ComposePoll.gs

const CHOICE_CUTOFF_LENGTH = 32;

var PollComposer = function() {
  
  this.split_choice_description = function(choice_text) {
    
    let description_marker_index = choice_text.indexOf('->');

    if (description_marker_index > -1)
      return { value: choice_text.substring(0, description_marker_index), description: choice_text.substring(description_marker_index + 2) };
              
    if (choice_text.length > CHOICE_CUTOFF_LENGTH)  // TODO: Choose a better way to introduce a hard break if the choice was too long
      return { value: choice_text.substring(0, CHOICE_CUTOFF_LENGTH), description: choice_text.substring(CHOICE_CUTOFF_LENGTH + 1) };
              
    return { value: choice_text, description: "" }
  }
  
  this.compose_vote_button = function(choice_value, poll, index, expired) {    
    
    return {
        textButton: {
          text: choice_value,
          disabled: expired,
          onClick: {
            action: {
              actionMethodName: "update-vote",
              parameters: [
                { key: "poll", value: JSON.stringify(poll) },
                { key: "index", value: index.toString() }
              ]
            }
          }
        }
      }
  }
  
  this.compose_vote_section = function(poll, index, total_votes, expired) {
    
    let response = poll.responses[index];
    let choice_text = poll.choices[index];
    let { value, description } = this.split_choice_description(choice_text);
    let widgets = [{ buttons: [this.compose_vote_button(value, poll, index, expired)] }];
    widgets.push({ textParagraph: { text: `<i><font color='#3b78e7'>${description}</font></i>` }});
    
    let vote_percent = total_votes > 0 ? 100 * response.voters.length / total_votes : 0;
    
    widgets.push({ textParagraph: { text: Utilities.formatString("%.2f\% / (%d)", vote_percent, response.voters.length) }});
    
    if (!poll.options.anonymous)
    {
      let voters_list = response.voters.join(", ");
      widgets.push({ textParagraph: { text: `<i><font color='#808080'>${voters_list}</font></i>` }});
    }
    
    return { widgets: widgets };
  }

  this.compose_footer_section = function(total_votes, expired) {
    let widgets = [{ textParagraph: { text: `<b>Total votes: ${total_votes}<b>` }}];
    
    if (expired)
      widgets.push({ textParagraph: { text: "<font color='#FF0000'>Poll has expired!</font>" }});
    
    return { widgets: widgets };
  }

  this.compose_message_body = function(poll, total_votes, expired, action_response_type) {

    let sections = [];
    
    let poll_options = `[Type: ${poll.options.single_choice ? "Single Choice" : "Multi Choice"}, Anonymous: ${poll.options.anonymous ? "Yes" : "No"}]`;    
    sections.push({ widgets: [{ textParagraph: { text: poll_options }}] });
    
    let initiated_on = new Date(poll.initiated_on);
    let expires_on = new Date(initiated_on.getTime() + 1000 * poll.options.expiration_time_in_seconds);
    initiated_on = Utilities.formatDate(initiated_on, "GMT", "yyyy-MM-dd HH:mm:ss z");  // TODO: Set the zone correctly per each user
    expires_on = Utilities.formatDate(expires_on, "GMT", "yyyy-MM-dd HH:mm:ss z");  // TODO: Set the zone correctly per each user
    let poll_expiration = `[Initiated On: ${initiated_on}, Expires On: ${poll.options.expiration_time_in_seconds == 0.0 ? "Unbounded" : expires_on}]`;
    sections.push({ widgets: [{ textParagraph: { text: poll_expiration }}] });
    
    for (let i = 0; i < poll.responses.length; ++i) {
      sections.push(this.compose_vote_section(poll, i, total_votes, expired));
    }
    
    sections.push(this.compose_footer_section(total_votes, expired));
    
    return {
      actionResponse: { type: action_response_type },
      cards: [{
        header: { title: poll.question, subtitle : `Poll created by ${poll.poller}.`, imageUrl : DEFAULT_IMAGE_URL },
        sections: sections
      }]
    };
  }

  this.compose = function(poll_details) {

    let poll = poll_details;
    
    // Add a placeholder to record votes
    poll.responses = [];
    for (let choice_index in poll.choices) {
      poll.responses.push({ voters: [] });
    }
    
    poll.initiated_on = new Date();
    
    return this.compose_message_body(poll, 0, false, "NEW_MESSAGE");
  }
  
  this.update_poll_multi_choice = function(voter, poll, index) {
    
    let response = poll.responses[index];
    let voter_index = response.voters.indexOf(voter);
    if (voter_index > -1)
      response.voters.splice(voter_index, 1);  // Already voted so remove
    else
      response.voters.push(voter);  // Didn't use this response yet
    
  }

  this.update_poll_single_choice = function(voter, poll, index) {

    // if the user clicked on the same choice then remove.
    let voter_response = poll.responses[index];
    let voter_index = voter_response.voters.indexOf(voter);
    if (voter_index > -1) {
      voter_response.voters.splice(voter_index, 1);
      return;
    }
    
    // search all other responses and see if the voter has already voted .. if so remove and then add the new selection
    for (let response of poll.responses) {
      
      if (response == voter_response)
        continue;

      let voter_index = response.voters.indexOf(voter);
      if (voter_index > -1) {
        response.voters.splice(voter_index, 1);
        break;
      }
      
    }
    
    voter_response.voters.push(voter);  // Set the new selection
  }
  
  this.is_poll_still_active = function(poll) {
    
    if (poll.options.expiration_time_in_seconds == 0.0)
      return true;
    
    let current_time = new Date();
    let initiated_on = new Date(poll.initiated_on);
    let date_diff_in_milliseconds = current_time - initiated_on;
    
    return date_diff_in_milliseconds <= 1000 * poll.options.expiration_time_in_seconds;
  }

  this.update = function(voter, poll, index) {

    let poll_active = this.is_poll_still_active(poll);
    
    if (poll_active) {
      let poll_update_method = poll.options.single_choice ? this.update_poll_single_choice : this.update_poll_multi_choice;
      poll_update_method(voter, poll, index);
    }
    
    let total_votes = poll.responses.reduce(function(total, response) { return total + response.voters.length; }, 0);
    
    return this.compose_message_body(poll, total_votes, !poll_active, "UPDATE_MESSAGE");
  }
}