None):
+    if category_id:
+        category = db.query(Category).filter(Category.id == category_id).first()
+        if not category:
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail=f"Category with ID {category_id} not found"
+            )
+        return category
+    return None
+
+def get_location(db: Session = Depends(get_db), location_id: int = None):
+    if location_id:
+        location = db.query(Location).filter(Location.id == location_id).first()
+        if not location:
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail=f"Location with ID {location_id} not found"
+            )
+        return location
+    return None
+
+def get_supplier(db: Session = Depends(get_db), supplier_id: int = None):
+    if supplier_id:
+        supplier = db.query(Supplier).filter(Supplier.id == supplier_id).first()
+        if not supplier:
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail=f"Supplier with ID {supplier_id} not found"
+            )
+        return supplier
+    return None

app/api/routes/__init__.py

@@ -0,0 +1,3 @@
+from app.api.routes.product import router as product_router
+from app.api.routes.inventory import router as inventory_router
+from app.api.routes.supplier import router as supplier_router

app/api/routes/inventory.py

@@ -0,0 +1,583 @@
+from typing import List, Optional, Dict, Any
+from fastapi import APIRouter, Depends, HTTPException, status, Query
+from sqlalchemy.orm import Session
+from sqlalchemy.exc import IntegrityError
+
+from app.db.session import get_db
+from app.models.inventory import (
+    Location, 
+    LocationType,
+    InventoryItem, 
+    InventoryTransaction, 
+    InventoryTransactionItem,
+    TransactionType
+)
+from app.models.product import Product
+from app.schemas.inventory import (
+    LocationCreate,
+    LocationUpdate,
+    LocationInDB,
+    InventoryItemCreate,
+    InventoryItemUpdate,
+    InventoryItemInDB,
+    InventoryItemWithDetails,
+    InventoryTransactionCreate,
+    InventoryTransactionWithItems,
+    InventoryTransactionInDB,
+    TransactionTypeEnum
+)
+from app.api.deps import get_product, get_location
+
+router = APIRouter(prefix="/api/v1")
+
+# Location endpoints
+@router.post("/locations/", response_model=LocationInDB, status_code=status.HTTP_201_CREATED)
+def create_location(
+    *,
+    db: Session = Depends(get_db),
+    location_in: LocationCreate
+):
+    """Create a new location"""
+    try:
+        # Convert from schema enum to model enum
+        type_value = LocationType(location_in.type.value)
+        
+        db_location = Location(
+            name=location_in.name,
+            type=type_value,
+            address=location_in.address,
+            description=location_in.description
+        )
+        db.add(db_location)
+        db.commit()
+        db.refresh(db_location)
+        return db_location
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Could not create location: {str(e)}"
+        )
+
+@router.get("/locations/", response_model=List[LocationInDB])
+def read_locations(
+    *,
+    db: Session = Depends(get_db),
+    skip: int = 0,
+    limit: int = 100,
+    search: Optional[str] = None,
+    location_type: Optional[str] = None
+):
+    """Get all locations with optional filters"""
+    query = db.query(Location)
+    
+    if search:
+        query = query.filter(Location.name.ilike(f"%{search}%"))
+    
+    if location_type:
+        try:
+            type_value = LocationType(location_type)
+            query = query.filter(Location.type == type_value)
+        except ValueError:
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail=f"Invalid location type: {location_type}"
+            )
+    
+    return query.offset(skip).limit(limit).all()
+
+@router.get("/locations/{location_id}", response_model=LocationInDB)
+def read_location(
+    *,
+    db: Session = Depends(get_db),
+    location: Location = Depends(get_location)
+):
+    """Get a specific location by ID"""
+    return location
+
+@router.put("/locations/{location_id}", response_model=LocationInDB)
+def update_location(
+    *,
+    db: Session = Depends(get_db),
+    location: Location = Depends(get_location),
+    location_in: LocationUpdate
+):
+    """Update a location"""
+    update_data = location_in.model_dump(exclude_unset=True)
+    
+    # Convert type enum if present
+    if "type" in update_data and update_data["type"]:
+        update_data["type"] = LocationType(update_data["type"].value)
+    
+    for field, value in update_data.items():
+        setattr(location, field, value)
+    
+    try:
+        db.add(location)
+        db.commit()
+        db.refresh(location)
+        return location
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Could not update location: {str(e)}"
+        )
+
+@router.delete("/locations/{location_id}", status_code=status.HTTP_204_NO_CONTENT)
+def delete_location(
+    *,
+    db: Session = Depends(get_db),
+    location: Location = Depends(get_location)
+):
+    """Delete a location"""
+    # Check if location has inventory items
+    if location.inventory_items:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Cannot delete location with existing inventory"
+        )
+    
+    db.delete(location)
+    db.commit()
+    return None
+
+# Inventory Item endpoints
+@router.post("/inventory/", response_model=InventoryItemInDB, status_code=status.HTTP_201_CREATED)
+def create_inventory_item(
+    *,
+    db: Session = Depends(get_db),
+    item_in: InventoryItemCreate
+):
+    """Create a new inventory item"""
+    # Check if product exists
+    product = db.query(Product).filter(Product.id == item_in.product_id).first()
+    if not product:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Product with ID {item_in.product_id} not found"
+        )
+    
+    # Check if location exists
+    location = db.query(Location).filter(Location.id == item_in.location_id).first()
+    if not location:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Location with ID {item_in.location_id} not found"
+        )
+    
+    # Check if inventory item already exists for this product and location
+    existing_item = db.query(InventoryItem).filter(
+        InventoryItem.product_id == item_in.product_id,
+        InventoryItem.location_id == item_in.location_id
+    ).first()
+    
+    if existing_item:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Inventory item already exists for this product and location"
+        )
+    
+    try:
+        db_item = InventoryItem(**item_in.model_dump())
+        db.add(db_item)
+        db.commit()
+        db.refresh(db_item)
+        return db_item
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Could not create inventory item: {str(e)}"
+        )
+
+@router.get("/inventory/", response_model=List[InventoryItemWithDetails])
+def read_inventory_items(
+    *,
+    db: Session = Depends(get_db),
+    skip: int = 0,
+    limit: int = 100,
+    product_id: Optional[int] = None,
+    location_id: Optional[int] = None,
+    low_stock: bool = False
+):
+    """Get inventory items with optional filters"""
+    query = db.query(InventoryItem)
+    
+    if product_id:
+        query = query.filter(InventoryItem.product_id == product_id)
+    
+    if location_id:
+        query = query.filter(InventoryItem.location_id == location_id)
+    
+    if low_stock:
+        query = query.filter(InventoryItem.quantity <= InventoryItem.minimum_stock)
+    
+    items = query.offset(skip).limit(limit).all()
+    
+    # Enhance with product and location details
+    result = []
+    for item in items:
+        item_dict = {
+            "id": item.id,
+            "product_id": item.product_id,
+            "location_id": item.location_id,
+            "quantity": item.quantity,
+            "minimum_stock": item.minimum_stock,
+            "maximum_stock": item.maximum_stock,
+            "created_at": item.created_at,
+            "updated_at": item.updated_at,
+            "product": {
+                "id": item.product.id,
+                "name": item.product.name,
+                "sku": item.product.sku,
+            },
+            "location": {
+                "id": item.location.id,
+                "name": item.location.name,
+                "type": item.location.type.value,
+            }
+        }
+        result.append(item_dict)
+    
+    return result
+
+@router.get("/inventory/{item_id}", response_model=InventoryItemWithDetails)
+def read_inventory_item(
+    *,
+    db: Session = Depends(get_db),
+    item_id: int
+):
+    """Get a specific inventory item by ID"""
+    item = db.query(InventoryItem).filter(InventoryItem.id == item_id).first()
+    if not item:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Inventory item with ID {item_id} not found"
+        )
+    
+    # Enhance with product and location details
+    item_dict = {
+        "id": item.id,
+        "product_id": item.product_id,
+        "location_id": item.location_id,
+        "quantity": item.quantity,
+        "minimum_stock": item.minimum_stock,
+        "maximum_stock": item.maximum_stock,
+        "created_at": item.created_at,
+        "updated_at": item.updated_at,
+        "product": {
+            "id": item.product.id,
+            "name": item.product.name,
+            "sku": item.product.sku,
+        },
+        "location": {
+            "id": item.location.id,
+            "name": item.location.name,
+            "type": item.location.type.value,
+        }
+    }
+    
+    return item_dict
+
+@router.put("/inventory/{item_id}", response_model=InventoryItemInDB)
+def update_inventory_item(
+    *,
+    db: Session = Depends(get_db),
+    item_id: int,
+    item_in: InventoryItemUpdate
+):
+    """Update an inventory item"""
+    item = db.query(InventoryItem).filter(InventoryItem.id == item_id).first()
+    if not item:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Inventory item with ID {item_id} not found"
+        )
+    
+    update_data = item_in.model_dump(exclude_unset=True)
+    for field, value in update_data.items():
+        setattr(item, field, value)
+    
+    try:
+        db.add(item)
+        db.commit()
+        db.refresh(item)
+        return item
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Could not update inventory item: {str(e)}"
+        )
+
+@router.delete("/inventory/{item_id}", status_code=status.HTTP_204_NO_CONTENT)
+def delete_inventory_item(
+    *,
+    db: Session = Depends(get_db),
+    item_id: int
+):
+    """Delete an inventory item"""
+    item = db.query(InventoryItem).filter(InventoryItem.id == item_id).first()
+    if not item:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Inventory item with ID {item_id} not found"
+        )
+    
+    db.delete(item)
+    db.commit()
+    return None
+
+# Inventory Transaction endpoints
+@router.post("/inventory-transactions/", response_model=InventoryTransactionInDB, status_code=status.HTTP_201_CREATED)
+def create_inventory_transaction(
+    *,
+    db: Session = Depends(get_db),
+    transaction_in: InventoryTransactionWithItems
+):
+    """Create a new inventory transaction with items"""
+    # Convert from schema enum to model enum
+    try:
+        transaction_type = TransactionType(transaction_in.type.value)
+        
+        # Create transaction
+        db_transaction = InventoryTransaction(
+            type=transaction_type,
+            reference_id=transaction_in.reference_id,
+            notes=transaction_in.notes
+        )
+        db.add(db_transaction)
+        db.flush()  # Get ID without committing
+        
+        # Process transaction items
+        transaction_items = []
+        for item in transaction_in.items:
+            # Validate product exists
+            product = db.query(Product).filter(Product.id == item.product_id).first()
+            if not product:
+                db.rollback()
+                raise HTTPException(
+                    status_code=status.HTTP_404_NOT_FOUND,
+                    detail=f"Product with ID {item.product_id} not found"
+                )
+            
+            # Process based on transaction type
+            if transaction_type == TransactionType.TRANSFER:
+                # For transfers, need both locations
+                if not item.from_location_id or not item.to_location_id:
+                    db.rollback()
+                    raise HTTPException(
+                        status_code=status.HTTP_400_BAD_REQUEST,
+                        detail="Transfer transactions require both from_location_id and to_location_id"
+                    )
+                
+                # Validate from_location exists
+                from_location = db.query(Location).filter(Location.id == item.from_location_id).first()
+                if not from_location:
+                    db.rollback()
+                    raise HTTPException(
+                        status_code=status.HTTP_404_NOT_FOUND,
+                        detail=f"From location with ID {item.from_location_id} not found"
+                    )
+                
+                # Validate to_location exists
+                to_location = db.query(Location).filter(Location.id == item.to_location_id).first()
+                if not to_location:
+                    db.rollback()
+                    raise HTTPException(
+                        status_code=status.HTTP_404_NOT_FOUND,
+                        detail=f"To location with ID {item.to_location_id} not found"
+                    )
+                
+                # Update inventory at from_location
+                from_inventory = db.query(InventoryItem).filter(
+                    InventoryItem.product_id == item.product_id,
+                    InventoryItem.location_id == item.from_location_id
+                ).first()
+                
+                if not from_inventory:
+                    db.rollback()
+                    raise HTTPException(
+                        status_code=status.HTTP_404_NOT_FOUND,
+                        detail=f"Product {item.product_id} not found at location {item.from_location_id}"
+                    )
+                
+                if from_inventory.quantity < item.quantity:
+                    db.rollback()
+                    raise HTTPException(
+                        status_code=status.HTTP_400_BAD_REQUEST,
+                        detail=f"Insufficient stock for product {item.product_id} at location {item.from_location_id}"
+                    )
+                
+                from_inventory.quantity -= item.quantity
+                
+                # Update inventory at to_location
+                to_inventory = db.query(InventoryItem).filter(
+                    InventoryItem.product_id == item.product_id,
+                    InventoryItem.location_id == item.to_location_id
+                ).first()
+                
+                if to_inventory:
+                    to_inventory.quantity += item.quantity
+                else:
+                    # Create new inventory item if it doesn't exist
+                    to_inventory = InventoryItem(
+                        product_id=item.product_id,
+                        location_id=item.to_location_id,
+                        quantity=item.quantity,
+                        minimum_stock=0
+                    )
+                    db.add(to_inventory)
+            
+            elif transaction_type in [TransactionType.PURCHASE, TransactionType.RETURN]:
+                # For purchases, need to_location (where items are added)
+                if not item.to_location_id:
+                    db.rollback()
+                    raise HTTPException(
+                        status_code=status.HTTP_400_BAD_REQUEST,
+                        detail=f"{transaction_type.value} transactions require to_location_id"
+                    )
+                
+                # Validate to_location exists
+                to_location = db.query(Location).filter(Location.id == item.to_location_id).first()
+                if not to_location:
+                    db.rollback()
+                    raise HTTPException(
+                        status_code=status.HTTP_404_NOT_FOUND,
+                        detail=f"Location with ID {item.to_location_id} not found"
+                    )
+                
+                # Update inventory at to_location
+                inventory = db.query(InventoryItem).filter(
+                    InventoryItem.product_id == item.product_id,
+                    InventoryItem.location_id == item.to_location_id
+                ).first()
+                
+                if inventory:
+                    inventory.quantity += item.quantity
+                else:
+                    # Create new inventory item if it doesn't exist
+                    inventory = InventoryItem(
+                        product_id=item.product_id,
+                        location_id=item.to_location_id,
+                        quantity=item.quantity,
+                        minimum_stock=0
+                    )
+                    db.add(inventory)
+            
+            elif transaction_type in [TransactionType.SALE, TransactionType.ADJUSTMENT]:
+                # For sales, need from_location (where items are removed)
+                if not item.from_location_id:
+                    db.rollback()
+                    raise HTTPException(
+                        status_code=status.HTTP_400_BAD_REQUEST,
+                        detail=f"{transaction_type.value} transactions require from_location_id"
+                    )
+                
+                # Validate from_location exists
+                from_location = db.query(Location).filter(Location.id == item.from_location_id).first()
+                if not from_location:
+                    db.rollback()
+                    raise HTTPException(
+                        status_code=status.HTTP_404_NOT_FOUND,
+                        detail=f"Location with ID {item.from_location_id} not found"
+                    )
+                
+                # Update inventory at from_location
+                inventory = db.query(InventoryItem).filter(
+                    InventoryItem.product_id == item.product_id,
+                    InventoryItem.location_id == item.from_location_id
+                ).first()
+                
+                if not inventory:
+                    db.rollback()
+                    raise HTTPException(
+                        status_code=status.HTTP_404_NOT_FOUND,
+                        detail=f"Product {item.product_id} not found at location {item.from_location_id}"
+                    )
+                
+                if inventory.quantity < item.quantity and transaction_type == TransactionType.SALE:
+                    db.rollback()
+                    raise HTTPException(
+                        status_code=status.HTTP_400_BAD_REQUEST,
+                        detail=f"Insufficient stock for product {item.product_id} at location {item.from_location_id}"
+                    )
+                
+                inventory.quantity -= item.quantity
+            
+            # Create transaction item
+            transaction_item = InventoryTransactionItem(
+                transaction_id=db_transaction.id,
+                product_id=item.product_id,
+                quantity=item.quantity,
+                from_location_id=item.from_location_id,
+                to_location_id=item.to_location_id
+            )
+            db.add(transaction_item)
+            transaction_items.append(transaction_item)
+        
+        db.commit()
+        db.refresh(db_transaction)
+        
+        # Refresh transaction items
+        for item in transaction_items:
+            db.refresh(item)
+        
+        return db_transaction
+    
+    except IntegrityError as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Database integrity error: {str(e)}"
+        )
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Could not create transaction: {str(e)}"
+        )
+
+@router.get("/inventory-transactions/", response_model=List[InventoryTransactionInDB])
+def read_inventory_transactions(
+    *,
+    db: Session = Depends(get_db),
+    skip: int = 0,
+    limit: int = 100,
+    transaction_type: Optional[str] = None,
+    reference_id: Optional[str] = None
+):
+    """Get inventory transactions with optional filters"""
+    query = db.query(InventoryTransaction)
+    
+    if transaction_type:
+        try:
+            type_value = TransactionType(transaction_type)
+            query = query.filter(InventoryTransaction.type == type_value)
+        except ValueError:
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail=f"Invalid transaction type: {transaction_type}"
+            )
+    
+    if reference_id:
+        query = query.filter(InventoryTransaction.reference_id == reference_id)
+    
+    return query.order_by(InventoryTransaction.created_at.desc()).offset(skip).limit(limit).all()
+
+@router.get("/inventory-transactions/{transaction_id}", response_model=InventoryTransactionInDB)
+def read_inventory_transaction(
+    *,
+    db: Session = Depends(get_db),
+    transaction_id: int
+):
+    """Get a specific inventory transaction by ID"""
+    transaction = db.query(InventoryTransaction).filter(InventoryTransaction.id == transaction_id).first()
+    if not transaction:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Inventory transaction with ID {transaction_id} not found"
+        )
+    
+    return transaction

app/api/routes/product.py

@@ -0,0 +1,225 @@
+from typing import List, Optional
+from fastapi import APIRouter, Depends, HTTPException, status, Query
+from sqlalchemy.orm import Session
+from sqlalchemy.exc import IntegrityError
+
+from app.db.session import get_db
+from app.models.product import Product, Category
+from app.schemas.product import (
+    ProductCreate, 
+    ProductUpdate, 
+    ProductInDB, 
+    CategoryCreate,
+    CategoryUpdate,
+    CategoryInDB
+)
+from app.api.deps import get_product, get_category
+
+router = APIRouter(prefix="/api/v1")
+
+# Category endpoints
+@router.post("/categories/", response_model=CategoryInDB, status_code=status.HTTP_201_CREATED)
+def create_category(
+    *,
+    db: Session = Depends(get_db),
+    category_in: CategoryCreate
+):
+    """Create a new category"""
+    try:
+        db_category = Category(**category_in.model_dump())
+        db.add(db_category)
+        db.commit()
+        db.refresh(db_category)
+        return db_category
+    except IntegrityError:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Category with this name already exists"
+        )
+
+@router.get("/categories/", response_model=List[CategoryInDB])
+def read_categories(
+    *,
+    db: Session = Depends(get_db),
+    skip: int = 0,
+    limit: int = 100,
+    search: Optional[str] = None
+):
+    """Get all categories with optional search filter"""
+    query = db.query(Category)
+    if search:
+        query = query.filter(Category.name.ilike(f"%{search}%"))
+    return query.offset(skip).limit(limit).all()
+
+@router.get("/categories/{category_id}", response_model=CategoryInDB)
+def read_category(
+    *,
+    db: Session = Depends(get_db),
+    category: Category = Depends(get_category)
+):
+    """Get a specific category by ID"""
+    return category
+
+@router.put("/categories/{category_id}", response_model=CategoryInDB)
+def update_category(
+    *,
+    db: Session = Depends(get_db),
+    category: Category = Depends(get_category),
+    category_in: CategoryUpdate
+):
+    """Update a category"""
+    update_data = category_in.model_dump(exclude_unset=True)
+    for field, value in update_data.items():
+        setattr(category, field, value)
+    
+    try:
+        db.add(category)
+        db.commit()
+        db.refresh(category)
+        return category
+    except IntegrityError:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Category with this name already exists"
+        )
+
+@router.delete("/categories/{category_id}", status_code=status.HTTP_204_NO_CONTENT)
+def delete_category(
+    *,
+    db: Session = Depends(get_db),
+    category: Category = Depends(get_category)
+):
+    """Delete a category"""
+    # Check if category has products
+    if category.products:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Cannot delete category with associated products"
+        )
+    
+    db.delete(category)
+    db.commit()
+    return None
+
+# Product endpoints
+@router.post("/products/", response_model=ProductInDB, status_code=status.HTTP_201_CREATED)
+def create_product(
+    *,
+    db: Session = Depends(get_db),
+    product_in: ProductCreate
+):
+    """Create a new product"""
+    # Check if category exists
+    if product_in.category_id:
+        category = db.query(Category).filter(Category.id == product_in.category_id).first()
+        if not category:
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail=f"Category with ID {product_in.category_id} not found"
+            )
+    
+    try:
+        db_product = Product(**product_in.model_dump())
+        db.add(db_product)
+        db.commit()
+        db.refresh(db_product)
+        return db_product
+    except IntegrityError:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Product with this SKU or barcode already exists"
+        )
+
+@router.get("/products/", response_model=List[ProductInDB])
+def read_products(
+    *,
+    db: Session = Depends(get_db),
+    skip: int = 0,
+    limit: int = 100,
+    search: Optional[str] = None,
+    category_id: Optional[int] = None
+):
+    """Get all products with optional filters"""
+    query = db.query(Product)
+    
+    if search:
+        query = query.filter(
+            (Product.name.ilike(f"%{search}%")) | 
+            (Product.sku.ilike(f"%{search}%")) |
+            (Product.description.ilike(f"%{search}%"))
+        )
+    
+    if category_id:
+        query = query.filter(Product.category_id == category_id)
+    
+    return query.offset(skip).limit(limit).all()
+
+@router.get("/products/{product_id}", response_model=ProductInDB)
+def read_product(
+    *,
+    db: Session = Depends(get_db),
+    product: Product = Depends(get_product)
+):
+    """Get a specific product by ID"""
+    return product
+
+@router.put("/products/{product_id}", response_model=ProductInDB)
+def update_product(
+    *,
+    db: Session = Depends(get_db),
+    product: Product = Depends(get_product),
+    product_in: ProductUpdate
+):
+    """Update a product"""
+    # Check if category exists
+    if product_in.category_id is not None:
+        category = db.query(Category).filter(Category.id == product_in.category_id).first()
+        if not category and product_in.category_id is not None:
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail=f"Category with ID {product_in.category_id} not found"
+            )
+    
+    update_data = product_in.model_dump(exclude_unset=True)
+    for field, value in update_data.items():
+        setattr(product, field, value)
+    
+    try:
+        db.add(product)
+        db.commit()
+        db.refresh(product)
+        return product
+    except IntegrityError:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Product with this SKU or barcode already exists"
+        )
+
+@router.delete("/products/{product_id}", status_code=status.HTTP_204_NO_CONTENT)
+def delete_product(
+    *,
+    db: Session = Depends(get_db),
+    product: Product = Depends(get_product)
+):
+    """Delete a product"""
+    # Check if product has inventory items
+    if product.inventory_items:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Cannot delete product with existing inventory"
+        )
+    
+    # Check if product is used in purchase items
+    if product.purchase_items:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Cannot delete product with purchase history"
+        )
+    
+    db.delete(product)
+    db.commit()
+    return None

app/api/routes/supplier.py

@@ -0,0 +1,450 @@
+from typing import List, Optional, Dict, Any
+from fastapi import APIRouter, Depends, HTTPException, status, Query
+from sqlalchemy.orm import Session
+from sqlalchemy.exc import IntegrityError
+from datetime import datetime
+
+from app.db.session import get_db
+from app.models.supplier import Supplier, Purchase, PurchaseItem
+from app.models.product import Product
+from app.models.inventory import (
+    InventoryTransaction, 
+    InventoryTransactionItem,
+    Location,
+    TransactionType
+)
+from app.schemas.supplier import (
+    SupplierCreate,
+    SupplierUpdate,
+    SupplierInDB,
+    PurchaseCreate,
+    PurchaseUpdate,
+    PurchaseInDB,
+    PurchaseWithItems
+)
+from app.api.deps import get_supplier, get_product
+
+router = APIRouter(prefix="/api/v1")
+
+# Supplier endpoints
+@router.post("/suppliers/", response_model=SupplierInDB, status_code=status.HTTP_201_CREATED)
+def create_supplier(
+    *,
+    db: Session = Depends(get_db),
+    supplier_in: SupplierCreate
+):
+    """Create a new supplier"""
+    try:
+        db_supplier = Supplier(**supplier_in.model_dump())
+        db.add(db_supplier)
+        db.commit()
+        db.refresh(db_supplier)
+        return db_supplier
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Could not create supplier: {str(e)}"
+        )
+
+@router.get("/suppliers/", response_model=List[SupplierInDB])
+def read_suppliers(
+    *,
+    db: Session = Depends(get_db),
+    skip: int = 0,
+    limit: int = 100,
+    search: Optional[str] = None,
+    is_active: Optional[bool] = None
+):
+    """Get all suppliers with optional filters"""
+    query = db.query(Supplier)
+    
+    if search:
+        query = query.filter(
+            (Supplier.name.ilike(f"%{search}%")) |
+            (Supplier.contact_name.ilike(f"%{search}%")) |
+            (Supplier.email.ilike(f"%{search}%"))
+        )
+    
+    if is_active is not None:
+        query = query.filter(Supplier.is_active == is_active)
+    
+    return query.offset(skip).limit(limit).all()
+
+@router.get("/suppliers/{supplier_id}", response_model=SupplierInDB)
+def read_supplier(
+    *,
+    db: Session = Depends(get_db),
+    supplier: Supplier = Depends(get_supplier)
+):
+    """Get a specific supplier by ID"""
+    return supplier
+
+@router.put("/suppliers/{supplier_id}", response_model=SupplierInDB)
+def update_supplier(
+    *,
+    db: Session = Depends(get_db),
+    supplier: Supplier = Depends(get_supplier),
+    supplier_in: SupplierUpdate
+):
+    """Update a supplier"""
+    update_data = supplier_in.model_dump(exclude_unset=True)
+    for field, value in update_data.items():
+        setattr(supplier, field, value)
+    
+    try:
+        db.add(supplier)
+        db.commit()
+        db.refresh(supplier)
+        return supplier
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Could not update supplier: {str(e)}"
+        )
+
+@router.delete("/suppliers/{supplier_id}", status_code=status.HTTP_204_NO_CONTENT)
+def delete_supplier(
+    *,
+    db: Session = Depends(get_db),
+    supplier: Supplier = Depends(get_supplier)
+):
+    """Delete a supplier"""
+    # Check if supplier has purchases
+    if supplier.purchases:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Cannot delete supplier with purchase history"
+        )
+    
+    db.delete(supplier)
+    db.commit()
+    return None
+
+# Purchase endpoints
+@router.post("/purchases/", response_model=PurchaseInDB, status_code=status.HTTP_201_CREATED)
+def create_purchase(
+    *,
+    db: Session = Depends(get_db),
+    purchase_in: PurchaseCreate
+):
+    """Create a new purchase with items"""
+    # Check if supplier exists
+    supplier = db.query(Supplier).filter(Supplier.id == purchase_in.supplier_id).first()
+    if not supplier:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Supplier with ID {purchase_in.supplier_id} not found"
+        )
+    
+    # Set order date if not provided
+    if not purchase_in.order_date:
+        purchase_in.order_date = datetime.now()
+    
+    try:
+        # Create purchase record
+        total_amount = 0
+        purchase_data = purchase_in.model_dump(exclude={"items"})
+        db_purchase = Purchase(**purchase_data)
+        db.add(db_purchase)
+        db.flush()  # Get ID without committing
+        
+        # Process purchase items
+        for item_data in purchase_in.items:
+            # Validate product exists
+            product = db.query(Product).filter(Product.id == item_data.product_id).first()
+            if not product:
+                db.rollback()
+                raise HTTPException(
+                    status_code=status.HTTP_404_NOT_FOUND,
+                    detail=f"Product with ID {item_data.product_id} not found"
+                )
+            
+            # Calculate total price if not provided
+            if not item_data.total_price:
+                item_data.total_price = item_data.quantity * item_data.unit_price
+            
+            # Create purchase item
+            db_item = PurchaseItem(
+                purchase_id=db_purchase.id,
+                product_id=item_data.product_id,
+                quantity=item_data.quantity,
+                unit_price=item_data.unit_price,
+                total_price=item_data.total_price
+            )
+            db.add(db_item)
+            
+            # Update total amount
+            total_amount += item_data.total_price
+        
+        # Update purchase with total amount
+        db_purchase.total_amount = total_amount
+        
+        db.commit()
+        db.refresh(db_purchase)
+        return db_purchase
+    
+    except IntegrityError as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Database integrity error: {str(e)}"
+        )
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Could not create purchase: {str(e)}"
+        )
+
+@router.post("/purchases/{purchase_id}/receive", response_model=PurchaseInDB)
+def receive_purchase(
+    *,
+    db: Session = Depends(get_db),
+    purchase_id: int,
+    location_id: int
+):
+    """Receive a purchase into inventory at specified location"""
+    # Check if purchase exists
+    purchase = db.query(Purchase).filter(Purchase.id == purchase_id).first()
+    if not purchase:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Purchase with ID {purchase_id} not found"
+        )
+    
+    # Check if location exists
+    location = db.query(Location).filter(Location.id == location_id).first()
+    if not location:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Location with ID {location_id} not found"
+        )
+    
+    try:
+        # Create inventory transaction
+        transaction = InventoryTransaction(
+            type=TransactionType.PURCHASE,
+            reference_id=f"PO-{purchase.id}",
+            notes=f"Receiving purchase order {purchase.reference_number}"
+        )
+        db.add(transaction)
+        db.flush()
+        
+        # Get purchase items
+        purchase_items = db.query(PurchaseItem).filter(PurchaseItem.purchase_id == purchase.id).all()
+        
+        for item in purchase_items:
+            # Create inventory transaction item
+            transaction_item = InventoryTransactionItem(
+                transaction_id=transaction.id,
+                product_id=item.product_id,
+                quantity=item.quantity,
+                to_location_id=location_id
+            )
+            db.add(transaction_item)
+            
+            # Update or create inventory item
+            inventory_item = db.query(InventoryItem).filter(
+                InventoryItem.product_id == item.product_id,
+                InventoryItem.location_id == location_id
+            ).first()
+            
+            if inventory_item:
+                inventory_item.quantity += item.quantity
+            else:
+                from app.models.inventory import InventoryItem
+                new_item = InventoryItem(
+                    product_id=item.product_id,
+                    location_id=location_id,
+                    quantity=item.quantity,
+                    minimum_stock=0
+                )
+                db.add(new_item)
+        
+        # Update purchase delivery date if not set
+        if not purchase.delivery_date:
+            purchase.delivery_date = datetime.now()
+        
+        db.commit()
+        db.refresh(purchase)
+        return purchase
+    
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Could not receive purchase: {str(e)}"
+        )
+
+@router.get("/purchases/", response_model=List[PurchaseInDB])
+def read_purchases(
+    *,
+    db: Session = Depends(get_db),
+    skip: int = 0,
+    limit: int = 100,
+    supplier_id: Optional[int] = None,
+    reference_number: Optional[str] = None
+):
+    """Get all purchases with optional filters"""
+    query = db.query(Purchase)
+    
+    if supplier_id:
+        query = query.filter(Purchase.supplier_id == supplier_id)
+    
+    if reference_number:
+        query = query.filter(Purchase.reference_number.ilike(f"%{reference_number}%"))
+    
+    return query.order_by(Purchase.order_date.desc()).offset(skip).limit(limit).all()
+
+@router.get("/purchases/{purchase_id}", response_model=PurchaseWithItems)
+def read_purchase(
+    *,
+    db: Session = Depends(get_db),
+    purchase_id: int
+):
+    """Get a specific purchase by ID with all items"""
+    purchase = db.query(Purchase).filter(Purchase.id == purchase_id).first()
+    if not purchase:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Purchase with ID {purchase_id} not found"
+        )
+    
+    # Get purchase items with product details
+    items = db.query(PurchaseItem).filter(PurchaseItem.purchase_id == purchase_id).all()
+    
+    result_items = []
+    for item in items:
+        product = db.query(Product).filter(Product.id == item.product_id).first()
+        
+        item_dict = {
+            "id": item.id,
+            "purchase_id": item.purchase_id,
+            "product_id": item.product_id,
+            "quantity": item.quantity,
+            "unit_price": item.unit_price,
+            "total_price": item.total_price,
+            "created_at": item.created_at,
+            "updated_at": item.updated_at,
+            "product": {
+                "id": product.id,
+                "name": product.name,
+                "sku": product.sku
+            }
+        }
+        result_items.append(item_dict)
+    
+    # Get supplier details
+    supplier = db.query(Supplier).filter(Supplier.id == purchase.supplier_id).first()
+    
+    # Create final result
+    result = {
+        "id": purchase.id,
+        "supplier_id": purchase.supplier_id,
+        "reference_number": purchase.reference_number,
+        "order_date": purchase.order_date,
+        "delivery_date": purchase.delivery_date,
+        "total_amount": purchase.total_amount,
+        "notes": purchase.notes,
+        "created_at": purchase.created_at,
+        "updated_at": purchase.updated_at,
+        "items": result_items,
+        "supplier": {
+            "id": supplier.id,
+            "name": supplier.name,
+            "contact_name": supplier.contact_name,
+            "email": supplier.email,
+            "phone": supplier.phone
+        }
+    }
+    
+    return result
+
+@router.put("/purchases/{purchase_id}", response_model=PurchaseInDB)
+def update_purchase(
+    *,
+    db: Session = Depends(get_db),
+    purchase_id: int,
+    purchase_in: PurchaseUpdate
+):
+    """Update a purchase (header only, not items)"""
+    purchase = db.query(Purchase).filter(Purchase.id == purchase_id).first()
+    if not purchase:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Purchase with ID {purchase_id} not found"
+        )
+    
+    # Check if supplier exists if supplier_id is being updated
+    if purchase_in.supplier_id:
+        supplier = db.query(Supplier).filter(Supplier.id == purchase_in.supplier_id).first()
+        if not supplier:
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail=f"Supplier with ID {purchase_in.supplier_id} not found"
+            )
+    
+    update_data = purchase_in.model_dump(exclude_unset=True)
+    for field, value in update_data.items():
+        setattr(purchase, field, value)
+    
+    try:
+        db.add(purchase)
+        db.commit()
+        db.refresh(purchase)
+        return purchase
+    except IntegrityError as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Database integrity error: {str(e)}"
+        )
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Could not update purchase: {str(e)}"
+        )
+
+@router.delete("/purchases/{purchase_id}", status_code=status.HTTP_204_NO_CONTENT)
+def delete_purchase(
+    *,
+    db: Session = Depends(get_db),
+    purchase_id: int
+):
+    """Delete a purchase and its items"""
+    purchase = db.query(Purchase).filter(Purchase.id == purchase_id).first()
+    if not purchase:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Purchase with ID {purchase_id} not found"
+        )
+    
+    # Check if this purchase has been received (has inventory transactions)
+    transaction = db.query(InventoryTransaction).filter(
+        InventoryTransaction.type == TransactionType.PURCHASE,
+        InventoryTransaction.reference_id == f"PO-{purchase.id}"
+    ).first()
+    
+    if transaction:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Cannot delete purchase that has been received into inventory"
+        )
+    
+    try:
+        # Delete purchase items first
+        db.query(PurchaseItem).filter(PurchaseItem.purchase_id == purchase_id).delete()
+        
+        # Delete purchase
+        db.delete(purchase)
+        db.commit()
+        return None
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Could not delete purchase: {str(e)}"
+        )

app/db/base.py

@@ -0,0 +1,13 @@
+# Import all models here so Alembic can discover them
+from app.db.session import Base
+from app.models.product import Product, Category
+from app.models.inventory import (
+    Location, 
+    InventoryItem, 
+    InventoryTransaction, 
+    InventoryTransactionItem
+)
+from app.models.supplier import Supplier, Purchase, PurchaseItem
+
+# Create a base that includes all models
+# This allows Alembic's autogenerate to pick up your models

app/db/init_db.py

@@ -0,0 +1,32 @@
+from sqlalchemy.orm import Session
+from app.models.product import Category
+from app.models.inventory import Location, LocationType
+
+def init_db(db: Session) -> None:
+    """Initialize database with default data"""
+    
+    # Check if we already have data
+    if db.query(Category).first():
+        return  # Database already initialized
+    
+    # Create default categories
+    default_categories = [
+        Category(name="General", description="General products"),
+        Category(name="Electronics", description="Electronic products"),
+        Category(name="Office Supplies", description="Office supplies and stationery"),
+        Category(name="Furniture", description="Furniture items"),
+    ]
+    
+    db.add_all(default_categories)
+    
+    # Create default locations
+    default_locations = [
+        Location(name="Main Warehouse", type=LocationType.WAREHOUSE, 
+                description="Main storage warehouse"),
+        Location(name="Store Front", type=LocationType.STORE, 
+                description="Main store front"),
+    ]
+    
+    db.add_all(default_locations)
+    
+    db.commit()

app/db/session.py

@@ -0,0 +1,31 @@
+from sqlalchemy import create_engine
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import sessionmaker
+from pathlib import Path
+
+# Create database directory
+DB_DIR = Path("/app") / "storage" / "db"
+DB_DIR.mkdir(parents=True, exist_ok=True)
+
+# Database URL
+SQLALCHEMY_DATABASE_URL = f"sqlite:///{DB_DIR}/db.sqlite"
+
+# Create engine
+engine = create_engine(
+    SQLALCHEMY_DATABASE_URL,
+    connect_args={"check_same_thread": False}
+)
+
+# Create SessionLocal class
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+# Create Base class
+Base = declarative_base()
+
+# Dependency to get db session
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()

app/models/__init__.py

@@ -0,0 +1,11 @@
+from app.models.base import BaseModel
+from app.models.product import Product, Category
+from app.models.inventory import (
+    Location, 
+    LocationType,
+    InventoryItem, 
+    InventoryTransaction, 
+    InventoryTransactionItem,
+    TransactionType
+)
+from app.models.supplier import Supplier, Purchase, PurchaseItem

app/models/base.py

@@ -0,0 +1,10 @@
+from sqlalchemy import Column, Integer, DateTime, func
+from app.db.session import Base
+
+class BaseModel(Base):
+    """Base model for all database models"""
+    __abstract__ = True
+    
+    id = Column(Integer, primary_key=True, index=True)
+    created_at = Column(DateTime, default=func.now())
+    updated_at = Column(DateTime, default=func.now(), onupdate=func.now())

app/models/inventory.py

@@ -0,0 +1,69 @@
+from sqlalchemy import Column, String, Float, Integer, ForeignKey, Enum
+from sqlalchemy.orm import relationship
+import enum
+from app.models.base import BaseModel
+
+class LocationType(str, enum.Enum):
+    WAREHOUSE = "warehouse"
+    STORE = "store"
+    SUPPLIER = "supplier"
+
+class Location(BaseModel):
+    """Location model for inventory storage"""
+    __tablename__ = "locations"
+    
+    name = Column(String(100), nullable=False)
+    type = Column(Enum(LocationType), nullable=False, default=LocationType.WAREHOUSE)
+    address = Column(String(255), nullable=True)
+    description = Column(String(255), nullable=True)
+    
+    # Relationships
+    inventory_items = relationship("InventoryItem", back_populates="location")
+
+class TransactionType(str, enum.Enum):
+    PURCHASE = "purchase"
+    SALE = "sale"
+    TRANSFER = "transfer"
+    ADJUSTMENT = "adjustment"
+    RETURN = "return"
+
+class InventoryTransaction(BaseModel):
+    """Inventory transaction model to track changes"""
+    __tablename__ = "inventory_transactions"
+    
+    type = Column(Enum(TransactionType), nullable=False)
+    reference_id = Column(String(100), nullable=True)
+    notes = Column(String(255), nullable=True)
+    
+    # Relationships
+    transaction_items = relationship("InventoryTransactionItem", back_populates="transaction")
+
+class InventoryTransactionItem(BaseModel):
+    """Inventory transaction item model"""
+    __tablename__ = "inventory_transaction_items"
+    
+    transaction_id = Column(Integer, ForeignKey("inventory_transactions.id"), nullable=False)
+    product_id = Column(Integer, ForeignKey("products.id"), nullable=False)
+    quantity = Column(Float, nullable=False)
+    from_location_id = Column(Integer, ForeignKey("locations.id"), nullable=True)
+    to_location_id = Column(Integer, ForeignKey("locations.id"), nullable=True)
+    
+    # Relationships
+    transaction = relationship("InventoryTransaction", back_populates="transaction_items")
+    product = relationship("Product")
+    from_location = relationship("Location", foreign_keys=[from_location_id])
+    to_location = relationship("Location", foreign_keys=[to_location_id])
+
+class InventoryItem(BaseModel):
+    """Inventory item model representing product stock at a location"""
+    __tablename__ = "inventory_items"
+    
+    product_id = Column(Integer, ForeignKey("products.id"), nullable=False)
+    location_id = Column(Integer, ForeignKey("locations.id"), nullable=False)
+    quantity = Column(Float, nullable=False, default=0)
+    minimum_stock = Column(Float, nullable=False, default=0)
+    maximum_stock = Column(Float, nullable=True)
+    
+    # Relationships
+    product = relationship("Product", back_populates="inventory_items")
+    location = relationship("Location", back_populates="inventory_items")

app/models/product.py

@@ -0,0 +1,30 @@
+from sqlalchemy import Column, String, Float, Integer, Text, ForeignKey
+from sqlalchemy.orm import relationship
+from app.models.base import BaseModel
+
+class Category(BaseModel):
+    """Product category model"""
+    __tablename__ = "categories"
+    
+    name = Column(String(100), unique=True, index=True, nullable=False)
+    description = Column(Text, nullable=True)
+    
+    # Relationships
+    products = relationship("Product", back_populates="category")
+    
+class Product(BaseModel):
+    """Product model for inventory items"""
+    __tablename__ = "products"
+    
+    name = Column(String(255), nullable=False, index=True)
+    description = Column(Text, nullable=True)
+    sku = Column(String(50), unique=True, index=True, nullable=False)
+    category_id = Column(Integer, ForeignKey("categories.id"), nullable=True)
+    price = Column(Float, nullable=False)
+    cost_price = Column(Float, nullable=False)
+    barcode = Column(String(100), unique=True, nullable=True)
+    
+    # Relationships
+    category = relationship("Category", back_populates="products")
+    inventory_items = relationship("InventoryItem", back_populates="product")
+    purchase_items = relationship("PurchaseItem", back_populates="product")

app/models/supplier.py

@@ -0,0 +1,47 @@
+from sqlalchemy import Column, String, Float, Integer, Text, Boolean, ForeignKey, DateTime
+from sqlalchemy.orm import relationship
+from app.models.base import BaseModel
+
+class Supplier(BaseModel):
+    """Supplier model"""
+    __tablename__ = "suppliers"
+    
+    name = Column(String(255), nullable=False, index=True)
+    contact_name = Column(String(100), nullable=True)
+    email = Column(String(255), nullable=True)
+    phone = Column(String(20), nullable=True)
+    address = Column(Text, nullable=True)
+    notes = Column(Text, nullable=True)
+    is_active = Column(Boolean, default=True)
+    
+    # Relationships
+    purchases = relationship("Purchase", back_populates="supplier")
+
+class Purchase(BaseModel):
+    """Purchase model for orders from suppliers"""
+    __tablename__ = "purchases"
+    
+    supplier_id = Column(Integer, ForeignKey("suppliers.id"), nullable=False)
+    reference_number = Column(String(100), nullable=True, unique=True)
+    order_date = Column(DateTime, nullable=True)
+    delivery_date = Column(DateTime, nullable=True)
+    total_amount = Column(Float, nullable=False, default=0)
+    notes = Column(Text, nullable=True)
+    
+    # Relationships
+    supplier = relationship("Supplier", back_populates="purchases")
+    purchase_items = relationship("PurchaseItem", back_populates="purchase")
+
+class PurchaseItem(BaseModel):
+    """Purchase item model for items in a purchase"""
+    __tablename__ = "purchase_items"
+    
+    purchase_id = Column(Integer, ForeignKey("purchases.id"), nullable=False)
+    product_id = Column(Integer, ForeignKey("products.id"), nullable=False)
+    quantity = Column(Float, nullable=False)
+    unit_price = Column(Float, nullable=False)
+    total_price = Column(Float, nullable=False)
+    
+    # Relationships
+    purchase = relationship("Purchase", back_populates="purchase_items")
+    product = relationship("Product", back_populates="purchase_items")

app/schemas/inventory.py

@@ -0,0 +1,109 @@
+from typing import List, Optional, Dict, Any
+from pydantic import BaseModel, Field
+from datetime import datetime
+from enum import Enum
+
+from app.models.inventory import LocationType, TransactionType
+
+# Location schemas
+class LocationTypeEnum(str, Enum):
+    WAREHOUSE = "warehouse"
+    STORE = "store"
+    SUPPLIER = "supplier"
+
+class LocationBase(BaseModel):
+    name: str
+    type: LocationTypeEnum = LocationTypeEnum.WAREHOUSE
+    address: Optional[str] = None
+    description: Optional[str] = None
+
+class LocationCreate(LocationBase):
+    pass
+
+class LocationUpdate(BaseModel):
+    name: Optional[str] = None
+    type: Optional[LocationTypeEnum] = None
+    address: Optional[str] = None
+    description: Optional[str] = None
+
+class LocationInDB(LocationBase):
+    id: int
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True
+
+# Inventory item schemas
+class InventoryItemBase(BaseModel):
+    product_id: int
+    location_id: int
+    quantity: float
+    minimum_stock: float = 0
+    maximum_stock: Optional[float] = None
+
+class InventoryItemCreate(InventoryItemBase):
+    pass
+
+class InventoryItemUpdate(BaseModel):
+    quantity: Optional[float] = None
+    minimum_stock: Optional[float] = None
+    maximum_stock: Optional[float] = None
+
+class InventoryItemInDB(InventoryItemBase):
+    id: int
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True
+
+class InventoryItemWithDetails(InventoryItemInDB):
+    product: Dict[str, Any]
+    location: Dict[str, Any]
+
+# Transaction schemas
+class TransactionTypeEnum(str, Enum):
+    PURCHASE = "purchase"
+    SALE = "sale"
+    TRANSFER = "transfer"
+    ADJUSTMENT = "adjustment"
+    RETURN = "return"
+
+class InventoryTransactionBase(BaseModel):
+    type: TransactionTypeEnum
+    reference_id: Optional[str] = None
+    notes: Optional[str] = None
+
+class InventoryTransactionCreate(InventoryTransactionBase):
+    pass
+
+class InventoryTransactionItemBase(BaseModel):
+    product_id: int
+    quantity: float
+    from_location_id: Optional[int] = None
+    to_location_id: Optional[int] = None
+
+class InventoryTransactionItemCreate(InventoryTransactionItemBase):
+    pass
+
+class InventoryTransactionWithItems(InventoryTransactionBase):
+    items: List[InventoryTransactionItemCreate]
+
+class InventoryTransactionItemInDB(InventoryTransactionItemBase):
+    id: int
+    transaction_id: int
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True
+
+class InventoryTransactionInDB(InventoryTransactionBase):
+    id: int
+    created_at: datetime
+    updated_at: datetime
+    transaction_items: List[InventoryTransactionItemInDB] = []
+
+    class Config:
+        from_attributes = True

app/schemas/product.py

@@ -0,0 +1,53 @@
+from typing import List, Optional
+from pydantic import BaseModel, Field
+from datetime import datetime
+
+# Category schemas
+class CategoryBase(BaseModel):
+    name: str
+    description: Optional[str] = None
+
+class CategoryCreate(CategoryBase):
+    pass
+
+class CategoryUpdate(CategoryBase):
+    name: Optional[str] = None
+
+class CategoryInDB(CategoryBase):
+    id: int
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True
+
+# Product schemas
+class ProductBase(BaseModel):
+    name: str
+    description: Optional[str] = None
+    sku: str = Field(..., description="Stock Keeping Unit, unique identifier")
+    price: float = Field(..., gt=0)
+    cost_price: float = Field(..., gt=0)
+    barcode: Optional[str] = None
+    category_id: Optional[int] = None
+
+class ProductCreate(ProductBase):
+    pass
+
+class ProductUpdate(BaseModel):
+    name: Optional[str] = None
+    description: Optional[str] = None
+    sku: Optional[str] = None
+    price: Optional[float] = Field(None, gt=0)
+    cost_price: Optional[float] = Field(None, gt=0)
+    barcode: Optional[str] = None
+    category_id: Optional[int] = None
+
+class ProductInDB(ProductBase):
+    id: int
+    created_at: datetime
+    updated_at: datetime
+    category: Optional[CategoryInDB] = None
+
+    class Config:
+        from_attributes = True

app/schemas/supplier.py

@@ -0,0 +1,85 @@
+from typing import List, Optional, Dict, Any
+from pydantic import BaseModel, Field
+from datetime import datetime
+
+# Supplier schemas
+class SupplierBase(BaseModel):
+    name: str
+    contact_name: Optional[str] = None
+    email: Optional[str] = None
+    phone: Optional[str] = None
+    address: Optional[str] = None
+    notes: Optional[str] = None
+    is_active: bool = True
+
+class SupplierCreate(SupplierBase):
+    pass
+
+class SupplierUpdate(BaseModel):
+    name: Optional[str] = None
+    contact_name: Optional[str] = None
+    email: Optional[str] = None
+    phone: Optional[str] = None
+    address: Optional[str] = None
+    notes: Optional[str] = None
+    is_active: Optional[bool] = None
+
+class SupplierInDB(SupplierBase):
+    id: int
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True
+
+# Purchase schemas
+class PurchaseItemBase(BaseModel):
+    product_id: int
+    quantity: float
+    unit_price: float
+    total_price: float = None  # Will be calculated server-side
+
+class PurchaseItemCreate(PurchaseItemBase):
+    pass
+
+class PurchaseItemInDB(PurchaseItemBase):
+    id: int
+    purchase_id: int
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True
+
+class PurchaseItemWithDetails(PurchaseItemInDB):
+    product: Dict[str, Any]
+
+class PurchaseBase(BaseModel):
+    supplier_id: int
+    reference_number: Optional[str] = None
+    order_date: datetime = None
+    delivery_date: Optional[datetime] = None
+    notes: Optional[str] = None
+    total_amount: float = 0
+
+class PurchaseCreate(PurchaseBase):
+    items: List[PurchaseItemCreate]
+
+class PurchaseUpdate(BaseModel):
+    supplier_id: Optional[int] = None
+    reference_number: Optional[str] = None
+    order_date: Optional[datetime] = None
+    delivery_date: Optional[datetime] = None
+    notes: Optional[str] = None
+
+class PurchaseInDB(PurchaseBase):
+    id: int
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True
+
+class PurchaseWithItems(PurchaseInDB):
+    items: List[PurchaseItemWithDetails] = []
+    supplier: Dict[str, Any]

main.py

@@ -0,0 +1,52 @@
+from fastapi import FastAPI, Depends
+from fastapi.middleware.cors import CORSMiddleware
+import uvicorn
+from pathlib import Path
+from sqlalchemy.orm import Session
+
+from app.db.session import get_db, engine
+from app.db.base import Base
+from app.db.init_db import init_db
+
+# Import routers
+from app.api.routes import product_router, inventory_router, supplier_router
+
+# Create database tables
+Base.metadata.create_all(bind=engine)
+
+# Create FastAPI app
+app = FastAPI(
+    title="Small Business Inventory Management System",
+    description="API for managing inventory for small businesses",
+    version="0.1.0"
+)
+
+# Configure CORS
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],  # Update with specific origins in production
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+# Include routers
+app.include_router(product_router)
+app.include_router(inventory_router)
+app.include_router(supplier_router)
+
+@app.get("/")
+async def root():
+    return {"message": "Welcome to the Small Business Inventory Management System API"}
+
+@app.get("/health")
+async def health():
+    return {"status": "healthy"}
+
+@app.on_event("startup")
+async def startup_event():
+    db = next(get_db())
+    init_db(db)
+
+if __name__ == "__main__":
+    uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=True)

migrations/env.py

@@ -0,0 +1,80 @@
+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+from pathlib import Path
+
+# 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 app.db.base import Base
+target_metadata = Base.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+# Ensure the DB directory exists
+DB_DIR = Path("/app") / "storage" / "db"
+DB_DIR.mkdir(parents=True, exist_ok=True)
+
+def run_migrations_offline():
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online():
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection, target_metadata=target_metadata
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

migrations/script.py.mako

@@ -0,0 +1,24 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+branch_labels = ${repr(branch_labels)}
+depends_on = ${repr(depends_on)}
+
+
+def upgrade():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}

migrations/versions/001_initial_migration.py

@@ -0,0 +1,220 @@
+"""initial migration
+
+Revision ID: 001
+Revises: 
+Create Date: 2025-05-12
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy import Column, Integer, String, Float, DateTime, Text, Boolean, ForeignKey, Enum
+import enum
+
+# revision identifiers, used by Alembic.
+revision = '001'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+# Enum classes for migration
+class LocationType(str, enum.Enum):
+    WAREHOUSE = "warehouse"
+    STORE = "store"
+    SUPPLIER = "supplier"
+
+class TransactionType(str, enum.Enum):
+    PURCHASE = "purchase"
+    SALE = "sale"
+    TRANSFER = "transfer"
+    ADJUSTMENT = "adjustment"
+    RETURN = "return"
+
+def upgrade():
+    # Categories table
+    op.create_table(
+        'categories',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('name', sa.String(length=100), 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)
+    
+    # Products table
+    op.create_table(
+        'products',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        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('category_id', sa.Integer(), nullable=True),
+        sa.Column('price', sa.Float(), nullable=False),
+        sa.Column('cost_price', sa.Float(), nullable=False),
+        sa.Column('barcode', sa.String(length=100), nullable=True),
+        sa.ForeignKeyConstraint(['category_id'], ['categories.id'], ),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_products_id'), 'products', ['id'], unique=False)
+    op.create_index(op.f('ix_products_name'), 'products', ['name'], unique=False)
+    op.create_index(op.f('ix_products_sku'), 'products', ['sku'], unique=True)
+    op.create_index(op.f('ix_products_barcode'), 'products', ['barcode'], unique=True)
+    
+    # Locations table
+    op.create_table(
+        'locations',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('name', sa.String(length=100), nullable=False),
+        sa.Column('type', sa.Enum('warehouse', 'store', 'supplier', name='locationtype'), nullable=False),
+        sa.Column('address', sa.String(length=255), nullable=True),
+        sa.Column('description', sa.String(length=255), nullable=True),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_locations_id'), 'locations', ['id'], unique=False)
+    
+    # Inventory Transactions table
+    op.create_table(
+        'inventory_transactions',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('type', sa.Enum('purchase', 'sale', 'transfer', 'adjustment', 'return', name='transactiontype'), nullable=False),
+        sa.Column('reference_id', sa.String(length=100), nullable=True),
+        sa.Column('notes', sa.String(length=255), nullable=True),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_inventory_transactions_id'), 'inventory_transactions', ['id'], unique=False)
+    
+    # Inventory Items table
+    op.create_table(
+        'inventory_items',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('product_id', sa.Integer(), nullable=False),
+        sa.Column('location_id', sa.Integer(), nullable=False),
+        sa.Column('quantity', sa.Float(), nullable=False),
+        sa.Column('minimum_stock', sa.Float(), nullable=False),
+        sa.Column('maximum_stock', sa.Float(), nullable=True),
+        sa.ForeignKeyConstraint(['location_id'], ['locations.id'], ),
+        sa.ForeignKeyConstraint(['product_id'], ['products.id'], ),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_inventory_items_id'), 'inventory_items', ['id'], unique=False)
+    
+    # Inventory Transaction Items table
+    op.create_table(
+        'inventory_transaction_items',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('transaction_id', sa.Integer(), nullable=False),
+        sa.Column('product_id', sa.Integer(), nullable=False),
+        sa.Column('quantity', sa.Float(), nullable=False),
+        sa.Column('from_location_id', sa.Integer(), nullable=True),
+        sa.Column('to_location_id', sa.Integer(), nullable=True),
+        sa.ForeignKeyConstraint(['from_location_id'], ['locations.id'], ),
+        sa.ForeignKeyConstraint(['product_id'], ['products.id'], ),
+        sa.ForeignKeyConstraint(['to_location_id'], ['locations.id'], ),
+        sa.ForeignKeyConstraint(['transaction_id'], ['inventory_transactions.id'], ),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_inventory_transaction_items_id'), 'inventory_transaction_items', ['id'], unique=False)
+    
+    # Suppliers table
+    op.create_table(
+        'suppliers',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('name', sa.String(length=255), nullable=False),
+        sa.Column('contact_name', sa.String(length=100), nullable=True),
+        sa.Column('email', sa.String(length=255), nullable=True),
+        sa.Column('phone', sa.String(length=20), nullable=True),
+        sa.Column('address', sa.Text(), nullable=True),
+        sa.Column('notes', sa.Text(), nullable=True),
+        sa.Column('is_active', sa.Boolean(), nullable=True),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_suppliers_id'), 'suppliers', ['id'], unique=False)
+    op.create_index(op.f('ix_suppliers_name'), 'suppliers', ['name'], unique=False)
+    
+    # Purchases table
+    op.create_table(
+        'purchases',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('supplier_id', sa.Integer(), nullable=False),
+        sa.Column('reference_number', sa.String(length=100), nullable=True),
+        sa.Column('order_date', sa.DateTime(), nullable=True),
+        sa.Column('delivery_date', sa.DateTime(), nullable=True),
+        sa.Column('total_amount', sa.Float(), nullable=False),
+        sa.Column('notes', sa.Text(), nullable=True),
+        sa.ForeignKeyConstraint(['supplier_id'], ['suppliers.id'], ),
+        sa.PrimaryKeyConstraint('id'),
+        sa.UniqueConstraint('reference_number')
+    )
+    op.create_index(op.f('ix_purchases_id'), 'purchases', ['id'], unique=False)
+    
+    # Purchase Items table
+    op.create_table(
+        'purchase_items',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('purchase_id', sa.Integer(), nullable=False),
+        sa.Column('product_id', sa.Integer(), nullable=False),
+        sa.Column('quantity', sa.Float(), nullable=False),
+        sa.Column('unit_price', sa.Float(), nullable=False),
+        sa.Column('total_price', sa.Float(), nullable=False),
+        sa.ForeignKeyConstraint(['product_id'], ['products.id'], ),
+        sa.ForeignKeyConstraint(['purchase_id'], ['purchases.id'], ),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_purchase_items_id'), 'purchase_items', ['id'], unique=False)
+
+
+def downgrade():
+    # Drop tables in reverse order (considering foreign key constraints)
+    op.drop_index(op.f('ix_purchase_items_id'), table_name='purchase_items')
+    op.drop_table('purchase_items')
+    
+    op.drop_index(op.f('ix_purchases_id'), table_name='purchases')
+    op.drop_table('purchases')
+    
+    op.drop_index(op.f('ix_suppliers_name'), table_name='suppliers')
+    op.drop_index(op.f('ix_suppliers_id'), table_name='suppliers')
+    op.drop_table('suppliers')
+    
+    op.drop_index(op.f('ix_inventory_transaction_items_id'), table_name='inventory_transaction_items')
+    op.drop_table('inventory_transaction_items')
+    
+    op.drop_index(op.f('ix_inventory_items_id'), table_name='inventory_items')
+    op.drop_table('inventory_items')
+    
+    op.drop_index(op.f('ix_inventory_transactions_id'), table_name='inventory_transactions')
+    op.drop_table('inventory_transactions')
+    
+    op.drop_index(op.f('ix_locations_id'), table_name='locations')
+    op.drop_table('locations')
+    
+    op.drop_index(op.f('ix_products_barcode'), table_name='products')
+    op.drop_index(op.f('ix_products_sku'), table_name='products')
+    op.drop_index(op.f('ix_products_name'), table_name='products')
+    op.drop_index(op.f('ix_products_id'), table_name='products')
+    op.drop_table('products')
+    
+    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')
+    
+    # Drop enum types
+    op.execute("DROP TYPE locationtype")
+    op.execute("DROP TYPE transactiontype")

requirements.txt

@@ -0,0 +1,9 @@
+fastapi==0.115.0
+uvicorn==0.29.0
+sqlalchemy==2.0.34
+pydantic==2.7.1
+alembic==1.13.1
+python-dotenv==1.0.1
+python-multipart==0.0.9
+pathlib==1.0.1
+pytest==8.0.2