Cell.swift

import UIKit
import RxSwift
import RxCocoa

protocol AddDiscountTableViewCellDelegate: class {
    func didAdd(_ discount: DiscountViewModel)
    func didCancel(_ discount: DiscountViewModel)
    func didModify(_ discount: DiscountViewModel)
    func didRequest(present dropDown: SelectionDropDownView, options: [DropdownItem])
    func didRequestAvailableProducts() -> [SelectedProductViewModel]
}

class AddDiscountTableViewCell: UITableViewCell {
    
    @IBOutlet weak var discountTypeDropDown: SelectionDropDownView!
    @IBOutlet weak var amountTextField: PrimaryTextField!
    @IBOutlet weak var itemsDropDown: SelectionDropDownView!
    @IBOutlet weak var cancelButton: UIButton!
    
    static var identifier = "AddDiscountTableViewCell"
    
    private var disposeBag = DisposeBag()
    
    var viewModel: DiscountViewModel! {
        didSet {
            bind()
            update()
            verify()
        }
    }
    
    weak var delegate: AddDiscountTableViewCellDelegate?
    
    override func awakeFromNib() {
        super.awakeFromNib()
        configureView()
    }
    
    private func configureView() {
        discountTypeDropDown.placeholder = "discount".localized()
        amountTextField.placeholder = "amount".localized()
        itemsDropDown.placeholder = "item".localized()
        itemsDropDown.type = .checkmark
    }
    
    private func bind() {
        
        disposeBag = DisposeBag()
        
        discountTypeDropDown.value = viewModel.discountType?.title
        amountTextField.text = "\(String(describing: viewModel.amount))"
        itemsDropDown.value = String(format: "items-count".localized(), NSNumber(value: viewModel.productIds.count))
        
        amountTextField.rx.value.subscribe(onNext: { [unowned self] text in
            guard let text = text, let value = Double(text) else {
                return
            }
            self.viewModel.amount = value
            self.verify()
        }).disposed(by: disposeBag)
        
        discountTypeDropDown.rx.tap.subscribe(onNext: { [unowned self] in
            let types = ProductDiscountType.allCases
            let options = types.map {
                DropdownItem(id: $0.id, title: $0.title)
            }
            self.delegate?.didRequest(present: self.discountTypeDropDown, options: options)
            
        }).disposed(by: disposeBag)
        
        itemsDropDown.rx.tap.subscribe(onNext: { [unowned self] in
            guard let products = self.delegate?.didRequestAvailableProducts() else {
                return
            }
            let options = products.map {
                DropdownItem(id: $0.id, title: $0.name, subtitle: $0.details)
            }
            self.delegate?.didRequest(present: self.itemsDropDown, options: options)
        }).disposed(by: disposeBag)
        
        cancelButton.rx.tap.subscribe(onNext: {
            self.delegate?.didCancel(self.viewModel)
        }).disposed(by: disposeBag)
        
        discountTypeDropDown.delegate = self
        itemsDropDown.delegate = self
    }
    
    private func verify() {
        if viewModel.isReady && !viewModel.isVerified {
            delegate?.didAdd(viewModel)
            viewModel.isVerified = true
        }
    }
    
    private func update() {
        cancelButton.isHidden = !viewModel.isReady
    }
}

extension AddDiscountTableViewCell: SelectionDropDownViewDelegate {
    
    func didSelectItem(dropDown: SelectionDropDownView, item: DropdownItem) {
        if dropDown == discountTypeDropDown {
            didSelectDiscountType(item: item)
        } else if dropDown == itemsDropDown {
            didCheckedProductItems(items: dropDown.selectedItems)
        }
        verify()
    }
    
    func didDeselectItem(dropDown: SelectionDropDownView, item: DropdownItem) {
        
    }
    
    private func didSelectDiscountType(item: DropdownItem) {
        viewModel.discountType = ProductDiscountType(item.id)!
    }
    
    private func didCheckedProductItems(items: [DropdownItem]) {        
        viewModel.productIds = items.map {
            $0.id
        }
        delegate?.didModify(viewModel)
    }
}

Discount.swift

protocol AddDiscountViewControllerDelegate: class {
    func didAdd(_ discounts: [DiscountViewModel])
}

class AddDiscountViewController: BaseViewController, Storyboardable {
    
    @IBOutlet weak var tableView: UITableView!    
    @IBOutlet weak var applyButton: PrimaryButton!
    
    private var discounts = [DiscountViewModel]()
    private var remainingProducts = [SelectedProductViewModel]()
    
    private var disposeBag = DisposeBag()
    
    var viewModel: AddDiscountViewModel!
    
    weak var delegate: AddDiscountViewControllerDelegate?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        bind()
        configureView()
        remainingProducts = viewModel.selections
    }
    
    private func configureView() {
        parent?.title = discounts.isEmpty ? "add-discount".localized() : "edit-discount".localized()
    }
    
    private func bind() {
        applyButton.rx.tap.subscribe(onNext: {
            self.delegate?.didAdd(self.discounts)
        }).disposed(by: disposeBag)
    }
}

extension AddDiscountViewController: UITableViewDataSource {
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return discounts.count + 1
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        guard let cell = tableView.dequeueReusableCell(withIdentifier: AddDiscountTableViewCell.identifier, for: indexPath) as? AddDiscountTableViewCell else {
            return UITableViewCell()
        }
        if discounts.count > 0 {
            cell.viewModel = discounts[indexPath.row - 1]
        }
        cell.viewModel = DiscountViewModel()
        cell.delegate = self
        return cell
    }
}

extension AddDiscountViewController: UITableViewDelegate {
    
}

extension AddDiscountViewController: AddDiscountTableViewCellDelegate {
    
    func didModify(_ discount: DiscountViewModel) {
        let ids = discount.productIds
        ids.forEach { id in
            remainingProducts = remainingProducts.filter {
                $0.id != id
            }
        }
    }
    
    func didRequest(present dropDown: SelectionDropDownView, options: [DropdownItem]) {
        dropDown.present(in: self, options: options)
    }
    
    func didRequestAvailableProducts() -> [SelectedProductViewModel] {
        return remainingProducts
    }
    
    func didCancel(_ discount: DiscountViewModel) {
        guard let index = discounts.firstIndex(where: {
            $0 === discount
        }) else {
            return
        }
        discounts.remove(at: index)
        tableView.deleteRows(at: [IndexPath(row: index, section: 0)], with: .right)
    }
    
    func didAdd(_ discountViewModel: DiscountViewModel) {
        discounts.append(discountViewModel)
        tableView.reloadData()
    }
}