Tusker/Tusker/Screens/Conversation/ConversationTableViewController.swift

//
//  ConversationTableViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 8/28/18.
//  Copyright © 2018 Shadowfacts. All rights reserved.
//

import UIKit
import SafariServices
import Pachyderm

class ConversationTableViewController: EnhancedTableViewController {
    
    static let showPostsImage = UIImage(systemName: "eye.fill")!
    static let hidePostsImage = UIImage(systemName: "eye.slash.fill")!
    
    var mainStatusID: String!
    var statusIDs: [String] = [] {
        didSet {
            DispatchQueue.main.async {
                self.tableView.reloadData()
            }
        }
    }
    
    var showStatusesAutomatically = false
    var visibilityBarButtonItem: UIBarButtonItem!
    
    init(for mainStatusID: String) {
        self.mainStatusID = mainStatusID
        
        super.init(style: .plain)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        tableView.delegate = self
        tableView.dataSource = self
        
        tableView.register(UINib(nibName: "TimelineStatusTableViewCell", bundle: nil), forCellReuseIdentifier: "statusCell")
        tableView.register(UINib(nibName: "ConversationMainStatusTableViewCell", bundle: nil), forCellReuseIdentifier: "mainStatusCell")
        
        tableView.prefetchDataSource = self
        
        visibilityBarButtonItem = UIBarButtonItem(image: ConversationTableViewController.showPostsImage, style: .plain, target: self, action: #selector(toggleVisibilityButtonPressed))
        navigationItem.rightBarButtonItem = visibilityBarButtonItem

        statusIDs = [mainStatusID]
        
        guard let mainStatus = MastodonCache.status(for: mainStatusID) else { fatalError("Missing cached status \(mainStatusID!)") }
        
        let request = Status.getContext(mainStatus)
        MastodonController.client.run(request) { response in
            guard case let .success(context, _) = response else { fatalError() }
            let parents = self.getDirectParents(of: mainStatus, from: context.ancestors)
            MastodonCache.addAll(statuses: parents)
            MastodonCache.addAll(statuses: context.descendants)
            self.statusIDs = parents.map { $0.id } + [self.mainStatusID] + context.descendants.map { $0.id }
            let indexPath = IndexPath(row: self.statusIDs.firstIndex(of: self.mainStatusID)!, section: 0)
            DispatchQueue.main.async {
                self.tableView.scrollToRow(at: indexPath, at: .middle, animated: false)
            }
        }
    }

    func getDirectParents(of status: Status, from statuses: [Status]) -> [Status] {
        var statuses = statuses
        var parents: [Status] = []
        var currentStatus: Status? = status
        while currentStatus != nil {
            guard let index = statuses.firstIndex(where: { $0.id == currentStatus!.inReplyToID }) else { break }
            let parent = statuses.remove(at: index)
            parents.insert(parent, at: 0)
            currentStatus = parent
        }
        return parents
    }
    
    // MARK: - Table view data source

    override func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return statusIDs.count
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let statusID = statusIDs[indexPath.row]
        
        if statusID == mainStatusID {
            guard let cell = tableView.dequeueReusableCell(withIdentifier: "mainStatusCell", for: indexPath) as? ConversationMainStatusTableViewCell else { fatalError() }
            cell.selectionStyle = .none
            cell.showStatusAutomatically = showStatusesAutomatically
            cell.updateUI(statusID: statusID)
            cell.delegate = self
            return cell
        } else {
            guard let cell = tableView.dequeueReusableCell(withIdentifier: "statusCell", for: indexPath) as? TimelineStatusTableViewCell else { fatalError() }
            cell.showStatusAutomatically = showStatusesAutomatically
            cell.updateUI(statusID: statusID)
            cell.delegate = self
            return cell
        }
    }
    
    override func tableView(_ tableView: UITableView, willSelectRowAt indexPath: IndexPath) -> IndexPath? {
        let statusID = statusIDs[indexPath.row]
        return statusID == mainStatusID ? nil : indexPath
    }
    
    override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
        return true
    }
    
    override func tableView(_ tableView: UITableView, leadingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? {
        return (tableView.cellForRow(at: indexPath) as? TableViewSwipeActionProvider)?.leadingSwipeActionsConfiguration()
    }
    
    override func tableView(_ tableView: UITableView, trailingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? {
        return (tableView.cellForRow(at: indexPath) as? TableViewSwipeActionProvider)?.trailingSwipeActionsConfiguration()
    }
    
    @objc func toggleVisibilityButtonPressed() {
        showStatusesAutomatically = !showStatusesAutomatically
        
        for cell in tableView.visibleCells {
            guard let cell = cell as? BaseStatusTableViewCell,
                cell.collapsible else { continue }
            cell.showStatusAutomatically = showStatusesAutomatically
            cell.setCollapsed(!showStatusesAutomatically, animated: false)
        }
        statusCollapsedStateChanged()
        
        if showStatusesAutomatically {
            visibilityBarButtonItem.image = ConversationTableViewController.hidePostsImage
        } else {
            visibilityBarButtonItem.image = ConversationTableViewController.showPostsImage
        }
    }

}

extension ConversationTableViewController: StatusTableViewCellDelegate {
    func statusCollapsedStateChanged() {
        // causes the table view to recalculate the cell heights
        tableView.beginUpdates()
        tableView.endUpdates()
    }
}

extension ConversationTableViewController: UITableViewDataSourcePrefetching {
    func tableView(_ tableView: UITableView, prefetchRowsAt indexPaths: [IndexPath]) {
        for indexPath in indexPaths {
            guard let status = MastodonCache.status(for: statusIDs[indexPath.row]) else { continue }
            ImageCache.avatars.get(status.account.avatar, completion: nil)
            for attachment in status.attachments {
                ImageCache.attachments.get(attachment.url, completion: nil)
            }
        }
    }
    
    func tableView(_ tableView: UITableView, cancelPrefetchingForRowsAt indexPaths: [IndexPath]) {
        for indexPath in indexPaths {
            guard let status = MastodonCache.status(for: statusIDs[indexPath.row]) else { continue }
            ImageCache.avatars.cancel(status.account.avatar)
            for attachment in status.attachments {
                ImageCache.attachments.cancel(attachment.url)
            }
        }
    }
}