import { Meta, Story, Preview, Props } from "@storybook/addon-docs/blocks";
import { Form } from "./Form";

<Meta title="MDX|Form" component={Form} />

# Form

Form component provides a way to build simple forms at Grafana. It is built on top of [react-hook-form](https://react-hook-form.com/) library and incorporates the same concepts while adjusting the API slightly.

## Usage

```jsx
import { Forms } from '@grafana/ui';

interface UserDTO {
  name: string;
  email: string;
  //...
}

const defaultUser: Partial<UserDTO> = {
  name: 'Roger Waters',
  // ...
}

<Form
  defaultValues={defaultUser}
  onSubmit={async (user: UserDTO) => await createUser(user)}
>{({register, errors}) => {
  return (
    <Field>
      <Input name="name" ref={register}/>
      <Input type="email" name="email" ref={register({required: true})}/>
      <Button type="submit">Create User</Button>
    </Field>
  )
}}</Form>
```

### Form API

`Form` component exposes API via render prop. Three properties are exposed: `register`, `errors` and `control`

#### `register`

`register` allows to register form elements(inputs, selects, radios, etc) in the form. In order to do that you need to pass `register` as a `ref` property to the form input. For example:

```jsx
<Input name="inputName" ref={register} />
```

Register accepts an object which describes validation rules for a given input:

```jsx
<Input
  name="inputName"
  ref={register({
    required: true,
    minLength: 10,
    validate: v => { // custom validation rule }
  })}
/>
```

See [Validation](#validation) for examples on validation and validation rules.

#### `errors`

`errors` is an object that contains validation errors of the form. To show error message and invalid input indication in your form, wrap input element with `<Field ...>` component and pass `invalid` and `error` props to it:

```jsx
<Field label="Name" invalid={!!errors.name} error="Name is required">
  <Input name="name" ref={register({ required: true })} />
</Field>
```

#### `control`

By default `Form` component assumes form elements are uncontrolled (https://reactjs.org/docs/glossary.html#controlled-vs-uncontrolled-components).
There are some components like `RadioButton` or `Select` that are controlled-only and require some extra work. To make
them work with the form, you need to render those using `InputControl` component:

```jsx
import { Form, Field, InputControl } from '@grafana/ui';

// render function
<Form ...>{({register, errors, control}) => (
  <>
    <Field label="RadioButtonExample">
      <InputControl
        {/* Render InputControl as controlled input (RadioButtonGroup) */}
        as={RadioButtonGroup}
        {/* Pass control exposed from Form render prop */}
        control={control}
        name="radio"
        options={...}
      />
    </Field>

    <Field label="SelectExample">
      <InputControl
        {/* Render InputControl as controlled input (Select) */}
        as={Select}
        {/* Pass control exposed from Form render prop */}
        control={control}
        name="select"
        options={...}
      />
    </Field>
  </>
)}
</Form>
```

Note that when using `InputControl`, it expects the name of the prop that handles input change to be called `onChange`.
If the property is named differently for any specific component, additional `onChangeName` prop has to be provided, specifying the name.
Additionally, the `onChange` arguments passed as an array. Check [react-hook-form docs](https://react-hook-form.com/api/#Controller)
for more prop options.

```jsx
{/* DashboardPicker has onSelected prop instead of onChange */}
import { DashboardPicker } from 'app/core/components/Select/DashboardPicker';

{/* In case of Select the value has to be returned as an object with a `value` key for the value to be saved to form data */}
const onSelectChange = ([value]) => {
  // ...
  return { value };
}

<Field label="SelectExample">
  <InputControl
    as={DashboardPicker}
    control={control}
    name="select"
    onSelected={onSelectChange}
    {/* Pass the name of the onChange handler */}
    onChangeName='onSelected'
  />
</Field>

```

### Default values

Default values of the form can be passed either via `defaultValues` property on the `Form` element, or directly on
form's input via `defaultValue` prop.
Note that changing/updating `defaultValues` passed to the form will reset the form's state, which might be undesirable in
case it has both controlled and uncontrolled components. In that case it's better to pass `defaultValue` to each form component separately.

```jsx
// Passing default values to the Form

interface FormDTO {
  name: string;
  isAdmin: boolean;
}

const defaultValues: FormDto {
  name: 'Roger Waters',
  isAdmin: false,
}

<Form defaultValues={defaultValues} ...>{...}</Form>
```

```jsx
// Passing default value directly to form inputs

interface FormDTO {
  name: string;
  isAdmin: boolean;
}

const defaultValues: FormDto {
  name: 'Roger Waters',
  isAdmin: false,
}

<Form ...>{
  ({register}) => (
    <>
      <Input defaultValue={default.name} name="name" ref={register} />
    </>
  )}
</Form>
```

### Validation

Validation can be performed either synchronously or asynchronously. What's important here is that the validation function must return either a `boolean` or a `string`.

#### Basic required example

```jsx
<Form ...>{
  ({register, errors}) => (
    <>
      <Field invalid={!!errors.name} error={errors.name && 'Name is required'}
      <Input
        defaultValue={default.name}
        name="name"
        ref={register({ required: true })}
      />
    </>
  )}
</Form>
```

#### Required with synchronous custom validation

One important thing to note is that if you want to provide different error messages for different kind of validation errors you'll need to return a `string` instead of a `boolean`.

```jsx
<Form ...>{
  ({register, errors}) => (
    <>
      <Field invalid={!!errors.name} error={errors.name?.message }
      <Input
        defaultValue={default.name}
        name="name"
        ref={register({
          required: 'Name is required',
          validation: v => {
            return v !== 'John' && 'Name must be John'
          },
        )}
      />
    </>
  )}
</Form>
```

#### Asynchronous validation

For cases when you might want to validate fields asynchronously (on the backend or via some service) you can provide an asynchronous function to the field.

Consider this function that simulates a call to some service. Remember, if you want to display an error message replace `return true` or `return false` with `return 'your error message'`.

```jsx
validateAsync = (newValue: string) => {
  try {
    await new Promise<ValidateResult>((resolve, reject) => {
      setTimeout(() => {
        reject('Something went wrong...');
      }, 2000);
    });
    return true;
  } catch (e) {
    return false;
  }
};
```

```jsx
<Form ...>{
  ({register, errors}) => (
    <>
      <Field invalid={!!errors.name} error={errors.name?.message}
      <Input
        defaultValue={default.name}
        name="name"
        ref={register({
          required: 'Name is required',
          validation: async v => {
            return  await validateAsync(v);
          },
        )}
      />
    </>
  )}
</Form>
```

### Props

<Props of={Form} />
