from datetime import timedelta, datetime, timezone
from typing import Annotated

import jwt
from fastapi import Depends, HTTPException
from passlib.exc import InvalidTokenError
from starlette import status

from config import SECRET_KEY, get_fake_users_db, pwd_context, oauth2_scheme, ALGORITHM
from models import UserInDB, User

import base64
import hashlib
import hmac

def verify_password(plain_password, hashed_password):
    try:
        # Decode the stored hash
        decoded = base64.b64decode(hashed_password)
        salt, stored_hash = decoded[:16], decoded[16:]
        
        # Hash the plain password with the same salt
        key = hashlib.sha256(salt).digest()
        new_hash = hmac.new(key, plain_password.encode('utf-8'), hashlib.sha256).digest()
        
        # Compare the new hash with the stored hash
        return hmac.compare_digest(new_hash, stored_hash)
    except (TypeError, ValueError, base64.binascii.Error):
        # This will catch any decoding errors or incorrect hash format
        return False


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


def get_user(db, username: str):
    if username in db:
        user_dict = db[username]
        return UserInDB(**user_dict)


from fastapi import HTTPException, status

def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        print(f"User not found: {username}")  # Debug print
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect username",
            headers={"WWW-Authenticate": "Bearer"},
        )
    print(f"Stored hash: {user.hashed_password}")  # Debug print
    print(f"Provided password: {password}")  # Debug print
    if not verify_password(password, user.hashed_password):
        print("Password verification failed")  # Debug print
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect password",
            headers={"WWW-Authenticate": "Bearer"},
        )
    return user


def create_access_token(data: dict, expires_delta: timedelta | None = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + 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: Annotated[str, Depends(oauth2_scheme)]):
    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 = User(username=username)
    except InvalidTokenError:
        raise credentials_exception
    user = get_user(get_fake_users_db(), username=token_data.username)
    if user is None:
        raise credentials_exception
    return user


async def get_current_active_user(
        current_user: Annotated[User, Depends(get_current_user)],
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user