from datetime import timedelta, timezone, datetime
from typing import Annotated
from fastapi import Depends, HTTPException, Request, Response, status
from pydantic import BaseModel, ValidationError
import jwt
from jwt.exceptions import ExpiredSignatureError, InvalidTokenError
from sqlmodel import Session, select
from db import engine, User
from fastapi.security import (
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    SecurityScopes,
)
from pydantic_settings import BaseSettings, SettingsConfigDict
from passlib.context import CryptContext
from sqlalchemy.exc import OperationalError


class Config(BaseSettings):
    secret_key: str = ""
    access_token_expire_minutes: int = 15
    model_config = SettingsConfigDict(
        env_file=".env", env_file_encoding="utf-8", extra="ignore"
    )


config = Config()


class Token(BaseModel):
    access_token: str


class TokenData(BaseModel):
    username: str | None = None
    scopes: list[str] = []


pwd_context = CryptContext(schemes=["argon2"], deprecated="auto")


oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl="api/token",
    scopes={
        "analysis": "Access the results.",
    },
)


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 | None):
    if username:
        try:
            with Session(engine) as session:
                return session.exec(
                    select(User).where(User.username == username)
                ).one_or_none()
        except OperationalError:
            return


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: timedelta | None = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(
            seconds=config.access_token_expire_minutes
        )
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, config.secret_key, algorithm="HS256")
    return encoded_jwt


async def get_current_user(security_scopes: SecurityScopes, request: Request):
    if security_scopes.scopes:
        authenticate_value = f'Bearer scope="{security_scopes.scope_str}"'
    else:
        authenticate_value = "Bearer"
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": authenticate_value},
    )
    access_token = request.cookies.get("access_token")
    if not access_token:
        raise credentials_exception
    try:
        payload = jwt.decode(access_token, config.secret_key, algorithms=["HS256"])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(username=username, scopes=token_scopes)
    except ExpiredSignatureError:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Access token expired",
            headers={"WWW-Authenticate": authenticate_value},
        )
    except (InvalidTokenError, ValidationError):
        raise credentials_exception
    user = get_user(username=token_data.username)
    if user is None:
        raise credentials_exception
    for scope in security_scopes.scopes:
        if scope not in token_data.scopes:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Not enough permissions",
                headers={"WWW-Authenticate": authenticate_value},
            )
    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


async def login_for_access_token(
    form_data: Annotated[OAuth2PasswordRequestForm, Depends()], response: Response
) -> Token:
    user = authenticate_user(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"},
        )
    allowed_scopes = set(user.scopes.split())
    requested_scopes = set(form_data.scopes)
    access_token = create_access_token(
        data={"sub": user.username, "scopes": list(allowed_scopes)}
    )
    response.set_cookie(
        "access_token",
        value=access_token,
        httponly=True,
        samesite="strict",
        max_age=15,
    )
    return Token(access_token=access_token)


async def logout(response: Response):
    response.set_cookie("access_token", "", expires=0, httponly=True, samesite="strict")
    return {"message": "Successfully logged out"}


async def read_users_me(
    current_user: Annotated[User, Depends(get_current_active_user)],
):
    return current_user


async def read_own_items(
    current_user: Annotated[User, Depends(get_current_active_user)],
):
    return [{"item_id": "Foo", "owner": current_user.username}]