//
//  SourcesViewController.swift
//  AltStore
//
//  Created by Riley Testut on 3/17/20.
//  Copyright © 2020 Riley Testut. All rights reserved.
//

import UIKit
import CoreData

import AltStoreCore
import Roxas
import Nuke

struct SourceError: ALTLocalizedError
{
    enum Code: Int, ALTErrorCode
    {
        typealias Error = SourceError
        case unsupported
    }
    
    var code: Code
    var errorTitle: String?
    var errorFailure: String?
    @Managed var source: Source
    
    var errorFailureReason: String {
        switch self.code
        {
        case .unsupported: return String(format: NSLocalizedString("The source “%@” is not supported by this version of SideStore.", comment: ""), self.$source.name)
        }
    }
}

@objc(SourcesFooterView)
private final class SourcesFooterView: TextCollectionReusableView
{
    @IBOutlet var activityIndicatorView: UIActivityIndicatorView!
    @IBOutlet var textView: UITextView!
}

private extension UIAction.Identifier
{
    static let showDetails = UIAction.Identifier("io.altstore.showDetails")
    static let showError = UIAction.Identifier("io.altstore.showError")
}

final class SourcesViewController: UICollectionViewController
{
    var deepLinkSourceURL: URL? {
        didSet {
            self.handleAddSourceDeepLink()
        }
    }
    
    private lazy var dataSource = self.makeDataSource()
    
    private var placeholderView: RSTPlaceholderView!
    private var placeholderViewButton: UIButton!
    private var placeholderViewCenterYConstraint: NSLayoutConstraint!
    
    override func viewDidLoad()
    {
        super.viewDidLoad()
        
        let layout = self.makeLayout()
        self.collectionView.collectionViewLayout = layout
        
        self.navigationController?.view.tintColor = .altPrimary
        
        self.collectionView.register(AppBannerCollectionViewCell.self, forCellWithReuseIdentifier: RSTCellContentGenericCellIdentifier)
        
        self.collectionView.dataSource = self.dataSource
        self.collectionView.prefetchDataSource = self.dataSource
        self.collectionView.allowsSelectionDuringEditing = false
        
        let backgroundView = UIView(frame: .zero)
        backgroundView.backgroundColor = .altBackground
        self.collectionView.backgroundView = backgroundView
        
        self.placeholderView = RSTPlaceholderView(frame: .zero)
        self.placeholderView.translatesAutoresizingMaskIntoConstraints = false
        self.placeholderView.textLabel.text = NSLocalizedString("Add More Sources!", comment: "")
        self.placeholderView.detailTextLabel.text = NSLocalizedString("Sources determine what apps are available in AltStore. The more sources you add, the better your AltStore experience will be.\n\nDon’t know where to start? Try adding one of our Recommended Sources!", comment: "")
        self.placeholderView.detailTextLabel.textAlignment = .natural
        backgroundView.addSubview(self.placeholderView)
        
        let fontDescriptor = UIFontDescriptor.preferredFontDescriptor(withTextStyle: .title3).bolded()
        self.placeholderView.textLabel.font = UIFont(descriptor: fontDescriptor, size: 0.0)
        self.placeholderView.detailTextLabel.font = UIFont.preferredFont(forTextStyle: .body)
        self.placeholderView.detailTextLabel.textAlignment = .natural
        
        self.placeholderViewButton = UIButton(type: .system, primaryAction: UIAction(title: NSLocalizedString("View Recommended Sources", comment: "")) { [weak self] _ in
            self?.performSegue(withIdentifier: "addSource", sender: nil)
        })
        self.placeholderViewButton.titleLabel?.font = UIFont.preferredFont(forTextStyle: .body)
        self.placeholderView.stackView.spacing = 15
        self.placeholderView.stackView.directionalLayoutMargins = NSDirectionalEdgeInsets(top: 15, leading: 15, bottom: 15, trailing: 15)
        self.placeholderView.stackView.isLayoutMarginsRelativeArrangement = true
        self.placeholderView.stackView.addArrangedSubview(self.placeholderViewButton)
        
        self.placeholderViewCenterYConstraint = self.placeholderView.safeAreaLayoutGuide.centerYAnchor.constraint(equalTo: backgroundView.centerYAnchor, constant: 0)
        
        NSLayoutConstraint.activate([
            self.placeholderViewCenterYConstraint,
            self.placeholderView.centerXAnchor.constraint(equalTo: backgroundView.centerXAnchor),
            self.placeholderView.leadingAnchor.constraint(equalTo: backgroundView.leadingAnchor),
            self.placeholderView.trailingAnchor.constraint(equalTo: backgroundView.trailingAnchor),
            
            self.placeholderView.topAnchor.constraint(equalTo: self.placeholderView.stackView.topAnchor),
            self.placeholderView.bottomAnchor.constraint(equalTo: self.placeholderView.stackView.bottomAnchor),
        ])

        self.navigationItem.rightBarButtonItem = self.editButtonItem
        
        self.update()
    }
    
    override func viewDidAppear(_ animated: Bool)
    {
        super.viewDidAppear(animated)
        
        self.handleAddSourceDeepLink()
    }
    
    override func viewDidLayoutSubviews() 
    {
        super.viewDidLayoutSubviews()
        
        // Vertically center placeholder view in gap below first item.
        
        let indexPath = IndexPath(item: 0, section: 0)
        guard let layoutAttributes = self.collectionView.layoutAttributesForItem(at: indexPath) else { return }
        
        let maxY = layoutAttributes.frame.maxY
        
        let constant = maxY / 2
        if self.placeholderViewCenterYConstraint.constant != constant
        {
            self.placeholderViewCenterYConstraint.constant = constant
        }
    }
}

private extension SourcesViewController
{
    func makeLayout() -> UICollectionViewCompositionalLayout
    {
        var configuration = UICollectionLayoutListConfiguration(appearance: .grouped)
        configuration.showsSeparators = false
        configuration.backgroundColor = .clear
        
        configuration.trailingSwipeActionsConfigurationProvider = { [weak self] indexPath in
            guard let self else { return UISwipeActionsConfiguration(actions: []) }
            
            let source = self.dataSource.item(at: indexPath)
            var actions: [UIContextualAction] = []
            
            if source.identifier != Source.altStoreIdentifier
            {
                // Prevent users from removing AltStore source.
                
                let removeAction = UIContextualAction(style: .destructive,
                                                      title: NSLocalizedString("Remove", comment: "")) { _, _, completion in
                    self.remove(source, completionHandler: completion)
                }
                removeAction.image = UIImage(systemName: "trash.fill")
                
                actions.append(removeAction)
            }
            
            if let error = source.error
            {
                let viewErrorAction = UIContextualAction(style: .normal,
                                                         title: NSLocalizedString("View Error", comment: "")) { _, _, completion in
                    self.present(error)
                    completion(true)
                }
                viewErrorAction.backgroundColor = .systemYellow
                viewErrorAction.image = UIImage(systemName: "exclamationmark.circle.fill")
                
                actions.append(viewErrorAction)
            }
            
            let config = UISwipeActionsConfiguration(actions: actions)
            config.performsFirstActionWithFullSwipe = false
            
            return config
        }
        
        let layout = UICollectionViewCompositionalLayout.list(using: configuration)
        return layout
    }
    
    func makeDataSource() -> RSTFetchedResultsCollectionViewPrefetchingDataSource<Source, UIImage>
    {
        let fetchRequest = Source.fetchRequest() as NSFetchRequest<Source>
        fetchRequest.returnsObjectsAsFaults = false
        fetchRequest.sortDescriptors = [NSSortDescriptor(keyPath: \Source.name, ascending: true),
                                        
                                        // Can't sort by URLs or else app will crash.
                                        // NSSortDescriptor(keyPath: \Source.sourceURL, ascending: true),
                                        
                                        NSSortDescriptor(keyPath: \Source.identifier, ascending: true)]
        
        let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: DatabaseManager.shared.viewContext, sectionNameKeyPath: nil, cacheName: nil)
        fetchedResultsController.delegate = self
        
        let dataSource = RSTFetchedResultsCollectionViewPrefetchingDataSource<Source, UIImage>(fetchedResultsController: fetchedResultsController)
        dataSource.proxy = self
        dataSource.cellConfigurationHandler = { [weak self] (cell, source, indexPath) in
            guard let self else { return }
                        
            let cell = cell as! AppBannerCollectionViewCell
            cell.layoutMargins.top = 5
            cell.layoutMargins.bottom = 5
            cell.layoutMargins.left = self.view.layoutMargins.left
            cell.layoutMargins.right = self.view.layoutMargins.right
            
            cell.bannerView.configure(for: source)
            
            cell.bannerView.iconImageView.image = nil
            cell.bannerView.iconImageView.isIndicatingActivity = true
            
            let numberOfApps = source.apps.filter { StoreApp.visibleAppsPredicate.evaluate(with: $0) }.count
            
            if let error = source.error
            {
                let image = UIImage(systemName: "exclamationmark")?.withTintColor(.white, renderingMode: .alwaysOriginal)
                
                cell.bannerView.button.setImage(image, for: .normal)
                cell.bannerView.button.setTitle(nil, for: .normal)
                cell.bannerView.button.tintColor = .systemYellow.withAlphaComponent(0.75)
                
                let action = UIAction(identifier: .showError) { _ in
                    self.present(error)
                }
                cell.bannerView.button.addAction(action, for: .primaryActionTriggered)
                cell.bannerView.button.removeAction(identifiedBy: .showDetails, for: .primaryActionTriggered)
            }
            else
            {
                cell.bannerView.button.setImage(nil, for: .normal)
                cell.bannerView.button.setTitle(numberOfApps.description, for: .normal)
                cell.bannerView.button.tintColor = .white.withAlphaComponent(0.2)
                
                let action = UIAction(identifier: .showDetails) { _ in
                    self.showSourceDetails(for: source)
                }
                cell.bannerView.button.addAction(action, for: .primaryActionTriggered)
                cell.bannerView.button.removeAction(identifiedBy: .showError, for: .primaryActionTriggered)
            }
            
            let dateText: String
            if let lastUpdatedDate = source.lastUpdatedDate
            {
                dateText = Date().relativeDateString(since: lastUpdatedDate, dateFormatter: Date.shortDateFormatter)
            }
            else
            {
                dateText = NSLocalizedString("Never", comment: "")
            }
                            
            let text = String(format: NSLocalizedString("Last Updated: %@", comment: ""), dateText)
            cell.bannerView.subtitleLabel.text = text
            cell.bannerView.subtitleLabel.numberOfLines = 1
            
            let numberOfAppsText: String
            if #available(iOS 15, *)
            {
                let attributedOutput = AttributedString(localized: "^[\(numberOfApps) app](inflect: true)")
                numberOfAppsText = String(attributedOutput.characters)
            }
            else
            {
                numberOfAppsText = ""
            }
            
            let accessibilityLabel = source.name + "\n" + text + ".\n" + numberOfAppsText
            cell.bannerView.accessibilityLabel = accessibilityLabel
                        
            if source.identifier != Source.altStoreIdentifier
            {
                cell.accessories = [.delete(displayed: .whenEditing)]
            }
            else
            {
                cell.accessories = []
            }
            
            cell.bannerView.accessibilityTraits.remove(.button)
            
            // Make sure refresh button is correct size.
            cell.layoutIfNeeded()
        }
        dataSource.prefetchHandler = { (source, indexPath, completionHandler) in
            guard let imageURL = source.effectiveIconURL else { return nil }
            return RSTAsyncBlockOperation() { (operation) in
                ImagePipeline.shared.loadImage(with: imageURL, progress: nil) { result in
                    guard !operation.isCancelled else { return operation.finish() }
                    
                    switch result
                    {
                    case .success(let response): completionHandler(response.image, nil)
                    case .failure(let error): completionHandler(nil, error)
                    }
                }
            }
        }
        dataSource.prefetchCompletionHandler = { (cell, image, indexPath, error) in
            let cell = cell as! AppBannerCollectionViewCell
            cell.bannerView.iconImageView.isIndicatingActivity = false
            cell.bannerView.iconImageView.image = image
            
            if let error = error
            {
                print("Error loading image:", error)
            }
        }
        
        return dataSource
    }
    
    @IBSegueAction
    func makeSourceDetailViewController(_ coder: NSCoder, sender: Any?) -> UIViewController?
    {
        guard let source = sender as? Source else { return nil }
        
        let sourceDetailViewController = SourceDetailViewController(source: source, coder: coder)
        return sourceDetailViewController
    }
    
    @IBAction
    func unwindFromAddSource(_ segue: UIStoryboardSegue)
    {
    }
}

private extension SourcesViewController
{
    func handleAddSourceDeepLink()
    {
        let alertController = UIAlertController(title: NSLocalizedString("Add Source", comment: ""), message: nil, preferredStyle: .alert)
        alertController.addTextField { (textField) in
            textField.placeholder = "https://apps.sidestore.io"
            textField.textContentType = .URL
        }
        alertController.addAction(.cancel)
        alertController.addAction(UIAlertAction(title: NSLocalizedString("Add", comment: ""), style: .default) { (action) in
            guard let text = alertController.textFields![0].text else { return }
            guard var sourceURL = URL(string: text) else { return }
            if sourceURL.scheme == nil {
                guard let httpsSourceURL = URL(string: "https://" + text) else { return }
                sourceURL = httpsSourceURL
            }
            
            self.navigationItem.leftBarButtonItem?.isIndicatingActivity = true
            
            self.addSource(url: sourceURL) { _ in
                self.navigationItem.leftBarButtonItem?.isIndicatingActivity = false
            }
        })
        guard let url = self.deepLinkSourceURL, self.view.window != nil else { return }
        
        // Only handle deep link once.
        self.deepLinkSourceURL = nil
        
        self.navigationItem.leftBarButtonItem?.isIndicatingActivity = true
        
        func finish(_ result: Result<Void, Error>)
        {
            DispatchQueue.main.async {
                switch result
                {
                case .success: break
                case .failure(OperationError.cancelled): break
                    
                case .failure(var error as SourceError):
                    let title = String(format: NSLocalizedString("“%@” could not be added to AltStore.", comment: ""), error.$source.name)
                    error.errorTitle = title
                    self.present(error)
                    
                case .failure(let error as NSError):
                    self.present(error.withLocalizedTitle(NSLocalizedString("Unable to Add Source", comment: "")))
                }
                
                self.navigationItem.leftBarButtonItem?.isIndicatingActivity = false
            }
        }
        
        AppManager.shared.fetchSource(sourceURL: url) { (result) in
            do
            {
                // Use @Managed before calling perform() to keep
                // strong reference to source.managedObjectContext.
                @Managed var source = try result.get()
                
                DispatchQueue.main.async {
                    self.showSourceDetails(for: source)
                }
                
                finish(.success(()))
            }
            catch
            {
                finish(.failure(error))
            }
        }
    }

    func present(_ error: Error)
    {
        if let transitionCoordinator = self.transitionCoordinator
        {
            transitionCoordinator.animate(alongsideTransition: nil) { _ in
                self.present(error)
            }
            
            return
        }
        
        let nsError = error as NSError
        let title = nsError.localizedTitle // OK if nil.
        let message = [nsError.localizedDescription, nsError.localizedDebugDescription, nsError.localizedRecoverySuggestion].compactMap { $0 }.joined(separator: "\n\n")
        
        let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
        alertController.addAction(.ok)
        self.present(alertController, animated: true, completion: nil)
    }
    
    func remove(_ source: Source, completionHandler: ((Bool) -> Void)? = nil)
    {
        Task<Void, Never> {
            do
            {
                try await AppManager.shared.remove(source, presentingViewController: self)
                
                completionHandler?(true)
            }
            catch is CancellationError
            {
                completionHandler?(false)
            }
            catch
            {
                completionHandler?(false)
                
                let dispatchGroup = DispatchGroup()
                
                var sourcesByURL = [URL: Source]()
                var fetchError: Error?
                
                for sourceURL in featuredSourceURLs
                {
                    dispatchGroup.enter()
                    
                    AppManager.shared.fetchSource(sourceURL: sourceURL, managedObjectContext: context) { result in
                        // Serialize access to sourcesByURL.
                        context.performAndWait {
                            switch result
                            {
                            case .failure(let error): fetchError = error
                            case .success(let source): sourcesByURL[source.sourceURL] = source
                            }
                            
                            dispatchGroup.leave()
                        }
                    }
                }
                
                dispatchGroup.notify(queue: .main) {
                    if let error = fetchError
                    {
                        print(error)
                        // 1 error doesn't mean all trusted sources failed to load! Riley, why did you do this???????
//                        finish(.failure(error))
                    }
                    let sources = featuredSourceURLs.compactMap { sourcesByURL[$0] }
                    finish(.success(sources))
                }
                self.present(error)
            }
        }
    }
    
    func showSourceDetails(for source: Source)
    {
        self.performSegue(withIdentifier: "showSourceDetails", sender: source)
    }
    
    func update()
    {
        if self.dataSource.itemCount < 2
        {
            // Show placeholder view
            
            self.placeholderView.isHidden = false
            self.collectionView.alwaysBounceVertical = false
            
            self.setEditing(false, animated: true)
            self.editButtonItem.isEnabled = false
        }
        else
        {
            self.placeholderView.isHidden = true
            self.collectionView.alwaysBounceVertical = true
            
            self.editButtonItem.isEnabled = true
        }
    }
}

extension SourcesViewController
{
    override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
    {
        self.collectionView.deselectItem(at: indexPath, animated: true)
        
        let source = self.dataSource.item(at: indexPath)
        self.showSourceDetails(for: source)
    }
    
    // override func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView
    // {
    //     let headerView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: kind, for: indexPath) as! UICollectionViewListCell
        
    //     var configuation = UIListContentConfiguration.cell()
    //     configuation.text = NSLocalizedString("Sources control what apps are available to download through AltStore.", comment: "")
    //     configuation.textProperties.color = .secondaryLabel
    //     configuation.textProperties.alignment = .natural
        
    //     headerView.contentConfiguration = configuation
        
    //     switch kind
    //     {
    //     case UICollectionView.elementKindSectionHeader:
    //         switch Section.allCases[indexPath.section]
    //         {
    //         case .added:
    //             headerView.textLabel.text = NSLocalizedString("Sources control what apps are available to download through SideStore.", comment: "")
    //             headerView.textLabel.font = UIFont.preferredFont(forTextStyle: .callout)
    //             headerView.textLabel.textAlignment = .natural
                
    //             headerView.topLayoutConstraint.constant = 14
    //             headerView.bottomLayoutConstraint.constant = 30
                
    //         case .trusted:
    //             switch self.fetchTrustedSourcesResult
    //             {
    //             case .failure: headerView.textLabel.text = NSLocalizedString("Error Loading Trusted Sources", comment: "")
    //             case .success, .none: headerView.textLabel.text = NSLocalizedString("Trusted Sources", comment: "")
    //             }
                
    //             let descriptor = UIFontDescriptor.preferredFontDescriptor(withTextStyle: .callout).withSymbolicTraits(.traitBold)!
    //             headerView.textLabel.font = UIFont(descriptor: descriptor, size: 0)
    //             headerView.textLabel.textAlignment = .center
                
    //             headerView.topLayoutConstraint.constant = 54
    //             headerView.bottomLayoutConstraint.constant = 15
    //         }
            
    //     case UICollectionView.elementKindSectionFooter:
    //         let footerView = headerView as! SourcesFooterView
    //         let font = UIFont.preferredFont(forTextStyle: .subheadline)
            
    //         switch self.fetchTrustedSourcesResult
    //         {
    //         case .failure(let error):
    //             footerView.textView.font = font
    //             footerView.textView.text = error.localizedDescription
                
    //             footerView.activityIndicatorView.stopAnimating()
    //             footerView.topLayoutConstraint.constant = 0
    //             footerView.textView.textAlignment = .center
                
    //         case .success, .none:
    //             footerView.textView.delegate = self
                
    //             let attributedText = NSMutableAttributedString(
    //                 string: NSLocalizedString("SideStore has reviewed these sources to make sure they meet our safety standards.", comment: ""),
    //                 attributes: [.font: font, .foregroundColor: UIColor.gray]
    //             )
    //             //attributedText.mutableString.append(" ")
                
    //             //let boldedFont = UIFont(descriptor: font.fontDescriptor.withSymbolicTraits(.traitBold)!, size: font.pointSize)
    //             //let openPatreonURL = URL(string: "https://SideStore.io/")!
                
    //             // let joinPatreonText = NSAttributedString(
    //                 // string: NSLocalizedString("", comment: ""),
    //                 // attributes: [.font: boldedFont, .link: openPatreonURL, .underlineColor: UIColor.clear]
    //             //)
    //             //attributedText.append(joinPatreonText)
                
    //             footerView.textView.attributedText = attributedText
    //             footerView.textView.textAlignment = .natural
                
    //             if self.fetchTrustedSourcesResult != nil
    //             {
    //                 footerView.activityIndicatorView.stopAnimating()
    //                 footerView.topLayoutConstraint.constant = 20
    //             }
    //             else
    //             {
    //                 footerView.activityIndicatorView.startAnimating()
    //                 footerView.topLayoutConstraint.constant = 0
    //             }
    //         }
            
    //     default: break
    //     }
                
    //     return headerView
    // }
}

extension SourcesViewController: NSFetchedResultsControllerDelegate
{
    func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) 
    {
        self.dataSource.controllerWillChangeContent(controller)
    }
    
    func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) 
    {
        self.update()
        
        self.dataSource.controllerDidChangeContent(controller)
    }
    
    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) 
    {
        self.dataSource.controller(controller, didChange: anObject, at: indexPath, for: type, newIndexPath: newIndexPath)
    }
    
    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) 
    {
        self.dataSource.controller(controller, didChange: sectionInfo, atSectionIndex: UInt(sectionIndex), for: type)
    }
}

@available(iOS 17, *)
#Preview(traits: .portrait) {
    DatabaseManager.shared.startForPreview()
    
    let storyboard = UIStoryboard(name: "Sources", bundle: nil)
    let sourcesViewController = storyboard.instantiateInitialViewController()!
    
    let context = DatabaseManager.shared.persistentContainer.newBackgroundContext()
    context.performAndWait {
        _ = Source.make(name: "OatmealDome's AltStore Source",
                        identifier: "me.oatmealdome.altstore",
                        sourceURL: URL(string: "https://altstore.oatmealdome.me")!,
                        context: context)
        
        _ = Source.make(name: "UTM Repository",
                        identifier: "com.utmapp.repos.UTM",
                        sourceURL: URL(string: "https://alt.getutm.app")!,
                        context: context)
        
        _ = Source.make(name: "Flyinghead",
                        identifier: "com.flyinghead.source",
                        sourceURL: URL(string: "https://flyinghead.github.io/flycast-builds/altstore.json")!,
                        context: context)
        
        _ = Source.make(name: "Provenance",
                        identifier: "org.provenance-emu.AltStore",
                        sourceURL: URL(string: "https://provenance-emu.com/apps.json")!,
                        context: context)
        
        _ = Source.make(name: "PojavLauncher Repository",
                        identifier: "dev.crystall1ne.repos.PojavLauncher",
                        sourceURL: URL(string: "http://alt.crystall1ne.dev")!,
                        context: context)
        
        try! context.save()
    }
    
    AppManager.shared.fetchSources { result in
        do
        {
            let (_, context) = try result.get()
            try context.save()
        }
        catch
        {
            print("Preview failed to fetch sources:", error)
        }
    }
    
    return sourcesViewController
}