static class SlackMsg {
  S user, botName; // one of these is going to be set
  S userName; // looked up if user != null
  S type, text, ts;
  O reactions;
  S channelID;
}

static L<SlackMsg> slackReadChannel(S channelID, S token, int limit) {
  ret slackReadChannel(channelID, token, limit, null);
}

static L<SlackMsg> slackReadChannel(S channelID, S token, int limit, S oldest) {
  S url = "https://slack.com/api/channels.history";
  S postData = "token=" + urlencode(token) + "&channel=" + urlencode(channelID) + "&count=" + limit
    + (oldest != null ? "&oldest=" + urlencode(oldest) : "");
  S data = doPostWithTimeout(postData, url, slackSetTimeout_get());
  Map map = cast jsonDecode(data);
  if (!isTrue(map.get("ok")))
    fail(structure(map));
  List<Map> _msgs = cast map.get("messages");
  new L<SlackMsg> msgs;
  for (Map msg : reversedList(_msgs)) {
    new SlackMsg m;
    m.type = (S) msg.get("type");
    m.user = (S) msg.get("user");
    m.botName = (S) msg.get("username");
    m.text = htmldecode((S) msg.get("text"));
    m.ts = (S) msg.get("ts");
    m.reactions = msg.get("reactions");
    m.channelID = channelID;
    m.userName = slackGetUserName(token, m.user);
    msgs.add(m);
    //print(structure(m));
  }
  //print(l(msgs) + " messages sucked from slack channel.");
  ret msgs;
}

Began life as a copy of #1001907