module.exports = (sequelize, DataTypes) => {
  const Message = sequelize.define('Message', {
    id: {
      type: DataTypes.UUID,
      defaultValue: DataTypes.UUIDV4,
      primaryKey: true
    },
    conversation_id: {
      type: DataTypes.UUID,
      allowNull: false,
      references: {
        model: 'conversations',
        key: 'id'
      }
    },
    plan_id: {
      type: DataTypes.UUID,
      allowNull: true,
      references: {
        model: 'plans',
        key: 'id'
      }
    },
    role: {
      type: DataTypes.ENUM('user', 'assistant', 'system'),
      allowNull: false
    },
    content: {
      type: DataTypes.TEXT,
      allowNull: false
    },
    message_type: {
      type: DataTypes.ENUM('text', 'plan', 'execution', 'feedback'),
      defaultValue: 'text'
    },
    metadata: {
      type: DataTypes.JSONB,
      defaultValue: {}
    },
    tokens_used: {
      type: DataTypes.INTEGER,
      defaultValue: 0
    },
    processing_time: {
      type: DataTypes.FLOAT,
      defaultValue: 0
    }
  }, {
    tableName: 'messages',
    indexes: [
      { fields: ['conversation_id'] },
      { fields: ['plan_id'] },
      { fields: ['role'] },
      { fields: ['message_type'] },
      { fields: ['created_at'] }
    ]
  });

  return Message;
};