//
//  ViewController.swift
//  MastoSearchMobile
//
//  Created by Shadowfacts on 7/3/22.
//

import UIKit
import MastoSearchCore
import Combine
import SafariServices
import AuthenticationServices

class ViewController: UIViewController {
    
    private let searchQueue = DispatchQueue(label: "Search", qos: .userInitiated)
    
    private var collectionView: UICollectionView!
    private var dataSource: UICollectionViewDiffableDataSource<Section, Item>!
    
    private var searchQuerySubject = CurrentValueSubject<String, Never>("")
    private var cancellables = Set<AnyCancellable>()

    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = .systemBackground
        
        navigationItem.title = "MastoSearch"
        navigationItem.leadingItemGroups = [
            UIBarButtonItemGroup(barButtonItems: [
                UIBarButtonItem(title: "Account", menu: createAccountMenu()),
                UIBarButtonItem(title: "Import", style: .plain, target: self, action: #selector(importPressed)),
            ], representativeItem: nil)
        ]
        let searchController = UISearchController(searchResultsController: nil)
        searchController.searchResultsUpdater = self
        navigationItem.searchController = searchController
        
        var config = UICollectionLayoutListConfiguration(appearance: .plain)
        config.headerMode = .supplementary
        config.itemSeparatorHandler = { indexPath, config in
            if indexPath.row == 0 {
                var config = config
                config.topSeparatorVisibility = .hidden
                return config
            } else {
                return config
            }
        }
        let layout = UICollectionViewCompositionalLayout.list(using: config)
        collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        collectionView.allowsMultipleSelection = true
        collectionView.delegate = self
        view.addSubview(collectionView)
        NSLayoutConstraint.activate([
            collectionView.topAnchor.constraint(equalTo: view.topAnchor),
            collectionView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            collectionView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            collectionView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
        ])
        
        let header = UICollectionView.SupplementaryRegistration<StatusTableHeaderView>(elementKind: UICollectionView.elementKindSectionHeader) { supplementaryView, elementKind, indexPath in
        }
        let cell = UICollectionView.CellRegistration<StatusTableRowCollectionViewCell, Status> { cell, indexPath, status in
            cell.updateUI(status: status)
            cell.backgroundColor = indexPath.row % 2 == 0 ? .alternatingTableRow : .systemBackground
        }
        
        dataSource = UICollectionViewDiffableDataSource(collectionView: collectionView) { collectionView, indexPath, item in
            collectionView.dequeueConfiguredReusableCell(using: cell, for: indexPath, item: item.status)
        }
        dataSource.supplementaryViewProvider = { collectionView, elementKind, indexPath in
            guard elementKind == UICollectionView.elementKindSectionHeader else {
                return nil
            }
            return collectionView.dequeueConfiguredReusableSupplementary(using: header, for: indexPath)
        }
        
        searchQuerySubject
            .debounce(for: .milliseconds(100), scheduler: DispatchQueue.main)
            .sink { [unowned self] query in
                self.updateStatuses(query: query)
            }
            .store(in: &cancellables)
        
        updateStatuses(query: "")
        
        SyncController.shared.onSync
            .sink { [unowned self] _ in
                self.updateStatuses(query: searchQuerySubject.value)
            }
            .store(in: &cancellables)
    }
    
    private func updateStatuses(query: String) {
        searchQueue.async {
            if query.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty {
                DatabaseController.shared.getStatuses(sortDescriptor: NSSortDescriptor(key: "published", ascending: false)) { seq in
                    self.applyUpdate(statuses: seq)
                }
            } else {
                DatabaseController.shared.getStatuses(query: query, sortDescriptor: NSSortDescriptor(key: "published", ascending: false)) { seq in
                    self.applyUpdate(statuses: seq)
                }
            }
        }
    }
    
    private func applyUpdate(statuses: StatusSequence) {
        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
        snapshot.appendSections([.statuses])
        snapshot.appendItems(statuses.map { Item(status: $0) })
        DispatchQueue.main.async {
            self.dataSource.apply(snapshot, animatingDifferences: false)
        }
    }
    
    private func createAccountMenu() -> UIMenu {
        if let account = LocalData.account {
            return UIMenu(children: [
                UIAction(title: "Logged in to \(account.instanceURL.host!)", attributes: .disabled, handler: { _ in }),
                UIAction(title: "Log out", attributes: .destructive, handler: { [unowned self] _ in
                    self.logout()
                }),
            ])
        } else {
            return UIMenu(children: [
                UIAction(title: "Log in...", handler: { [unowned self] _ in
                    self.login()
                }),
            ])
        }
    }
    
    private func login() {
        let alert = UIAlertController(title: "Instance URL", message: nil, preferredStyle: .alert)
        alert.addTextField { textField in
            textField.placeholder = "https://mastodon.social/"
        }
        alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: { _ in
            guard let text = alert.textFields!.first!.text,
                  let url = URL(string: text) else {
                return
            }
            LoginController.shared.logIn(with: url, presentationContextProvider: self) {
                self.navigationItem.leadingItemGroups.first!.barButtonItems.first!.menu = self.createAccountMenu()
                (self.view.window!.windowScene!.delegate as! SceneDelegate).syncStatuses()
            }
        }))
        alert.addAction(UIAlertAction(title: "Cancel", style: .cancel))
        present(alert, animated: true)
    }
    
    private func logout() {
        LocalData.account = nil
        self.navigationItem.leadingItemGroups.first!.barButtonItems.first!.menu = self.createAccountMenu()
    }
    
    @objc private func importPressed() {
    }

}

extension ViewController {
    enum Section {
        case statuses
    }
    struct Item: Equatable, Hashable {
        let status: Status
        
        static func ==(lhs: Item, rhs: Item) -> Bool {
            return lhs.status.url == rhs.status.url
        }
        
        func hash(into hasher: inout Hasher) {
            hasher.combine(status.url)
        }
    }
}

extension ViewController: UISearchResultsUpdating {
    func updateSearchResults(for searchController: UISearchController) {
        searchQuerySubject.send(searchController.searchBar.text ?? "")
    }
}

extension ViewController: UICollectionViewDelegate {
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        guard let status = dataSource.itemIdentifier(for: indexPath)?.status else {
            return
        }
        present(SFSafariViewController(url: URL(string: status.url)!), animated: true)
    }
    
    func collectionView(_ collectionView: UICollectionView, contextMenuConfigurationForItemsAt indexPaths: [IndexPath], point: CGPoint) -> UIContextMenuConfiguration? {
        let statuses = indexPaths.compactMap { dataSource.itemIdentifier(for: $0)?.status }
        switch statuses.count {
        case 0:
            return nil
        case 1:
            let url = URL(string: statuses.first!.url)!
            return UIContextMenuConfiguration {
                SFSafariViewController(url: url)
            } actionProvider: { _ in
                UIMenu(children: [
                    UIAction(title: "Open in Safari", image: UIImage(systemName: "safari"), handler: { [unowned self] _ in
                        self.present(SFSafariViewController(url: url), animated: true)
                    }),
                    UIAction(title: "Copy URL", image: UIImage(systemName: "list.bullet.clipboard"), handler: { _ in
                        UIPasteboard.general.url = url
                    })
                ])
            }
        default:
            return UIContextMenuConfiguration(actionProvider: { _ in
                UIMenu(children: [
                    UIAction(title: "Copy URLs", image: UIImage(systemName: "list.bullet.clipboard"), handler: { _ in
                        UIPasteboard.general.urls = statuses.map { URL(string: $0.url)! }
                    })
                ])
            })
        }
    }
    
    func collectionView(_ collectionView: UICollectionView, willPerformPreviewActionForMenuWith configuration: UIContextMenuConfiguration, animator: UIContextMenuInteractionCommitAnimating) {
        if let viewController = animator.previewViewController,
           viewController is SFSafariViewController {
            animator.preferredCommitStyle = .pop
            animator.addCompletion {
                self.present(viewController, animated: true)
            }
        }
    }
}

extension ViewController: ASWebAuthenticationPresentationContextProviding {
    func presentationAnchor(for session: ASWebAuthenticationSession) -> ASPresentationAnchor {
        return view.window!
    }
}