requestor/lib/DatabaseCrudOptionsReader.ts

import { Request, Response } from 'express';
import { KnexCrudOptions, Authorization } from './DatabaseCrudOptions';

type AuthRunner = {
  (req: Request, res: Response): Promise<boolean>;
}

export class KnexCrudOptionsReader {
  private options: KnexCrudOptions;

  public constructor (options: KnexCrudOptions) {
    this.options = options;
  }

  private get_auth_runner (
    auth?: Authorization
  ): AuthRunner {
    if (typeof auth === 'undefined')
      return (): Promise<boolean> => new Promise ((r) => r (true));
    return (req, res): Promise<boolean> => new Promise ((resolve) => {
      const result = auth (req, res, resolve);
      if (typeof result !== 'undefined')
        resolve (result as boolean);
    });
  }

  public get optional_columns (): Array<string> | undefined {
    return this.options.optional_columns;
  }

  public get create_authorization (): Authorization {
    const general = this.get_auth_runner (this.options.general_authorization);
    const specific = this.get_auth_runner (this.options.create_authorization);
    return async (req: Request, res: Response): Promise<boolean> => {
      const result = (await general (req, res)) && (await specific (req, res));
      return result;
    };
  }

  public get read_authorization (): Authorization {
    const general = this.get_auth_runner (this.options.general_authorization);
    const specific = this.get_auth_runner (this.options.read_authorization);
    return async (req: Request, res: Response): Promise<boolean> => {
      const result = (await general (req, res)) && (await specific (req, res));
      return result;
    };
  }

  public get update_authorization (): Authorization {
    const general = this.get_auth_runner (this.options.general_authorization);
    const specific = this.get_auth_runner (this.options.update_authorization);
    return async (req: Request, res: Response): Promise<boolean> => {
      const result = (await general (req, res)) && (await specific (req, res));
      return result;
    };
  }

  public get delete_authorization (): Authorization {
    const general = this.get_auth_runner (this.options.general_authorization);
    const specific = this.get_auth_runner (this.options.delete_authorization);
    return async (req: Request, res: Response): Promise<boolean> => {
      const result = (await general (req, res)) && (await specific (req, res));
      return result;
    };
  }
}