【Angular】in-memory-web-apiでクエリで返す値を絞る方法

2,3ヶ月に１回調べては忘れるということがあったのでメモとして

## この記事を書いたときのバージョン
```json
{
 "angular-in-memory-web-api": "^0.5.2"
}
```

## シチュエーション
種別の検索条件(kind)付きのGETリクエストで記事一覧を取得したい

## 期待動作

### 全取得

リクエスト

```
api/articles?kind=
```
レスポンス

```typescript
[
    {
        title: 'Test Page 01',
        description: 'This is Test Page 01',
        image: 'path/your/image.png',
        kind: Kind.Sports
    },
    {
        title: 'Test Page 02',
        description: 'This is Test Page 02',
        image: 'path/your/image.png',
        kind: Kind.People
    },
    {
        title: 'Test Page 03',
        description: 'This is Test Page 03',
        image: 'path/your/image.png',
        kind: Kind.Technology
    }
]
```

### 検索条件有り（kind=sports）

リクエスト

```
api/artiles?kind=sports
```

レスポンス

```typescript
[
    {
        title: 'Test Page 01',
        description: 'This is Test Page 01',
        image: 'path/your/image.png',
        kind: Kind.Sports
    }
]
```

## コード

実コードから引っ張ったので、一部無理やりAnyにしてます。

```in-memory-data.service.ts
import {
    InMemoryDbService,
    RequestInfo,
    RequestInfoUtilities,
    ParsedRequestUrl,
    ResponseOptions,
    getStatusText,
    STATUS
} from 'angular-in-memory-web-api';

enum Kind {
    Sports = 'sports',
    People = 'people',
    Technology = 'technology'
}

const feed: Any[] = [
    {
        title: 'Test Page 01',
        description: 'This is Test Page 01',
        image: 'path/your/image.png',
        kind: Kind.Sports
    },
    {
        title: 'Test Page 02',
        description: 'This is Test Page 02',
        image: 'path/your/image.png',
        kind: Kind.People
    },
    {
        title: 'Test Page 03',
        description: 'This is Test Page 03',
        image: 'path/your/image.png',
        kind: Kind.Technology
    }
];

export class InMemoryDataService implements InMemoryDbService {

    // オーバーライド
    get(reqInfo: RequestInfo) {
        const collectionName = reqInfo.collectionName;
        if (collectionName === 'articles') {
            return this.getArticles(reqInfo);
        }
        return undefined;
    }

    private getArticles(reqInfo: RequestInfo) {
        return reqInfo.utils.createResponse$(() => {
            console.log('HTTP GET override');

            const collection = feed.slice();
            const dataEncapsulation = reqInfo.utils.getConfig().dataEncapsulation;

            const kind = reqInfo.query.get('kind');
            const data = kind === undefined ? collection : this.filterFeed(kind[0]);

            const options: any = data ?
                {
                    body: dataEncapsulation ? { data } : data,
                    status: STATUS.OK
                } :
                {
                    body: { error: 'error' },
                    status: STATUS.NOT_FOUND
                };
            return this.finishOptions(options, reqInfo);
        });
    }

    private finishOptions(options: ResponseOptions, { headers, url }: RequestInfo) {
        options.statusText = getStatusText(options.status);
        options.headers = headers;
        options.url = url;
        return options;
    }

    private filterFeed(kind: string) {
        return feed.filter((value: FeedItem, index: number, array: FeedItem[]) => {
            return (value.kind === kind);
        });
    }

    createDb() {
        return { feed };
    }

}

```