DifferenceKitCrash.playground

/*:
 ## Welcome to `DifferenceKit` Playground
 ----
 > 1. Open DifferenceKit.xcworkspace.
 > 2. Build the DifferenceKit.
 > 3. Open DifferenceKit playground in project navigator.
 > 4. Show the live view in assistant editor.
 */
import DifferenceKit
import PlaygroundSupport
import UIKit

class TestTableViewController: UITableViewController {
    public var refreshAction: (() -> Void)?

    public var dataInput: [SectionViewModel] {
        get { return data }
        set {
            let changeset = StagedChangeset(source: data, target: newValue)
            print(changeset)
            tableView.reload(using: changeset, with: .fade) { data in
                self.data = data
            }
        }
    }

    private var data = [SectionViewModel]()

    public init() {
        super.init(style: .grouped)
        tableView.sectionHeaderHeight = 30
        tableView.sectionFooterHeight = 0
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: String(describing: UITableViewCell.self))
        navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .refresh, target: self, action: #selector(refresh))
    }

    public required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    @objc private func refresh() {
        refreshAction?()
    }

    public override func numberOfSections(in tableView: UITableView) -> Int {
        return data.count
    }

    public override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return data[section].elements.count
    }

    public override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: String(describing: UITableViewCell.self), for: indexPath)
        cell.textLabel?.text = data[indexPath.section].elements[indexPath.row].identifier
        return cell
    }

    public override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        return data[section].title
    }
}

enum Status {
    case going
    case notGoing
}

class SectionViewModel: DifferentiableSection {
    let title: String
    let status: Status
    var elements: [CellViewModel]
    var differenceIdentifier: String {
        get {
            SectionViewModel.string(for: status)
        }
    }

    /// Used for DifferentiableSection
    public required convenience init<C: Swift.Collection>(source: SectionViewModel, elements: C) where C.Element == CellViewModel {
        self.init(status: source.status, elements: source.elements)
    }

    init(status: Status, elements: [CellViewModel]) {
        self.status = status
        self.title = SectionViewModel.title(status: status, count: elements.count)
        self.elements = elements
    }

    private static func title(status: Status, count: Int) -> String {
        String(format: "%@ (%@)", string(for: status), String(count))
    }

    private static func string(for status: Status) -> String {
        switch status {
        case .going:
            return NSLocalizedString("Going", comment: "Going")
        case .notGoing:
            return NSLocalizedString("Not Going", comment: "Not Going")
        }
    }

    func isContentEqual(to source: SectionViewModel) -> Bool {
        guard type(of: source) == type(of: self) else {
            return false
        }

        if source.status != status {
            return false
        }

        if source.title != title {
            return false
        }

        return true
    }
}

class CellViewModel {
    let identifier: String
    let status: Status

    init(identifier: String, status: Status) {
        self.identifier = identifier
        self.status = status
    }
}

extension CellViewModel: Differentiable {
    func isContentEqual(to other: CellViewModel) -> Bool {
        if status != other.status {
            return false
        }

        return true
    }

    var differenceIdentifier: String {
        identifier
    }
}

let viewController = TestTableViewController()
let navigationController = UINavigationController(rootViewController: viewController)
navigationController.view.frame = CGRect(x: 0, y: 0, width: 320, height: 480)

PlaygroundPage.current.needsIndefiniteExecution = true
PlaygroundPage.current.liveView = navigationController.view

let source = [
    SectionViewModel(status: .going, elements: [CellViewModel(identifier: "A", status: .going),
                                                CellViewModel(identifier: "B", status: .going)]),
    SectionViewModel(status: .notGoing, elements: [CellViewModel(identifier: "C", status: .notGoing),
                                                   CellViewModel(identifier: "D", status: .notGoing)])
]

let target = [
    SectionViewModel(status: .going, elements: [CellViewModel(identifier: "B", status: .going)]),
    SectionViewModel(status: .notGoing, elements: [CellViewModel(identifier: "A", status: .going),
                                                   CellViewModel(identifier: "C", status: .notGoing),
                                                   CellViewModel(identifier: "D", status: .notGoing)])
]

viewController.dataInput = source

var isSourceShown = true
viewController.refreshAction = {
    viewController.dataInput = isSourceShown ? target : source
    isSourceShown = !isSourceShown
}