safe-ios/Multisig/UI/Settings/OwnerKeyManagement/ImportOwnerKey/KeyPickerController/KeyPickerController.swift

//
//  KeyPickerController.swift
//  Multisig
//
//  Created by Dmitry Bespalov on 20.01.21.
//  Copyright © 2021 Gnosis Ltd. All rights reserved.
//

import UIKit

class KeyPickerController: UITableViewController {
    private enum Section {
        static let address = 0
        static let showMore = 1
    }

    private enum Index {
        static let `default` = 0
        static let showMore = 0
    }

    private enum ListState {
        case collapsed, expanded
    }

    typealias Item = KeyAddressInfo

    var completion: () -> Void = { }
    var privateKey: PrivateKey? {
        viewModel.selectedPrivateKey
    }

    var addKeystoneKeyParameters: AddKeystoneKeyParameters? {
        viewModel.selectedKeystoneKeyParameters
    }
    
    private var viewModel: SelectOwnerAddressViewModelProtocol!
    private lazy var listState: ListState = viewModel.maxItemCount < viewModel.pageSize ? .expanded: .collapsed
    private var items: [Item] {
        switch listState {
        case .collapsed:
            return viewModel.items.isEmpty ? [] : Array(viewModel.items[0..<1])
        case .expanded:
            return viewModel.items
        }
    }

    private lazy var importButton: UIBarButtonItem = {
        let button = UIBarButtonItem(
            title: "Import",
            style: .done,
            target: self,
            action: #selector(didTapImport))
        return button
    }()

    convenience init(viewModel: SelectOwnerAddressViewModelProtocol) {
        self.init()
        self.viewModel = viewModel
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.registerCell(DefaultKeyTableViewCell.self)
        tableView.registerCell(DerivedKeyTableViewCell.self)
        tableView.registerCell(ButtonTableViewCell.self)
        tableView.rowHeight = UITableView.automaticDimension
        tableView.estimatedRowHeight = 44
        navigationItem.title = "Import Owner Key"
        navigationItem.rightBarButtonItem = importButton
        tableView.backgroundColor = .backgroundPrimary
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        Tracker.trackEvent(.ownerSelectAccount)
    }

    @objc func didTapImport() {
        guard viewModel.selectedPrivateKey != nil || viewModel.selectedKeystoneKeyParameters != nil else { return }
        self.completion()
    }

    override func numberOfSections(in tableView: UITableView) -> Int {
        2
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        switch section {
        case Section.address:
            return items.count
        case Section.showMore:
            return viewModel.canLoadMoreAddresses ? 1 : 0
        default:
            preconditionFailure()
        }
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        switch indexPath.section {

        case Section.address:
            let item = items[indexPath.row]

            switch indexPath.row {

            case Index.default:
                let cell = tableView.dequeueCell(DefaultKeyTableViewCell.self, for: indexPath)
                cell.setHeader("Default")
                cell.setLeft("#\(item.index + 1)")
                cell.setAddress(item.address, label: item.name)
                cell.setSelected(isSelected(indexPath))
                cell.setEnabled(!item.exists)

                switch listState {
                case .collapsed:
                    cell.setDetail(nil)
                    cell.separatorInset = UIEdgeInsets(top: 0, left: .greatestFiniteMagnitude, bottom: 0, right: 0)
                case .expanded:
                    cell.setDetail("Derived keys are generated from your seed phrase. Select a key you would like to import.")
                    cell.separatorInset = .zero
                }
                return cell

            default:
                let cell = tableView.dequeueCell(DerivedKeyTableViewCell.self, for: indexPath)
                cell.setLeft("#\(item.index + 1)")
                cell.setAddress(item.address)
                cell.setSelected(isSelected(indexPath))
                cell.setEnabled(!item.exists)
                return cell
            }

        case Section.showMore:
            let cell = tableView.dequeueCell(ButtonTableViewCell.self)
            cell.height = listState == .collapsed ? 44 : 76
            let label = listState == .collapsed ?
                "Show more derived keys" :
                "Show more"
            cell.setText(label) { [unowned self] in
                self.showMore()
            }
            return cell

        default:
            preconditionFailure()
        }
    }

    private func isSelected(_ indexPath: IndexPath) -> Bool {
        viewModel.selectedIndex == indexPath.row
    }

    private func showMore() {
        var updatedPaths: [IndexPath] = []
        var inserted: [IndexPath] = []
        var deleted: [IndexPath] = []

        if listState == .collapsed {
            listState = .expanded
            updatedPaths = [
                IndexPath(row: Index.default, section: Section.address),
                IndexPath(row: Index.showMore, section: Section.showMore)
            ]

            // we already have 1 address as a default one
            inserted = (1..<viewModel.pageSize).map { IndexPath(row: $0, section: 0) }
        } else {
            inserted = (items.count..<(items.count + viewModel.pageSize))
                .map { IndexPath(row: $0, section: 0) }

            viewModel.generateNextPage()

            if !viewModel.canLoadMoreAddresses {
                deleted = [IndexPath(row: Index.showMore, section: Section.showMore)]
            }
        }

        tableView.beginUpdates()
        do {
            tableView.deleteRows(at: deleted, with: .automatic)
            tableView.reloadRows(at: updatedPaths, with: .automatic)
            tableView.insertRows(at: inserted, with: .bottom)
        }
        tableView.endUpdates()
    }

    override func tableView(_ tableView: UITableView, willSelectRowAt indexPath: IndexPath) -> IndexPath? {
        let item = items[indexPath.row]
        let shouldSelect = indexPath.section == Section.address && indexPath.row != viewModel.selectedIndex && !item.exists
        return shouldSelect ? indexPath : nil
    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.deselectRow(at: indexPath, animated: true)
        let item = items[indexPath.row]
        guard indexPath.section == Section.address && indexPath.row != viewModel.selectedIndex && !item.exists else { return }

        var updatedPaths = [indexPath]

        if viewModel.selectedIndex != SelectOwnerAddressViewModel.notSelectedIndex {
            updatedPaths.append(IndexPath(row: viewModel.selectedIndex, section: 0))
        }

        viewModel.selectedIndex = indexPath.row

        tableView.beginUpdates()
        do {
            tableView.reloadRows(at: updatedPaths, with: .automatic)
        }
        tableView.endUpdates()
    }
}