export class TypeValidation {
  private readonly _general_type: string;

  public get general_type (): string {
    return this._general_type;
  }

  public get string_type (): 'string'|'number'|'boolean'|'array' {
    return this._general_type as 'string'|'number'|'boolean'|'array';
  }

  public constructor (type: string) {
    this._general_type = type;
  }

  public validate_type (value: unknown): boolean {
    return typeof value === this.general_type;
  }

  public to_type (value: unknown): Promise<unknown> {
    if (this.general_type === 'string')
      return Promise.resolve (String (value));

    if (this.general_type === 'number') {
      const as_num = parseInt (String (value));
      if (isNaN (as_num))
        throw new Error ('value is not a number');
      return Promise.resolve (as_num);
    }

    if (this.general_type === 'boolean') {
      const as_num = parseInt (String (value));
      if (
        as_num !== 1 && as_num !== 0
        && !(/^(?:true|false)$/iu).test (String (value))
      )
        throw new Error ('value is not a boolean');
      return Promise.resolve (
        as_num === 1 || (/true/iu).test (String (value))
      );
    }
    throw new Error ('unknown type');
  }
}