UISearchToken.swift

import UIKit
import MobileCoreServices

class PastePlan: NSObject, NSItemProviderReading, NSItemProviderWriting, Codable {
    let plan: Plan
    init(_ plan: Plan) {
        self.plan = plan
    }
    static var readableTypeIdentifiersForItemProvider: [String] = [(kUTTypeJSON) as String]
    static var writableTypeIdentifiersForItemProvider: [String] = [(kUTTypeJSON) as String]

    static func object(withItemProviderData data: Data, typeIdentifier: String) throws -> Self {
        try JSONDecoder().decode(self, from: data)
    }

    func loadData(withTypeIdentifier typeIdentifier: String, forItemProviderCompletionHandler completionHandler: @escaping (Data?, Error?) -> Void) -> Progress? {
        let progress = Progress(totalUnitCount: 100)
        do {
            let data = try JSONEncoder().encode(self)
            progress.completedUnitCount = 100
            completionHandler(data, nil)
       } catch {
           completionHandler(nil, error)
       }

       return progress
    }
}

enum Plan: String, CaseIterable, Equatable, Codable {
    case business
    case travel
    case shopping

    init?(_ text: String) {
        if text.starts(with: "bu") {
            self = .business
        } else if text.starts(with: "tr") {
            self = .travel
        } else if text.starts(with: "sh") {
            self = .shopping
        } else {
            return nil
        }
    }

    var iconName: String {
        switch self {
        case .business:
            return "bag"
        case .travel:
            return "airplane"
        case .shopping:
            return "cart"
        }
    }

    var items: [String] {
        switch self {
        case .business:
            return ["会議", "商談", "プレゼン", "勉強会"]
        case .travel:
            return ["宿泊", "日帰り"]
        case .shopping:
            return ["スーパー", "デパート"]
        }
    }
}

class ViewController: UIViewController {
    @IBOutlet weak private var tableView: UITableView!

    private var searchController = UISearchController()

    private var filteredItems: [[String]] = []

    private var searchBar: UISearchBar {
        searchController.searchBar
    }

    private var isSearchBarEmpty: Bool {
        if !searchBar.searchTextField.tokens.isEmpty {
            return false
        }
        return searchBar.text?.isEmpty ?? true
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        setupSearchBar()
        setupTableView()
    }

    private func setupSearchBar() {
        searchController.searchResultsUpdater = self
        searchController.obscuresBackgroundDuringPresentation = false
        searchBar.placeholder = "検索キーワード"
        definesPresentationContext = true

        // UISearchTextField
        searchBar.searchTextField.backgroundColor = .systemOrange
        searchBar.searchTextField.textColor = .systemPurple
        searchBar.searchTextField.font = UIFont(name: "American Typewriter", size: 18)
        searchBar.searchTextField.tokenBackgroundColor = .systemBlue

        // Delete
        searchBar.searchTextField.allowsDeletingTokens = true

        // Copy & Paste
        searchBar.searchTextField.allowsCopyingTokens = true
        searchBar.searchTextField.delegate = self
        searchBar.searchTextField.pasteDelegate = self
    }

    private func setupTableView() {
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
        tableView.dataSource = self
        tableView.tableHeaderView = searchController.searchBar
    }
}

extension ViewController: UISearchTextFieldDelegate {
    func searchTextField(_ searchTextField: UISearchTextField, itemProviderForCopying token: UISearchToken) -> NSItemProvider {
        guard let plan = token.representedObject as? Plan else {
            return NSItemProvider()
        }
        return NSItemProvider(object: PastePlan(plan))
    }
}

extension ViewController: UITextPasteDelegate {
    func textPasteConfigurationSupporting(_ textPasteConfigurationSupporting: UITextPasteConfigurationSupporting, transform item: UITextPasteItem) {
        guard let item = item as? UISearchTextFieldPasteItem else {
            return
        }

        item.itemProvider.loadObject(ofClass: PastePlan.self) {
            (pastePlan, error) in
            guard let plan = (pastePlan as? PastePlan)?.plan else {
                return
            }
            let token = UISearchToken(icon: UIImage(systemName: plan.iconName), text: plan.rawValue)
            item.setSearchTokenResult(token)
        }
    }
}

extension ViewController: UITableViewDataSource {
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        if isSearchBarEmpty {
            return Plan.allCases[section].items.count
        }
        if !filteredItems.isEmpty {
            return filteredItems[section].count
        }
        return 0
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
        var item: String? = nil
        if isSearchBarEmpty {
            item = Plan.allCases[indexPath.section].items[indexPath.row]
        } else if !filteredItems.isEmpty {
            item = filteredItems[indexPath.section][indexPath.row]
        }
        cell.textLabel?.text = item
        return cell
    }
}

extension ViewController: UITableViewDelegate {
    func numberOfSections(in tableView: UITableView) -> Int {
        if isSearchBarEmpty {
            return Plan.allCases.count
        }

        if !filteredItems.isEmpty {
            return filteredItems.count
        }

        return 0
    }

    func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        Plan.allCases[section].rawValue
    }
}

extension ViewController: UISearchResultsUpdating {
    func updateSearchResults(for searchController: UISearchController) {
        var text = searchBar.text!.lowercased().trimmingCharacters(in: .whitespacesAndNewlines)
        guard !isSearchBarEmpty else {
            return
        }
        
        var searchPlans: [Plan] = extractSearchPlans()
        if let plan = Plan(text) {
            setToken(from: plan)
            searchPlans.append(plan)
            text = ""
        } else if let plan = extractPlanFromPasteboard() {
            searchPlans.append(plan)
            text = ""
        }
        updateUI(plans: searchPlans, text: text)
    }

    private func extractPlanFromPasteboard() -> Plan? {
        guard let data = UIPasteboard.general.data(forPasteboardType: (kUTTypeJSON as String)) else {
            return nil
        }
        UIPasteboard.general.items = []
        return try? JSONDecoder().decode(PastePlan.self, from: data).plan
    }

    private func extractSearchPlans() -> [Plan] {
        searchBar.searchTextField.tokens.compactMap { $0.representedObject as? Plan }
    }

    private func setToken(from plan: Plan) {
        let planToken = UISearchToken(icon: UIImage(systemName: plan.iconName), text: plan.rawValue)
        planToken.representedObject = plan
        let field = searchBar.searchTextField
        field.replaceTextualPortion(of: field.textualRange, with: planToken, at: field.tokens.count)
    }

    private func updateUI(plans: [Plan], text: String) {
        filteredItems = []
        if !plans.isEmpty {
            filteredItems = Plan.allCases.filter { plans.contains($0) }
                .map {
                    $0.items.filter { $0.starts(with: text) }
            }
        } else {
            filteredItems = Plan.allCases.map {
                    $0.items.filter { $0.starts(with: text) } }
        }
        tableView.reloadData()
    }
}