main.py

# main.py
from fastapi import FastAPI, HTTPException, Depends, status
from fastapi.security import OAuth2PasswordBearer, OAuth2PasswordRequestForm
from fastapi.middleware.cors import CORSMiddleware
from pydantic import BaseModel
from typing import List, Optional
from sqlalchemy import create_engine, Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, Session
from passlib.context import CryptContext
from datetime import datetime, timedelta
from jose import JWTError, jwt
import os
from dotenv import load_dotenv

# JWT Configuration
load_dotenv()  # This loads variables from a .env file
SECRET_KEY = os.getenv("SECRET_KEY")
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30

app = FastAPI()

# CORS configuration
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# SQLite Database setup
SQLALCHEMY_DATABASE_URL = "sqlite:///./test.db"
engine = create_engine(SQLALCHEMY_DATABASE_URL, connect_args={"check_same_thread": False})
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
Base = declarative_base()

class UserDB(Base):
    __tablename__ = "users"

    id = Column(Integer, primary_key=True, index=True)
    username = Column(String, unique=True, index=True)
    hashed_password = Column(String)

class ItemDB(Base):
    __tablename__ = "items"

    id = Column(Integer, primary_key=True, index=True)
    name = Column(String, index=True)
    description = Column(String)
    owner_id = Column(Integer)

Base.metadata.create_all(bind=engine)

# Pydantic models
class UserCreate(BaseModel):
    username: str
    password: str

class User(BaseModel):
    id: int
    username: str

    class Config:
        orm_mode = True

class ItemCreate(BaseModel):
    name: str
    description: str

class Item(ItemCreate):
    id: int
    owner_id: int

    class Config:
        orm_mode = True

class Token(BaseModel):
    access_token: str
    token_type: str

# Password hashing
pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

# Dependency to get database session
def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()

# Helper functions
def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)

def get_password_hash(password):
    return pwd_context.hash(password)

def authenticate_user(db: Session, username: str, password: str):
    user = db.query(UserDB).filter(UserDB.username == username).first()
    if not user or not verify_password(password, user.hashed_password):
        return False
    return user

def create_access_token(data: dict, expires_delta: Optional[timedelta] = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.utcnow() + expires_delta
    else:
        expire = datetime.utcnow() + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt

async def get_current_user(token: str = Depends(oauth2_scheme), db: Session = Depends(get_db)):
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception
    user = db.query(UserDB).filter(UserDB.username == username).first()
    if user is None:
        raise credentials_exception
    return user

# Authentication endpoints
@app.post("/register", response_model=User)
def register(user: UserCreate, db: Session = Depends(get_db)):
    db_user = db.query(UserDB).filter(UserDB.username == user.username).first()
    if db_user:
        raise HTTPException(status_code=400, detail="Username already registered")
    hashed_password = get_password_hash(user.password)
    db_user = UserDB(username=user.username, hashed_password=hashed_password)
    db.add(db_user)
    db.commit()
    db.refresh(db_user)
    return db_user

@app.post("/token", response_model=Token)
async def login(form_data: OAuth2PasswordRequestForm = Depends(), db: Session = Depends(get_db)):
    user = authenticate_user(db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect username or password",
            headers={"WWW-Authenticate": "Bearer"},
        )
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.username}, expires_delta=access_token_expires
    )
    return {"access_token": access_token, "token_type": "bearer"}

# Protected item endpoints
@app.post("/items/", response_model=Item)
def create_item(item: ItemCreate, current_user: User = Depends(get_current_user), db: Session = Depends(get_db)):
    db_item = ItemDB(name=item.name, description=item.description, owner_id=current_user.id)
    db.add(db_item)
    db.commit()
    db.refresh(db_item)
    return db_item

@app.get("/items/", response_model=List[Item])
def read_items(skip: int = 0, limit: int = 100, current_user: User = Depends(get_current_user), db: Session = Depends(get_db)):
    items = db.query(ItemDB).filter(ItemDB.owner_id == current_user.id).offset(skip).limit(limit).all()
    return items

@app.get("/items/{item_id}", response_model=Item)
def read_item(item_id: int, current_user: User = Depends(get_current_user), db: Session = Depends(get_db)):
    item = db.query(ItemDB).filter(ItemDB.id == item_id, ItemDB.owner_id == current_user.id).first()
    if item is None:
        raise HTTPException(status_code=404, detail="Item not found")
    return item

@app.put("/items/{item_id}", response_model=Item)
def update_item(item_id: int, item: ItemCreate, current_user: User = Depends(get_current_user), db: Session = Depends(get_db)):
    db_item = db.query(ItemDB).filter(ItemDB.id == item_id, ItemDB.owner_id == current_user.id).first()
    if db_item is None:
        raise HTTPException(status_code=404, detail="Item not found")
    db_item.name = item.name
    db_item.description = item.description
    db.commit()
    db.refresh(db_item)
    return db_item

@app.delete("/items/{item_id}")
def delete_item(item_id: int, current_user: User = Depends(get_current_user), db: Session = Depends(get_db)):
    db_item = db.query(ItemDB).filter(ItemDB.id == item_id, ItemDB.owner_id == current_user.id).first()
    if db_item is None:
        raise HTTPException(status_code=404, detail="Item not found")
    db.delete(db_item)
    db.commit()
    return {"message": "Item deleted successfully"}

if __name__ == "__main__":
    import uvicorn
    uvicorn.run(app, host="0.0.0.0", port=8000)