//
//  ProfileStatusesViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 7/3/20.
//  Copyright © 2020 Shadowfacts. All rights reserved.
//

import UIKit
import Pachyderm

class ProfileStatusesViewController: EnhancedTableViewController {

    weak var mastodonController: MastodonController!
    
    private(set) var headerView: ProfileHeaderView!
    
    var accountID: String!
    
    let kind: Kind
    
    private var pinnedStatuses: [(id: String, state: StatusState)] = []
    private var timelineSegments: [[(id: String, state: StatusState)]] = []
    
    private var older: RequestRange?
    private var newer: RequestRange?
    
    var loaded = false
    
    init(accountID: String?, kind: Kind, mastodonController: MastodonController) {
        self.accountID = accountID
        self.kind = kind
        self.mastodonController = mastodonController
        
        super.init(style: .plain)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .systemBackground
        
        #if !targetEnvironment(macCatalyst)
        refreshControl = UIRefreshControl()
        refreshControl!.addTarget(self, action: #selector(refreshStatuses), for: .valueChanged)
        #endif
        
        addKeyCommand(MenuController.refreshCommand(discoverabilityTitle: NSLocalizedString("Refresh Statuses", comment: "refresh statuses command discoverability title")))
        
        tableView.rowHeight = UITableView.automaticDimension
        tableView.estimatedRowHeight = 140
        
        tableView.register(UINib(nibName: "TimelineStatusTableViewCell", bundle: .main), forCellReuseIdentifier: "statusCell")
        
        tableView.prefetchDataSource = self
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        if !loaded,
           let accountID = accountID,
           let account = mastodonController.persistentContainer.account(for: accountID) {
            updateUI(account: account)
        }
    }
    
    func updateUI(account: AccountMO) {
        guard !loaded else { return }
        loaded = true
        
        if kind == .statuses {
            getPinnedStatuses { (response) in
                guard case let .success(statuses, _) = response else {
                    // todo: error message
                    return
                }
                if statuses.isEmpty { return }
                
                self.mastodonController.persistentContainer.addAll(statuses: statuses) {
                    self.pinnedStatuses = statuses.map { ($0.id, .unknown) }
                    let indexPaths = (0..<statuses.count).map { IndexPath(row: $0, section: 0) }
                    DispatchQueue.main.async {
                        UIView.performWithoutAnimation {
                            self.tableView.insertRows(at: indexPaths, with: .none)
                        }
                    }
                }
            }
        }
        
        getStatuses { (response) in
            guard case let .success(statuses, pagination) = response else {
                // todo: error message
                return
            }
            if statuses.isEmpty { return }
            
            self.mastodonController.persistentContainer.addAll(statuses: statuses) {
                self.timelineSegments.append(statuses.map { ($0.id, .unknown) })
                
                self.older = pagination?.older
                self.newer = pagination?.newer
                
                DispatchQueue.main.async {
                    UIView.performWithoutAnimation {
                        self.tableView.insertSections(IndexSet(integer: 1), with: .none)
                    }
                }
            }
        }
    }
    
    private func getStatuses(for range: RequestRange = .default, completion: @escaping Client.Callback<[Status]>) {
        let request: Request<[Status]>
        switch kind {
        case .statuses:
            request = Account.getStatuses(accountID, range: range, onlyMedia: false, pinned: false, excludeReplies: true)
        case .withReplies:
            request = Account.getStatuses(accountID, range: range, onlyMedia: false, pinned: false, excludeReplies: false)
        case .onlyMedia:
            request = Account.getStatuses(accountID, range: range, onlyMedia: true, pinned: false, excludeReplies: false)
        }
        mastodonController.run(request, completion: completion)
    }
    
    private func getPinnedStatuses(completion: @escaping Client.Callback<[Status]>) {
        let request = Account.getStatuses(accountID, range: .default, onlyMedia: false, pinned: true, excludeReplies: false)
        mastodonController.run(request, completion: completion)
    }

    // MARK: Interaction
    
    @objc func refreshStatuses() {
        guard let newer = newer else { return }
        
        getStatuses(for: newer) { (response) in
            guard case let .success(newStatuses, pagination) = response else {
                // todo: error message
                return
            }
            
            self.mastodonController.persistentContainer.addAll(statuses: newStatuses) {
                // if there's no newer request range (because no statuses were returned),
                // we don't want to change the current newer pagination, so that we can
                // continue to load statuses newer than whatever was last loaded
                if let newer = pagination?.newer {
                    self.newer = newer
                }
                
                let indexPaths = (0..<newStatuses.count).map { IndexPath(row: $0, section: 1) }
                DispatchQueue.main.async {
                    self.timelineSegments[0].insert(contentsOf: newStatuses.map { ($0.id, .unknown) }, at: 0)
                    UIView.performWithoutAnimation {
                        self.tableView.insertRows(at: indexPaths, with: .none)
                    }
                    
                    self.refreshControl?.endRefreshing()
                }
            }
        }
        
        if kind == .statuses {
            getPinnedStatuses { (response) in
                guard case let .success(newPinnedStatuses, _) = response else {
                    // todo: error message
                    return
                }
                
                self.mastodonController.persistentContainer.addAll(statuses: newPinnedStatuses) {
                    let oldPinnedStatuses = self.pinnedStatuses
                    let pinnedStatuses = newPinnedStatuses.map { (status) -> (id: String, state: StatusState) in
                        let state: StatusState
                        if let (_, oldState) = oldPinnedStatuses.first(where: { $0.id == status.id }) {
                            state = oldState
                        } else {
                            state = .unknown
                        }
                        return (status.id, state)
                    }
                    DispatchQueue.main.async {
                        self.pinnedStatuses = pinnedStatuses
                        UIView.performWithoutAnimation {
                            self.tableView.reloadSections(IndexSet(integer: 0), with: .none)
                        }
                    }
                }
            }
        }
    }
    
    // MARK: Table view data source

    override func numberOfSections(in tableView: UITableView) -> Int {
        // 1 for pinned, rest for timeline
        return 1 + timelineSegments.count
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        if section == 0 {
            return pinnedStatuses.count
        } else {
            return timelineSegments[section - 1].count
        }
    }

    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "statusCell", for: indexPath) as! TimelineStatusTableViewCell

        cell.delegate = self
        
        if indexPath.section == 0 {
            cell.showPinned = true
            let (id, state) = pinnedStatuses[indexPath.row]
            cell.updateUI(statusID: id, state: state)
        } else {
            cell.showPinned = false
            let (id, state) = timelineSegments[indexPath.section - 1][indexPath.row]
            cell.updateUI(statusID: id, state: state)
        }

        return cell
    }
    
    override func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
        // load older statuses if at bottom
        if timelineSegments.count > 0,
           indexPath.section == timelineSegments.count,
           indexPath.row == timelineSegments[indexPath.section - 1].count - 1 {
            guard let older = older else { return }
            
            getStatuses(for: older) { (response) in
                guard case let .success(newStatuses, pagination) = response else {
                    // todo: error message
                    return
                }
                
                self.mastodonController.persistentContainer.addAll(statuses: newStatuses) {
                    // if there is no older request range, we want to set ours to nil
                    // otherwise we would end up loading the same statuses again
                    self.older = pagination?.older
                    
                    DispatchQueue.main.async {
                        let start = self.timelineSegments[indexPath.section - 1].count
                        let indexPaths = (0..<newStatuses.count).map { IndexPath(row: start + $0, section: indexPath.section) }
                        self.timelineSegments[indexPath.section - 1].append(contentsOf: newStatuses.map { ($0.id, .unknown) })
                        UIView.performWithoutAnimation {
                            self.tableView.insertRows(at: indexPaths, with: .none)
                        }
                    }
                }
            }
        }
    }
    
    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()
    }

}

extension ProfileStatusesViewController {
    enum Kind {
        case statuses, withReplies, onlyMedia
    }
}

extension ProfileStatusesViewController: StatusTableViewCellDelegate {
    var apiController: MastodonController { mastodonController }
    
    func statusCellCollapsedStateChanged(_ cell: BaseStatusTableViewCell) {
        // causes the table view to recalculate the cell heights
        tableView.beginUpdates()
        tableView.endUpdates()
    }
}

extension ProfileStatusesViewController: UITableViewDataSourcePrefetching {
    func tableView(_ tableView: UITableView, prefetchRowsAt indexPaths: [IndexPath]) {
        for indexPath in indexPaths {
            let statusID: String
            if indexPath.section == 0 {
                statusID = pinnedStatuses[indexPath.row].id
            } else {
                statusID = timelineSegments[indexPath.section - 1][indexPath.row].id
            }
            guard let status = mastodonController.persistentContainer.status(for: statusID) else { continue }
            _ = ImageCache.avatars.get(status.account.avatar, completion: nil)
            for attachment in status.attachments where attachment.kind == .image {
                _ = ImageCache.attachments.get(attachment.url, completion: nil)
            }
        }
    }
    
    func tableView(_ tableView: UITableView, cancelPrefetchingForRowsAt indexPaths: [IndexPath]) {
        for indexPath in indexPaths {
            let statusID: String
            if indexPath.section == 0 {
                statusID = pinnedStatuses[indexPath.row].id
            } else {
                statusID = timelineSegments[indexPath.section - 1][indexPath.row].id
            }
            guard let status = mastodonController.persistentContainer.status(for: statusID) else { continue }
            ImageCache.avatars.cancelWithoutCallback(status.account.avatar)
            for attachment in status.attachments where attachment.kind == .image {
                ImageCache.avatars.cancelWithoutCallback(attachment.url)
            }
        }
    }
}

extension ProfileStatusesViewController: RefreshableViewController {
    func refresh() {
        refreshStatuses()
    }
}