from dataclasses import dataclass
from uuid import UUID

import jwt
from fastapi import Depends, HTTPException, Request, status
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.config import settings
from app.core.database import get_session
from app.models.user import User


@dataclass
class AuthUser:
    """Authenticated user info extracted from JWT."""

    id: str  # Supabase user UUID
    email: str | None = None
    role: str | None = None


def _extract_token(request: Request) -> str | None:
    """Extract Bearer token from Authorization header."""
    auth_header = request.headers.get("Authorization")
    if not auth_header:
        return None
    parts = auth_header.split()
    if len(parts) != 2 or parts[0].lower() != "bearer":
        return None
    return parts[1]


def _verify_jwt(token: str) -> dict | None:
    """Verify JWT against Supabase JWT secret. Returns payload or None."""
    if not settings.supabase_jwt_secret:
        return None
    try:
        payload = jwt.decode(
            token,
            settings.supabase_jwt_secret,
            algorithms=["HS256"],
            audience="authenticated",
        )
        return payload
    except jwt.ExpiredSignatureError:
        return None
    except jwt.InvalidTokenError:
        return None


def get_current_user(request: Request) -> AuthUser | None:
    """
    Extract and verify the current user from the request.
    Returns AuthUser if valid token, None otherwise.
    """
    token = _extract_token(request)
    if not token:
        return None

    payload = _verify_jwt(token)
    if not payload:
        return None

    # Supabase JWT has 'sub' as user ID
    user_id = payload.get("sub")
    if not user_id:
        return None

    return AuthUser(
        id=user_id,
        email=payload.get("email"),
        role=payload.get("role"),
    )


def require_auth(user: AuthUser | None = Depends(get_current_user)) -> AuthUser:
    """
    Dependency that requires authentication.
    Raises 401 if no valid token is present.
    """
    if user is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Authentication required",
            headers={"WWW-Authenticate": "Bearer"},
        )
    return user


async def require_admin(
    user: AuthUser = Depends(require_auth),
    session: AsyncSession = Depends(get_session),
) -> AuthUser:
    """
    Dependency that requires admin privileges.
    Raises 401 if not authenticated, 403 if not an admin.
    """
    result = await session.execute(select(User).where(User.id == UUID(user.id)))
    db_user = result.scalar_one_or_none()

    if db_user is None or not db_user.is_admin:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Admin access required",
        )
    return user