# UI: input pills

This is a high level and API explanation of the input pill interface in the
frontend of the Zulip web application.

## Setup

A pill container should have the following markup:

```html
<div class="pill-container">
    <div class="input" contenteditable="true"></div>
</div>
```

The pills will automatically be inserted in before the ".input" in order.

## Basic usage

```js
var $pill_container = $("#input_container");
var pills = input_pill.create({
    $container: $pill_container,
    create_item_from_text: user_pill.create_item_from_email,
    get_text_from_item: user_pill.get_email_from_item,
    get_display_value_from_item: user_pill.get_display_value_from_item,
});
```

You can look at `web/src/user_pill.ts` to see how the above
methods are implemented. Essentially you just need to convert
from raw data (like an email) to structured data (like an object
with display_value, email, and user_id for a user), and vice
versa.

## Typeahead

Pills almost always work in conjunction with typeahead, and
you will want to provide a `source` function to typeahead
that can exclude items from the prior pills. Here is an
example snippet from our user group settings code.

```js
source: function () {
    return user_pill.typeahead_source(pills);
},
```

And then in `user_pill.ts`...

```js
export function typeahead_source(pill_widget) {
    const persons = people.get_realm_users();
    return filter_taken_users(persons, pill_widget);
}

export function filter_taken_users(items, pill_widget) {
    const taken_user_ids = get_user_ids(pill_widget);
    items = items.filter((item) => !taken_user_ids.includes(item.user_id));
    return items;
}
```

### `onPillCreate` and `onPillRemove` methods

You can get notifications from the pill code that pills have been
created/remove.

```js
pills.onPillCreate(function () {
    update_save_state();
});

pills.onPillRemove(function () {
    update_save_state();
});
```