robotty/dank-twitch-irc

import { TwitchFlag } from "../flag";
import { TwitchFlagList } from "../flags";

export function parseFlags(
  messageText: string,
  flagsSrc: string
): TwitchFlagList {
  const flags: TwitchFlagList = [];

  const regex = /^(,?(?:[0-9]+-[0-9]+:)(?:(?:[ISAP]\.[0-9]+\/?)+)?)+$/g;

  const matchFlagsSrc = flagsSrc.match(regex);

  if (flagsSrc.length <= 0 || matchFlagsSrc === null) {
    return flags;
  }

  const messageCharacters = [...messageText];

  for (const flagInstancesSrc of flagsSrc.split(",")) {
    const [indexes, instancesSrc] = flagInstancesSrc.split(":", 2);

    let [startIndex, endIndex] = indexes.split("-").map((s) => Number(s));

    // to make endIndex exclusive
    endIndex = endIndex + 1;

    // flags tag can have wildly out-of-bounds indexes
    if (startIndex < 0) {
      startIndex = 0;
    }
    if (endIndex > messageCharacters.length) {
      endIndex = messageCharacters.length;
    }

    const flagText = messageCharacters.slice(startIndex, endIndex).join("");

    const categories: TwitchFlag["categories"] = [];
    for (const instanceSrc of instancesSrc.split("/")) {
      if (instanceSrc.length > 0) {
        const [category, score] = instanceSrc.split(".");
        categories.push({
          category,
          score: Number(score),
        });
      }
    }

    flags.push(new TwitchFlag(startIndex, endIndex, flagText, categories));
  }

  // sort by start index
  flags.sort((a, b) => a.startIndex - b.startIndex);

  return flags;
}