from datetime import datetime, timedelta
from typing import Optional
from fastapi import APIRouter, Depends, HTTPException, Response
from fastapi.security import OAuth2PasswordBearer, OAuth2PasswordRequestForm
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel

router = APIRouter()

# Constants
SECRET_KEY = "your-secret-key-here"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30

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

# Models
class User(BaseModel):
    username: str
    email: str
    full_name: Optional[str] = None
    disabled: Optional[bool] = False

class UserInDB(User):
    hashed_password: str

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

class TokenData(BaseModel):
    username: Optional[str] = None

# 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 get_user(username: str):
    if username in fake_users_db:
        user_dict = fake_users_db[username]
        return UserInDB(**user_dict)
    return None

def authenticate_user(username: str, password: str):
    user = get_user(username)
    if not user:
        return False
    if 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)):
    credentials_exception = HTTPException(
        status_code=401,
        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
        token_data = TokenData(username=username)
    except JWTError:
        raise credentials_exception
    user = get_user(username=token_data.username)
    if user is None:
        raise credentials_exception
    return user

# Login endpoint
@router.post("/login", response_model=Token)
async def login(response: Response, form_data: OAuth2PasswordRequestForm = Depends()):
    """Authenticate user and return JWT token"""
    user = authenticate_user(form_data.username, form_data.password)
    if not user:
        raise HTTPException(
            status_code=401,
            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
    )
    
    # Set cookie
    response.set_cookie(
        key="access_token",
        value=f"Bearer {access_token}",
        httponly=True,
        max_age=1800,
        expires=1800,
        secure=True,
        samesite="lax"
    )
    
    return {
        "access_token": access_token,
        "token_type": "bearer",
        "message": "Login successful",
        "user": {
            "username": user.username,
            "email": user.email,
            "full_name": user.full_name
        }
    }

# Protected route example
@router.get("/me", response_model=User)
async def read_users_me(current_user: User = Depends(get_current_user)):
    """Get current user information"""
    return current_user