from datetime import datetime, timezone
from app import db
import bcrypt


def utc_now():
    """Return current UTC time as timezone-aware datetime"""
    return datetime.now(timezone.utc)


def format_datetime(dt: datetime) -> str:
    """Format datetime to ISO format with UTC timezone indicator"""
    if dt is None:
        return None
    # If datetime is naive (no timezone), assume it's UTC
    if dt.tzinfo is None:
        dt = dt.replace(tzinfo=timezone.utc)
    return dt.isoformat()


class User(db.Model):
    """User model for authentication and authorization"""
    __tablename__ = 'users'
    
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(50), unique=True, nullable=False, index=True)
    email = db.Column(db.String(100), unique=True, nullable=False, index=True)
    password_hash = db.Column(db.String(255), nullable=False)
    role = db.Column(db.Enum('admin', 'power_user', 'user', name='user_role'), default='user')
    created_at = db.Column(db.DateTime, default=utc_now)
    is_active = db.Column(db.Boolean, default=True)
    
    # Relationships
    credentials = db.relationship('UserCredential', back_populates='user', cascade='all, delete-orphan')
    tasks = db.relationship('Task', back_populates='created_by_user', cascade='all, delete-orphan')
    
    def set_password(self, password: str) -> None:
        """Hash and set the user's password"""
        self.password_hash = bcrypt.hashpw(
            password.encode('utf-8'), 
            bcrypt.gensalt()
        ).decode('utf-8')
    
    def check_password(self, password: str) -> bool:
        """Verify the user's password"""
        return bcrypt.checkpw(
            password.encode('utf-8'), 
            self.password_hash.encode('utf-8')
        )
    
    def to_dict(self) -> dict:
        """Convert user to dictionary (excluding sensitive data)"""
        return {
            'id': self.id,
            'username': self.username,
            'email': self.email,
            'role': self.role,
            'created_at': format_datetime(self.created_at),
            'is_active': self.is_active
        }
    
    def __repr__(self):
        return f'<User {self.username}>'