import { InstallTabs } from '@site/src/components/InstallTabs';

# Vue Query

## Installation

<InstallTabs packageName="@ts-rest/vue-query @tanstack/vue-query" />

This is a client using `@ts-rest/vue-query`, using `@tanstack/vue-query` under the hood.

## Init TanStack Query Vue plugin

To use the query client in your Vue app, you'll need to initialise the `vue-query` client in your app.

```ts
import { VueQueryPlugin } from '@tanstack/vue-query';

createApp(App).use(VueQueryPlugin).mount('#app');
```

## initQueryClient

The below snippet is how you'd create a query client, this is pretty much the same structure as the `@ts-rest/core` client.

```tsx
import { initQueryClient } from '@ts-rest/vue-query';

export const client = initQueryClient(router, {
  baseUrl: 'http://localhost:3333',
  baseHeaders: {},
  api?: () => ... // <- Optional Custom API Fetcher (see below)
});
```

To customise the API, follow the same docs as the core client [here](/docs/core/custom)

:::tip

By default, ts-rest encodes query parameters as regular URL encoded strings (with support for nested objects, arrays etc) with full decode compatibility from [`qs`](https://www.npmjs.com/package/qs)

To encode query parameters as JSON, you can use the `jsonQuery` option, please note you'll need to configure your backend to support decoding JSON query parameters.

```tsx
export const client = initQueryClient(router, {
  ...,
  jsonQuery: true
});

```

:::

## useQuery and useMutation

Once you've created a client using `initQueryClient`, you may traverse the object (in the exact same structure as your contract layout) to find the query or mutation you want to use.

```tsx
const queryResult = client.posts.get.useQuery(
  ['posts'], // <- queryKey
  () => ({
    params: {
      id: '1';
    }
  }), // <- Query params, Params, Body etc (all typed)
  { staleTime: 1000 } // <- vue-query options (optional)
);
```

### using dynamic parameters

To use dynamic parameters, you can add a reactive vue `Ref` to the `queryKey` to trigger automatic refetching, when the reference changes.

The following example will refetch the query everytime the `postId` changes and is truthy.

```tsx
const postId = computed(() => selectedPost.value.id);

const queryResult = client.posts.get.useQuery(
  ['posts', postId], // <- queryKey with reactive ref
  (context) => ({
    params: {
      id: postId.value; //  or use queryKey passed to context: context.queryKey[1]
    }
  }),
  { enabled: computed(() => !!postId.value) } // <- make sure to use computed values for reactive options
);
```

:::tip

The design philosophy of `@ts-rest/vue-query` is to make it as easy as possible to use `vue-query` with `@ts-rest`. This means that the `useQuery` and `useMutation` hooks are as close to the original `vue-query` hooks as possible, as such we don't abstract away from the query keys or the options. Only the query function itself!

:::

```html
<template>
  <div class="App">
    <h1>Posts from posts-service</h1>

    <div v-if="isLoading">Loading...</div>
    <div v-if="error">Error: {{ error }}</div>

    <div v-if="data">
      <div v-for="post in data.body" :key="post.id">
        <h2>{{ post.title }}</h2>
        <p>{{ post.content }}</p>
      </div>
    </div>
  </div>
</template>

<script lang="ts" setup>
  // Effectively a useQuery hook
  const { data, error, isLoading } = client.getPosts.useQuery(['posts']);

  // Effectively a useMutation hook
  const { mutate, isLoading } = client.posts.create.useMutation();
</script>
```

:::info

When destructing the response from `useQuery` or `useMutation`, remember that ts-rest returns a `status` and `body` property, so you'll need to destructure those as well.

The reason for this is error handling! Please see the [Relevant Docs](/docs/core/errors#client-error-typing)

:::

## Regular Query and Mutations

`@ts-rest/vue-query` allows for a regular fetch or mutation if you want, without having to initialise two different clients, one with `@ts-rest/core` and one with `@ts-rest/vue-query`.

```typescript
// Normal fetch
const { body, status } = await client.posts.get.query();

// useQuery hook
const { data, isLoading } = client.posts.get.useQuery();
```

## useInfiniteQuery

One fantastic feature of `vue-query` is the ability to create infinite queries. This is a great way to handle pagination.

[Prisma's Docs](https://www.prisma.io/docs/concepts/components/prisma-client/pagination) explain the concepts of cursor and offset pagination fantastically, especially if you use Prisma client with `@ts-rest`

### Cursor Pagination

This is a simple cursor based pagination example,

```typescript
const { isLoading, data, hasNextPage, fetchNextPage } = useInfiniteQuery(
  queryKey,
  ({ pageParam = 1 }) => pageParam,
  {
    getNextPageParam: (lastPage, allPages) => lastPage.nextCursor,
    getPreviousPageParam: (firstPage, allPages) => firstPage.prevCursor,
  }
);
```

### Offset Pagination

This example specifically uses an API with `skip` and `take` query parameters, so this is requires slightly more configuration than a regular query (hence the complicated looking getNextPageParam)

```tsx
const PAGE_SIZE = 5;

export function Index() {
  const { isLoading, data, hasNextPage, fetchNextPage } =
    client.getPosts.useInfiniteQuery(
      ['posts'],
      ({ pageParam = { skip: 0, take: PAGE_SIZE } }) => ({
        query: { skip: pageParam.skip, take: pageParam.take },
      }),
      {
        getNextPageParam: (lastPage, allPages) =>
          lastPage.status === 200
            ? lastPage.body.count > allPages.length * PAGE_SIZE
              ? { take: PAGE_SIZE, skip: allPages.length * PAGE_SIZE }
              : undefined
            : undefined,
      }
    );

  if (isLoading) {
    return <div>Loading...</div>;
  }

  if (!data) {
    return <div>No posts found</div>;
  }

  const posts = data.pages.flatMap((page) =>
    page.status === 200 ? page.body.posts : []
  );

  //...
}
```
