block-employee-directory-interview/EmployeeDirectory/ViewControllers/EmployeesViewController.swift

//
//  ViewController.swift
//  EmployeeDirectory
//
//  Created by Matt Bruce on 1/20/25.
//

import UIKit
import Combine

class EmployeesViewController: UIViewController {
    private let tableView = UITableView()
    private let activityIndicator = UIActivityIndicatorView(style: .large)
    private let viewModel = EmployeesViewModel()
    private var cancellables = Set<AnyCancellable>()

    public override func viewDidLoad() {
        super.viewDidLoad()
        setupUI()
        bindViewModel()
        viewModel.changeMode(to: .malformed)
        //viewModel.fetchEmployees()
    }
    
    private func setupUI() {
        view.backgroundColor = .white
        
        // Configure TableView
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
        tableView.dataSource = self
        
        view.addSubview(tableView)
        tableView.frame = view.bounds
        
        // Configure Activity Indicator
        activityIndicator.center = view.center
        view.addSubview(activityIndicator)
    }
    
    private func bindViewModel() {
        viewModel.$employees
            .receive(on: RunLoop.main)
            .sink { [weak self] _ in
                self?.updateFooter()
                self?.tableView.reloadData()
                self?.tableView.refreshControl?.endRefreshing()
            }
            .store(in: &cancellables)
        
        viewModel.$isLoading
            .receive(on: RunLoop.main)
            .sink { [weak self] isLoading in
                if isLoading {
                    self?.activityIndicator.startAnimating()
                } else {
                    self?.activityIndicator.stopAnimating()
                }
            }
            .store(in: &cancellables)
        
        viewModel.$errorMessage
            .receive(on: RunLoop.main)
            .sink { [weak self] _ in
                self?.updateFooter()
            }
            .store(in: &cancellables)
    }
    
    private func updateFooter() {
        var message: String? {
            guard !viewModel.isLoading else { return nil }
            return viewModel.errorMessage ?? (viewModel.employees.isEmpty ? "No employees found, please try to refresh." : nil)
        }
        
        if let message, !viewModel.isLoading {
            let footerView = UILabel()
            footerView.font = .systemFont(ofSize: 17, weight: .medium)
            footerView.text = message
            footerView.frame = CGRect(x: 0, y: 0, width: tableView.frame.width, height: 150)
            tableView.tableFooterView = footerView
        } else {
            tableView.tableFooterView = nil
        }
    }
}

extension EmployeesViewController: UITableViewDataSource {
    public func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return viewModel.employees.count
    }
    
    public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
        let employee = viewModel.employees[indexPath.row]
        cell.textLabel?.text = employee.fullName
        cell.detailTextLabel?.text = employee.emailAddress
        return cell
    }
}