//
//  GeneralSettingsViewController.swift
//  GeneralSettingsViewController
//
//  Created by James Magahern on 6/25/21.
//

import UIKit

struct LabelContentConfiguration : UIContentConfiguration
{
    var text: String = ""
    var insets: UIEdgeInsets = .zero
    var textAlignment: NSTextAlignment = .natural
        
    func makeContentView() -> UIView & UIContentView {
        let label = UILabel(frame: .zero)
        let contentView = GenericContentView<UILabel, LabelContentConfiguration>(configuration: self, view: label) { config, label in
            label.text = config.text
            label.textAlignment = config.textAlignment
        }
        contentView.insets = UIEdgeInsets(top: 0, left: 10, bottom: 0, right: 10)
        return contentView
    }
    
    func updated(for state: UIConfigurationState) -> Self {
        self
    }
}

struct TextFieldContentConfiguration : UIContentConfiguration
{
    var text: String = ""
    var placeholderText: String? = nil
    var textChanged: ((String) -> Void)? = nil
    var pressedReturn: ((UITextField) -> Void)? = nil
    var keyboardType: UIKeyboardType = .default
    var returnKeyType: UIReturnKeyType = .default
    
    func makeContentView() -> UIView & UIContentView {
        let textField = UITextField(frame: .zero)
        textField.borderStyle = .roundedRect
        textField.autocorrectionType = .no
        textField.autocapitalizationType = .none
        textField.keyboardType = keyboardType
        textField.returnKeyType = returnKeyType
        
        return GenericContentView<UITextField, TextFieldContentConfiguration>(configuration: self, view: textField) { config, textField in
            textField.text = config.text
            textField.placeholder = config.placeholderText
            
            if let textChanged = config.textChanged {
                textField.addAction(UIAction { _ in textChanged(textField.text ?? "") }, for: .editingChanged)
            }
            
            if let pressedReturn = config.pressedReturn {
                class ReturnDelegate : NSObject, UITextFieldDelegate {
                    var pressedReturn: ((UITextField) -> Void)
                    
                    public init(pressedReturn: @escaping ((UITextField) -> Void)) {
                        self.pressedReturn = pressedReturn
                    }
                    
                    public func textFieldShouldReturn(_ textField: UITextField) -> Bool {
                        pressedReturn(textField)
                        return false
                    }
                }
                
                let delegate = ReturnDelegate(pressedReturn: pressedReturn)
                objc_setAssociatedObject(textField, "returnDelegate", delegate, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
                textField.delegate = delegate
            }
        }
    }
    
    func updated(for state: UIConfigurationState) -> TextFieldContentConfiguration {
        self
    }
}

struct ButtonContentConfiguration : UIContentConfiguration
{
    var menu: UIMenu
    
    func makeContentView() -> UIView & UIContentView {
        let button = UIButton(primaryAction: nil)
        return GenericContentView<UIButton, ButtonContentConfiguration>(configuration: self, view: button) { config, button in
            button.menu = menu
            button.showsMenuAsPrimaryAction = true
            if #available(macCatalyst 15.0, iOS 15.0, *) {
                var buttonConfiguration = UIButton.Configuration.plain()
                buttonConfiguration.titleAlignment = .trailing
                
                button.configuration = buttonConfiguration
                button.changesSelectionAsPrimaryAction = true
            }
        }
    }
    
    func updated(for state: UIConfigurationState) -> ButtonContentConfiguration {
        self
    }
}

class GeneralSettingsViewController: UIViewController
{
    enum Section: String, CaseIterable {
        case searchEngine = "Search Engine"
        case syncServer = "Sync Server"
    }
    
    typealias Item = String
    
    static let SearchProviderPopupItem = "searchProvider.popup"
    static let SearchEngineNameFieldItem = "searchEngine.add.name"
    static let SearchEngineURLFieldItem = "searchEngine.add.url"
    static let SyncServerItem = "syncServer.field"
    
    let dataSource: UICollectionViewDiffableDataSource<Section, Item>
    let collectionView: UICollectionView
    
    private var pendingEngineName: String = ""
    private var pendingEngineURL: String = ""
    
    static func createLayout(forIdiom idiom: UIUserInterfaceIdiom) -> UICollectionViewLayout {
        #if targetEnvironment(macCatalyst)
            let itemSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1.0),
                                                 heightDimension: .fractionalHeight(1.0))
            let item = NSCollectionLayoutItem(layoutSize: itemSize)

            let groupSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(0.60),
                                                  heightDimension: .absolute(44))
            
            let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitem: item, count: 1)
            group.edgeSpacing = NSCollectionLayoutEdgeSpacing(leading: .flexible(1.0), top: nil, trailing: nil, bottom: nil)
            
            let insets = NSDirectionalEdgeInsets(top: 24.0, leading: 64.0, bottom: 24.0, trailing: 64.0)
            
            let headerFooterSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(0.40),
                                                          heightDimension: .estimated(44.0))
            let sectionHeader = NSCollectionLayoutBoundarySupplementaryItem(
                layoutSize: headerFooterSize,
                elementKind: UICollectionView.elementKindSectionHeader,
                alignment: .topLeading,
                absoluteOffset: CGPoint(x: insets.leading, y: insets.top + 5.0)
            )
            sectionHeader.extendsBoundary = false
            sectionHeader.contentInsets = insets

            let section = NSCollectionLayoutSection(group: group)
            // section.interGroupSpacing = spacing
            section.contentInsets = insets
            section.supplementariesFollowContentInsets = true
            section.boundarySupplementaryItems = [ sectionHeader ]

            let layout = UICollectionViewCompositionalLayout(section: section)
            return layout
        #else
            var listConfiguration = UICollectionLayoutListConfiguration(appearance: .insetGrouped)
            listConfiguration.headerMode = .supplementary
            return UICollectionViewCompositionalLayout.list(using: listConfiguration)
        #endif
    }
    
    static func sectionHeaderConfiguration(forIdiom idiom: UIUserInterfaceIdiom, sectionName: String) -> UIContentConfiguration {
        if idiom == .mac {
            return LabelContentConfiguration(
                text: sectionName + ": ",
                insets: UIEdgeInsets(top: 0.0, left: 10.0, bottom: 0, right: 10.0),
                textAlignment: .right
            )
        } else {
            var config = UIListContentConfiguration.plainHeader()
            config.text = sectionName
            return config
        }
    }

    #if targetEnvironment(macCatalyst)
    static let staticIdiom = UIUserInterfaceIdiom.mac
    #else
    static let staticIdiom = UIUserInterfaceIdiom.pad
    #endif
    
    init() {
        let actionHandler = { (action: UIAction) in
            let engineName = action.title
            Settings.shared.defaultSearchEngineName = engineName
        }
        
        let itemCellRegistry = UICollectionView.CellRegistration<UICollectionViewCell, Item> { cell, indexPath, identifier in
            if identifier == Self.SearchProviderPopupItem {
                let names = Settings.shared.searchEngines.keys.sorted()
                let menu = UIMenu(children: names.map { name in
                    let action = UIAction(title: name, handler: actionHandler)
                    action.state = (Settings.shared.defaultSearchEngineName == name) ? .on : .off
                    return action
                })
                cell.contentConfiguration = ButtonContentConfiguration(menu: menu)
            } else if identifier == Self.SearchEngineNameFieldItem {
                cell.contentConfiguration = TextFieldContentConfiguration(
                    text: self.pendingEngineName,
                    placeholderText: "Name (e.g., Startpage)",
                    textChanged: { [weak self] newString in
                        self?.pendingEngineName = newString
                    },
                    pressedReturn: { $0.resignFirstResponder() },
                    keyboardType: .default,
                    returnKeyType: .next
                )
            } else if identifier == Self.SearchEngineURLFieldItem {
                cell.contentConfiguration = TextFieldContentConfiguration(
                    text: self.pendingEngineURL,
                    placeholderText: "URL template (use %q or %s)",
                    textChanged: { [weak self] newString in
                        self?.pendingEngineURL = newString
                    },
                    pressedReturn: { [weak self] textField in
                        guard let self = self else { return }
                        self.tryAddPendingSearchEngine()
                        textField.resignFirstResponder()
                    },
                    keyboardType: .URL,
                    returnKeyType: .done
                )
            } else if identifier == Self.SyncServerItem {
                cell.contentConfiguration = TextFieldContentConfiguration(
                    text: Settings.shared.syncServer ?? "",
                    placeholderText: "https://sync.server.com",
                    textChanged: { newString in
                        Settings.shared.syncServer = newString
                    },
                    pressedReturn: { $0.resignFirstResponder() },
                    keyboardType: .URL,
                    returnKeyType: .done
                )
            }
            
#if !targetEnvironment(macCatalyst)
            cell.backgroundConfiguration = UIBackgroundConfiguration.listGroupedCell()
#endif
        }
                
        let sectionHeaderRegistry = UICollectionView.SupplementaryRegistration<UICollectionViewCell>(elementKind: UICollectionView.elementKindSectionHeader, handler: {
        (cell, string, indexPath) in
            let sectionName = Section.allCases[indexPath.section].rawValue
            cell.contentConfiguration = Self.sectionHeaderConfiguration(forIdiom: Self.staticIdiom, sectionName: sectionName)
        })
        
        let layout = Self.createLayout(forIdiom: Self.staticIdiom)
        collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
        collectionView.backgroundColor = .systemGroupedBackground
        
        dataSource = UICollectionViewDiffableDataSource<Section, Item>(collectionView: collectionView) {
        (collectionView, indexPath, identifier) in
            return collectionView.dequeueConfiguredReusableCell(using: itemCellRegistry, for: indexPath, item: identifier)
        }
        
        dataSource.supplementaryViewProvider = { collectionView, elementKind, indexPath in
            return collectionView.dequeueConfiguredReusableSupplementary(using: sectionHeaderRegistry, for: indexPath)
        }
        
        super.init(nibName: nil, bundle: nil)
        
        collectionView.delegate = self
        tabBarItem.title = "General"
        tabBarItem.image = UIImage(systemName: "gear")
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func loadView() {
        self.view = collectionView
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        applySnapshot(animatingDifferences: false)
    }

}

extension GeneralSettingsViewController : UICollectionViewDelegate {
    func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
        false
    }
}

private extension GeneralSettingsViewController {
    func applySnapshot(animatingDifferences: Bool) {
        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
        snapshot.appendSections(Section.allCases)
        snapshot.appendItems([ Self.SearchProviderPopupItem,
                               Self.SearchEngineNameFieldItem,
                               Self.SearchEngineURLFieldItem ], toSection: .searchEngine)
        snapshot.appendItems([ Self.SyncServerItem ], toSection: .syncServer)
        dataSource.apply(snapshot, animatingDifferences: animatingDifferences)
    }
    
    func tryAddPendingSearchEngine() {
        let name = pendingEngineName.trimmingCharacters(in: .whitespacesAndNewlines)
        let url = pendingEngineURL.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !name.isEmpty, !url.isEmpty else { return }
        // Require placeholder
        guard url.contains("%q") || url.contains("%s") else { return }
        
        // Save
        var engines = Settings.shared.searchEngines
        engines[name] = url
        Settings.shared.searchEngines = engines
        
        // Reset inputs and refresh UI
        pendingEngineName = ""
        pendingEngineURL = ""
        applySnapshot(animatingDifferences: true)
    }
}