//
//  SourceDetailViewController.swift
//  AltStore
//
//  Created by Riley Testut on 3/15/23.
//  Copyright © 2023 Riley Testut. All rights reserved.
//

import UIKit
import SafariServices
import Combine

import AltStoreCore
import Roxas

import Nuke

extension SourceDetailViewController
{
    private class ViewModel: ObservableObject
    {
        let source: Source
        
        @Published
        var isSourceAdded: Bool? = nil
        
        @Published
        var isAddingSource: Bool = false
        
        init(source: Source)
        {
            self.source = source
            
            let sourceID = source.identifier
            
            let addedPublisher = NotificationCenter.default.publisher(for: AppManager.didAddSourceNotification, object: nil)
            let removedPublisher = NotificationCenter.default.publisher(for: AppManager.didRemoveSourceNotification, object: nil)
            
            Publishers.Merge(addedPublisher, removedPublisher)
                .filter { notification -> Bool in
                    guard let source = notification.object as? Source, let context = source.managedObjectContext else { return false }
                    
                    let updatedSourceID = context.performAndWait { source.identifier }
                    return sourceID == updatedSourceID
                }
                .compactMap { notification in
                    switch notification.name
                    {
                    case AppManager.didAddSourceNotification: return true
                    case AppManager.didRemoveSourceNotification: return false
                    default: return nil
                    }
                }
                .filter { $0 != nil }
                .receive(on: RunLoop.main)
                .assign(to: &self.$isSourceAdded)
            
            Task<Void, Never> {
                do
                {
                    self.isSourceAdded = try await self.source.isAdded
                }
                catch
                {
                    print("[ALTLog] Failed to check if source is added.", error)
                }
            }
        }
    }
}

class SourceDetailViewController: HeaderContentViewController<SourceHeaderView, SourceDetailContentViewController>
{
    @Managed private(set) var source: Source
    
    var addedSourceHandler: ((Source) -> Void)?
    
    private let viewModel: ViewModel
    
    private var addButton: VibrantButton!
    
    private var previousBounds: CGRect?
    private var cancellable: AnyCancellable?
    
    init?(source: Source, coder: NSCoder)
    {
        let isolatedContext: NSManagedObjectContext
        
        if source.managedObjectContext == DatabaseManager.shared.viewContext
        {
            do
            {
                // Source is persisted to disk, so we can create a new view context
                // that's pinned to current query generation to ensure information
                // doesn't disappear out from under us if we remove (delete) the source.
                let context = DatabaseManager.shared.persistentContainer.newViewContext(withParent: nil)
                try context.setQueryGenerationFrom(.current)
                isolatedContext = context
            }
            catch
            {
                print("[ATLog] Failed to set query generation for context.", error)
                isolatedContext = DatabaseManager.shared.persistentContainer.newViewContext(withParent: source.managedObjectContext)
            }
        }
        else
        {
            // Source is not persisted to disk, so create child view context with source's managedObjectContext as parent.
            // This also maintains a strong reference to source.managedObjectContext, which may be necessary.
            isolatedContext = DatabaseManager.shared.persistentContainer.newViewContext(withParent: source.managedObjectContext)
        }
               
        // Ignore changes from other contexts so we can delete source without UI automatically updating.
        isolatedContext.automaticallyMergesChangesFromParent = false
        
        let source = isolatedContext.object(with: source.objectID) as! Source
        self.source = source
        
        self.viewModel = ViewModel(source: source)
        
        super.init(coder: coder)
        
        self.title = source.name
        self.tintColor = source.effectiveTintColor
    }
    
    required init?(coder: NSCoder)
    {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad()
    {
        super.viewDidLoad()
        
        self.addButton = VibrantButton(type: .system)
        self.addButton.contentInsets = PillButton.contentInsets
        self.addButton.addTarget(self, action: #selector(SourceDetailViewController.addSource), for: .primaryActionTriggered)
        self.addButton.sizeToFit()
        self.view.addSubview(self.addButton)
        
        self.navigationBarButton.addTarget(self, action: #selector(SourceDetailViewController.addSource), for: .primaryActionTriggered)
        
        Nuke.loadImage(with: self.source.effectiveIconURL, into: self.navigationBarIconView)
        Nuke.loadImage(with: self.source.effectiveHeaderImageURL, into: self.backgroundImageView)
        
        self.update()
        self.preparePipeline()
    }
    
    override func viewDidLayoutSubviews()
    {
        super.viewDidLayoutSubviews()
        
        self.addButton.layer.cornerRadius = self.addButton.bounds.midY
        self.navigationBarIconView.layer.cornerRadius = self.navigationBarIconView.bounds.midY
        
        var addButtonSize = self.addButton.sizeThatFits(CGSize(width: Double.infinity, height: .infinity))
        addButtonSize.width = max(addButtonSize.width, PillButton.minimumSize.width)
        addButtonSize.height = max(addButtonSize.height, PillButton.minimumSize.height)
        self.addButton.frame.size = addButtonSize
        
        // Place in top-right corner.
        let inset = 15.0
        self.addButton.center.y = self.backButton.center.y
        self.addButton.frame.origin.x = self.view.bounds.width - inset - self.addButton.bounds.width
        
        guard self.view.bounds != self.previousBounds else { return }
        self.previousBounds = self.view.bounds
        
        let headerSize = self.headerView.systemLayoutSizeFitting(CGSize(width: self.view.bounds.width - inset * 2, height: UIView.layoutFittingCompressedSize.height))
        self.headerView.frame.size.height = headerSize.height
    }
    
    //MARK: Override
    
    override func makeContentViewController() -> SourceDetailContentViewController
    {
        guard let storyboard = self.storyboard else { fatalError("SourceDetailViewController must be initialized via UIStoryboard.") }
        
        let contentViewController = storyboard.instantiateViewController(identifier: "sourceDetailContentViewController") { coder in
            SourceDetailContentViewController(source: self.source, coder: coder)
        }
        return contentViewController
    }
    
    override func makeHeaderView() -> SourceHeaderView
    {
        let sourceAboutView = SourceHeaderView(frame: CGRect(x: 0, y: 0, width: 375, height: 200))
        sourceAboutView.configure(for: self.source)
        sourceAboutView.websiteButton.addTarget(self, action: #selector(SourceDetailViewController.showWebsite), for: .primaryActionTriggered)
        return sourceAboutView
    }
    
    override func update()
    {
        super.update()
        
        if self.source.identifier == Source.altStoreIdentifier
        {
            // Users can't remove default AltStore source, so hide buttons.
            self.addButton.isHidden = true
            self.navigationBarButton.isHidden = true
        }
        else
        {
            // Update isIndicatingActivity first to ensure later updates are applied correctly.
            self.addButton.isIndicatingActivity = self.viewModel.isAddingSource
            self.navigationBarButton.isIndicatingActivity = self.viewModel.isAddingSource
            
            let title: String
            
            switch self.viewModel.isSourceAdded
            {
            case true?:
                title = NSLocalizedString("REMOVE", comment: "")
                self.navigationBarButton.tintColor = .refreshRed
                
                self.addButton.isHidden = false
                self.navigationBarButton.isHidden = false
                
                if #available(iOS 16, *)
                {
                    // Hide REMOVE button in navigation bar.
                    self.navigationItem.rightBarButtonItem?.isHidden = true
                }
                
            case false?:
                title = NSLocalizedString("ADD", comment: "")
                self.navigationBarButton.tintColor = self.source.effectiveTintColor?.adjustedForDisplay ?? .altPrimary
                
                self.addButton.isHidden = false
                self.navigationBarButton.isHidden = false
                
                if #available(iOS 16, *)
                {
                    // Show ADD button in navigation bar.
                    self.navigationItem.rightBarButtonItem?.isHidden = false
                }
                
            case nil:
                title = ""
                
                self.addButton.isHidden = true
                self.navigationBarButton.isHidden = true
            }
            
            if title != self.addButton.title
            {
                self.addButton.title = title
            }
            
            if title != self.navigationBarButton.title(for: .normal) && !self.navigationBarButton.isIndicatingActivity
            {
                self.navigationBarButton.setTitle(title, for: .normal)
            }
            
            self.view.setNeedsLayout()
        }
    }
    
    //MARK: Actions
    
    @objc private func addSource()
    {
        self.viewModel.isAddingSource = true
        
        Task<Void, Never> { /* @MainActor in */ // Already on MainActor, even though this function wasn't called from async context.
            var errorTitle = NSLocalizedString("Unable to Add Source", comment: "")
            
            do
            {
                let isAdded = try await self.source.isAdded
                if isAdded
                {
                    errorTitle = NSLocalizedString("Unable to Remove Source", comment: "")
                    try await AppManager.shared.remove(self.source, presentingViewController: self)
                }
                else
                {
                    try await AppManager.shared.add(self.source, presentingViewController: self)
                    
                    self.addedSourceHandler?(self.source)
                }
            }
            catch is CancellationError {}
            catch
            {
                await self.presentAlert(title: errorTitle, message: error.localizedDescription)
            }
            
            self.viewModel.isAddingSource = false
        }
    }
    
    @objc private func showWebsite()
    {
        guard let websiteURL = self.source.websiteURL else { return }
        
        let safariViewController = SFSafariViewController(url: websiteURL)
        safariViewController.preferredControlTintColor = self.source.effectiveTintColor ?? .altPrimary
        self.present(safariViewController, animated: true, completion: nil)
    }
}

private extension SourceDetailViewController
{
    func preparePipeline()
    {
        self.cancellable = Publishers
            .CombineLatest(self.viewModel.$isSourceAdded, self.viewModel.$isAddingSource)
            .receive(on: RunLoop.main)
            .sink { [weak self] _ in
                self?.update()
            }
    }
}