Code.gs

/**
 * Responds to an ADDED_TO_SPACE event
 *  in Google Chat.
 *
 * @param event the event object from Google Chat
 * @return JSON-formatted response
 */
function onAddToSpace(event) {
  console.info(event);

  var message = "";

  if (event.space.type === "DM") {
    message = "Thank you for adding me to a DM, " +
      event.user.displayName + "!";
  } else {
    message = "Thank you for adding me to " +
      event.space.displayName;
  }

  return { "text": message };
}

/**
 * Responds to a REMOVED_FROM_SPACE event
 * in Google Chat.
 *
 * @param event the event object from Google Chat
 */
function onRemoveFromSpace(event) {
  console.info(event);
  console.info("Chat app removed from ", event.space.name);
}

var DEFAULT_IMAGE_URL = "https://goo.gl/bMqzYS";
var header = {
  "header": {
    "title" : "Attendance Chat app",
    "subtitle" : "Log your vacation time",
    "imageUrl" : DEFAULT_IMAGE_URL
  }
};

/**
 * Creates a card-formatted response.
 *
 * @param widgets the UI components to send
 * @return JSON-formatted response
 */
function createCardResponse(widgets) {
  return {
    "cards": [
      header,
      {
        "sections": [{
          "widgets": widgets
        }]
      }]
  };
}

var REASON_SICK = "Out sick";
var REASON_OTHER = "Out of office";

/**
 * Responds to a MESSAGE event triggered in Google Chat.
 *
 * @param event the event object from Google Chat
 * @return JSON-formatted response
 */
function onMessage(event) {
  console.info(event);

  var reason = REASON_OTHER;
  var name = event.user.displayName;
  var userMessage = event.message.text;

  // If the user said that they were "sick", adjust the image in the
  // header sent in response.
  if (userMessage.indexOf("sick") > -1) {

    // Hospital material icon
    header.header.imageUrl = "https://goo.gl/mnZ37b";
    reason = REASON_SICK;

  } else if (userMessage.indexOf("vacation") > -1) {

    // Spa material icon
    header.header.imageUrl = "https://goo.gl/EbgHuc";
  }

  var widgets = [{
      "textParagraph": {
        "text": "Hello, " + name +
          ".<br/>Are you taking time off today?"
      }
    }, {
      "buttons": [{
        "textButton": {
          "text": "Set vacation in Gmail",
          "onClick": {
            "action": {
              "actionMethodName": "turnOnAutoResponder",
              "parameters": [{
                "key": "reason",
                "value": reason
              }]
            }
          }
        }
      }, {
        "textButton": {
          "text": "Block out day in Calendar",
          "onClick": {
            "action": {
              "actionMethodName": "blockOutCalendar",
                "parameters": [{
                  "key": "reason",
                  "value": reason
                }]
            }
          }
        }
      }]
  }];

  return createCardResponse(widgets);
}

/**
 * Responds to a CARD_CLICKED event triggered in Google Chat.
 *
 * @param event the event object from Google Chat
 * @return JSON-formatted response
 */
function onCardClick(event) {
  console.info(event);

  var message = "";
  var reason = event.action.parameters[0].value;

  if (event.action.actionMethodName == "turnOnAutoResponder") {
    turnOnAutoResponder(reason);
    message = "Turned on vacation settings.";
  } else if (event.action.actionMethodName == "blockOutCalendar") {
    blockOutCalendar(reason);
    message = "Blocked out your calendar for the day.";
  } else {
    message = "I'm sorry; I'm not sure which button you clicked.";
  }

  return { "text": message };
}

var ONE_DAY_MILLIS = 24 * 60 * 60 * 1000;

/**
 * Turns on the user's vacation response for today in Gmail.
 *
 * @param reason the reason for vacation, either REASON_SICK or REASON_OTHER
 */
function turnOnAutoResponder(reason) {
  var currentTime = (new Date()).getTime();

  Gmail.Users.Settings.updateVacation({
    "enableAutoReply": true,
    "responseSubject": reason,
    "responseBodyHtml": "I'm out of the office today; will be back on the next business day.<br><br><i>Created by Attendance Chat app!</i>",
    "restrictToContacts": true,
    "restrictToDomain": true,
    "startTime": currentTime,
    "endTime": currentTime + ONE_DAY_MILLIS
  }, "me");
}

/**
 * Places an all-day meeting on the user's Calendar.
 *
 * @param reason the reason for vacation, either REASON_SICK or REASON_OTHER
 */
function blockOutCalendar(reason) {
  CalendarApp.createAllDayEvent(reason, new Date(), new Date(Date.now() + ONE_DAY_MILLIS));
}