# Data Source · [![npm version](https://img.shields.io/npm/v/@gravity-ui/data-source?logo=npm&label=version)](https://www.npmjs.com/package/@gravity-ui/data-source) [![ci](https://img.shields.io/github/actions/workflow/status/gravity-ui/data-source/ci.yml?branch=main&label=ci&logo=github)](https://github.com/gravity-ui/data-source/actions/workflows/ci.yml?query=branch:main)

**Data Source** is a simple wrapper around data fetching. It is a kind of "port" in [clean architecture](https://blog.cleancoder.com/uncle-bob/2012/08/13/the-clean-architecture.html). It allows you to make wrappers for stuff around data fetching depending on your use cases. **Data Source** uses [react-query](https://tanstack.com/query/latest) under the hood.

## Installation

```bash
npm install @gravity-ui/data-source @tanstack/react-query
```

`@tanstack/react-query` is a peer dependency.

## Getting started

Firstly, define a type of error and make your constructors for data sources and your error based on default constructors (makePlainQueryDataSource / makeInfiniteQueryDataSource). For example:

```ts
import {makePlainQueryDataSource as makePlainQueryDataSourceBase} from '@gravity-ui/data-source';

export interface ApiError {
  title: string;
  code?: number;
  description?: string;
}

export const makePlainQueryDataSource = <TParams, TRequest, TResponse, TData, TError = ApiError>(
  config: Omit<PlainQueryDataSource<TParams, TRequest, TResponse, TData, TError>, 'type'>,
): PlainQueryDataSource<TParams, TRequest, TResponse, TData, TError> => {
  return makePlainQueryDataSourceBase(config);
};
```

Write a `DataLoader` component based on default. This is convenient to define your display of the loading status and errors. For example:

```tsx
import {
  DataLoader as DataLoaderBase,
  DataLoaderProps as DataLoaderPropsBase,
  ErrorViewProps,
} from '@gravity-ui/data-source';

export interface DataLoaderProps
  extends Omit<DataLoaderPropsBase<ApiError>, 'LoadingView' | 'ErrorView'> {
  LoadingView?: ComponentType;
  ErrorView?: ComponentType<ErrorViewProps<ApiError>>;
}

export const DataLoader: React.FC<DataLoaderProps> = ({
  LoadingView = YourLoader,
  ErrorView = YourError,
  ...restProps
}) => {
  return <DataLoaderBase LoadingView={LoadingView} ErrorView={ErrorView} {...restProps} />;
};
```

Define your first data source:

```ts
export const objectDataSource = makePlainQueryDataSource({
  // Keys have to be unique. Maybe you should create a helper for making names of data sources
  name: 'object',
  // skipContext is just a helper to skip 2 first parameters in the function (context and fetchContext)
  fetch: skipContext(objectFetch),
});
```

Use it in the application:

```tsx
import {useQueryData} from '@gravity-ui/data-source';

export const SomeComponent: React.FC = () => {
  const {data, status, error, refetch} = useQueryData(objectDataSource, {objectId: 1});

  return (
    <DataLoader status={status} error={error} errorAction={refetch}>
      {data && <ObjectComponent object={data} />}
    </DataLoader>
  );
};
```