Pair Programming Scripts

v1.js

const contacts = {};

let prospectiveUsersCache = {};

const isZiinaUser = (phoneNumber) => {
  return false;
};

const syncContacts = (userId, phoneNumbers) => {
  contacts[userId] = phoneNumbers;

  prospectiveUsersCache[userId] = phoneNumbers.reduce((acc, phoneNumber) => {
    if (isZiinaUser(phoneNumber)) {
      return acc;
    }

    const friendsOnZiina = Object.entries(contacts)
      .filter(([uid, numbers]) => uid !== userId && numbers.includes(phoneNumber))
      .length;

    return [
      ...acc,
      {
        phoneNumber,
        friendsOnZiina,
      },
    ];
  }, []);

  prospectiveUsersCache = Object.keys(prospectiveUsersCache).map(uid => {
    const friends = prospectiveUsersCache[uid];

    return friends.map(friend => {
      return {
        phoneNumber: friend.phoneNumber,
        friendsOnZiina: Object.entries(contacts)
          .filter(([uid, numbers]) => uid !== userId && numbers.includes(friend.phoneNumber))
          .length,
      };
    });
  });
};

const prospectiveUsers = (userId) => {
  if (!contacts.hasOwnProperty(userId) || !prospectiveUsersCache.hasOwnProperty(userId)) {
    return [];
  }

  return prospectiveUsersCache[userId];
};

syncContacts(1, [111, 222, 333]);
// console.log(prospectiveUsersCache);
syncContacts(2, [111, 333, 444]);
// console.log(prospectiveUsersCache);
syncContacts(3, [555, 666, 444]);
// console.log(prospectiveUsersCache);

// console.log(contacts);

console.log(prospectiveUsers(1));
console.log(prospectiveUsers(2));
console.log(prospectiveUsers(3));

v2.ts

type ProspectiveUser = {
  phoneNumber: string,
  friendsOnZiina: number,
}

type User = {
  userId: string,
  contacts: ProspectiveUser[],
}

const users: Map<string, User> = new Map();

const getZiinaUsersCount = (excludedUserId: string, phoneNumber: string): number => {
  let count: number = 0;

  users.forEach(user => {
    if (
      user.userId !== excludedUserId
      && user.contacts.some(contact => contact.phoneNumber === phoneNumber)
    ) {
      count = count + 1;
    }
  });

  return count;
};

const getProspectiveUser = (userId: string, phoneNumber: string): ProspectiveUser => ({
  phoneNumber,
  friendsOnZiina: getZiinaUsersCount(userId, phoneNumber),
});

const syncContacts = (userId: string, phoneNumbers: string[]): void => {
  // Update the user to sync first...
  users.set(userId, {
    userId,
    contacts: phoneNumbers.map(phoneNumber => getProspectiveUser(userId, phoneNumber)),
  });

  // Then update the remaining users
  users.forEach(user => {
    if (user.userId !== userId) {
      users.set(user.userId, {
        ...user,
        contacts: user.contacts.map(contact => getProspectiveUser(user.userId, contact.phoneNumber)),
      });
    }
  });
};

const prospectiveUsers = (userId: string): ProspectiveUser[] => {
  const user = users.get(userId);
  return user ? user.contacts : [];
};

syncContacts('1', ['111', '222', '333']);
syncContacts('2', ['111', '222', '333', '444']);
syncContacts('3', ['111', '444', '333']);
syncContacts('4', ['111', '555']);
// Ensure updates are handled
syncContacts('1', ['111', '222', '333', '444']);


const one = prospectiveUsers('1');
const two = prospectiveUsers('2');
const three = prospectiveUsers('3');
const four = prospectiveUsers('4');
const five = prospectiveUsers('5');

console.log('one ==>', one);
console.log('two ==>', two);
console.log('three ==>', three);
console.log('four ==>', four);
console.log('five ==>', five);

// Some very basic tests...
console.assert(one.length === 4);
console.assert(two.length === 4);
console.assert(three.length === 3);
console.assert(four.length === 2);
console.assert(five.length === 0);

const assertNumberAndCount = (users: ProspectiveUser[], phoneNumber: string, count: number): boolean =>
  users.find(user => user.phoneNumber === phoneNumber)?.friendsOnZiina === count;

console.assert(assertNumberAndCount(one, '111', 3));
console.assert(assertNumberAndCount(one, '222', 1));
console.assert(assertNumberAndCount(one, '333', 2));
console.assert(assertNumberAndCount(one, '444', 2));

console.assert(assertNumberAndCount(two, '111', 3));
console.assert(assertNumberAndCount(two, '222', 1));
console.assert(assertNumberAndCount(two, '333', 2));
console.assert(assertNumberAndCount(two, '444', 2));

console.assert(assertNumberAndCount(three, '111', 3));
console.assert(assertNumberAndCount(three, '333', 2));
console.assert(assertNumberAndCount(three, '444', 2));

console.assert(assertNumberAndCount(four, '111', 3));
console.assert(assertNumberAndCount(four, '555', 0));