"""
Category Model

SQLAlchemy model for transaction categories.
Handles categorization of financial transactions.
"""

from datetime import datetime
from app.extensions import db


class Category(db.Model):
    """
    Category model for organizing transactions.
    
    Attributes:
        id (int): Primary key
        name (str): Category name (unique)
        description (str): Optional description
        color (str): Hex color code for UI representation
        is_active (bool): Whether category is active
        created_at (datetime): Creation timestamp
    """
    
    __tablename__ = 'categories'
    
    # Primary key
    id = db.Column(db.Integer, primary_key=True)
    
    # Category information
    name = db.Column(db.String(100), nullable=False, unique=True)
    description = db.Column(db.Text)
    color = db.Column(db.String(7))  # Hex color code (#FFFFFF)
    is_active = db.Column(db.Boolean, default=True, nullable=False)
    
    # Timestamps
    created_at = db.Column(db.DateTime, default=datetime.utcnow, nullable=False)
    
    # Relationships
    transactions = db.relationship('Transaction', backref='category', lazy=True)
    
    def __repr__(self):
        """String representation of Category."""
        return f'<Category {self.name}>'
    
    def to_dict(self):
        """Convert category to dictionary for JSON serialization."""
        return {
            'id': self.id,
            'name': self.name,
            'description': self.description,
            'color': self.color,
            'is_active': self.is_active,
            'created_at': self.created_at.isoformat() if self.created_at else None
        }
    
    def get_transaction_count(self):
        """Get transaction count without loading all transactions."""
        from app.models.transaction import Transaction
        return db.session.query(Transaction).filter_by(category_id=self.id).count()
    
    @classmethod
    def get_categories_with_counts(cls):
        """Get categories with transaction counts efficiently."""
        from app.models.transaction import Transaction
        return db.session.query(
            cls, 
            db.func.count(Transaction.id).label('transaction_count')
        ).outerjoin(Transaction).group_by(cls.id).all()
    
    @classmethod
    def get_active_categories(cls):
        """Get all active categories."""
        return cls.query.filter_by(is_active=True).all()
    
    @classmethod
    def find_by_name(cls, name):
        """Find category by name."""
        return cls.query.filter_by(name=name).first()