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‎.gitignore‎

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# TernJS port file
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.tern-port
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#package-lock.json
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package-lock.json

‎README.md‎

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# Yape Code Challenge :rocket:
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# app-nodejs-codechallenge
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Our code challenge will let you marvel us with your Jedi coding skills :smile:.
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Este repositorio es un microservicio en NestJS para manejar transacciones financieras. Usa PostgreSQL para persistencia y Kafka para la validación asíncrona (anti-fraud).
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Don't forget that the proper way to submit your work is to fork the repo and create a PR :wink: ... have fun !!
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Este README describe cómo levantar el entorno, cómo usar los servicios (endpoints) y cómo comprobar el flujo de mensajes con Kafka.
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- [Problem](#problem)
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- [Tech Stack](#tech_stack)
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- [Send us your challenge](#send_us_your_challenge)
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## Resumen técnico
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- Framework: NestJS
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- Persistencia: PostgreSQL (TypeORM)
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- Mensajería: Kafka
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- Arquitectura: monolito modular con flujo event-driven para validación anti-fraud
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# Problem
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## Requisitos
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- Docker & Docker Compose
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- Node 18+ y npm o yarn
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Every time a financial transaction is created it must be validated by our anti-fraud microservice and then the same service sends a message back to update the transaction status.
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For now, we have only three transaction statuses:
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## Configuración (.env)
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Crear un archivo `.env` en la raíz con las variables de Postgres:
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<ol>
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<li>pending</li>
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<li>approved</li>
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<li>rejected</li>
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</ol>
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```
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POSTGRES_HOST=localhost
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POSTGRES_PORT=5432
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POSTGRES_USER=postgres
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POSTGRES_PASSWORD=postgres
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POSTGRES_DB=postgres
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```
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Nota: la app por defecto usa `localhost:9092` como broker Kafka. Si ejecutas la app dentro de Docker, usa `kafka:29092` como broker.
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## Levantar el entorno
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Every transaction with a value greater than 1000 should be rejected.
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1. Instala dependencias:
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```mermaid
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flowchart LR
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Transaction -- Save Transaction with pending Status --> transactionDatabase[(Database)]
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Transaction --Send transaction Created event--> Anti-Fraud
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Anti-Fraud -- Send transaction Status Approved event--> Transaction
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Anti-Fraud -- Send transaction Status Rejected event--> Transaction
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Transaction -- Update transaction Status event--> transactionDatabase[(Database)]
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```bash
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npm install
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# o
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yarn install
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```
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# Tech Stack
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2. Levanta infra con Docker Compose (Postgres, Zookeeper, Kafka):
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<ol>
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<li>Node. You can use any framework you want (i.e. Nestjs with an ORM like TypeOrm or Prisma) </li>
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<li>Any database</li>
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<li>Kafka</li>
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</ol>
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```bash
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docker compose up -d
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```
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We do provide a `Dockerfile` to help you get started with a dev environment.
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3. Ejecuta la aplicación en modo desarrollo:
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You must have two resources:
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```bash
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npm run local
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# o
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yarn local
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```
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1. Resource to create a transaction that must containt:
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### Levantar los dos servicios (transaction + anti-fraud)
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```json
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{
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"accountExternalIdDebit": "Guid",
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"accountExternalIdCredit": "Guid",
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"tranferTypeId": 1,
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"value": 120
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}
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Abre dos terminales separados y en cada uno ejecuta:
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Terminal A (transaction):
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```bash
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cd transaction
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npm install
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npm run local
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```
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Terminal B (anti-fraud):
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```bash
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cd anti-fraud
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npm install
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npm run local
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```
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2. Resource to retrieve a transaction
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Ambos servicios deben poder conectar al broker Kafka que levantaste con `docker compose up -d`.
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## Cómo usar los servicios (endpoints)
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Base URL: `http://localhost:3000`
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1) Crear transacción — POST `/transaction`
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- Descripción: crea una transacción y publica el evento para validación anti-fraud.
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- Body (JSON):
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```json
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{
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"transactionExternalId": "Guid",
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"transactionType": {
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"name": ""
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},
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"transactionStatus": {
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"name": ""
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},
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"value": 120,
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"createdAt": "Date"
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"accountExternalIdDebit": "5429d629-c239-45fa-8235-1a386258c536",
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"accountExternalIdCredit": "d6cd54da-8ce3-4f79-abda-bd5be9b19e68",
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"tranferTypeId": 1,
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"value": 120
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}
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```
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## Optional
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Ejemplos `curl`:
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```bash
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curl -i -X POST http://localhost:3000/transaction \
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-H "Content-Type: application/json" \
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-d '{
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"accountExternalIdDebit": "5429d629-c239-45fa-8235-1a386258c536",
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"accountExternalIdCredit": "d6cd54da-8ce3-4f79-abda-bd5be9b19e68",
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"tranferTypeId": 1,
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"value": 120
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}'
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```
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2) Listar transacciones — GET `/transaction`
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You can use any approach to store transaction data but you should consider that we may deal with high volume scenarios where we have a huge amount of writes and reads for the same data at the same time. How would you tackle this requirement?
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- Descripción: devuelve todas las transacciones guardadas (útil para debug local).
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You can use Graphql;
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```bash
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curl http://localhost:3000/transaction
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```
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# Send us your challenge
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## Flujo Kafka (anti-fraud)
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When you finish your challenge, after forking a repository, you **must** open a pull request to our repository. There are no limitations to the implementation, you can follow the programming paradigm, modularization, and style that you feel is the most appropriate solution.
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- Al crear una transacción se publica un evento `transaction.created` con los datos básicos.
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- Un consumidor (anti-fraud) valida la transacción y emite `transaction.validated` con `{ id, status }`.
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- La app escucha `transaction.validated` y actualiza el `status` en la base de datos.
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Regla implementada en el anti-fraud (ejemplo): `if value > 1000 => rejected`; else `approved`.
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3. Consultar la última transacción:
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```sql
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select * from transaction where "accountExternalIdDebit" = {{ID}};
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```
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## DDL (esquema) para probar localmente
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```sql
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CREATE TABLE public.transaction
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(
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"accountExternalIdDebit" varchar NOT NULL,
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"accountExternalIdCredit" varchar NOT NULL,
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"tranferTypeId" integer NOT NULL,
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value numeric NOT NULL,
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id uuid DEFAULT uuid_generate_v4() NOT NULL
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CONSTRAINT "PK_89eadb93a89810556e1cbcd6ab9"
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PRIMARY KEY,
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"createdAt" timestamp DEFAULT now() NOT NULL,
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"updatedAt" timestamp DEFAULT now() NOT NULL,
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status integer NOT NULL
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);
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```
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If you have any questions, please let us know.
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Si usas TypeORM, la entidad del proyecto crea automáticamente la tabla al iniciar (si `synchronize: true`). Usa este DDL solo si quieres preparar la tabla manualmente o probar fuera del ciclo de arranque de la app.

‎anti-fraud/.eslintrc.js‎

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module.exports = {
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parser: '@typescript-eslint/parser',
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parserOptions: {
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project: 'tsconfig.json',
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tsconfigRootDir: __dirname,
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sourceType: 'module',
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},
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plugins: ['@typescript-eslint/eslint-plugin'],
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extends: [
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'plugin:@typescript-eslint/recommended',
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'plugin:prettier/recommended',
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],
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root: true,
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env: {
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node: true,
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jest: true,
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},
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ignorePatterns: ['.eslintrc.js'],
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rules: {
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'@typescript-eslint/interface-name-prefix': 'off',
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'@typescript-eslint/explicit-function-return-type': 'off',
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'@typescript-eslint/explicit-module-boundary-types': 'off',
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'@typescript-eslint/no-explicit-any': 'off',
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},
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};

‎anti-fraud/.prettierrc‎

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{
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"singleQuote": true,
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"trailingComma": "all"
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}

‎anti-fraud/nest-cli.json‎

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{
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"$schema": "https://json.schemastore.org/nest-cli",
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"collection": "@nestjs/schematics",
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"sourceRoot": "src",
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"compilerOptions": {
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"deleteOutDir": true
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}
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}

‎anti-fraud/package.json‎

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{
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"name": "anti-fraud",
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"version": "0.0.1",
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"description": "",
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"author": "",
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"private": true,
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"license": "UNLICENSED",
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"scripts": {
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"build": "nest build",
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"format": "prettier --write \"src/**/*.ts\" \"test/**/*.ts\"",
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"start": "nest start",
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"local": "nest start --watch",
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"start:debug": "nest start --debug --watch",
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"start:prod": "node dist/main",
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"lint": "eslint \"{src,apps,libs,test}/**/*.ts\" --fix",
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"test": "jest",
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"test:watch": "jest --watch",
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"test:cov": "jest --coverage",
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"test:debug": "node --inspect-brk -r tsconfig-paths/register -r ts-node/register node_modules/.bin/jest --runInBand",
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"test:e2e": "jest --config ./test/jest-e2e.json"
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},
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"dependencies": {
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"@nestjs/common": "^10.0.0",
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"@nestjs/config": "^4.0.2",
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"@nestjs/core": "^10.0.0",
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"@nestjs/microservices": "^10.4.18",
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"@nestjs/platform-express": "^10.0.0",
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"@nestjs/typeorm": "^11.0.0",
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"class-transformer": "^0.5.1",
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"class-validator": "^0.14.2",
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"kafkajs": "^2.2.4",
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"pg": "^8.16.0",
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"reflect-metadata": "^0.2.0",
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"rxjs": "^7.8.1",
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"typeorm": "^0.3.24"
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},
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"devDependencies": {
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"@nestjs/cli": "^10.0.0",
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"@nestjs/schematics": "^10.0.0",
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"@nestjs/testing": "^10.0.0",
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"@types/express": "^5.0.0",
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"@types/jest": "^29.5.2",
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"@types/node": "^20.3.1",
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"@types/supertest": "^6.0.0",
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"@typescript-eslint/eslint-plugin": "^8.0.0",
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"@typescript-eslint/parser": "^8.0.0",
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"eslint": "^8.0.0",
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"eslint-config-prettier": "^9.0.0",
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"eslint-plugin-prettier": "^5.0.0",
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"jest": "^29.5.0",
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"prettier": "^3.0.0",
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"source-map-support": "^0.5.21",
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"supertest": "^7.0.0",
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"ts-jest": "^29.1.0",
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"ts-loader": "^9.4.3",
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"ts-node": "^10.9.1",
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"tsconfig-paths": "^4.2.0",
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"typescript": "^5.1.3"
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},
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"jest": {
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"moduleFileExtensions": [
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"js",
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"json",
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"ts"
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],
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"rootDir": "src",
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"testRegex": ".*\\.spec\\.ts$",
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"transform": {
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"^.+\\.(t|j)s$": "ts-jest"
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},
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"collectCoverageFrom": [
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"**/*.(t|j)s"
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],
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"coverageDirectory": "../coverage",
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"testEnvironment": "node"
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}
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}

‎anti-fraud/src/app.controller.ts‎

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import { Controller, Logger } from '@nestjs/common';
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import { MessagePattern, Payload } from '@nestjs/microservices';
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import { AppService } from './app.service';
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import { TransactionCreatedEvent } from './models/transaction-created.event';
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@Controller()
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export class AppController {
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constructor(private readonly appService: AppService) {}
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@MessagePattern('transaction.created')
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async approvedTransaction(
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@Payload() payload: TransactionCreatedEvent,
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): Promise<void> {
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Logger.debug(payload);
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await this.appService.evaluateTransaction(payload);
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}
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}

‎anti-fraud/src/app.module.ts‎

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import { Module } from '@nestjs/common';
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import { ConfigModule } from '@nestjs/config';
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import { ClientsModule, Transport } from '@nestjs/microservices';
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import { AppController } from './app.controller';
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import { AppService } from './app.service';
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@Module({
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imports: [
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ConfigModule.forRoot(),
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ClientsModule.register([
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{
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name: 'KAFKA',
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transport: Transport.KAFKA,
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options: {
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client: {
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clientId: 'anti-fraud',
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brokers: [`${process.env.KAFKA_HOST}:9092`],
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},
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consumer: {
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groupId: 'anti-fraud-consumer',
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},
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},
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},
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]),
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],
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controllers: [AppController],
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providers: [AppService]
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})
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export class AppModule { }

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