index.js

const BOARD_NAME = 'FamilySearch Research Tasks';
const BOARD_DESCRIPTION = 'Track your research tasks in Trello. Used by the FamilySearch Custom Trello Tab.';

setup();

function setup() {
  
  // When the login is clicked we initiate interactive login meaning we use the popup
  $('#login').click(function(){
    login(true);
  });
  
  // Noninteractive login to check if an auth token already exists in storage
  login(false);
}

/**
 * Initiate the auth sequence and handle the result
 * 
 * @param {Boolean=} interactive Whether to use the popup or just try to authenticate with existing tokens stored locally.
 */
async function login(interactive = true) {
  const loggedIn = await trelloAuth(interactive);
  if(!loggedIn) {
    $('#login').show();
  } else {
    begin();
  }
}

/**
 * Initiate Authentication with Trello.
 * 
 * @param {Boolean=} interactive Whether to use the popup or just try to authenticate with existing tokens stored locally.
 * @return {Promise<boolean>} resolves to true (authenticated) or false (not authenticated)
 */
function trelloAuth(interactive = true){
  return new Promise((resolve, reject) => {
    Trello.authorize({
      type: 'popup',
      name: 'FamilySearch Trello Tab',
      scope: {
        read: 'true',
        write: 'true'
      },
      interactive,
      expiration: 'never',
      success: () => resolve(true),
      error: () => resolve(false)
    });
  });
}

/**
 * Promisify the Trello.rest() method provided by the client.js Trello library
 * 
 * @param {String} method
 * @param {String} url
 * @param {Object=} params
 * @return {Promise} resolves to response object
 */
function trelloRequest(method, url, params = {}) {
  return new Promise((resolve, reject) => {
    Trello.rest(method, url, params, resolve, reject);
  });
}

async function begin() {
  $('#login').hide();
  document.write('<h2>Authenticated</h2>');
  const boardId = await getBoardId();
  const listId = await getListId(boardId, getFSPersonId());
  
  console.log(listId);
}

function getFSPersonId() {
  const params = (new URL(document.location.href)).searchParams;
  return params.get('pid');
}

/**
 * Get the ID of the Trello list for this person, or create a new one
 * 
 * @param {String} boardId Trello board ID
 * @param {String} pid FamilySearch person ID
 */
async function getListId(boardId, pid) {
  
  const nameRegex = new RegExp(`${pid}$`);
  
  // Get all lists for this board
  const existingList = await trelloRequest('GET', `/board/${boardId}/lists`, {
    filter: 'open'
  }).then((lists) => {
    return lists.find(l => nameRegex.test(l.name));
  });
  
  if(existingList) {
    return existingList.id;
  } 
  
  // Create a new board for this person
  else {
    const response = await trelloRequest('POST', `/board/${boardId}/lists`, {
      // TODO: add person's name to the board name
      name: pid,
      pos: 'bottom'
    });
    return response.id;
  }
}

/**
 * Get the ID of the FamilySearch board or create a new board and return its ID
 */
async function getBoardId() {
  
  // Get a list of open boards
  const existingFamilySearchBoard = await trelloRequest('GET', '/members/me/boards', {
    filter: 'open'
  })
  
  // Filter to just personal boards
  .then((boards) => {
    return boards.filter(b => b.idOrganization === null);
  })
  
  // Choose a FamilySearch board if one exists
  .then((boards) => {
    return boards.find(b => b.name === BOARD_NAME);
  });
  
  if(existingFamilySearchBoard) {
    return existingFamilySearchBoard.id;
  } 
  
  // Create a board if one doesn't exist
  else {
    const response = await trelloRequest('POST', '/boards', {
      name: BOARD_NAME,
      desc: BOARD_DESCRIPTION,
      defaultLists: false
    });
    return response.id;
  }
  
}