Tusker/Tusker/Screens/Lists/ListTimelineViewController.swift

//
//  ListTimelineViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 12/17/19.
//  Copyright © 2019 Shadowfacts. All rights reserved.
//

import UIKit
import Pachyderm
import Combine

class ListTimelineViewController: TimelineViewController {

    private(set) var list: List
    
    var presentEditOnAppear = false
    
    private var noContentView: UIStackView!
    
    private var listRenamedCancellable: AnyCancellable?
    
    init(for list: List, mastodonController: MastodonController) {
        self.list = list
        
        super.init(for: .list(id: list.id), mastodonController: mastodonController)
        
        listChanged()
        
        listRenamedCancellable = mastodonController.$lists
            .compactMap { $0.first { $0.id == list.id } }
            .removeDuplicates(by: { $0.title == $1.title })
            .sink { [unowned self] in
                self.list = $0
                self.listChanged()
            }
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .edit, target: self, action: #selector(editListButtonPressed))
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        
        if presentEditOnAppear {
            presentEdit(animated: true)
            presentEditOnAppear = false
        }
    }
    
    private func createNoContentView() {
        let title = UILabel()
        title.textColor = .secondaryLabel
        title.font = .preferredFont(forTextStyle: .title1).withTraits(.traitBold)!
        title.adjustsFontForContentSizeCategory = true
        title.text = "No Posts"
        
        let subtitle = UILabel()
        subtitle.textColor = .secondaryLabel
        subtitle.font = .preferredFont(forTextStyle: .body)
        subtitle.adjustsFontForContentSizeCategory = true
        subtitle.numberOfLines = 0
        subtitle.textAlignment = .center
        subtitle.text = "This list doesn't currently have any posts. Edit it to add accounts if necessary."
        
        noContentView = UIStackView(arrangedSubviews: [
            title,
            subtitle,
        ])
        noContentView.axis = .vertical
        noContentView.spacing = 8
        noContentView.alignment = .center
        noContentView.isAccessibilityElement = true
        noContentView.accessibilityLabel = subtitle.text
        noContentView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(noContentView)
        NSLayoutConstraint.activate([
            noContentView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
            noContentView.leadingAnchor.constraint(equalToSystemSpacingAfter: view.safeAreaLayoutGuide.leadingAnchor, multiplier: 1),
            view.safeAreaLayoutGuide.trailingAnchor.constraint(equalToSystemSpacingAfter: noContentView.trailingAnchor, multiplier: 1),
        ])
    }
    
    private func listChanged() {
        title = list.title
    }
    
    func presentEdit(animated: Bool) {
        let editListAccountsController = EditListAccountsViewController(list: list, mastodonController: mastodonController)
        editListAccountsController.navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(editListDoneButtonPressed))
        let navController = UINavigationController(rootViewController: editListAccountsController)
        navController.sheetPresentationController?.delegate = self
        present(navController, animated: animated)
    }
    
    private func reloadIfNecessary(editViewController: EditListAccountsViewController) {
        guard editViewController.shouldReloadListTimeline else {
            return
        }
        noContentView?.removeFromSuperview()
        noContentView = nil
        Task {
            applyInitialSnapshot()
            await controller.loadInitial()
        }
    }
    
    // MARK: Interaction
    
    @objc func editListButtonPressed() {
        presentEdit(animated: true)
    }
    
    @objc func editListDoneButtonPressed() {
        let presented = (presentedViewController as? UINavigationController)?.viewControllers.first as? EditListAccountsViewController
        
        dismiss(animated: true)
        
        if let presented {
            self.reloadIfNecessary(editViewController: presented)
        }
    }
    
    // MARK: TimelineLikeControllerDelegate
    
    override func handleReplaceAllItems(_ timelineItems: [String]) async {
        if timelineItems.isEmpty {
            createNoContentView()
        }
        await super.handleReplaceAllItems(timelineItems)
    }

}

extension ListTimelineViewController: UISheetPresentationControllerDelegate {
    func presentationControllerWillDismiss(_ presentationController: UIPresentationController) {
        guard let nav = presentationController.presentedViewController as? UINavigationController,
              let edit = nav.viewControllers.first as? EditListAccountsViewController else {
            return
        }
        reloadIfNecessary(editViewController: edit)
    }
}