"""
Authentication and security utilities
"""
from datetime import datetime, timedelta, timezone
from typing import Optional, Union, Tuple
from uuid import uuid4
from jose import JWTError, jwt
from passlib.context import CryptContext
from sqlalchemy.orm import Session
from fastapi import HTTPException, status, Depends
from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials

from app.config import settings
from app.database.base import get_db
from app.models.user import User
from app.models.auth import RefreshToken

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

# JWT Security
security = HTTPBearer()


def verify_password(plain_password: str, hashed_password: str) -> bool:
    """Verify a plain password against its hash"""
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password: str) -> str:
    """Generate password hash"""
    return pwd_context.hash(password)


def _encode_with_rotation(payload: dict) -> str:
    """Encode JWT with active secret and algorithm."""
    return jwt.encode(payload, settings.secret_key, algorithm=settings.algorithm)


def _decode_with_rotation(token: str) -> dict:
    """Decode JWT trying current then previous secret if set."""
    try:
        return jwt.decode(token, settings.secret_key, algorithms=[settings.algorithm])
    except JWTError:
        # Try previous secret to allow seamless rotation
        if settings.previous_secret_key:
            try:
                return jwt.decode(token, settings.previous_secret_key, algorithms=[settings.algorithm])
            except JWTError:
                pass
        raise


def create_access_token(data: dict, expires_delta: Optional[timedelta] = None) -> str:
    """Create JWT access token"""
    to_encode = data.copy()
    expire = datetime.now(timezone.utc) + (
        expires_delta if expires_delta else timedelta(minutes=settings.access_token_expire_minutes)
    )
    to_encode.update({
        "exp": expire,
        "iat": datetime.now(timezone.utc),
        "type": "access",
    })
    return _encode_with_rotation(to_encode)


def create_refresh_token(user: User, user_agent: Optional[str], ip_address: Optional[str], db: Session) -> str:
    """Create refresh token, store its JTI in DB for revocation."""
    jti = uuid4().hex
    expire = datetime.now(timezone.utc) + timedelta(minutes=settings.refresh_token_expire_minutes)
    payload = {
        "sub": user.username,
        "uid": user.id,
        "jti": jti,
        "type": "refresh",
        "exp": expire,
        "iat": datetime.now(timezone.utc),
    }
    token = _encode_with_rotation(payload)

    db_token = RefreshToken(
        user_id=user.id,
        jti=jti,
        user_agent=user_agent,
        ip_address=ip_address,
        issued_at=datetime.now(timezone.utc),
        expires_at=expire,
        revoked=False,
    )
    db.add(db_token)
    db.commit()
    return token


def _to_utc_aware(dt: Optional[datetime]) -> Optional[datetime]:
    """Convert a datetime to UTC-aware. If naive, assume it's already UTC and attach tzinfo."""
    if dt is None:
        return None
    if dt.tzinfo is None:
        return dt.replace(tzinfo=timezone.utc)
    return dt.astimezone(timezone.utc)


def verify_token(token: str) -> Optional[str]:
    """Verify JWT token and return username"""
    try:
        payload = _decode_with_rotation(token)
        username: str = payload.get("sub")
        token_type: str = payload.get("type")
        if username is None:
            return None
        # Only accept access tokens for auth
        if token_type and token_type != "access":
            return None
        return username
    except JWTError:
        return None


def decode_refresh_token(token: str) -> Optional[dict]:
    """Decode refresh token and return payload if valid and not revoked."""
    try:
        payload = _decode_with_rotation(token)
        if payload.get("type") != "refresh":
            return None
        return payload
    except JWTError:
        return None


def is_refresh_token_revoked(jti: str, db: Session) -> bool:
    token_row = db.query(RefreshToken).filter(RefreshToken.jti == jti).first()
    if not token_row:
        return True
    if token_row.revoked:
        return True
    expires_at_utc = _to_utc_aware(token_row.expires_at)
    now_utc = datetime.now(timezone.utc)
    return expires_at_utc is not None and expires_at_utc <= now_utc


def revoke_refresh_token(jti: str, db: Session) -> None:
    token_row = db.query(RefreshToken).filter(RefreshToken.jti == jti).first()
    if token_row and not token_row.revoked:
        token_row.revoked = True
        token_row.revoked_at = datetime.now(timezone.utc)
        db.commit()


def authenticate_user(db: Session, username: str, password: str) -> Optional[User]:
    """Authenticate user credentials"""
    user = db.query(User).filter(User.username == username).first()
    if not user:
        return None
    if not verify_password(password, user.hashed_password):
        return None
    return user


def get_current_user(
    credentials: HTTPAuthorizationCredentials = Depends(security),
    db: Session = Depends(get_db)
) -> User:
    """Get current authenticated user"""
    token = credentials.credentials
    username = verify_token(token)
    
    if username is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Could not validate credentials",
            headers={"WWW-Authenticate": "Bearer"},
        )
    
    user = db.query(User).filter(User.username == username).first()
    if user is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="User not found",
            headers={"WWW-Authenticate": "Bearer"},
        )
    
    if not user.is_active:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Inactive user"
        )
    
    return user


def get_admin_user(current_user: User = Depends(get_current_user)) -> User:
    """Require admin privileges"""
    if not current_user.is_admin:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Not enough permissions"
        )
    return current_user