"""Base model classes and database setup for the chat agent."""

from datetime import datetime
from uuid import uuid4
from sqlalchemy import Column, DateTime, String, TypeDecorator
from sqlalchemy.dialects.postgresql import UUID
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from flask_sqlalchemy import SQLAlchemy

# Create SQLAlchemy instance
db = SQLAlchemy()

# Custom UUID type that works with both PostgreSQL and SQLite
class GUID(TypeDecorator):
    """Platform-independent GUID type.
    Uses PostgreSQL's UUID type, otherwise uses String(36).
    """
    impl = String
    cache_ok = True

    def load_dialect_impl(self, dialect):
        if dialect.name == 'postgresql':
            return dialect.type_descriptor(UUID(as_uuid=True))
        else:
            return dialect.type_descriptor(String(36))

    def process_bind_param(self, value, dialect):
        if value is None:
            return value
        elif dialect.name == 'postgresql':
            return value
        else:
            return str(value)

    def process_result_value(self, value, dialect):
        if value is None:
            return value
        else:
            return value

# Base model class with common fields
class BaseModel(db.Model):
    """Base model class with common fields and methods."""
    
    __abstract__ = True
    
    id = Column(GUID(), primary_key=True, default=lambda: str(uuid4()))
    created_at = Column(DateTime, default=datetime.utcnow, nullable=False)
    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False)
    
    def to_dict(self):
        """Convert model instance to dictionary."""
        return {
            column.name: getattr(self, column.name)
            for column in self.__table__.columns
        }
    
    def __repr__(self):
        """String representation of the model."""
        return f"<{self.__class__.__name__}(id={self.id})>"