from datetime import datetime, timedelta
from typing import Optional
from fastapi import APIRouter, Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer, OAuth2PasswordRequestForm
from jose import JWTError, jwt
import bcrypt
from sqlalchemy.orm import Session

from database import get_db
import models.db_models as db_models
import models.schemas as schemas
import os
from google.oauth2 import id_token
from google.auth.transport import requests

# Configuration
SECRET_KEY = os.getenv("JWT_SECRET_KEY", "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7")
GOOGLE_CLIENT_ID = os.getenv("GOOGLE_CLIENT_ID", "YOUR_GOOGLE_CLIENT_ID")
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 60 * 24 * 7 # 1 week

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/auth/login", auto_error=False)

router = APIRouter(prefix="/auth", tags=["Authentication"])

def verify_password(plain_password: str, hashed_password: str) -> bool:
    # Handle the case where passlib originally generated the hash
    try:
        return bcrypt.checkpw(plain_password.encode('utf-8'), hashed_password.encode('utf-8'))
    except ValueError:
        return False

def get_password_hash(password: str) -> str:
    return bcrypt.hashpw(password.encode('utf-8'), bcrypt.gensalt()).decode('utf-8')

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

def get_current_user(token: str = Depends(oauth2_scheme), db: Session = Depends(get_db)):
    if not token or token == "null" or token == "undefined":
        return None
        
    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
        token_data = schemas.TokenData(username=username)
    except JWTError:
        raise credentials_exception
        
    user = db.query(db_models.User).filter(db_models.User.username == token_data.username).first()
    if user is None:
        raise credentials_exception
    return user

@router.post("/register", response_model=schemas.UserResponse)
def register_user(user: schemas.UserCreate, db: Session = Depends(get_db)):
    db_user = db.query(db_models.User).filter(
        (db_models.User.username == user.username) | (db_models.User.email == user.email)
    ).first()
    if db_user:
        raise HTTPException(status_code=400, detail="Username or email already registered")
    
    hashed_password = get_password_hash(user.password)
    db_user = db_models.User(
        username=user.username,
        email=user.email,
        hashed_password=hashed_password
    )
    db.add(db_user)
    db.commit()
    db.refresh(db_user)
    return db_user

@router.post("/login", response_model=schemas.Token)
def login_for_access_token(form_data: OAuth2PasswordRequestForm = Depends(), db: Session = Depends(get_db)):
    user = db.query(db_models.User).filter(db_models.User.username == form_data.username).first()
    if not user or not verify_password(form_data.password, user.hashed_password):
        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"}

@router.get("/me", response_model=schemas.UserResponse)
def read_users_me(current_user: db_models.User = Depends(get_current_user)):
    if not current_user:
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Not authenticated")
    return current_user

@router.post("/google", response_model=schemas.Token)
def google_auth(google_token: schemas.GoogleToken, db: Session = Depends(get_db)):
    try:
        # Verify the Google token
        idinfo = id_token.verify_oauth2_token(
            google_token.token, 
            requests.Request(), 
            GOOGLE_CLIENT_ID,
            clock_skew_in_seconds=10
        )
        
        email = idinfo['email']
        name = idinfo.get('name', email.split('@')[0])
        
        # Check if user exists
        user = db.query(db_models.User).filter(db_models.User.email == email).first()
        
        if not user:
            # Create a new user if they don't exist
            # Generate a random password since they use Google to login
            import secrets
            random_password = secrets.token_urlsafe(32)
            hashed_password = get_password_hash(random_password)
            
            # Ensure username is unique
            base_username = name.lower().replace(" ", "")
            username = base_username
            counter = 1
            while db.query(db_models.User).filter(db_models.User.username == username).first():
                username = f"{base_username}{counter}"
                counter += 1
                
            user = db_models.User(
                username=username,
                email=email,
                hashed_password=hashed_password
            )
            db.add(user)
            db.commit()
            db.refresh(user)
            
        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"}
        
    except ValueError as e:
        # Invalid token
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail=f"Invalid Google token: {str(e)}",
            headers={"WWW-Authenticate": "Bearer"},
        )