Implementing OrderLoaderViewController

Author: jleandroperez

WooCommerce/Classes/ViewRelated/Orders/OrderDetails/OrderLoaderViewController.swift

@@ -0,0 +1,241 @@
+import Foundation
+import UIKit
+import Yosemite
+
+
+// MARK: - OrderLoaderViewController: Loads asynchronously an Order (given it's OrderID + SiteID).
+//         On Success the OrderDetailsViewController will be rendered "in place".
+//
+class OrderLoaderViewController: UIViewController {
+
+    /// UI Spinner
+    ///
+    private let activityIndicator = UIActivityIndicatorView(style: .gray)
+
+    /// Target OrderID
+    ///
+    private let orderID: Int
+
+    /// Target Order's SiteID
+    ///
+    private let siteID: Int
+
+    /// UI Active State
+    ///
+    private var state: State = .loading {
+        didSet {
+            didLeave(state: oldValue)
+            didEnter(state: state)
+        }
+    }
+
+
+    // MARK: - Initializers
+
+    init(orderID: Int, siteID: Int) {
+        self.orderID = orderID
+        self.siteID = siteID
+
+        super.init(nibName: nil, bundle: nil)
+    }
+
+    required init?(coder aDecoder: NSCoder) {
+        fatalError("Please specify the OrderID and SiteID!")
+    }
+
+
+    // MARK: - Overridden Methods
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+
+        configureNavigationItem()
+        configureSpinner()
+        configureMainView()
+    }
+
+    override func viewWillAppear(_ animated: Bool) {
+        super.viewWillAppear(animated)
+        reloadOrder()
+    }
+}
+
+
+// MARK: - Actions
+//
+private extension OrderLoaderViewController {
+
+    /// Loads (and displays) the specified Order.
+    ///
+    func reloadOrder() {
+        let action = OrderAction.retrieveOrder(siteID: siteID, orderID: orderID) { [weak self] (order, error) in
+            guard let `self` = self else {
+                return
+            }
+
+            guard let order = order else {
+                DDLogError("## Error loading Order \(self.siteID).\(self.orderID): \(error.debugDescription)")
+                self.state = .failure
+                return
+            }
+
+            self.state = .success(order: order)
+        }
+
+        state = .loading
+        StoresManager.shared.dispatch(action)
+    }
+}
+
+
+// MARK: - Configuration
+//
+private extension OrderLoaderViewController {
+
+    /// Setup: Navigation
+    ///
+    func configureNavigationItem() {
+        title = NSLocalizedString("Loading Order", comment: "Displayed when an Order is being retrieved")
+        navigationItem.backBarButtonItem = UIBarButtonItem(title: String(), style: .plain, target: nil, action: nil)
+    }
+
+    /// Setup: Main View
+    ///
+    func configureMainView() {
+        view.backgroundColor = StyleManager.tableViewBackgroundColor
+        view.addSubview(activityIndicator)
+        view.pinSubviewAtCenter(activityIndicator)
+    }
+
+    /// Setup: Spinner
+    ///
+    func configureSpinner() {
+        activityIndicator.hidesWhenStopped = true
+        activityIndicator.translatesAutoresizingMaskIntoConstraints = false
+    }
+}
+
+
+// MARK: - Overlays
+//
+private extension OrderLoaderViewController {
+
+    /// Starts the Spinner
+    ///
+    func startSpinner() {
+        activityIndicator.startAnimating()
+    }
+
+    /// Stops the Spinner
+    ///
+    func stopSpinner() {
+        activityIndicator.stopAnimating()
+    }
+
+    /// Displays the Loading Overlay.
+    ///
+    func displayFailureOverlay() {
+        let overlayView: OverlayMessageView = OverlayMessageView.instantiateFromNib()
+        overlayView.messageImage = .waitingForCustomersImage
+        overlayView.messageText = NSLocalizedString("The Order couldn't be loaded!", comment: "Fetching an Order Failed")
+        overlayView.actionText = NSLocalizedString("Retry", comment: "Retry the last action")
+        overlayView.onAction = { [weak self] in
+            self?.reloadOrder()
+        }
+
+        overlayView.attach(to: view)
+    }
+
+    /// Removes all of the the OverlayMessageView instances in the view hierarchy.
+    ///
+    func removeAllOverlays() {
+        for subview in view.subviews where subview is OverlayMessageView {
+            subview.removeFromSuperview()
+        }
+    }
+
+    /// Presents the OrderDetailsViewController, as a childViewController, for a given Order.
+    ///
+    func presentOrderDetails(for order: Order) {
+        let identifier = OrderDetailsViewController.classNameWithoutNamespaces
+        guard let detailsViewController = UIStoryboard.orders.instantiateViewController(withIdentifier: identifier) as? OrderDetailsViewController else {
+            fatalError()
+        }
+
+        // Setup the DetailsViewController
+        detailsViewController.viewModel = OrderDetailsViewModel(order: order)
+
+        // Attach
+        addChild(detailsViewController)
+        attachSubview(detailsViewController.view)
+        detailsViewController.didMove(toParent: self)
+
+        // And, of course, borrow the Child's Title
+        title = detailsViewController.title
+    }
+
+    /// Removes all of the children UIViewControllers
+    ///
+    func detachChildrenViewControllers() {
+        for child in children {
+            child.view.removeFromSuperview()
+            child.removeFromParent()
+            child.didMove(toParent: nil)
+        }
+    }
+}
+
+
+// MARK: - UI Methods
+//
+private extension OrderLoaderViewController {
+
+    /// Attaches a given Subview, and ensures it's pinned to all the edges
+    ///
+    func attachSubview(_ subview: UIView) {
+        subview.translatesAutoresizingMaskIntoConstraints = false
+        view.addSubview(subview)
+        view.pinSubviewToAllEdges(subview)
+    }
+}
+
+
+// MARK: - Finite State Machine Management
+//
+private extension OrderLoaderViewController {
+
+    /// Runs whenever the FSM enters a State.
+    ///
+    func didEnter(state: State) {
+        switch state {
+        case .loading:
+            startSpinner()
+        case .success(let order):
+            presentOrderDetails(for: order)
+        case .failure:
+            displayFailureOverlay()
+        }
+    }
+
+    /// Runs whenever the FSM leaves a State.
+    ///
+    func didLeave(state: State) {
+        switch state {
+        case .loading:
+            stopSpinner()
+        case .success(_):
+            detachChildrenViewControllers()
+        case .failure:
+            removeAllOverlays()
+        }
+    }
+}
+
+
+// MARK: - OrderLoader Possible Status(es)
+//
+private enum State {
+    case loading
+    case success(order: Order)
+    case failure
+}