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

import UIKit
import Pachyderm

class ProfileStatusesViewController: DiffableTimelineLikeTableViewController<ProfileStatusesViewController.Section, ProfileStatusesViewController.Item> {
    
    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) {
        if isViewLoaded {
            reloadInitial()
        }
    }
    
    override class func refreshCommandTitle() -> String {
        return NSLocalizedString("Refresh Statuses", comment: "refresh statuses command discoverability title")
    }
    
    override func cellProvider(_ tableView: UITableView, _ indexPath: IndexPath, _ item: Item) -> UITableViewCell? {
        let cell = tableView.dequeueReusableCell(withIdentifier: "statusCell", for: indexPath) as! TimelineStatusTableViewCell
        
        cell.delegate = self
        // todo: dataSource.sectionIdentifier is only available on iOS 15
        cell.showPinned = dataSource.snapshot().indexOfSection(.pinned) == indexPath.section
        cell.updateUI(statusID: item.id, state: item.state)
        
        return cell
    }
    
    override func loadInitialItems(completion: @escaping (LoadResult) -> Void) {
        guard accountID != nil else {
            completion(.failure(.noClient))
            return
        }
        
        getStatuses { (response) in
            switch response {
            case let .failure(error):
                completion(.failure(.client(error)))
                
            case let .success(statuses, pagination):
                self.older = pagination?.older
                self.newer = pagination?.newer
                
                self.mastodonController.persistentContainer.addAll(statuses: statuses) {
                    DispatchQueue.main.async {
                        var snapshot = self.dataSource.snapshot()
                        snapshot.appendSections([.statuses])
                        snapshot.appendItems(statuses.map { Item(id: $0.id, state: .unknown) }, toSection: .statuses)
                        if self.kind == .statuses {
                            self.loadPinnedStatuses(snapshot: { snapshot }, completion: completion)
                        } else {
                            completion(.success(snapshot))
                        }
                    }
                }
            }
        }
    }
    
    private func loadPinnedStatuses(snapshot: @escaping () -> Snapshot, completion: @escaping (LoadResult) -> Void) {
        guard kind == .statuses else {
            completion(.success(snapshot()))
            return
        }
        getPinnedStatuses { (response) in
            switch response {
            case let .failure(error):
                completion(.failure(.client(error)))
                
            case let .success(statuses, _):
                self.mastodonController.persistentContainer.addAll(statuses: statuses) {
                    DispatchQueue.main.async {
                        var snapshot = snapshot()
                        if snapshot.indexOfSection(.pinned) != nil {
                            snapshot.deleteSections([.pinned])
                        }
                        snapshot.insertSections([.pinned], beforeSection: .statuses)
                        snapshot.appendItems(statuses.map { Item(id: $0.id, state: .unknown) }, toSection: .pinned)
                        completion(.success(snapshot))
                    }
                }
            }
        }
    }
    
    override func loadOlderItems(currentSnapshot: @escaping () -> Snapshot, completion: @escaping (LoadResult) -> Void) {
        guard let older = older else {
            completion(.failure(.noOlder))
            return
        }
        
        getStatuses(for: older) { (response) in
            switch response {
            case let .failure(error):
                completion(.failure(.client(error)))
                
            case let .success(statuses, pagination):
                guard !statuses.isEmpty else {
                    completion(.failure(.noOlder))
                    return
                }
                
                if let older = pagination?.older {
                    self.older = older
                }
                
                self.mastodonController.persistentContainer.addAll(statuses: statuses) {
                    var snapshot = currentSnapshot()
                    snapshot.appendItems(statuses.map { Item(id: $0.id, state: .unknown) }, toSection: .statuses)
                    completion(.success(snapshot))
                }
            }
        }
    }
   
    
    override func loadNewerItems(currentSnapshot: @escaping () -> Snapshot, completion: @escaping (LoadResult) -> Void) {
        guard let newer = newer else {
            completion(.failure(.noNewer))
            return
        }

        getStatuses(for: newer) { (response) in
            switch response {
            case let .failure(error):
                completion(.failure(.client(error)))
                
            case let .success(statuses, pagination):
                guard !statuses.isEmpty else {
                    completion(.failure(.noNewer))
                    return
                }
                
                if let newer = pagination?.newer {
                    self.newer = newer
                }
                
                self.mastodonController.persistentContainer.addAll(statuses: statuses) {
                    var snapshot = currentSnapshot()
                    let items = statuses.map { Item(id: $0.id, state: .unknown) }
                    if let first = snapshot.itemIdentifiers(inSection: .statuses).first {
                        snapshot.insertItems(items, beforeItem: first)
                    } else {
                        snapshot.appendItems(items, toSection: .statuses)
                    }
                    completion(.success(snapshot))
                }
            }
        }
    }
    
    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 {
            loadPinnedStatuses(snapshot: dataSource.snapshot) { (result) in
                switch result {
                case .failure(_):
                    break
                    
                case let .success(snapshot):
                    DispatchQueue.main.async {
                        self.dataSource.apply(snapshot)
                    }
                }
            }
        }
    }
    
}

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

extension ProfileStatusesViewController {
    enum Section: CaseIterable {
        case pinned
        case statuses
    }
    struct Item: Hashable {
        let id: String
        let state: StatusState
    }
}

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.compactMap { dataSource.itemIdentifier(for: $0)?.id }
        prefetchStatuses(with: ids)
    }
    
    func tableView(_ tableView: UITableView, cancelPrefetchingForRowsAt indexPaths: [IndexPath]) {
        let ids = indexPaths.compactMap { dataSource.itemIdentifier(for: $0)?.id }
        cancelPrefetchingStatuses(with: ids)
    }
}