01. Company

class Company {
  constructor() {
    this.departments = [];
  }

  addEmployee(...args) {
    const [username, salary, position, department] = args;

    const isInvalidInput = args.some((empl) => empl === null || empl === undefined || empl === '') || salary < 0;

    if (isInvalidInput) {
      throw new Error('Invalid input!');
    } else {
      const newEmployee = {
        username,
        salary,
        position,
        department,
      };

      if (this.departments.filter((e) => e.name === department).length > 0) {
        for (const existingDepartment of this.departments) {
          if (existingDepartment.name === department) {
            existingDepartment.users.push(newEmployee);
            existingDepartment.totalSalary += salary;
          }
        }
      } else {
        const newDepartment = {
          name: department,
          users: [newEmployee],
          totalSalary: salary,
          averageSalary() {
            return this.totalSalary / this.users.length;
          },
        };

        this.departments.push(newDepartment);
      }

      return `New employee is hired. Name: ${username}. Position: ${position}`;
    }
  }

  bestDepartment() {
    const bestDepartment = this.departments.sort((a, b) => a.averageSalary - b.averageSalary)[0];

    bestDepartment.users = bestDepartment.users.sort((a, b) => {
      if (a.username === b.username) {
        return b.username - a.username;
      }
      return a.salary < b.salary ? 1 : -1;
    });

    let result = `Best Department is: ${bestDepartment.name}\nAverage salary: ${bestDepartment.averageSalary().toFixed(2)}`;

    for (const user of bestDepartment.users) {
      result += `\n${user.username} ${user.salary} ${user.position}`;
    }

    return result;
  }
}