NestJS Proxy module

<h1> 
NestJS Proxy module
<img src="https://nestjs.com/img/logo-small.svg" height="20" alt="Nest Logo" />
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NestJS module to decorate and proxy calls.\
It exposes a `/proxy` endpoint.

## Use it

You can import the module like so :

`app.module.ts`

```typescript
ProxyModule.forRoot({
    config: {},
    services: [
      {
        id: 'ACCOUNT_INFORMATION_US',
        url: `https://api.fusionfabric.cloud/retail-us/me/account/v1/accounts`,
        config: {}
      }
    ]
}),
```

### Or asynchronously

`app.module.ts`

```typescript
ProxyModule.forRootAsync({
    useClass: ProxyConfigService,
    imports: [ConfigModule],
}),
```

`proxy-config.service.ts`

```typescript
import { ConfigService } from '@nestjs/config';
import { Injectable, Logger } from '@nestjs/common';
import { ProxyModuleOptions, ProxyModuleOptionsFactory } from '@finastra/nestjs-proxy';

@Injectable()
export class ProxyConfigService implements ProxyModuleOptionsFactory {
  constructor(private configService: ConfigService) {}

  createModuleConfig(): ProxyModuleOptions {
    const FFDC = this.configService.get('FFDC');

    const services = [
      {
        id: 'ACCOUNT_INFORMATION_US',
        url: `${FFDC}/retail-us/me/account/v1/accounts`,
        config: {}
      };
    ];

    return {
      services,
    };
  }
}
```

## Configuration

Whether synchronously or asynchronously, the module takes two parameters (both optionals).

- **services** : which is a collection of urls with a given id so that you can query them more efficiently
- **config** : which is the configuration from [http-proxy](https://github.com/http-party/node-http-proxy) which we're using under the hood. Find the offical documentation of this configuration [here](https://github.com/http-party/node-http-proxy#options).

> A service can also take an optional `config`, which is the same signature as the parent one, allowing you to override configuration for that particular service !

### Token forwarding

By default, OAuth token are forwarded to the service call being proxied. You can disable this by setting the `forwardToken` property to `false` in the service configuration.

```typescript
services: [
  {
    id: 'THIRD_PARTY_SERVICE',
    url: 'https://some-service.com/some-endpoint',
    forwardToken: false,
  },
];
```

> &#x26A0; Be careful to only forward tokens to internal services. Don't forward the token to third party services.

### Cookies forwarding

Cookies are not proxied by default. You can opt in by listing the cookie names in the `allowedCookies` option:

```typescript
allowedCookies: ['cookie1', 'cookie2'],
```


### Default module configuration

If you do not provide any, the default proxy configuration for this module can be found in [proxy.constants.ts](./src/proxy.constants.ts), under `defaultProxyOptions`

## Client-side usage examples

```typescript
const serverUri = 'http://localhost:3000';
const serviceId = 'ACCOUNT_INFORMATION_US';

fetch(`${serverUri}/proxy?serviceId=${serviceId}`);

// Defining path
const accountId = '112';
const target = `${accountId}/details`;
fetch(`${serverUri}/proxy?serviceId=${serviceId}&target=${target}`);
```

> `target` parameter is optional

## Using module with a service using OIDC module with multitenancy configuration

All proxy calls need to be prefixed by `/${TENANT_ID}/${CHANEL_TYPE}`