from datetime import datetime, timedelta, timezone
from typing import Optional, List
from jose import JWTError, jwt
from passlib.context import CryptContext
from fastapi import Depends, HTTPException, status
from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
from sqlalchemy.orm import Session
import os
import secrets
from database import get_db
from models import User, UserRole, Permission, RolePermission, Role

pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
security = HTTPBearer()

JWT_SECRET = os.environ.get('JWT_SECRET', 'your-secret-key')
JWT_ALGORITHM = os.environ.get('JWT_ALGORITHM', 'HS256')
ACCESS_TOKEN_EXPIRE_MINUTES = int(os.environ.get('ACCESS_TOKEN_EXPIRE_MINUTES', 30))

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 generate_reset_token():
    """Generate secure random token for password reset"""
    return secrets.token_urlsafe(32)

def create_password_reset_token(user, db):
    """Create reset token with 1-hour expiration"""
    token = generate_reset_token()
    expires = datetime.now(timezone.utc) + timedelta(hours=1)

    user.password_reset_token = token
    user.password_reset_expires = expires
    db.commit()

    return token

def verify_reset_token(token, db):
    """Verify token is valid and not expired"""
    user = db.query(User).filter(User.password_reset_token == token).first()

    if not user:
        return None

    if user.password_reset_expires < datetime.now(timezone.utc):
        return None  # Token expired

    return user

def get_user_role_code(user: User) -> str:
    """
    Get user's role code from either dynamic role system or legacy enum.
    Supports backward compatibility during migration (Phase 3).

    Args:
        user: User object

    Returns:
        Role code string (e.g., "superadmin", "admin", "member", "guest")
    """
    # Prefer dynamic role if set (Phase 3+)
    if user.role_id is not None and user.role_obj is not None:
        return user.role_obj.code

    # Fallback to legacy enum (Phase 1-2)
    return user.role.value

def create_access_token(data: dict, expires_delta: Optional[timedelta] = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, JWT_SECRET, algorithm=JWT_ALGORITHM)
    return encoded_jwt

def decode_token(token: str):
    try:
        payload = jwt.decode(token, JWT_SECRET, algorithms=[JWT_ALGORITHM])
        return payload
    except JWTError:
        return None

async def get_current_user(
    credentials: HTTPAuthorizationCredentials = Depends(security),
    db: Session = Depends(get_db)
) -> User:
    token = credentials.credentials
    payload = decode_token(token)
    
    if payload is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid authentication credentials",
            headers={"WWW-Authenticate": "Bearer"},
        )
    
    user_id: str = payload.get("sub")
    if user_id is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid authentication credentials",
            headers={"WWW-Authenticate": "Bearer"},
        )
    
    user = db.query(User).filter(User.id == user_id).first()
    if user is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="User not found",
            headers={"WWW-Authenticate": "Bearer"},
        )
    
    return user

async def get_current_admin_user(current_user: User = Depends(get_current_user)) -> User:
    """Require user to be admin or superadmin"""
    role_code = get_user_role_code(current_user)
    if role_code not in ["admin", "superadmin"]:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Not enough permissions"
        )
    return current_user

async def get_active_member(current_user: User = Depends(get_current_user)) -> User:
    """Require user to be active member with valid payment"""
    from models import UserStatus

    if current_user.status != UserStatus.active:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Active membership required. Please complete payment."
        )

    role_code = get_user_role_code(current_user)
    if role_code not in ["member", "admin", "superadmin"]:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Member access only"
        )

    return current_user


# ============================================================
# RBAC Permission System
# ============================================================

async def get_user_permissions(user: User, db: Session) -> List[str]:
    """
    Get all permission codes for user's role.
    Superadmin automatically gets all permissions.
    Uses request-level caching to avoid repeated DB queries.
    Supports both dynamic roles (role_id) and legacy enum (role).

    Args:
        user: Current authenticated user
        db: Database session

    Returns:
        List of permission code strings (e.g., ["users.view", "events.create"])
    """
    # Check if permissions are already cached for this request
    if hasattr(user, '_permission_cache'):
        return user._permission_cache

    # Get role code using helper
    role_code = get_user_role_code(user)

    # Superadmin gets all permissions automatically
    if role_code == "superadmin":
        all_perms = db.query(Permission.code).all()
        permissions = [p[0] for p in all_perms]
    else:
        # Fetch permissions assigned to this role
        # Prefer dynamic role_id, fallback to enum
        if user.role_id is not None:
            # Use role_id for dynamic roles
            permissions = db.query(Permission.code)\
                .join(RolePermission)\
                .filter(RolePermission.role_id == user.role_id)\
                .all()
        else:
            # Fallback to legacy enum
            permissions = db.query(Permission.code)\
                .join(RolePermission)\
                .filter(RolePermission.role == user.role)\
                .all()
        permissions = [p[0] for p in permissions]

    # Cache permissions on user object for this request
    user._permission_cache = permissions
    return permissions


def require_permission(permission_code: str):
    """
    Dependency injection for permission-based access control.

    Usage:
        @app.get("/admin/users", dependencies=[Depends(require_permission("users.view"))])
        async def get_users():
            ...

    Args:
        permission_code: Permission code to check (e.g., "users.create")

    Returns:
        Async function that checks if current user has the permission

    Raises:
        HTTPException 403 if user lacks the required permission
    """
    async def permission_checker(
        current_user: User = Depends(get_current_user),
        db: Session = Depends(get_db)
    ) -> User:
        # Get user's permissions
        user_perms = await get_user_permissions(current_user, db)

        # Check if user has the required permission
        if permission_code not in user_perms:
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail=f"Permission required: {permission_code}"
            )

        return current_user

    return permission_checker


async def get_current_superadmin(current_user: User = Depends(get_current_user)) -> User:
    """
    Require user to be superadmin.
    Used for endpoints that should only be accessible to superadmins.
    """
    role_code = get_user_role_code(current_user)
    if role_code != "superadmin":
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Superadmin access required"
        )
    return current_user