import { Story, Meta, html } from '@open-wc/demoing-storybook';
import { Required, Validator, loadDefaultFeedbackMessages } from '@lion/validate';

import '../lion-checkbox-group.js';
import '../lion-checkbox.js';

<Meta title="Forms/Checkbox Group" parameters={{ component: 'lion-checkbox-group' }} />

# Checkbox Group

`lion-checkbox-group` component enhances the functionality of the native `<input type="checkbox">` element.
Its purpose is to provide a way for users to check **multiple** options amongst a set of choices, or to function as a single toggle.

> You should use <a href="https://github.com/ing-bank/lion/tree/master/packages/checkbox" target="_blank">`<lion-checkbox>`</a> elements as the children of the `<lion-checkbox-group>`.

<Story name="Default">
  {html`
    <lion-checkbox-group
      name="scientists[]"
      label="Favorite scientists"
    >
      <lion-checkbox label="Archimedes" .choiceValue=${'Archimedes'}></lion-checkbox>
      <lion-checkbox label="Francis Bacon" .choiceValue=${'Francis Bacon'}></lion-checkbox>
      <lion-checkbox label="Marie Curie" .choiceValue=${'Marie Curie'}></lion-checkbox>
    </lion-checkbox-group>
  `}
</Story>

```html
<lion-checkbox-group
  name="scientists[]"
  label="Favourite scientists"
>
  <lion-checkbox label="Archimedes" .choiceValue=${'Archimedes'}></lion-checkbox>
  <lion-checkbox label="Francis Bacon" .choiceValue=${'Francis Bacon'}></lion-checkbox>
  <lion-checkbox label="Marie Curie" .choiceValue=${'Marie Curie'}></lion-checkbox>
</lion-checkbox-group>
```

> Make sure that the checkbox-group also has a name attribute, this is necessary for the [lion-form](?path=/docs/forms-form-overview--page)'s serialization result.

## Features

Since it extends from [lion-fieldset](?path=/docs/forms-fieldset-overview--page), it has all the features a fieldset has.

## How to use

### Installation

```sh
npm i --save @lion/checkbox-group
```

```js
import '@lion/checkbox-group/lion-checkbox-group.js';
import '@lion/checkbox-group/lion-checkbox.js';
```

### Model value

The `modelValue` of a `lion-checkbox-group` is an array containing the `choiceValues` of the `lion-checkbox` elements that have been checked.

Given the scientists example above, say that we were to select the first and last options (Archimedes & Marie Curie).

Then the `modelValue` of the `lion-checkbox-group` will look as follows:

```js
const groupElement = [parent].querySelector('lion-checkbox-group');
groupElement.modelValue;
  => ["Archimedes", "Marie Curie"];
```

### The `name` attribute

The `name` attribute of a `lion-checkbox-group` automatically gets assigned to its `lion-checkbox` children. You can also specify names for the `lion-checkbox` elements, but if this name is different from the name assigned to `lion-checkbox-group`, then an exception will be thrown.

Our recommendation would be to set the `name` attribute only on the `lion-checkbox-group` and not on the `lion-checkbox` elements.

## Examples

### Pre-select

You can pre-select options by targeting the `modelValue` object of the option and setting the `checked` property to `true`.

<Story name="Pre-select">
  {html`
    <lion-checkbox-group name="scientists" label="Favorite scientists">
      <lion-checkbox
        label="Archimedes"
        .choiceValue=${'Archimedes'}
      ></lion-checkbox>
      <lion-checkbox
        label="Francis Bacon"
        .choiceValue=${'Francis Bacon'}
        checked
      ></lion-checkbox>
      <lion-checkbox
        label="Marie Curie"
        .modelValue=${{ value: 'Marie Curie', checked: true }}
      ></lion-checkbox>
    </lion-checkbox-group>
  `}
</Story>

```html
<lion-checkbox-group name="scientists[]" label="Favorite scientists">
  <lion-checkbox
    label="Archimedes"
    .choiceValue=${'Archimedes'}
  ></lion-checkbox>
  <lion-checkbox
    label="Francis Bacon"
    .choiceValue=${'Francis Bacon'}
    checked
  ></lion-checkbox>
  <lion-checkbox
    label="Marie Curie"
    .modelValue=${{ value: 'Marie Curie', checked: true }}
  ></lion-checkbox>
</lion-checkbox-group>
```

### Disabled

You can disable the entire group by setting the `disabled` attribute on the `<lion-checkbox-group>`.

<Story name="Disabled">
  {html`
    <lion-checkbox-group name="scientists[]" label="Favorite scientists" disabled>
      <lion-checkbox
        label="Archimedes"
        .choiceValue=${'Archimedes'}
      ></lion-checkbox>
      <lion-checkbox
        label="Francis Bacon"
        .choiceValue=${'Francis Bacon'}
      ></lion-checkbox>
      <lion-checkbox
        label="Marie Curie"
        .modelValue=${{ value: 'Marie Curie', checked: true }}
      ></lion-checkbox>
    </lion-checkbox-group>
  `}
</Story>

```html
<lion-checkbox-group name="scientists[]" label="Favorite scientists" disabled>
  <lion-checkbox
    label="Archimedes"
    .choiceValue=${'Archimedes'}
  ></lion-checkbox>
  <lion-checkbox
    label="Francis Bacon"
    .choiceValue=${'Francis Bacon'}
  ></lion-checkbox>
  <lion-checkbox
    label="Marie Curie"
    .modelValue=${{ value: 'Marie Curie', checked: true }}
  ></lion-checkbox>
</lion-checkbox-group>
```

### Validation

You can apply validation to the `<lion-checkbox-group>`, similar to how you would do so in any fieldset.
The interaction states of the `<lion-checkbox-group>` are evaluated in order to hide or show feedback messages.

<Story name="Validation">
  {() => {
    loadDefaultFeedbackMessages();
    const validate = () => {
      const checkboxGroup = document.querySelector('#scientists');
      checkboxGroup.submitted = !checkboxGroup.submitted;
    };
    return html`
      <lion-checkbox-group
        id="scientists"
        name="scientists[]"
        label="Favorite scientists"
        .validators=${[new Required()]}
      >
        <lion-checkbox
          label="Archimedes"
          .choiceValue=${'Archimedes'}
        ></lion-checkbox>
        <lion-checkbox
          label="Francis Bacon"
          .choiceValue=${'Francis Bacon'}
        ></lion-checkbox>
        <lion-checkbox
          label="Marie Curie"
          .choiceValue=${'Marie Curie'}
        ></lion-checkbox>
      </lion-checkbox-group>
      <button @click="${() => validate()}">Validate</button>
    `;
  }}
</Story>

```js
import { Required, loadDefaultFeedbackMessages } from '@lion/validate';
loadDefaultFeedbackMessages();
const validate = () => {
  const checkboxGroup = document.querySelector('#scientists');
  checkboxGroup.submitted = !checkboxGroup.submitted;
};
```

```html
<lion-checkbox-group
  id="scientists"
  name="scientists[]"
  label="Favorite scientists"
  .validators=${[new Required()]}
>
  <lion-checkbox
    label="Archimedes"
    .choiceValue=${'Archimedes'}
  ></lion-checkbox>
  <lion-checkbox
    label="Francis Bacon"
    .choiceValue=${'Francis Bacon'}
  ></lion-checkbox>
  <lion-checkbox
    label="Marie Curie"
    .choiceValue=${'Marie Curie'}
  ></lion-checkbox>
</lion-checkbox-group>
<button @click="${() => validate()}">Validate</button>
```

### Validation advanced

Below is a more advanced validator on the group that evaluates the children checkboxes' checked states.

<Story name="Validation Advanced">
  {() => {
    loadDefaultFeedbackMessages();
    class HasMinTwoChecked extends Validator {
      execute(value) {
        return value.length < 2;
      }
      static get validatorName() {
        return 'HasMinTwoChecked';
      }
      static async getMessage() {
        return 'You need to select at least 2 values.';
      }
    }
    const validate = () => {
      const checkboxGroup = document.querySelector('#scientists2');
      checkboxGroup.submitted = !checkboxGroup.submitted;
    };
    return html`
      <lion-checkbox-group
        id="scientists2"
        name="scientists[]"
        label="Favorite scientists"
        help-text="You should have at least 2 of those"
        .validators=${[new Required(), new HasMinTwoChecked()]}
      >
        <lion-checkbox
          label="Archimedes"
          .choiceValue=${'Archimedes'}
        ></lion-checkbox>
        <lion-checkbox
          label="Francis Bacon"
          .choiceValue=${'Francis Bacon'}
        ></lion-checkbox>
        <lion-checkbox
          label="Marie Curie"
          .choiceValue=${'Marie Curie'}
        ></lion-checkbox>
      </lion-checkbox-group>
      <button @click="${() => validate()}">Validate</button>
    `;
  }}
</Story>

```js
import { Required, Validator, loadDefaultFeedbackMessages } from '@lion/validate';

loadDefaultFeedbackMessages();

class HasMinTwoChecked extends Validator {

  execute(value) {
    return value.length < 2;
  }

  static get validatorName() {
    return 'HasMinTwoChecked';
  }

  static async getMessage() {
    return 'You need to select at least 2 values.';
  }
}

const validate = () => {
  const checkboxGroup = document.querySelector('#scientists2');
  checkboxGroup.submitted = !checkboxGroup.submitted;
};
```

```html
<lion-checkbox-group
  id="scientists2"
  name="scientists[]"
  label="Favorite scientists"
  help-text="You should have at least 2 of those"
  .validators=${[new Required(), new HasMinTwoChecked()]}
>
  <lion-checkbox
    label="Archimedes"
    .choiceValue=${'Archimedes'}
  ></lion-checkbox>
  <lion-checkbox
    label="Francis Bacon"
    .choiceValue=${'Francis Bacon'}
  ></lion-checkbox>
  <lion-checkbox
    label="Marie Curie"
    .choiceValue=${'Marie Curie'}
  ></lion-checkbox>
</lion-checkbox-group>
<button @click="${() => validate()}">Validate</button>
```
