//
//  ExploreViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 12/14/19.
//  Copyright © 2019 Shadowfacts. All rights reserved.
//

import UIKit
import Combine
import Pachyderm

class ExploreViewController: EnhancedTableViewController {

    let mastodonController: MastodonController
    
    var dataSource: DataSource!
    
    var resultsController: SearchResultsViewController!
    var searchController: UISearchController!
    
    init(mastodonController: MastodonController) {
        self.mastodonController = mastodonController
        
        super.init(style: .insetGrouped)
        
        title = NSLocalizedString("Explore", comment: "explore tab title")
        tabBarItem.image = UIImage(systemName: "magnifyingglass")
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        tableView.register(UINib(nibName: "BasicTableViewCell", bundle: .main), forCellReuseIdentifier: "basicCell")

        dataSource = DataSource(tableView: tableView, cellProvider: { (tableView, indexPath, item) -> UITableViewCell? in
            let cell = tableView.dequeueReusableCell(withIdentifier: "basicCell", for: indexPath)
            
            switch item {
            case .bookmarks:
                cell.imageView!.image = UIImage(systemName: "bookmark.fill")
                cell.textLabel!.text = NSLocalizedString("Bookmarks", comment: "bookmarks nav item title")
                cell.accessoryType = .disclosureIndicator

            case let .list(list):
                cell.imageView!.image = UIImage(systemName: "list.bullet")
                cell.textLabel!.text = list.title
                cell.accessoryType = .disclosureIndicator

            case .addList:
                cell.imageView!.image = UIImage(systemName: "plus")
                cell.textLabel!.text = NSLocalizedString("New List...", comment: "new list nav item title")
                cell.accessoryType = .none
                
            case let .savedHashtag(hashtag):
                cell.imageView!.image = UIImage(systemName: "number")
                cell.textLabel!.text = hashtag.name
                cell.accessoryType = .disclosureIndicator
                
            case .addSavedHashtag:
                cell.imageView!.image = UIImage(systemName: "plus")
                cell.textLabel!.text = NSLocalizedString("Save Hashtag...", comment: "save hashtag nav item title")
                cell.accessoryType = .none
                
            case let .savedInstance(url):
                cell.imageView!.image = UIImage(systemName: "globe")
                cell.textLabel!.text = url.host!
                cell.accessoryType = .disclosureIndicator
                
            case .findInstance:
                cell.imageView!.image = UIImage(systemName: "magnifyingglass")
                cell.textLabel!.text = NSLocalizedString("Find An Instance...", comment: "find instance nav item title")
                cell.accessoryType = .none
            }
            
            return cell
        })
        dataSource.exploreController = self
        
        let account = mastodonController.accountInfo!
        
        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
        snapshot.appendSections([.bookmarks, .lists, .savedHashtags, .savedInstances])
        snapshot.appendItems([.bookmarks], toSection: .bookmarks)
        snapshot.appendItems([.addList], toSection: .lists)
        snapshot.appendItems(SavedDataManager.shared.sortedHashtags(for: account).map { .savedHashtag($0) } + [.addSavedHashtag], toSection: .savedHashtags)
        snapshot.appendItems(SavedDataManager.shared.savedInstances(for: account).map { .savedInstance($0) } + [.findInstance], toSection: .savedInstances)
        // the initial, static items should not be displayed with an animation
        UIView.performWithoutAnimation {
            dataSource.apply(snapshot)
        }

        resultsController = SearchResultsViewController(mastodonController: mastodonController)
        resultsController.exploreNavigationController = self.navigationController!
        searchController = UISearchController(searchResultsController: resultsController)
        searchController.searchResultsUpdater = resultsController
        searchController.searchBar.autocapitalizationType = .none
        searchController.searchBar.delegate = resultsController
        definesPresentationContext = true
        
        navigationItem.searchController = searchController
        navigationItem.hidesSearchBarWhenScrolling = false
        
        NotificationCenter.default.addObserver(self, selector: #selector(savedHashtagsChanged), name: .savedHashtagsChanged, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(savedInstancesChanged), name: .savedInstancesChanged, object: nil)
        
        reloadLists()
    }
    
    func reloadLists() {
        let request = Client.getLists()
        mastodonController.run(request) { (response) in
            guard case let .success(lists, _) = response else {
                fatalError()
            }
            
            var snapshot = self.dataSource.snapshot()
            snapshot.deleteItems(snapshot.itemIdentifiers(inSection: .lists))
            snapshot.appendItems(lists.map { .list($0) } + [.addList], toSection: .lists)

            DispatchQueue.main.async {
                self.dataSource.apply(snapshot)
            }
        }
    }
    
    @objc func savedHashtagsChanged() {
        let account = mastodonController.accountInfo!
        var snapshot = dataSource.snapshot()
        snapshot.deleteItems(snapshot.itemIdentifiers(inSection: .savedHashtags))
        snapshot.appendItems(SavedDataManager.shared.sortedHashtags(for: account).map { .savedHashtag($0) } + [.addSavedHashtag], toSection: .savedHashtags)
        dataSource.apply(snapshot)
    }
    
    @objc func savedInstancesChanged() {
        let account = mastodonController.accountInfo!
        var snapshot = dataSource.snapshot()
        snapshot.deleteItems(snapshot.itemIdentifiers(inSection: .savedInstances))
        snapshot.appendItems(SavedDataManager.shared.savedInstances(for: account).map { .savedInstance($0) } + [.findInstance], toSection: .savedInstances)
        dataSource.apply(snapshot)
    }
    
    func deleteList(_ list: List) {
        let title = String(format: NSLocalizedString("Are you sure want to delete the '%@' list?", comment: "delete list alert title"), list.title)
        let alert = UIAlertController(title: title, message: nil, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: NSLocalizedString("Cancel", comment: "delete list alert cancel button"), style: .cancel, handler: nil))
        alert.addAction(UIAlertAction(title: NSLocalizedString("Delete List", comment: "delete list alert confirm button"), style: .destructive, handler: { (_) in
            
            let request = List.delete(list)
            self.mastodonController.run(request) { (response) in
                guard case .success(_, _) = response else {
                    fatalError()
                }
                
                var snapshot = self.dataSource.snapshot()
                snapshot.deleteItems([.list(list)])
                DispatchQueue.main.async {
                    self.dataSource.apply(snapshot)
                }
            }
        }))
        present(alert, animated: true)
    }
    
    func removeSavedHashtag(_ hashtag: Hashtag) {
        let account = mastodonController.accountInfo!
        SavedDataManager.shared.remove(hashtag: hashtag, for: account)
    }
    
    func removeSavedInstance(_ instanceURL: URL) {
        let account = mastodonController.accountInfo!
        SavedDataManager.shared.remove(instance: instanceURL, for: account)
    }
    
    // MARK: - Table view delegate
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        switch dataSource.itemIdentifier(for: indexPath) {
        case nil:
            return
            
        case .bookmarks:
            show(BookmarksTableViewController(mastodonController: mastodonController), sender: nil)
            
        case let .list(list):
            show(ListTimelineViewController(for: list, mastodonController: mastodonController), sender: nil)
            
        case .addList:
            tableView.selectRow(at: nil, animated: true, scrollPosition: .none)
            let alert = UIAlertController(title: NSLocalizedString("New List", comment: "new list alert title"), message: NSLocalizedString("Choose a title for your new list", comment: "new list alert message"), preferredStyle: .alert)
            alert.addTextField(configurationHandler: nil)
            alert.addAction(UIAlertAction(title: NSLocalizedString("Cancel", comment: "new list alert cancel button"), style: .cancel, handler: nil))
            alert.addAction(UIAlertAction(title: NSLocalizedString("Create List", comment: "new list create button"), style: .default, handler: { (_) in
                guard let title = alert.textFields?.first?.text else {
                    fatalError()
                }
                
                let request = Client.createList(title: title)
                self.mastodonController.run(request) { (response) in
                    guard case let .success(list, _) = response else { fatalError() }
                    
                    self.reloadLists()
                    
                    DispatchQueue.main.async {
                        let listTimelineController = ListTimelineViewController(for: list, mastodonController: self.mastodonController)
                        listTimelineController.presentEditOnAppear = true
                        self.show(listTimelineController, sender: nil)
                    }
                }
            }))
            present(alert, animated: true)
            
        case let .savedHashtag(hashtag):
            show(HashtagTimelineViewController(for: hashtag, mastodonController: mastodonController), sender: nil)
            
        case .addSavedHashtag:
            tableView.selectRow(at: nil, animated: true, scrollPosition: .none)
            let navController = UINavigationController(rootViewController: AddSavedHashtagViewController(mastodonController: mastodonController))
            present(navController, animated: true)
            
        case let .savedInstance(url):
            show(InstanceTimelineViewController(for: url, parentMastodonController: mastodonController), sender: nil)
            
        case .findInstance:
            tableView.selectRow(at: nil, animated: true, scrollPosition: .none)
            let findController = FindInstanceViewController(parentMastodonController: mastodonController)
            findController.instanceTimelineDelegate = self
            let navController = UINavigationController(rootViewController: findController)
            present(navController, animated: true)
        }
    }

    override func tableView(_ tableView: UITableView, editingStyleForRowAt indexPath: IndexPath) -> UITableViewCell.EditingStyle {
        return .delete
    }
    
}

extension ExploreViewController {
    enum Section: CaseIterable {
        case bookmarks
        case lists
        case savedHashtags
        case savedInstances
    }
    enum Item: Hashable {
        case bookmarks
        case list(List)
        case addList
        case savedHashtag(Hashtag)
        case addSavedHashtag
        case savedInstance(URL)
        case findInstance

        static func == (lhs: ExploreViewController.Item, rhs: ExploreViewController.Item) -> Bool {
            switch (lhs, rhs) {
            case (.bookmarks, .bookmarks):
                return true
            case let (.list(a), .list(b)):
                return a.id == b.id
            case (.addList, .addList):
                return true
            case let (.savedHashtag(a), .savedHashtag(b)):
                return a == b
            case (.addSavedHashtag, .addSavedHashtag):
                return true
            case let (.savedInstance(a), .savedInstance(b)):
                return a == b
            case (.findInstance, .findInstance):
                return true
            default:
                return false
            }
        }
        func hash(into hasher: inout Hasher) {
            switch self {
            case .bookmarks:
                hasher.combine("bookmarks")
            case let .list(list):
                hasher.combine("list")
                hasher.combine(list.id)
            case .addList:
                hasher.combine("addList")
            case let .savedHashtag(hashtag):
                hasher.combine("savedHashtag")
                hasher.combine(hashtag.name)
            case .addSavedHashtag:
                hasher.combine("addSavedHashtag")
            case let .savedInstance(url):
                hasher.combine("savedInstance")
                hasher.combine(url)
            case .findInstance:
                hasher.combine("findInstance")
            }
        }
    }
    
    class DataSource: UITableViewDiffableDataSource<Section, Item> {
        
        weak var exploreController: ExploreViewController?
        
        override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
            switch section {
            case 1:
                return NSLocalizedString("Lists", comment: "explore lists section title")
            case 2:
                return NSLocalizedString("Saved Hashtags", comment: "explore saved hashtags section title")
            case 3:
                return NSLocalizedString("Instance Timelines", comment: "explore instance timelines section title")
            default:
                return nil
            }
        }
        
        override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
            switch itemIdentifier(for: indexPath) {
            case .list(_):
                return true
            case .savedHashtag(_):
                return true
            case .savedInstance(_):
                return true
            default:
                return false
            }
        }

        override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
            guard editingStyle == .delete,
                let exploreController = exploreController else {
                return
            }
            
            switch itemIdentifier(for: indexPath) {
            case let .list(list):
                exploreController.deleteList(list)
            case let .savedHashtag(hashtag):
                exploreController.removeSavedHashtag(hashtag)
            case let .savedInstance(url):
                exploreController.removeSavedInstance(url)
            default:
                return
            }

        }
        
    }
}

extension ExploreViewController: InstanceTimelineViewControllerDelegate {
    func didSaveInstance(url: URL) {
        dismiss(animated: true) {
            self.show(InstanceTimelineViewController(for: url, parentMastodonController: self.mastodonController), sender: nil)
        }
    }
    
    func didUnsaveInstance(url: URL) {
        dismiss(animated: true)
    }
}