//  Simple MVVM ViewController
class PlansViewController: UIViewController {
    typealias ArrangedType = Plan
    var viewModel: PlansViewModel

    var delegate: PlansViewControllerDelegate?

    @IBOutlet var tableView: UITableView!

    required init?(coder aDecoder: NSCoder) { fatalError("init(coder:) has not been implemented") }
    init(viewModel: PlansViewModel) {
        self.viewModel = viewModel
        super.init(nibName: nil, bundle: nil)
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.delegate = self
        tableView.register(R.nib.planSummaryCell(), forCellReuseIdentifier: R.nib.planSummaryCell.identifier)

        viewModel.tableDataSource = ArrangedTableViewDataSource(tableView: tableView, arrangedObjects: viewModel.arrangedObjects, cellBuilder: { (tableView, indexPath, object) -> (UITableViewCell) in
            let cell = tableView.dequeueReusableCell(withIdentifier: R.nib.planSummaryCell.identifier) as! PlanSummaryCell
            cell.textLabel?.text = (object as? BudgetPlan)?.title ?? object.id
            return cell
        })
    }
}

extension PlansViewController: UITableViewDelegate {
    //  Only Triggered by a long tap ???
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        self.delegate?.plansViewController(self, didSelectPlan: viewModel.arrangedObjects[indexPath])
    }
}

//  DataSource: Simple object, holding the data in a "ArrangedObjects"-class, which is at least a generic nested array  which filters and groups its contents and notifies it delegate about changes
class ArrangedTableViewDataSource<ArrangedType: Equatable>: NSObject, UITableViewDataSource {
    fileprivate let cellBuilder: (UITableView, IndexPath, ArrangedType) -> (UITableViewCell)
    fileprivate let arrangedObjects: ArrangedObjects<ArrangedType>
    fileprivate let tableView: UITableView

    init(tableView: UITableView, arrangedObjects: ArrangedObjects<ArrangedType>, cellBuilder: @escaping (UITableView, IndexPath, ArrangedType) -> (UITableViewCell)) {
        self.tableView = tableView
        self.arrangedObjects = arrangedObjects
        self.cellBuilder = cellBuilder

        super.init()

        self.tableView.dataSource = self
        self.arrangedObjects.delegate = self
    }

    func numberOfSections(in tableView: UITableView) -> Int {
        return arrangedObjects.arranged.count
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return arrangedObjects.arranged[section].count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        return cellBuilder(tableView, indexPath, arrangedObjects[indexPath])
    }
}

extension ArrangedTableViewDataSource: ArrangedObjectsDelegate {
    func arrangedObjects<ArrangedType>(_ arrangedObjects: ArrangedObjects<ArrangedType>, didInsertSection section: Int) {
        tableView.insertSections([section], with:.automatic)
    }

    func arrangedObjects<ArrangedType>(_ arrangedObjects: ArrangedObjects<ArrangedType>, didRemoveSection section: Int) {
        tableView.deleteSections([section], with: .automatic)
    }

    func arrangedObjects<ArrangedType>(_ arrangedObjects: ArrangedObjects<ArrangedType>, willInsertObject: ArrangedType) {
        self.tableView.beginUpdates()
    }

    func arrangedObjects<ArrangedType>(_ arrangedObjects: ArrangedObjects<ArrangedType>, willRemoveObject: ArrangedType) {
        self.tableView.beginUpdates()
    }


    func arrangedObjects<ArrangedType>(_ arrangedObjects: ArrangedObjects<ArrangedType>, didInsertObject: ArrangedType) {
        self.tableView.insertRows(at: [arrangedObjects.indexPath(for: didInsertObject)!], with: .automatic)
        self.tableView.endUpdates()
    }

    func arrangedObjects<ArrangedType>(_ arrangedObjects: ArrangedObjects<ArrangedType>, didRemoveObject: ArrangedType) {
        self.tableView.deleteRows(at: arrangedObjects.popRemovableIndexPaths(), with: .automatic)
        self.tableView.endUpdates()
    }
}