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

import UIKit
import Pachyderm

class ProfileStatusesViewController: TimelineLikeTableViewController<TimelineEntry> {
    
    weak var mastodonController: MastodonController!
    
    private(set) var headerView: ProfileHeaderView!
    
    var accountID: String!
    
    let kind: Kind
    
    private var older: RequestRange?
    private var newer: RequestRange?
    
    init(accountID: String?, kind: Kind, mastodonController: MastodonController) {
        self.accountID = accountID
        self.kind = kind
        self.mastodonController = mastodonController
        
        super.init()
        
        dragEnabled = true
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        tableView.register(UINib(nibName: "TimelineStatusTableViewCell", bundle: .main), forCellReuseIdentifier: "statusCell")
    }
    
    func updateUI(account: AccountMO) {
        loadInitial()
    }
    
    override class func refreshCommandTitle() -> String {
        return NSLocalizedString("Refresh Statuses", comment: "refresh statuses command discoverability title")
    }
    
    override func headerSectionsCount() -> Int {
        return 1
    }
    
    override func loadInitial() {
        guard accountID != nil else {
            return
        }
        
        if !loaded {
            loadPinnedStatuses()
        }
        
        super.loadInitial()
    }
    
    private func loadPinnedStatuses() {
        guard kind == .statuses else {
            return
        }
        getPinnedStatuses { (response) in
            guard case let .success(statuses, _) = response,
                  !statuses.isEmpty else {
                // todo: error message
                return
            }
            
            self.mastodonController.persistentContainer.addAll(statuses: statuses) {
                let items = statuses.map { ($0.id, StatusState.unknown) }
                DispatchQueue.main.async {
                    UIView.performWithoutAnimation {
                        if self.sections.count < 1 {
                            self.sections.append(items)
                            self.tableView.insertSections(IndexSet(integer: 0), with: .none)
                        } else {
                            self.sections[0] = items
                            self.tableView.reloadSections(IndexSet(integer: 0), with: .none)
                        }
                    }
                }
            }
        }
    }
    
    override func loadInitialItems(completion: @escaping ([TimelineEntry]) -> Void) {
        getStatuses { (response) in
            guard case let .success(statuses, pagination) = response,
                  !statuses.isEmpty else {
                // todo: error message
                completion([])
                return
            }
            
            self.older = pagination?.older
            self.newer = pagination?.newer
            
            self.mastodonController.persistentContainer.addAll(statuses: statuses) {
                completion(statuses.map { ($0.id, .unknown) })
            }
        }
    }
    
    override func loadOlder(completion: @escaping ([TimelineEntry]) -> Void) {
        guard let older = older else {
            completion([])
            return
        }
        
        getStatuses(for: older) { (response) in
            guard case let .success(statuses, pagination) = response else {
                // todo: error message
                completion([])
                return
            }
            
            self.older = pagination?.older
            
            self.mastodonController.persistentContainer.addAll(statuses: statuses) {
                completion(statuses.map { ($0.id, .unknown) })
            }
        }
    }
    
    override func loadNewer(completion: @escaping ([TimelineEntry]) -> Void) {
        guard let newer = newer else {
            completion([])
            return
        }
        
        getStatuses(for: newer) { (response) in
            guard case let .success(statuses, pagination) = response else {
                // todo: error message
                completion([])
                return
            }
            
            if let newer = pagination?.newer {
                self.newer = newer
            }
            
            self.mastodonController.persistentContainer.addAll(statuses: statuses) {
                completion(statuses.map { ($0.id, .unknown) })
            }
        }
    }
    
    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)
    }
    
    override func refresh() {
        super.refresh()
        
        if kind == .statuses {
            getPinnedStatuses { (response) in
                guard case let .success(newPinnedStatues, _) = response else {
                    // todo: error message
                    return
                }
                
                self.mastodonController.persistentContainer.addAll(statuses: newPinnedStatues) {
                    // if the user refreshes before the initial pinned statuses request completes, self.sections will be empty
                    let oldPinnedStatuses = self.sections.isEmpty ? [] : self.sections[0]
                    let pinnedStatues = newPinnedStatues.map { (status) -> TimelineEntry 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 {
                        UIView.performWithoutAnimation {
                            if self.sections.count < 1 {
                                self.sections.append(pinnedStatues)
                                self.tableView.insertSections(IndexSet(integer: 0), with: .none)
                            } else {
                                self.sections[0] = pinnedStatues
                                self.tableView.reloadSections(IndexSet(integer: 0), with: .none)
                            }
                        }
                    }
                }
            }
        }
    }
    
    // MARK: - UITableViewDatasource
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "statusCell", for: indexPath) as! TimelineStatusTableViewCell
        
        cell.delegate = self
        cell.showPinned = indexPath.section == 0
        
        let (id, state) = item(for: indexPath)
        cell.updateUI(statusID: id, state: state)
        
        return cell
    }
    
}

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

extension ProfileStatusesViewController: TuskerNavigationDelegate {
    var apiController: MastodonController { mastodonController }
}

extension ProfileStatusesViewController: StatusTableViewCellDelegate {
    func statusCellCollapsedStateChanged(_ cell: BaseStatusTableViewCell) {
        cellHeightChanged()
    }
}

extension ProfileStatusesViewController: UITableViewDataSourcePrefetching, StatusTablePrefetching {
    func tableView(_ tableView: UITableView, prefetchRowsAt indexPaths: [IndexPath]) {
        let ids = indexPaths.map { item(for: $0).id }
        prefetchStatuses(with: ids)
    }
    
    func tableView(_ tableView: UITableView, cancelPrefetchingForRowsAt indexPaths: [IndexPath]) {
        let ids: [String] = indexPaths.compactMap {
            guard $0.section < sections.count,
                  $0.row < sections[$0.section].count else {
                return nil
            }
            return item(for: $0).id
        }
        cancelPrefetchingStatuses(with: ids)
    }
}