Handling the API request with an API Controller

// CreateUsersController - Handling the request data from 
// the internet and passing it to the dependency injected 
// use case class for execution.

// users/useCases/createUser/CreateUserController.ts

import { CreateUserUseCase } from "./CreateUserUseCase"
import { CreateUserDTO } from "./CreateUserDTO"
import { CreateUserErrors } from "./CreateUserErrors"
import { BaseController } from "../../../../shared/infra/http/models/BaseController"
import { TextUtils } from "../../../../shared/utils/TextUtils"
import { DecodedExpressRequest } from "../../infra/http/models/decodedRequest"
import * as express from "express"

export class CreateUserController extends BaseController {
  private useCase: CreateUserUseCase

  constructor(useCase: CreateUserUseCase) {
    super()
    this.useCase = useCase
  }

  async executeImpl(
    req: DecodedExpressRequest,
    res: express.Response
  ): Promise<any> {
    let dto: CreateUserDTO = req.body as CreateUserDTO

    dto = {
      username: TextUtils.sanitize(dto.username),
      email: TextUtils.sanitize(dto.email),
      password: dto.password,
    }

    try {
      /**
       * Execute the CreateUserUseCase use case.
       */

      const result = await this.useCase.execute(dto)

      if (result.isLeft()) {
        const error = result.value

        /**
         * This is an example of how one can standardize a
         * RESTful API's error messages.
         *
         * We utilize the Use Case Error types.
         */

        switch (error.constructor) {
          case CreateUserErrors.UsernameTakenError:
            return this.conflict(error.errorValue().message)
          case CreateUserErrors.EmailAlreadyExistsError:
            return this.conflict(error.errorValue().message)
          default
            return this.fail(res, error.errorValue().message)
        }
      } else {
        return this.ok(res)
      }
    } catch (err) {
      return this.fail(res, err)
    }
  }
}