Tusker/Tusker/Screens/Explore/ExploreViewController.swift

//
//  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 {

    var dataSource: DataSource!
    
    var resultsController: SearchResultsViewController!
    var searchController: UISearchController!
    
    init() {
        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 = nil
                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
            }
            
            return cell
        })
        dataSource.exploreController = self
        
        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
        snapshot.appendSections([.bookmarks, .lists])
        snapshot.appendItems([.bookmarks], toSection: .bookmarks)
        snapshot.appendItems([.addList], toSection: .lists)
        // the initial, static items should not be displayed with an animation
        UIView.performWithoutAnimation {
            dataSource.apply(snapshot)
        }

        resultsController = SearchResultsViewController()
        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
        
        reloadLists()
    }
    
    func reloadLists() {
        let request = MastodonController.client.getLists()
        MastodonController.client.run(request) { (response) in
            guard case let .success(lists, _) = response else {
                fatalError()
            }
            
            var snapshot = self.dataSource.snapshot()
            snapshot.deleteSections([.lists])
            snapshot.appendSections([.lists])
            snapshot.appendItems(lists.map { .list($0) } + [.addList], toSection: .lists)
            
            DispatchQueue.main.async {
                self.dataSource.apply(snapshot)
            }
        }
    }
    
    // MARK: - Table view delegate
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        switch dataSource.itemIdentifier(for: indexPath) {
        case nil:
            return
            
        case .bookmarks:
            show(BookmarksTableViewController(), sender: nil)
            
        case let .list(list):
            show(ListTimelineViewController(for: list), 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 = MastodonController.client.createList(title: title)
                MastodonController.client.run(request) { (response) in
                    guard case let .success(list, _) = response else { fatalError() }
                    
                    self.reloadLists()
                    
                    DispatchQueue.main.async {
                        self.show(ListTimelineViewController(for: list), sender: nil)
                    }
                }
            }))
            present(alert, animated: true)
        }
    }

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

extension ExploreViewController {
    enum Section: CaseIterable {
        case bookmarks
        case lists
    }
    enum Item: Hashable {
        case bookmarks
        case list(List)
        case addList
        
        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
            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")
            }
        }
    }
    
    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")
            default:
                return nil
            }
        }
        
        override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
            if case .list(_) = itemIdentifier(for: indexPath) {
                return true
            }
            return false
        }

        override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
            guard editingStyle == .delete,
                case let .list(list) = itemIdentifier(for: indexPath) else {
                    return
            }
            
            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)
                MastodonController.client.run(request) { (response) in
                    guard case .success(_, _) = response else {
                        fatalError()
                    }
                    
                    var snapshot = self.snapshot()
                    snapshot.deleteItems([.list(list)])
                    DispatchQueue.main.async {
                        self.apply(snapshot)
                    }
                }
            }))
            self.exploreController?.present(alert, animated: true)
        }
        
    }
}