text: import * as peer_data from "./peer_data";
  import * as stream_data from "./stream_data";
  
  function display_pill(sub) {
      const sub_count = peer_data.get_subscriber_count(sub.stream_id);
      return "#" + sub.name + ": " + sub_count + " users";
  }
  
  export function create_item_from_stream_name(stream_name, current_items) {
      stream_name = stream_name.trim();
      if (!stream_name.startsWith("#")) {
          return undefined;
      }
      stream_name = stream_name.slice(1);
  
      const sub = stream_data.get_sub(stream_name);
      if (!sub) {
          return undefined;
      }
  
      const existing_ids = current_items.map((item) => item.stream_id);
      if (existing_ids.includes(sub.stream_id)) {
          return undefined;
      }
  
      const item = {
          display_value: display_pill(sub),
          stream_id: sub.stream_id,
          stream_name: sub.name,
      };
  
      return item;
  }
  
  export function get_stream_name_from_item(item) {
      return item.stream_name;
  }
  
  function get_user_ids_from_subs(items) {
      let user_ids = [];
      for (const item of items) {
          // only some of our items have streams (for copy-from-stream)
          if (item.stream_id !== undefined) {
              user_ids = user_ids.concat(peer_data.get_subscribers(item.stream_id));
          }
      }
      return user_ids;
  }
  
  export function get_user_ids(pill_widget) {
      const items = pill_widget.items();
      let user_ids = get_user_ids_from_subs(items);
      user_ids = Array.from(new Set(user_ids));
  
      user_ids = user_ids.filter(Boolean);
      return user_ids;
  }
  
  export function append_stream(stream, pill_widget) {
      pill_widget.appendValidatedData({
          display_value: display_pill(stream),
          stream_id: stream.stream_id,
          stream_name: stream.name,
      });
      pill_widget.clear_text();
  }
  
  export function get_stream_ids(pill_widget) {
      const items = pill_widget.items();
      let stream_ids = items.map((item) => item.stream_id);
      stream_ids = stream_ids.filter(Boolean);
  
      return stream_ids;
  }
  
  export function filter_taken_streams(items, pill_widget) {
      const taken_stream_ids = get_stream_ids(pill_widget);
      items = items.filter((item) => !taken_stream_ids.includes(item.stream_id));
      return items;
  }
  
  export function typeahead_source(pill_widget) {
      const potential_streams = stream_data.get_unsorted_subs();
      return filter_taken_streams(potential_streams, pill_widget);
  }
  