import util from "util";
import ParameterType from "./ParameterType";

export default class GeneratedExpression {
  constructor(
    private readonly expressionTemplate: string,
    public readonly parameterTypes: Array<ParameterType<any>>
  ) {}

  get source() {
    return util.format(
      this.expressionTemplate,
      ...this.parameterTypes.map(t => t.name)
    );
  }

  /**
   * Returns an array of parameter names to use in generated function/method signatures
   *
   * @returns {Array.<String>}
   */
  get parameterNames() {
    const usageByTypeName: { [key: string]: number } = {};
    return this.parameterTypes.map(t =>
      getParameterName(t.name, usageByTypeName)
    );
  }
}

function getParameterName(
  typeName: string,
  usageByTypeName: { [key: string]: number }
) {
  let count = usageByTypeName[typeName];
  count = count ? count + 1 : 1;
  usageByTypeName[typeName] = count;

  return count === 1 ? typeName : `${typeName}${count}`;
}