sS botUserName = "celestia";
sS logFile = "slack.log";

static new ThreadLocal<Bool> dedicated;
static new ThreadLocal<Channel> channel;
static new ThreadLocal<S> slackUserName;

static int maxAnswerLength = 1000, shortenTo = 200;

sbool actuallyPost = true;
static int slackSpeed = 5000, slackTimeout = 20000;

static int historySuckSize = 1;
sbool checkReactions = false;

static new L actionsAfterPost;

static new L<Channel> channels;

static class Channel {
  S channelName; // includes the site
  S channelID, token;
  boolean generalRelease, postAsUser, dedicated;
  
  boolean firstTime = true;

  new Map<S, Map> userInfos;
  
  S lastQuestion, lastAnswer;
  S lastAnswerTimestamp; // only for posted in this session
  int lastAnswerScore;
  
  void tendTo() {
    if (lastAnswerTimestamp != null && checkReactions) {
      // Poll reactions to our last answer - is there a more efficient way?
      int score = slackReactionScore(token, channelID, lastAnswerTimestamp);
      if (score != lastAnswerScore) {
        print("Reaction score changes to " + score);
        //recordFeedback(lastQuestion, lastAnswer, lastAnswerTimestamp, "emoji", score-lastAnswerScore);
        lastAnswerScore = score;
      }
    }
    
    L<SlackMsg> qs = getNewQuestions();
    //print(l(qs) + " question(s).");
    //printList(qs);
    for (SlackMsg msg : qs) if (!isMyAnswer(msg)) {
      S q = msg.text;
      S userName = getUserName(msg.user);
      Map userInfo = getUserInfo(msg.user);
      if (userInfo != null && eq(true, userInfo.get("is_bot"))) {
        print("Skipping question from bot " + userName + ": " + quote(q));
        continue;
      }
      
      slackUserName.set(userName);
      
      q = q.trim();
      print("Processing question: " + quote(q));
      if (lastAnswer != null) { // TODO: maybe check the time delay
        int score = feedbackScore(q);
        if (score != 0) {
          //recordFeedback(lastQuestion /*lastPostByUser.get(userName)*/, lastAnswer, lastAnswerTimestamp, q, score);
          if (score > 0)
            pcall { slackSmile(token, channelID, msg.ts); }
          else
            pcall { slackReact(token, channelID, msg.ts, "thinking_face"); }
        }
        lastAnswer = null;
      }
      //if (userName != null) lastPostByUser.put(userName, msg.text);
      print("dedicated: " + dedicated);
      main.dedicated.set(dedicated);
      main.channel.set(this);
      S a;
      try {
        a = callStaticAnswerMethod(q);
      } catch e {
        printStackTrace(e);
        a = "?" + getInnerMessage(e);
      }
      logStructure(logFile, ll(now(), channelID, channelName, msg.ts, msg.userName, a));
      if (nempty(a)) {
        // slack snippets have some size limit - let's forget that
        /*if (l(a) > maxAnswerLength)
          a = "```" + a + "```";*/
          
        // post long stuff to tinybrain instead
        if (l(a) > maxAnswerLength) {
          S title = "Answer for " + userName + " (>> " + q + ")";
          S id = ntUpload("eleutheria-for-user", title, unSlackSnippet(a));
          boolean isSnippet = a.contains("```");
          a = shorten(a, shortenTo) + (isSnippet ? "```" : "") + "\nFull answer here: tinybrain.de/" + parseSnippetID(id);
        }
        if (userName != null)
          a = "<@" + userName + "> " + a;
        print("Answering with: " + quote(a));
        lastAnswer = a;
        lastQuestion = q;
        if (actuallyPost) {
          S answerTime = postAnswer(a);
          Map logEntry = litmap("question", q, "answertime", answerTime, "answer", a, "user", userName, "dedicated", dedicated);
          //historyAdd(logEntry);
        }
      }
    }
  }
  
  Map getUserInfo(S userID) {
    if (userID == null) ret null;
    Map userInfo = userInfos.get(userID);
    if (userInfo == null) pcall {
      userInfo = slackGetUserInfo(token, userID);
      userInfos.put(userID, userInfo);
    }
    ret userInfo;
  }
  
  S getUserName(S userID) {
    Map userInfo = getUserInfo(userID);
    ret userInfo == null ? null : (S) userInfo.get("name");
  }
  
  // returns the slack timestamp
  S postAnswer(S text) {
    S postAs = null; // main.postAs.get();
    S username = or(postAs, botUserName);
    S botIcon = null; // main.botIcon.get();
    S url = "https://slack.com/api/chat.postMessage";
    Map postData = litmap(
      "token", token,
      "channel", channelID,
      "text", text,
      "username", username/*,
      "parse", "none",
      "link_names", "1"*/,
      "icon_url", botIcon);
    if (postAsUser && postAs == null)
      postData.put("as_user", "true");
    printStructure(postData);
    S data = doPostWithTimeout(postData, url, slackTimeout);
    Map map = jsonDecodeMap(data);
    lastAnswerTimestamp = (S) map.get("ts");
    lastAnswerScore = 0;
    print("postAnswer: " + data);
    ret lastAnswerTimestamp;
  }
  
  S getNewQuestions_lastSeen;
  
  L<SlackMsg> getNewQuestions() {
    // Get historySuckSize on first call (history before bot start)
    // and 1000 thereafter (just grab anything new)
    int limit = getNewQuestions_lastSeen == null ? historySuckSize : 1000;
    L<SlackMsg> msgs = slackReadChannel(channelID, token, limit, getNewQuestions_lastSeen);
    if (!msgs.isEmpty()) getNewQuestions_lastSeen = last(msgs).ts;
    int i = indexOfLastBotAnswer(msgs);
    if (i >= 0) {
      print("Last bot answer at " + (i+1) + "/" + l(msgs) + ": " + structure(msgs.get(i)));
      
      // update variables
      lastAnswer = msgs.get(i).text;
      for (int j = 0; j < i; j++) {
        SlackMsg msg = msgs.get(j);
        S userName = getUserName(msg.user);
        //if (userName != null) lastPostByUser.put(userName, msg.text);
      }
  
      if (firstTime)
        msgs = subList(msgs, i+1);
    }
    firstTime = false;
    ret msgs;
  }

} // end of class Channel

static boolean slackBot_inited;

static void initSlackBot() {
  if (slackBot_inited) ret;
  slackBot_inited = true;
  
  Channel c;
      
  c = new Channel;
  c.channelName = "buildingcoolstuff, #bot";
  c.channelID = "C4XAPALRG";
  c.token = celestiaToken();
  c.postAsUser = true;
  c.dedicated = true;
  channels.add(c);
  
  c = new Channel;
  c.channelName = "buildingcoolstuff, #general";
  c.channelID = "C4XTX60LF";
  c.token = celestiaToken();
  c.postAsUser = true;
  c.dedicated = false;
  channels.add(c);
}

static int indexOfLastBotAnswer(L<SlackMsg> msgs) {
  for (int i = l(msgs)-1; i >= 0; i--)
    if (isMyAnswer(msgs.get(i))) ret i;
  ret -1;
}

static boolean isMyAnswer(SlackMsg msg) {
  ret msg.botName != null /*|| actualBotUserNames.contains(msg.userName)*/;
}

static void slackBotLoop() {
  slackSetTimeout(slackTimeout);
  try {
    long lastPrinted = now();
    while licensed {
      runAndClear(actionsAfterPost);
      for (Channel c : channels) pcall {
        c.tendTo();
      }
      sleep(slackSpeed);
      if (now() > lastPrinted + 60*1000) {
        lastPrinted = now();
        print("Slack loop still going. " + unixTime());
      }
    }
  } finally {
    print("Slack bot loop exit!?");
  }
}

static void sayInDedicated(S s) {
  for (Channel c : channels) pcall {
    if (c.dedicated)
      c.postAnswer(s);
  }
}

static void dediSay(S s) {
  sayInDedicated(s);
}

Began life as a copy of #1002268