Implement Small Business Inventory Management System

- Created project structure with FastAPI framework - Set up SQLite database with SQLAlchemy ORM - Implemented models: User, Item, Supplier, Transaction - Created CRUD operations for all models - Added API endpoints for all resources - Implemented JWT authentication and authorization - Added Alembic migration scripts - Created health endpoint - Updated documentation generated with BackendIM... (backend.im)
2025-05-13 09:48:37 +00:00 · 2025-05-13 09:48:37 +00:00 · 4dc182713c
commit 4dc182713c
parent 7b50fb73bf
35 changed files with 1753 additions and 2 deletions
--- a/README.md
+++ b/README.md
@ -1,3 +1,98 @@
-# FastAPI Application
+# Small Business Inventory Management System

-This is a FastAPI application bootstrapped by BackendIM, the AI-powered backend generation platform.
+A FastAPI application for managing inventory for small businesses.
+
+## Features
+
+- **User Authentication**: Secure user authentication with JWT tokens
+- **Inventory Management**: Track inventory items with details like SKU, quantity, price, and location
+- **Supplier Management**: Manage supplier information and relationships with inventory items
+- **Transaction Tracking**: Record and monitor inventory transactions (purchases, sales, adjustments, returns)
+- **API Documentation**: Interactive API documentation using FastAPI's built-in Swagger UI
+
+## Tech Stack
+
+- **Backend**: Python 3.7+ with FastAPI
+- **Database**: SQLite with SQLAlchemy ORM
+- **Authentication**: JWT token-based authentication
+- **Migration**: Alembic for database migrations
+
+## Project Structure
+
+```
+.
+├── alembic/              # Database migration scripts
+├── app/                  # Main application code
+│   ├── api/              # API endpoints
+│   ├── core/             # Core functionality (config, security)
+│   ├── crud/             # CRUD operations
+│   ├── db/               # Database session and connection
+│   ├── models/           # SQLAlchemy models
+│   └── schemas/          # Pydantic schemas/models
+├── storage/              # Data storage
+│   └── db/               # SQLite database files
+├── main.py               # Application entry point
+├── alembic.ini           # Alembic configuration
+└── requirements.txt      # Project dependencies
+```
+
+## Installation and Setup
+
+1. Clone the repository
+2. Install dependencies:
+   ```
+   pip install -r requirements.txt
+   ```
+3. Apply migrations:
+   ```
+   alembic upgrade head
+   ```
+4. Run the application:
+   ```
+   uvicorn main:app --reload
+   ```
+
+## API Documentation
+
+Once the application is running, you can access:
+- Swagger UI documentation: http://localhost:8000/docs
+- ReDoc documentation: http://localhost:8000/redoc
+
+## API Endpoints
+
+### Authentication
+- `POST /api/v1/login/access-token` - Get JWT access token
+- `POST /api/v1/login/test-token` - Test token validity
+
+### Users
+- `GET /api/v1/users/` - List users (admin only)
+- `POST /api/v1/users/` - Create new user (admin only)
+- `GET /api/v1/users/me` - Get current user info
+- `PUT /api/v1/users/me` - Update current user info
+- `GET /api/v1/users/{user_id}` - Get user by ID
+- `PUT /api/v1/users/{user_id}` - Update user (admin only)
+
+### Items
+- `GET /api/v1/items/` - List inventory items (with optional filtering)
+- `POST /api/v1/items/` - Add new inventory item
+- `GET /api/v1/items/{id}` - Get item by ID
+- `PUT /api/v1/items/{id}` - Update item
+- `DELETE /api/v1/items/{id}` - Delete item (admin only)
+
+### Suppliers
+- `GET /api/v1/suppliers/` - List suppliers
+- `POST /api/v1/suppliers/` - Add new supplier
+- `GET /api/v1/suppliers/{id}` - Get supplier by ID
+- `PUT /api/v1/suppliers/{id}` - Update supplier
+- `DELETE /api/v1/suppliers/{id}` - Delete supplier (admin only)
+
+### Transactions
+- `GET /api/v1/transactions/` - List transactions (with optional filtering)
+- `POST /api/v1/transactions/` - Record new transaction
+- `GET /api/v1/transactions/{id}` - Get transaction by ID
+- `PUT /api/v1/transactions/{id}` - Update transaction (admin only)
+- `DELETE /api/v1/transactions/{id}` - Delete transaction (admin only)
+
+## Health Check
+
+- `GET /health` - Application health check endpoint
--- a/alembic.ini
+++ b/alembic.ini
@ -0,0 +1,85 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = alembic
+
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# timezone to use when rendering the date
+# within the migration file as well as the filename.
+# string value is passed to dateutil.tz.gettz()
+# leave blank for localtime
+# timezone =
+
+# max length of characters to apply to the
+# "slug" field
+# truncate_slug_length = 40
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+# set to 'true' to allow .pyc and .pyo files without
+# a source .py file to be detected as revisions in the
+# versions/ directory
+# sourceless = false
+
+# version location specification; this defaults
+# to alembic/versions.  When using multiple version
+# directories, initial revisions must be specified with --version-path
+# version_locations = %(here)s/bar %(here)s/bat alembic/versions
+
+# the output encoding used when revision files
+# are written from script.py.mako
+# output_encoding = utf-8
+
+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
--- a/alembic/env.py
+++ b/alembic/env.py
@ -0,0 +1,84 @@
+import os
+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
+
+# 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 the parent directory to sys.path
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+# Import the SQLAlchemy models
+from app.db.base import Base
+
+# Target metadata
+target_metadata = Base.metadata
+
+
+# Other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline():
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online():
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection, target_metadata=target_metadata
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()
--- a/alembic/script.py.mako
+++ b/alembic/script.py.mako
@ -0,0 +1,24 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+branch_labels = ${repr(branch_labels)}
+depends_on = ${repr(depends_on)}
+
+
+def upgrade():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}
--- a/alembic/versions/initial_migration.py
+++ b/alembic/versions/initial_migration.py
@ -0,0 +1,108 @@
+"""Initial migration
+
+Revision ID: 001
+Revises: 
+Create Date: 2025-05-13
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import sqlite
+
+# revision identifiers, used by Alembic.
+revision = '001'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # Create user table
+    op.create_table('user',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('full_name', sa.String(), nullable=True),
+        sa.Column('email', sa.String(), nullable=False),
+        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.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 supplier table
+    op.create_table('supplier',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('name', sa.String(), nullable=True),
+        sa.Column('contact_name', sa.String(), nullable=True),
+        sa.Column('email', sa.String(), nullable=True),
+        sa.Column('phone', sa.String(), nullable=True),
+        sa.Column('address', sa.String(), 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), 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 item table
+    op.create_table('item',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('name', sa.String(), nullable=True),
+        sa.Column('description', sa.String(), nullable=True),
+        sa.Column('sku', sa.String(), nullable=True),
+        sa.Column('quantity', sa.Integer(), nullable=True),
+        sa.Column('unit_price', sa.Float(), nullable=False),
+        sa.Column('category', sa.String(), nullable=True),
+        sa.Column('location', sa.String(), 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), nullable=True),
+        sa.Column('supplier_id', sa.Integer(), nullable=True),
+        sa.ForeignKeyConstraint(['supplier_id'], ['supplier.id'], ),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_item_category'), 'item', ['category'], unique=False)
+    op.create_index(op.f('ix_item_id'), 'item', ['id'], unique=False)
+    op.create_index(op.f('ix_item_name'), 'item', ['name'], unique=False)
+    op.create_index(op.f('ix_item_sku'), 'item', ['sku'], unique=True)
+    
+    # Create transaction table
+    op.create_table('transaction',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('transaction_type', sa.Enum('PURCHASE', 'SALE', 'ADJUSTMENT', 'RETURN', name='transactiontype'), nullable=False),
+        sa.Column('quantity', sa.Integer(), nullable=False),
+        sa.Column('price_per_unit', sa.Float(), nullable=False),
+        sa.Column('reference_number', sa.String(), nullable=True),
+        sa.Column('notes', sa.String(), nullable=True),
+        sa.Column('transaction_date', 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), nullable=True),
+        sa.Column('item_id', sa.Integer(), nullable=False),
+        sa.Column('user_id', sa.Integer(), nullable=True),
+        sa.ForeignKeyConstraint(['item_id'], ['item.id'], ),
+        sa.ForeignKeyConstraint(['user_id'], ['user.id'], ),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_transaction_id'), 'transaction', ['id'], unique=False)
+
+
+def downgrade():
+    # Drop tables in reverse order
+    op.drop_index(op.f('ix_transaction_id'), table_name='transaction')
+    op.drop_table('transaction')
+    
+    op.drop_index(op.f('ix_item_sku'), table_name='item')
+    op.drop_index(op.f('ix_item_name'), table_name='item')
+    op.drop_index(op.f('ix_item_id'), table_name='item')
+    op.drop_index(op.f('ix_item_category'), table_name='item')
+    op.drop_table('item')
+    
+    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_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')
--- a/app/api/api.py
+++ b/app/api/api.py
@ -0,0 +1,10 @@
+from fastapi import APIRouter
+
+from app.api.endpoints import items, login, suppliers, transactions, users
+
+api_router = APIRouter()
+api_router.include_router(login.router, tags=["login"])
+api_router.include_router(users.router, prefix="/users", tags=["users"])
+api_router.include_router(items.router, prefix="/items", tags=["items"])
+api_router.include_router(suppliers.router, prefix="/suppliers", tags=["suppliers"])
+api_router.include_router(transactions.router, prefix="/transactions", tags=["transactions"])
--- a/app/api/deps.py
+++ b/app/api/deps.py
@ -0,0 +1,63 @@
+from typing import Generator, Optional
+
+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.core import security
+from app.core.config import settings
+from app.db.session import SessionLocal
+from app.models.user import User
+from app.schemas.token import TokenPayload
+
+
+oauth2_scheme = 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(oauth2_scheme)
+) -> User:
+    try:
+        payload = jwt.decode(
+            token, settings.SECRET_KEY, algorithms=[security.ALGORITHM]
+        )
+        token_data = TokenPayload(**payload)
+    except (jwt.JWTError, ValidationError):
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Could not validate credentials",
+        )
+    user = db.query(User).filter(User.id == token_data.sub).first()
+    if not user:
+        raise HTTPException(status_code=404, detail="User not found")
+    return user
+
+
+def get_current_active_user(
+    current_user: User = Depends(get_current_user),
+) -> User:
+    if not current_user.is_active:
+        raise HTTPException(status_code=400, detail="Inactive user")
+    return current_user
+
+
+def get_current_active_superuser(
+    current_user: User = Depends(get_current_user),
+) -> User:
+    if not current_user.is_superuser:
+        raise HTTPException(
+            status_code=400, detail="The user doesn't have enough privileges"
+        )
+    return current_user
--- a/app/api/endpoints/items.py
+++ b/app/api/endpoints/items.py
@ -0,0 +1,129 @@
+from typing import Any, List, Optional
+
+from fastapi import APIRouter, Depends, HTTPException, Query
+from sqlalchemy.orm import Session
+
+from app import crud
+from app.api import deps
+from app.schemas.item import Item, ItemCreate, ItemUpdate
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[Item])
+def read_items(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    category: Optional[str] = None,
+    supplier_id: Optional[int] = None,
+    current_user: Any = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve items.
+    """
+    if supplier_id:
+        items = crud.item.get_by_supplier(db, supplier_id=supplier_id, skip=skip, limit=limit)
+    elif category:
+        items = crud.item.get_by_category(db, category=category, skip=skip, limit=limit)
+    else:
+        items = crud.item.get_multi(db, skip=skip, limit=limit)
+    return items
+
+
+@router.post("/", response_model=Item)
+def create_item(
+    *,
+    db: Session = Depends(deps.get_db),
+    item_in: ItemCreate,
+    current_user: Any = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new item.
+    """
+    # Check if the item with this SKU already exists
+    item = crud.item.get_by_sku(db, sku=item_in.sku)
+    if item:
+        raise HTTPException(
+            status_code=400,
+            detail="An item with this SKU already exists in the system.",
+        )
+    
+    # Check if supplier exists if supplier_id is provided
+    if item_in.supplier_id and not crud.supplier.get(db, id=item_in.supplier_id):
+        raise HTTPException(
+            status_code=400,
+            detail=f"Supplier with ID {item_in.supplier_id} does not exist.",
+        )
+    
+    item = crud.item.create(db, obj_in=item_in)
+    return item
+
+
+@router.put("/{id}", response_model=Item)
+def update_item(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    item_in: ItemUpdate,
+    current_user: Any = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update an item.
+    """
+    item = crud.item.get(db, id=id)
+    if not item:
+        raise HTTPException(status_code=404, detail="Item not found")
+    
+    # Check if the new SKU already exists and belongs to a different item
+    if item_in.sku and item_in.sku != item.sku:
+        existing_item = crud.item.get_by_sku(db, sku=item_in.sku)
+        if existing_item and existing_item.id != id:
+            raise HTTPException(
+                status_code=400,
+                detail="An item with this SKU already exists in the system.",
+            )
+    
+    # Check if supplier exists if supplier_id is provided
+    if item_in.supplier_id and item_in.supplier_id != item.supplier_id:
+        if not crud.supplier.get(db, id=item_in.supplier_id):
+            raise HTTPException(
+                status_code=400,
+                detail=f"Supplier with ID {item_in.supplier_id} does not exist.",
+            )
+    
+    item = crud.item.update(db, db_obj=item, obj_in=item_in)
+    return item
+
+
+@router.get("/{id}", response_model=Item)
+def read_item(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: Any = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get item by ID.
+    """
+    item = crud.item.get(db, id=id)
+    if not item:
+        raise HTTPException(status_code=404, detail="Item not found")
+    return item
+
+
+@router.delete("/{id}", response_model=Item)
+def delete_item(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: Any = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Delete an item.
+    """
+    item = crud.item.get(db, id=id)
+    if not item:
+        raise HTTPException(status_code=404, detail="Item not found")
+    item = crud.item.remove(db, id=id)
+    return item
--- a/app/api/endpoints/login.py
+++ b/app/api/endpoints/login.py
@ -0,0 +1,46 @@
+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
+from app.api import deps
+from app.core import security
+from app.core.config import settings
+from app.schemas.token import Token
+from app.schemas.user import User
+
+router = APIRouter()
+
+
+@router.post("/login/access-token", response_model=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=User)
+def test_token(current_user: User = Depends(deps.get_current_user)) -> Any:
+    """
+    Test access token
+    """
+    return current_user
--- a/app/api/endpoints/suppliers.py
+++ b/app/api/endpoints/suppliers.py
@ -0,0 +1,98 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from app import crud
+from app.api import deps
+from app.schemas.supplier import Supplier, SupplierCreate, SupplierUpdate
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[Supplier])
+def read_suppliers(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: Any = 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=Supplier)
+def create_supplier(
+    *,
+    db: Session = Depends(deps.get_db),
+    supplier_in: SupplierCreate,
+    current_user: Any = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new supplier.
+    """
+    supplier = crud.supplier.create(db, obj_in=supplier_in)
+    return supplier
+
+
+@router.put("/{id}", response_model=Supplier)
+def update_supplier(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    supplier_in: SupplierUpdate,
+    current_user: Any = 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.get("/{id}", response_model=Supplier)
+def read_supplier(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: Any = 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.delete("/{id}", response_model=Supplier)
+def delete_supplier(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: Any = Depends(deps.get_current_active_superuser),
+) -> 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 supplier has any items
+    items = crud.item.get_by_supplier(db, supplier_id=id)
+    if items:
+        raise HTTPException(
+            status_code=400,
+            detail="Cannot delete supplier with associated items. Remove the items first.",
+        )
+    
+    supplier = crud.supplier.remove(db, id=id)
+    return supplier
--- a/app/api/endpoints/transactions.py
+++ b/app/api/endpoints/transactions.py
@ -0,0 +1,144 @@
+from typing import Any, List, Optional
+
+from fastapi import APIRouter, Depends, HTTPException, Query
+from sqlalchemy.orm import Session
+
+from app import crud
+from app.api import deps
+from app.models.transaction import TransactionType
+from app.schemas.transaction import Transaction, TransactionCreate, TransactionUpdate
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[Transaction])
+def read_transactions(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    item_id: Optional[int] = None,
+    transaction_type: Optional[TransactionType] = None,
+    current_user: Any = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve transactions.
+    """
+    if item_id:
+        transactions = crud.transaction.get_by_item(db, item_id=item_id, skip=skip, limit=limit)
+    elif transaction_type:
+        transactions = crud.transaction.get_by_transaction_type(
+            db, transaction_type=transaction_type, skip=skip, limit=limit
+        )
+    else:
+        transactions = crud.transaction.get_multi(db, skip=skip, limit=limit)
+    return transactions
+
+
+@router.post("/", response_model=Transaction)
+def create_transaction(
+    *,
+    db: Session = Depends(deps.get_db),
+    transaction_in: TransactionCreate,
+    current_user: Any = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new transaction.
+    """
+    # Check if item exists
+    item = crud.item.get(db, id=transaction_in.item_id)
+    if not item:
+        raise HTTPException(
+            status_code=400,
+            detail=f"Item with ID {transaction_in.item_id} does not exist.",
+        )
+    
+    # Check if there's enough inventory for sales or returns
+    if transaction_in.transaction_type == TransactionType.SALE and item.quantity < transaction_in.quantity:
+        raise HTTPException(
+            status_code=400,
+            detail=f"Not enough inventory for item ID {transaction_in.item_id}. Available: {item.quantity}, Requested: {transaction_in.quantity}",
+        )
+    
+    # Set the user ID if not provided
+    if not transaction_in.user_id:
+        transaction_in_dict = transaction_in.dict()
+        transaction_in_dict["user_id"] = current_user.id
+        transaction_in = TransactionCreate(**transaction_in_dict)
+    
+    transaction = crud.transaction.create(db, obj_in=transaction_in)
+    return transaction
+
+
+@router.get("/{id}", response_model=Transaction)
+def read_transaction(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: Any = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get transaction by ID.
+    """
+    transaction = crud.transaction.get(db, id=id)
+    if not transaction:
+        raise HTTPException(status_code=404, detail="Transaction not found")
+    return transaction
+
+
+@router.put("/{id}", response_model=Transaction)
+def update_transaction(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    transaction_in: TransactionUpdate,
+    current_user: Any = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Update a transaction. Only superusers can update transactions.
+    """
+    transaction = crud.transaction.get(db, id=id)
+    if not transaction:
+        raise HTTPException(status_code=404, detail="Transaction not found")
+    
+    # Check if item exists if item_id is provided
+    if transaction_in.item_id and transaction_in.item_id != transaction.item_id:
+        if not crud.item.get(db, id=transaction_in.item_id):
+            raise HTTPException(
+                status_code=400,
+                detail=f"Item with ID {transaction_in.item_id} does not exist.",
+            )
+    
+    # TODO: Handle inventory adjustments when updating transactions
+    # This is complex and might require reversing the old transaction and applying the new one
+    
+    transaction = crud.transaction.update(db, db_obj=transaction, obj_in=transaction_in)
+    return transaction
+
+
+@router.delete("/{id}", response_model=Transaction)
+def delete_transaction(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: Any = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Delete a transaction. Only superusers can delete transactions.
+    """
+    transaction = crud.transaction.get(db, id=id)
+    if not transaction:
+        raise HTTPException(status_code=404, detail="Transaction not found")
+    
+    # Reverse the inventory impact of this transaction
+    item = crud.item.get(db, id=transaction.item_id)
+    quantity_change = transaction.quantity
+    if transaction.transaction_type in [TransactionType.PURCHASE, TransactionType.ADJUSTMENT]:
+        quantity_change = -quantity_change
+    elif transaction.transaction_type in [TransactionType.SALE, TransactionType.RETURN]:
+        quantity_change = quantity_change
+    
+    # Update item quantity
+    crud.item.update_quantity(db, item_id=transaction.item_id, quantity_change=quantity_change)
+    
+    transaction = crud.transaction.remove(db, id=id)
+    return transaction
--- a/app/api/endpoints/users.py
+++ b/app/api/endpoints/users.py
@ -0,0 +1,122 @@
+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
+from app.api import deps
+from app.core.config import settings
+from app.schemas.user import User, UserCreate, UserUpdate
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[User])
+def read_users(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: 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=User)
+def create_user(
+    *,
+    db: Session = Depends(deps.get_db),
+    user_in: UserCreate,
+    current_user: 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.put("/me", response_model=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: User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update own user.
+    """
+    current_user_data = jsonable_encoder(current_user)
+    user_in = 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("/me", response_model=User)
+def read_user_me(
+    db: Session = Depends(deps.get_db),
+    current_user: User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get current user.
+    """
+    return current_user
+
+
+@router.get("/{user_id}", response_model=User)
+def read_user_by_id(
+    user_id: int,
+    current_user: 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=User)
+def update_user(
+    *,
+    db: Session = Depends(deps.get_db),
+    user_id: int,
+    user_in: UserUpdate,
+    current_user: 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 id does not exist in the system",
+        )
+    user = crud.user.update(db, db_obj=user, obj_in=user_in)
+    return user
--- a/app/core/config.py
+++ b/app/core/config.py
@ -0,0 +1,31 @@
+import secrets
+from pathlib import Path
+from typing import Optional, Dict, Any, List
+
+from pydantic import BaseSettings, validator
+
+
+class Settings(BaseSettings):
+    API_V1_STR: str = "/api/v1"
+    SECRET_KEY: str = secrets.token_urlsafe(32)
+    # 60 minutes * 24 hours * 8 days = 8 days
+    ACCESS_TOKEN_EXPIRE_MINUTES: int = 60 * 24 * 8
+    
+    PROJECT_NAME: str = "Small Business Inventory Management System"
+    
+    # CORS allowed origins
+    BACKEND_CORS_ORIGINS: List[str] = ["*"]
+
+    @validator("BACKEND_CORS_ORIGINS", pre=True)
+    def assemble_cors_origins(cls, v: str | List[str]) -> List[str]:
+        if isinstance(v, str) and not v.startswith("["):
+            return [i.strip() for i in v.split(",")]
+        elif isinstance(v, (list, str)):
+            return v
+        raise ValueError(v)
+
+    class Config:
+        case_sensitive = True
+
+
+settings = Settings()
--- a/app/core/security.py
+++ b/app/core/security.py
@ -0,0 +1,33 @@
+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")
+
+ALGORITHM = "HS256"
+
+
+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=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)
--- a/app/crud/init.py
+++ b/app/crud/init.py
@ -0,0 +1,4 @@
+from app.crud.crud_item import item
+from app.crud.crud_supplier import supplier
+from app.crud.crud_transaction import transaction
+from app.crud.crud_user import user
--- a/app/crud/base.py
+++ b/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_class 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.dict(exclude_unset=True)
+        for field in obj_data:
+            if field in update_data:
+                setattr(db_obj, field, update_data[field])
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+
+    def remove(self, db: Session, *, id: int) -> ModelType:
+        obj = db.query(self.model).get(id)
+        db.delete(obj)
+        db.commit()
+        return obj
--- a/app/crud/crud_item.py
+++ b/app/crud/crud_item.py
@ -0,0 +1,49 @@
+from typing import List, Optional
+
+from fastapi.encoders import jsonable_encoder
+from sqlalchemy.orm import Session
+
+from app.crud.base import CRUDBase
+from app.models.item import Item
+from app.schemas.item import ItemCreate, ItemUpdate
+
+
+class CRUDItem(CRUDBase[Item, ItemCreate, ItemUpdate]):
+    def get_by_sku(self, db: Session, *, sku: str) -> Optional[Item]:
+        return db.query(Item).filter(Item.sku == sku).first()
+    
+    def get_by_supplier(
+        self, db: Session, *, supplier_id: int, skip: int = 0, limit: int = 100
+    ) -> List[Item]:
+        return (
+            db.query(Item)
+            .filter(Item.supplier_id == supplier_id)
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+    
+    def get_by_category(
+        self, db: Session, *, category: str, skip: int = 0, limit: int = 100
+    ) -> List[Item]:
+        return (
+            db.query(Item)
+            .filter(Item.category == category)
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+    
+    def update_quantity(
+        self, db: Session, *, item_id: int, quantity_change: int
+    ) -> Item:
+        item = self.get(db, id=item_id)
+        if item:
+            item.quantity += quantity_change
+            db.add(item)
+            db.commit()
+            db.refresh(item)
+        return item
+
+
+item = CRUDItem(Item)
--- a/app/crud/crud_supplier.py
+++ b/app/crud/crud_supplier.py
@ -0,0 +1,15 @@
+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()
+
+
+supplier = CRUDSupplier(Supplier)
--- a/app/crud/crud_transaction.py
+++ b/app/crud/crud_transaction.py
@ -0,0 +1,60 @@
+from typing import List, Optional
+
+from sqlalchemy.orm import Session
+
+from app.crud.base import CRUDBase
+from app.crud.crud_item import item as crud_item
+from app.models.transaction import Transaction, TransactionType
+from app.schemas.transaction import TransactionCreate, TransactionUpdate
+
+
+class CRUDTransaction(CRUDBase[Transaction, TransactionCreate, TransactionUpdate]):
+    def create(self, db: Session, *, obj_in: TransactionCreate) -> Transaction:
+        # Create transaction
+        db_obj = Transaction(
+            transaction_type=obj_in.transaction_type,
+            quantity=obj_in.quantity,
+            price_per_unit=obj_in.price_per_unit,
+            reference_number=obj_in.reference_number,
+            notes=obj_in.notes,
+            item_id=obj_in.item_id,
+            user_id=obj_in.user_id,
+            transaction_date=obj_in.transaction_date
+        )
+        db.add(db_obj)
+        
+        # Update item quantity based on transaction type
+        quantity_change = obj_in.quantity
+        if obj_in.transaction_type in [TransactionType.SALE, TransactionType.RETURN]:
+            quantity_change = -quantity_change
+        
+        crud_item.update_quantity(db, item_id=obj_in.item_id, quantity_change=quantity_change)
+        
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+    
+    def get_by_item(
+        self, db: Session, *, item_id: int, skip: int = 0, limit: int = 100
+    ) -> List[Transaction]:
+        return (
+            db.query(Transaction)
+            .filter(Transaction.item_id == item_id)
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+    
+    def get_by_transaction_type(
+        self, db: Session, *, transaction_type: TransactionType, skip: int = 0, limit: int = 100
+    ) -> List[Transaction]:
+        return (
+            db.query(Transaction)
+            .filter(Transaction.transaction_type == transaction_type)
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+
+
+transaction = CRUDTransaction(Transaction)
--- a/app/crud/crud_user.py
+++ b/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.dict(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)
--- a/app/db/base.py
+++ b/app/db/base.py
@ -0,0 +1,7 @@
+# Import all the models, so that Base has them before being
+# imported by Alembic
+from app.db.base_class import Base
+from app.models.item import Item
+from app.models.supplier import Supplier
+from app.models.transaction import Transaction
+from app.models.user import User
--- a/app/db/base_class.py
+++ b/app/db/base_class.py
@ -0,0 +1,14 @@
+from typing import Any
+
+from sqlalchemy.ext.declarative import as_declarative, declared_attr
+
+
+@as_declarative()
+class Base:
+    id: Any
+    __name__: str
+    
+    # Generate __tablename__ automatically based on class name
+    @declared_attr
+    def __tablename__(cls) -> str:
+        return cls.__name__.lower()
--- a/app/db/deps.py
+++ b/app/db/deps.py
@ -0,0 +1,60 @@
+from typing import Generator, Optional
+
+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.core import security
+from app.core.config import settings
+from app.db.session import SessionLocal
+from app.models.user import User
+from app.schemas.token import TokenPayload
+
+oauth2_scheme = 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(oauth2_scheme)
+) -> User:
+    try:
+        payload = jwt.decode(
+            token, settings.SECRET_KEY, algorithms=[security.ALGORITHM]
+        )
+        token_data = TokenPayload(**payload)
+    except (jwt.JWTError, ValidationError):
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Could not validate credentials",
+        )
+    user = db.query(User).filter(User.id == token_data.sub).first()
+    if not user:
+        raise HTTPException(status_code=404, detail="User not found")
+    return user
+
+
+def get_current_active_user(
+    current_user: User = Depends(get_current_user),
+) -> User:
+    if not current_user.is_active:
+        raise HTTPException(status_code=400, detail="Inactive user")
+    return current_user
+
+
+def get_current_active_superuser(
+    current_user: User = Depends(get_current_user),
+) -> User:
+    if not current_user.is_superuser:
+        raise HTTPException(
+            status_code=400, detail="The user doesn't have enough privileges"
+        )
+    return current_user
--- a/app/db/session.py
+++ b/app/db/session.py
@ -0,0 +1,15 @@
+from pathlib import Path
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+# Create DB directory
+DB_DIR = Path("/app") / "storage" / "db"
+DB_DIR.mkdir(parents=True, exist_ok=True)
+
+SQLALCHEMY_DATABASE_URL = f"sqlite:///{DB_DIR}/db.sqlite"
+
+engine = create_engine(
+    SQLALCHEMY_DATABASE_URL,
+    connect_args={"check_same_thread": False}
+)
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
--- a/app/models/item.py
+++ b/app/models/item.py
@ -0,0 +1,27 @@
+from sqlalchemy import Column, Integer, String, Float, ForeignKey, DateTime
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.db.base_class import Base
+
+
+class Item(Base):
+    id = Column(Integer, primary_key=True, index=True)
+    name = Column(String, index=True)
+    description = Column(String, nullable=True)
+    sku = Column(String, index=True, unique=True)
+    quantity = Column(Integer, default=0)
+    unit_price = Column(Float, nullable=False)
+    category = Column(String, index=True)
+    location = Column(String, nullable=True)
+    
+    # Timestamps
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now())
+    
+    # Foreign Keys
+    supplier_id = Column(Integer, ForeignKey("supplier.id"), nullable=True)
+    
+    # Relationships
+    supplier = relationship("Supplier", back_populates="items")
+    transactions = relationship("Transaction", back_populates="item")
--- a/app/models/supplier.py
+++ b/app/models/supplier.py
@ -0,0 +1,21 @@
+from sqlalchemy import Column, Integer, String, DateTime
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.db.base_class import Base
+
+
+class Supplier(Base):
+    id = Column(Integer, primary_key=True, index=True)
+    name = Column(String, index=True)
+    contact_name = Column(String, nullable=True)
+    email = Column(String, nullable=True)
+    phone = Column(String, nullable=True)
+    address = Column(String, nullable=True)
+    
+    # Timestamps
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now())
+    
+    # Relationships
+    items = relationship("Item", back_populates="supplier")
--- a/app/models/transaction.py
+++ b/app/models/transaction.py
@ -0,0 +1,37 @@
+from sqlalchemy import Column, Integer, String, Float, ForeignKey, DateTime, Enum
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+import enum
+
+from app.db.base_class import Base
+
+
+class TransactionType(str, enum.Enum):
+    PURCHASE = "purchase"
+    SALE = "sale"
+    ADJUSTMENT = "adjustment"
+    RETURN = "return"
+
+
+class Transaction(Base):
+    id = Column(Integer, primary_key=True, index=True)
+    transaction_type = Column(Enum(TransactionType), nullable=False)
+    quantity = Column(Integer, nullable=False)
+    price_per_unit = Column(Float, nullable=False)
+    
+    # Reference information
+    reference_number = Column(String, nullable=True)
+    notes = Column(String, nullable=True)
+    
+    # Timestamps
+    transaction_date = Column(DateTime(timezone=True), default=func.now())
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now())
+    
+    # Foreign Keys
+    item_id = Column(Integer, ForeignKey("item.id"), nullable=False)
+    user_id = Column(Integer, ForeignKey("user.id"), nullable=True)
+    
+    # Relationships
+    item = relationship("Item", back_populates="transactions")
+    user = relationship("User")
--- a/app/models/user.py
+++ b/app/models/user.py
@ -0,0 +1,13 @@
+from sqlalchemy import Boolean, Column, Integer, String
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import Base
+
+
+class User(Base):
+    id = Column(Integer, primary_key=True, index=True)
+    full_name = Column(String, index=True)
+    email = Column(String, unique=True, index=True, nullable=False)
+    hashed_password = Column(String, nullable=False)
+    is_active = Column(Boolean(), default=True)
+    is_superuser = Column(Boolean(), default=False)
--- a/app/schemas/item.py
+++ b/app/schemas/item.py
@ -0,0 +1,48 @@
+from typing import Optional
+from datetime import datetime
+from pydantic import BaseModel
+
+
+# Shared properties
+class ItemBase(BaseModel):
+    name: str
+    description: Optional[str] = None
+    sku: str
+    quantity: int = 0
+    unit_price: float
+    category: str
+    location: Optional[str] = None
+    supplier_id: Optional[int] = None
+
+
+# Properties to receive on item creation
+class ItemCreate(ItemBase):
+    pass
+
+
+# Properties to receive on item update
+class ItemUpdate(ItemBase):
+    name: Optional[str] = None
+    sku: Optional[str] = None
+    unit_price: Optional[float] = None
+    category: Optional[str] = None
+
+
+# Properties shared by models stored in DB
+class ItemInDBBase(ItemBase):
+    id: int
+    created_at: datetime
+    updated_at: Optional[datetime] = None
+
+    class Config:
+        orm_mode = True
+
+
+# Properties to return to client
+class Item(ItemInDBBase):
+    pass
+
+
+# Properties properties stored in DB
+class ItemInDB(ItemInDBBase):
+    pass
--- a/app/schemas/supplier.py
+++ b/app/schemas/supplier.py
@ -0,0 +1,42 @@
+from typing import Optional
+from datetime import datetime
+from pydantic import BaseModel, EmailStr
+
+
+# Shared properties
+class SupplierBase(BaseModel):
+    name: str
+    contact_name: Optional[str] = None
+    email: Optional[EmailStr] = None
+    phone: Optional[str] = None
+    address: Optional[str] = None
+
+
+# Properties to receive on supplier creation
+class SupplierCreate(SupplierBase):
+    pass
+
+
+# Properties to receive on supplier update
+class SupplierUpdate(SupplierBase):
+    name: Optional[str] = None
+
+
+# Properties shared by models stored in DB
+class SupplierInDBBase(SupplierBase):
+    id: int
+    created_at: datetime
+    updated_at: Optional[datetime] = None
+
+    class Config:
+        orm_mode = True
+
+
+# Properties to return to client
+class Supplier(SupplierInDBBase):
+    pass
+
+
+# Properties properties stored in DB
+class SupplierInDB(SupplierInDBBase):
+    pass
--- a/app/schemas/token.py
+++ b/app/schemas/token.py
@ -0,0 +1,12 @@
+from typing import Optional
+
+from pydantic import BaseModel
+
+
+class Token(BaseModel):
+    access_token: str
+    token_type: str
+
+
+class TokenPayload(BaseModel):
+    sub: Optional[int] = None
--- a/app/schemas/transaction.py
+++ b/app/schemas/transaction.py
@ -0,0 +1,50 @@
+from typing import Optional
+from datetime import datetime
+from pydantic import BaseModel
+
+from app.models.transaction import TransactionType
+
+
+# Shared properties
+class TransactionBase(BaseModel):
+    transaction_type: TransactionType
+    quantity: int
+    price_per_unit: float
+    reference_number: Optional[str] = None
+    notes: Optional[str] = None
+    item_id: int
+    user_id: Optional[int] = None
+    transaction_date: Optional[datetime] = None
+
+
+# Properties to receive on transaction creation
+class TransactionCreate(TransactionBase):
+    pass
+
+
+# Properties to receive on transaction update
+class TransactionUpdate(TransactionBase):
+    transaction_type: Optional[TransactionType] = None
+    quantity: Optional[int] = None
+    price_per_unit: Optional[float] = None
+    item_id: Optional[int] = None
+
+
+# Properties shared by models stored in DB
+class TransactionInDBBase(TransactionBase):
+    id: int
+    created_at: datetime
+    updated_at: Optional[datetime] = None
+
+    class Config:
+        orm_mode = True
+
+
+# Properties to return to client
+class Transaction(TransactionInDBBase):
+    pass
+
+
+# Properties properties stored in DB
+class TransactionInDB(TransactionInDBBase):
+    pass
--- a/app/schemas/user.py
+++ b/app/schemas/user.py
@ -0,0 +1,39 @@
+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:
+        orm_mode = True
+
+
+# Additional properties to return via API
+class User(UserInDBBase):
+    pass
+
+
+# Additional properties stored in DB
+class UserInDB(UserInDBBase):
+    hashed_password: str
--- a/main.py
+++ b/main.py
@ -0,0 +1,33 @@
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+
+from app.api.api import api_router
+from app.core.config import settings
+
+app = FastAPI(
+    title=settings.PROJECT_NAME,
+    openapi_url=f"{settings.API_V1_STR}/openapi.json",
+    version="0.1.0",
+)
+
+# Set all CORS enabled origins
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+app.include_router(api_router, prefix=settings.API_V1_STR)
+
+@app.get("/health", tags=["Health"])
+def health_check():
+    """
+    Health check endpoint
+    """
+    return {"status": "ok"}
+
+if __name__ == "__main__":
+    import uvicorn
+    uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=True)
--- a/requirements.txt
+++ b/requirements.txt
@ -0,0 +1,11 @@
+fastapi>=0.95.0
+uvicorn>=0.21.1
+sqlalchemy>=2.0.7
+pydantic>=1.10.7
+alembic>=1.10.2
+python-jose>=3.3.0
+passlib>=1.7.4
+python-multipart>=0.0.6
+email-validator>=2.0.0
+python-dateutil>=2.8.2
+bcrypt>=4.0.1