docs(either-errors): base book rental application

Author: kgajowy

articles/either-errors/package-lock.json

@@ -21,13 +21,17 @@
     "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",
+    "utility-types": "3.10.0",
+    "uuid": "8.3.2"
   },
   "devDependencies": {
     "@nestjs/cli": "^8.0.0",

articles/either-errors/package.json

@@ -0,0 +1,50 @@
+import { Controller, Get, Param, Post, Put } from '@nestjs/common';
+import { CommandBus, QueryBus } from '@nestjs/cqrs';
+import { GetAvailableBooks } from '../books-catalogue';
+import { BorrowBook, DeleteBook, NotAnAdmin, ReturnBook } from '../book-rental';
+import { BookSerializerService } from './book-serializer.service';
+import { Delete } from '@nestjs/common';
+
+@Controller()
+export class AppController {
+  constructor(
+    private readonly queryBus: QueryBus,
+    private readonly commandBus: CommandBus,
+    private readonly serializer: BookSerializerService,
+  ) {}
+
+  @Get()
+  books() {
+    return this.queryBus.execute(new GetAvailableBooks());
+  }
+
+  @Post(':isbn')
+  async borrowBook(@Param('isbn') isbn: string) {
+    const result = await this.commandBus.execute(new BorrowBook(isbn));
+    return this.serializer.serialize(result);
+  }
+
+  @Put(':isbn')
+  async returnBook(@Param('isbn') isbn: string) {
+    const result = await this.commandBus.execute(new ReturnBook(isbn));
+    return this.serializer.serialize(result);
+  }
+
+  @Delete(':isbn')
+  async removeBook(@Param('isbn') isbn: string) {
+    try {
+      await this.commandBus.execute(new DeleteBook(isbn));
+      return undefined;
+    } catch (error) {
+      if (error instanceof NotAnAdmin) {
+        return {
+          message: `How dare you? ${error}`,
+        };
+      } else {
+        return {
+          message: `Roaming?`,
+        };
+      }
+    }
+  }
+}

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

@@ -0,0 +1,41 @@
+import { Either, isRight } from 'fp-ts/Either';
+import {
+  ForbiddenException,
+  HttpException,
+  NotFoundException,
+} from '@nestjs/common';
+
+enum BorrowErrorViaEnum {
+  OutOfStock = 'out-of-stock',
+  BooksLimitReached = 'books-limit-reached',
+}
+
+enum ReturnErrorViaEnum {
+  PaymentRequired = 'payment-required',
+}
+
+export class BookSerializerWithEnumsService {
+  serialize(
+    result: Either<
+      BorrowErrorViaEnum | ReturnErrorViaEnum /** | and others...*/,
+      void
+    >,
+  ) {
+    if (isRight(result)) {
+      return;
+    }
+    const error = result.left;
+
+    switch (error) {
+      case ReturnErrorViaEnum.PaymentRequired:
+        throw new HttpException('Pay debt first.', 402);
+      case BorrowErrorViaEnum.OutOfStock:
+        throw new NotFoundException();
+      case BorrowErrorViaEnum.BooksLimitReached:
+        throw new ForbiddenException();
+      default:
+        const _exhaustiveCheck: never = error;
+        throw _exhaustiveCheck;
+    }
+  }
+}

articles/either-errors/src/api/book-serializer-with-enums.service.ts

@@ -0,0 +1,38 @@
+import {
+  Injectable,
+  HttpException,
+  NotFoundException,
+  ForbiddenException,
+} from '@nestjs/common';
+import { Either, isRight } from 'fp-ts/Either';
+import {
+  BorrowError,
+  ReturnError,
+  TimeLimitExceeded,
+  BooksLimitReached,
+  OutOfStock,
+} from '../book-rental';
+
+type BookRentalError = ReturnError | BorrowError;
+
+@Injectable()
+export class BookSerializerService {
+  serialize(response: Either<BookRentalError, void>): void {
+    if (isRight(response)) {
+      return;
+    }
+    const error = response.left;
+
+    switch (error) {
+      case TimeLimitExceeded:
+        throw new HttpException('Pay debt first.', 402);
+      case OutOfStock:
+        throw new NotFoundException();
+      case BooksLimitReached:
+        throw new ForbiddenException();
+      default:
+        const _exhaustiveCheck: never = error;
+        throw _exhaustiveCheck;
+    }
+  }
+}

articles/either-errors/src/api/book-serializer.service.ts

@@ -1,10 +1,14 @@
+import { CqrsModule } from '@nestjs/cqrs';
 import { Module } from '@nestjs/common';
-import { AppController } from './app.controller';
+import { AppController } from './api/app.controller';
 import { AppService } from './app.service';
+import { BookCatalogueModule } from './books-catalogue';
+import { BookRentalModule } from './book-rental';
+import { BookSerializerService } from './api/book-serializer.service';
 
 @Module({
-  imports: [],
+  imports: [CqrsModule, BookCatalogueModule, BookRentalModule],
   controllers: [AppController],
-  providers: [AppService],
+  providers: [AppService, BookSerializerService],
 })
 export class AppModule {}

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

@@ -0,0 +1,12 @@
+import { Module } from '@nestjs/common';
+import { CqrsModule } from '@nestjs/cqrs';
+
+import { BorrowBookHandler } from './borrow-book.handler';
+import { ReturnBookHandler } from './return-book.handler';
+import { DeleteBookHandler } from './delete-book.handler';
+
+@Module({
+  imports: [CqrsModule],
+  providers: [BorrowBookHandler, ReturnBookHandler, DeleteBookHandler],
+})
+export class BookRentalModule {}

articles/either-errors/src/app.controller.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();
+  }
+}