docs(either-errors): base book rental application

Author: kgajowy

articles/either-errors/package-lock.json

@@ -21,13 +21,16 @@
     "test:e2e": "jest --config ./test/jest-e2e.json"
   },
   "dependencies": {
+    "@nestjs-architects/typed-cqrs": "0.1.1",
     "@nestjs/common": "^8.0.0",
     "@nestjs/core": "^8.0.0",
+    "@nestjs/cqrs": "8.0.0",
     "@nestjs/platform-express": "^8.0.0",
     "fp-ts": "2.11.1",
     "reflect-metadata": "^0.1.13",
     "rimraf": "^3.0.2",
-    "rxjs": "^7.2.0"
+    "rxjs": "^7.2.0",
+    "uuid": "8.3.2"
   },
   "devDependencies": {
     "@nestjs/cli": "^8.0.0",

articles/either-errors/package.json

@@ -3,6 +3,8 @@ import { AppService } from './app.service';
 
 @Controller()
 export class AppController {
+  // TODO add get / rent / return
+  // TODO show mapper and symbols unions
   constructor(private readonly appService: AppService) {}
 
   @Get()

articles/either-errors/src/app.controller.ts

@@ -1,9 +1,11 @@
 import { Module } from '@nestjs/common';
 import { AppController } from './app.controller';
 import { AppService } from './app.service';
+import { BookCatalogueModule } from './books-catalogue';
+import { BookRentalModule } from './book-rental';
 
 @Module({
-  imports: [],
+  imports: [BookCatalogueModule, BookRentalModule],
   controllers: [AppController],
   providers: [AppService],
 })

articles/either-errors/src/app.module.ts

@@ -0,0 +1,11 @@
+import { Module } from '@nestjs/common';
+import { CqrsModule } from '@nestjs/cqrs';
+
+import { BorrowBookHandler } from './borrow-book.handler';
+import { ReturnBookHandler } from './return-book.handler';
+
+@Module({
+  imports: [CqrsModule],
+  providers: [BorrowBookHandler, ReturnBookHandler],
+})
+export class BookRentalModule {}

articles/either-errors/src/book-rental/book-rental.module.ts

@@ -0,0 +1,9 @@
+import { Command } from '@nestjs-architects/typed-cqrs';
+import { Either } from 'fp-ts/Either';
+import { BorrowError } from './borrow-errors';
+
+export class BorrowBook extends Command<Either<BorrowError, void>> {
+  constructor(public readonly isbn: string) {
+    super();
+  }
+}

articles/either-errors/src/book-rental/borrow-book.command.ts

@@ -0,0 +1,20 @@
+import { CommandHandler, IInferredCommandHandler } from '@nestjs/cqrs';
+import { Either, left, right } from 'fp-ts/Either';
+import { BorrowBook } from './borrow-book.command';
+import { BorrowError, OutOfStock } from './borrow-errors';
+
+import { outOfStockIsbn, limitReachedIsbn } from '../cheat-codes';
+
+@CommandHandler(BorrowBook)
+export class BorrowBookHandler implements IInferredCommandHandler<BorrowBook> {
+  async execute({ isbn }: BorrowBook): Promise<Either<BorrowError, void>> {
+    if (isbn === outOfStockIsbn) {
+      return left(OutOfStock);
+    }
+    if (isbn === limitReachedIsbn) {
+      return left(OutOfStock);
+    }
+
+    return right(undefined);
+  }
+}

articles/either-errors/src/book-rental/borrow-book.handler.ts

@@ -0,0 +1,4 @@
+export const OutOfStock = Symbol(`book out of stock`);
+export const BooksLimitReached = Symbol(`books limit reached`);
+
+export type BorrowError = typeof OutOfStock | typeof BooksLimitReached;

articles/either-errors/src/book-rental/borrow-errors.ts

@@ -0,0 +1,7 @@
+export { BorrowBook } from './borrow-book.command';
+export { ReturnBook } from './return-book.command';
+
+export { BookRentalModule } from './book-rental.module';
+
+export { BorrowError, BooksLimitReached, OutOfStock } from './borrow-errors';
+export { ReturnError } from './return-error';

articles/either-errors/src/book-rental/index.ts

@@ -0,0 +1,9 @@
+import { Command } from '@nestjs-architects/typed-cqrs';
+import { Either } from 'fp-ts/Either';
+import { ReturnError } from './return-error';
+
+export class ReturnBook extends Command<Either<ReturnError, void>> {
+  constructor(public readonly isbn: string) {
+    super();
+  }
+}