import Expression from '../sql/Expression.js';
import FieldMapping from './FieldMapping.js';
import { KeyOf } from './types.js';

class BaseExprBuilder<T> {
  private fieldMap: Map<string | number | symbol, FieldMapping>;
  private alias: string | undefined;

  constructor(fieldMap: Map<string | symbol, FieldMapping>, alias?: string) {
    this.fieldMap = fieldMap;
    this.alias = alias;
  }

  protected _expr(propName: KeyOf<T>) {
    let field = this.fieldMap.get(propName);
    if (!field) throw new TypeError('Field Not Found');
    let name = this.alias ? this.alias + '.' + field.colName : field.colName;
    return new Expression(name);
  }
}

export default BaseExprBuilder;