// @flow
import { MENTIONS } from './regexps';

export const getMentions = (text: string): Array<string> => {
  const matchedMentions = text.match(MENTIONS);
  const mentions = matchedMentions
    ? matchedMentions.filter(mention => !mention.startsWith('/'))
    : [];
  if (!mentions || mentions.length === 0) return [];
  // " @Mxstbr" => "@Mxstbr"
  const trimmed = mentions.map(
    mention => (typeof mention === 'string' ? mention.trim() : mention)
  );
  // "@Mxstbr" => "Mxstbr"
  const cleaned = removeAtSymbol(trimmed);
  // "Mxstbr" => "mxstbr"
  const lowercase = makeLowercase(cleaned);
  // ["mxstbr", "mxstbr"] => ["mxstbr"]
  const distinct = getDistinctMentions(lowercase);
  return distinct;
};

const makeLowercase = (usernames: Array<string>): Array<string> => {
  return usernames.map(u => u.toLowerCase());
};

const removeAtSymbol = (usernames: Array<string>): Array<string> => {
  return usernames.map(u => u.substr(1));
};

export const getDistinctMentions = (
  usernames: Array<string>
): Array<string> => {
  return usernames.filter((v, i, a) => a.indexOf(v) === i);
};

export default getMentions;