//

//  EmailListViewController.swift

//  pEpForiOS

//

//  Created by Dirk Zimmermann on 16/04/16.

//  Copyright © 2016 p≡p Security S.A. All rights reserved.

//

import UIKit

import MessageModel

import SwipeCellKit

class EmailListViewController: BaseTableViewController, SwipeTableViewCellDelegate {

    var folderToShow: Folder?

    func updateLastLookAt() {

        guard let saveFolder = folderToShow else {

            return

        }

        saveFolder.updateLastLookAt()

    }

    private var model: EmailListViewModel?

    private let queue: OperationQueue = {

        let createe = OperationQueue()

        createe.qualityOfService = .userInteractive

        createe.maxConcurrentOperationCount = 10

        return createe

    }()

    private var operations = [IndexPath:Operation]()

    public static let storyboardId = "EmailListViewController"

    fileprivate var lastSelectedIndexPath: IndexPath?

    let searchController = UISearchController(searchResultsController: nil)

    //swipe acctions types

    var buttonDisplayMode: ButtonDisplayMode = .titleAndImage

    var buttonStyle: ButtonStyle = .backgroundColor

    // MARK: - Outlets

    @IBOutlet weak var enableFilterButton: UIBarButtonItem!

    @IBOutlet weak var textFilterButton: UIBarButtonItem!

    @IBOutlet var showFoldersButton: UIBarButtonItem!

    // MARK: - Life Cycle

    override func viewDidLoad() {

        super.viewDidLoad()

        title = NSLocalizedString("Inbox", comment: "General name for (unified) inbox")

        UIHelper.emailListTableHeight(self.tableView)

        self.textFilterButton.isEnabled = false

        addSearchBar()

    }

    override func viewWillAppear(_ animated: Bool) {

        super.viewWillAppear(animated)

        self.navigationController?.setToolbarHidden(false, animated: true)

        if MiscUtil.isUnitTest() {

            return

        }

        setDefaultColors()

        setup()

        // Mark this folder as having been looked at by the user

        updateLastLookAt()

        setupFoldersBarButton()

    }

    // MARK: - NavigationBar

    private func hideFoldersNavigationBarButton() {

        self.showFoldersButton.isEnabled = false

        self.showFoldersButton.tintColor = UIColor.clear

    }

    private func showFoldersNavigationBarButton() {

        self.showFoldersButton.isEnabled = true

        self.showFoldersButton.tintColor = nil

    }

    private func resetModel() {

        if folderToShow != nil {

            model = EmailListViewModel(delegate: self,

                                       messageSyncService: appConfig.messageSyncService,

                                       folderToShow: folderToShow)

        }

    }

    private func setup() {

        if noAccountsExist() {

            // No account exists. Show account setup.

            performSegue(withIdentifier:.segueAddNewAccount, sender: self)

        } else if let vm = model {

            // We came back from e.g EmailView ...

            updateFilterText()

            // ... so we want to update "seen" status

            vm.reloadData()

        } else if folderToShow == nil {

            // We have not been created to show a specific folder, thus we show unified inbox

            folderToShow = UnifiedInbox()

            resetModel()

        } else if model == nil {

            // We still got no model, because:

            // - We are not coming back from a pushed view (for instance ComposeEmailView)

            // - We are not a UnifiedInbox

            // So we have been created to show a specific folder. Show it!

            resetModel()

        }

        self.title = realNameOfFolderToShow()

    }

    private func weCameBackFromAPushedView() -> Bool {

        return model != nil

    }

    private func noAccountsExist() -> Bool {

        return Account.all().isEmpty

    }

    private func setupFoldersBarButton() {

        if let size = navigationController?.viewControllers.count, size > 1 {

            hideFoldersNavigationBarButton()

        } else {

            showFoldersNavigationBarButton()

        }

    }

    private func addSearchBar() {

        searchController.searchResultsUpdater = self

        searchController.dimsBackgroundDuringPresentation = false

        searchController.delegate = self

        definesPresentationContext = true

        tableView.tableHeaderView = searchController.searchBar

        tableView.setContentOffset(CGPoint(x: 0.0, y: searchController.searchBar.frame.size.height), animated: false)

    }

    // MARK: - Other

    private func realNameOfFolderToShow() -> String? {

        return folderToShow?.realName

    }

    private func configure(cell: EmailListViewCell, for indexPath: IndexPath) {

        // Configure lightweight stuff on main thread ...

        guard let saveModel = model else {

            return

        }

        guard let row = saveModel.row(for: indexPath) else {

            Log.shared.errorAndCrash(component: #function, errorString: "We should have a row here")

            return

        }

        cell.senderLabel.text = row.from

        cell.subjectLabel.text = row.subject

        cell.summaryLabel.text = row.bodyPeek

        cell.isFlagged = row.isFlagged

        cell.isSeen = row.isSeen

        cell.hasAttachment = row.showAttchmentIcon

        cell.dateLabel.text = row.dateText

        // Set image from cache if any

        cell.setContactImage(image: row.senderContactImage)

        let op = BlockOperation() { [weak self] in

            // ... and expensive computations in background

            guard let strongSelf = self else {

                // View is gone, nothing to do.

                return

            }

            var senderImage: UIImage?

            if row.senderContactImage == nil {

                // image for identity has not been cached yet

                // Get and cache it here in the background ...

                senderImage = strongSelf.model?.senderImage(forCellAt: indexPath)

                // ... and set it on the main queue

                DispatchQueue.main.async {

                    if senderImage != nil && senderImage != cell.contactImageView.image {

                        cell.contactImageView.image  = senderImage

                    }

                }

            }

            let pEpRatingImage = strongSelf.model?.pEpRatingColorImage(forCellAt: indexPath)

            // In theory we want to set all data in *one* async call. But as pEpRatingColorImage takes

            // very long, we are setting the sender image seperatelly.

            DispatchQueue.main.async {

                if pEpRatingImage != nil {

                    cell.setPepRatingImage(image: pEpRatingImage)

                }

            }

        }

        queue(operation: op, for: indexPath)

    }

    // MARK: - Actions

    @IBAction func filterButtonHasBeenPressed(_ sender: UIBarButtonItem) {

        guard let vm = model else {

            Log.shared.errorAndCrash(component: #function, errorString: "We should have a model here")

            return

        }

        vm.isFilterEnabled = !vm.isFilterEnabled

        updateFilterButtonView()

    }

    func updateFilterButtonView() {

        guard let vm = model else {

            Log.shared.errorAndCrash(component: #function, errorString: "We should have a model here")

            return

        }

        textFilterButton.isEnabled = vm.isFilterEnabled

        if textFilterButton.isEnabled {

            enableFilterButton.image = UIImage(named: "unread-icon-active")

            updateFilterText()

        } else {

            textFilterButton.title = ""

            enableFilterButton.image = UIImage(named: "unread-icon")

        }

    }

    func updateFilterText() {

        if let vm = model, let txt = vm.activeFilter?.title {

            textFilterButton.title = "Filter by: " + txt

        }

    }

    // MARK: - UITableViewDataSource

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

        return model?.rowCount ?? 0

    }

    override func tableView(_ tableView: UITableView,

                            cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        guard let cell = tableView.dequeueReusableCell(withIdentifier: EmailListViewCell.storyboardId,

                                                       for: indexPath) as? EmailListViewCell

            else {

                Log.shared.errorAndCrash(component: #function, errorString: "Wrong cell!")

                return UITableViewCell()

        }

        cell.delegate = self

        configure(cell: cell, for: indexPath)

        return cell

    }

    // MARK: - UITableViewDelegate

    func tableView(_ tableView: UITableView, editActionsForRowAt indexPath: IndexPath, for orientation: SwipeActionsOrientation) -> [SwipeAction]? {

        if indexPath.section == 0 {

            let deleteAction = SwipeAction(style: .destructive, title: "Delete") { action, indexPath in

                self.deleteAction(forCellAt: indexPath)

            }

            configure(action: deleteAction, with: .trash)

            let flagAction = SwipeAction(style: .default, title: "Flag") { action, indexPath in

                self.flagAction(forCellAt: indexPath)

            }

            flagAction.hidesWhenSelected = true

            configure(action: flagAction, with: .flag)

            let moreAction = SwipeAction(style: .default, title: "More") { action, indexPath in

                self.moreAction(forCellAt: indexPath)

            }

            moreAction.hidesWhenSelected = true

            configure(action: moreAction, with: .more)

            return (orientation == .right ?   [deleteAction, flagAction, moreAction] : nil)

        }

        return nil

    }

    func tableView(_ tableView: UITableView, editActionsOptionsForRowAt indexPath: IndexPath, for orientation: SwipeActionsOrientation) -> SwipeTableOptions {

        var options = SwipeTableOptions()

        options.expansionStyle = .destructive

        options.transitionStyle = .border

        options.buttonSpacing = 11

        return options

    }

    func configure(action: SwipeAction, with descriptor: ActionDescriptor) {

        action.title = descriptor.title(forDisplayMode: buttonDisplayMode)

        action.image = descriptor.image(forStyle: buttonStyle, displayMode: buttonDisplayMode)

        switch buttonStyle {

        case .backgroundColor:

            action.backgroundColor = descriptor.color

        case .circular:

            action.backgroundColor = .clear

            action.textColor = descriptor.color

            action.font = .systemFont(ofSize: 13)

            action.transitionDelegate = ScaleTransition.default

        }

    }

    override func tableView(_ tableView: UITableView, didEndDisplaying cell: UITableViewCell, forRowAt indexPath: IndexPath) {

        cancelOperation(for: indexPath)

    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        lastSelectedIndexPath = indexPath

        tableView.selectRow(at: indexPath, animated: true, scrollPosition: .none)

        performSegue(withIdentifier: SegueIdentifier.segueShowEmail, sender: self)

    }

    // Implemented to get informed about the scrolling position.

    // If the user has scrolled down (almost) to the end, we need to get older emails to display.

    override func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell,

                            forRowAt indexPath: IndexPath) {

        guard let vm = model else {

            Log.shared.errorAndCrash(component: #function, errorString: "No model.")

            return

        }

        vm.fetchOlderMessagesIfRequired(forIndexPath: indexPath)

    }

    // MARK: - Queue Handling

    private func queue(operation op:Operation, for indexPath: IndexPath) {

        operations[indexPath] = op

        queue.addOperation(op)

    }

    private func cancelOperation(for indexPath:IndexPath) {

        guard let op = operations.removeValue(forKey: indexPath) else {

            return

        }

        if !op.isCancelled  {

            op.cancel()

        }

    }

    // MARK: -

    override func didReceiveMemoryWarning() {

        model?.freeMemory()

    }

}

// MARK: - UISearchResultsUpdating, UISearchControllerDelegate

extension EmailListViewController: UISearchResultsUpdating, UISearchControllerDelegate {

    public func updateSearchResults(for searchController: UISearchController) {

        guard let vm = model, let searchText = searchController.searchBar.text else {

            return

        }

        vm.setSearchFilter(forSearchText: searchText)

    }

    func didDismissSearchController(_ searchController: UISearchController) {

        guard let vm = model else {

            return

        }

        vm.removeSearchFilter()

    }

}

// MARK: - EmailListModelDelegate

extension EmailListViewController: EmailListViewModelDelegate {

    func emailListViewModel(viewModel: EmailListViewModel, didInsertDataAt indexPath: IndexPath) {

        tableView.beginUpdates()

        tableView.insertRows(at: [indexPath], with: .automatic)

        tableView.endUpdates()

    }

    func emailListViewModel(viewModel: EmailListViewModel, didRemoveDataAt indexPath: IndexPath) {

        tableView.beginUpdates()

        tableView.deleteRows(at: [indexPath], with: .automatic)

        tableView.endUpdates()

    }

    func emailListViewModel(viewModel: EmailListViewModel, didUpdateDataAt indexPath: IndexPath) {

        tableView.beginUpdates()

        tableView.reloadRows(at: [indexPath], with: .none)

        tableView.endUpdates()

    }

    func updateView() {

        self.tableView.reloadData()

    }

}

// MARK: - ActionSheet & ActionSheet Actions

extension EmailListViewController {

    func showMoreActionSheet(forRowAt indexPath: IndexPath) {

        lastSelectedIndexPath = indexPath

        let alertControler = UIAlertController(title: nil, message: nil, preferredStyle: .actionSheet)

        alertControler.view.tintColor = .pEpGreen

        let cancelAction = createCancelAction()

        let replyAction = createReplyAction()

        let replyAllAction = createReplyAllAction()

        let forwardAction = createForwardAction()

        alertControler.addAction(cancelAction)

        alertControler.addAction(replyAction)

        alertControler.addAction(replyAllAction)

        alertControler.addAction(forwardAction)

        if let popoverPresentationController = alertControler.popoverPresentationController {

            popoverPresentationController.sourceView = tableView

        }

        present(alertControler, animated: true, completion: nil)

    }

    // MARK: Action Sheet Actions

    func createCancelAction() -> UIAlertAction {

        return  UIAlertAction(title: "Cancel", style: .cancel) { (action) in

            self.tableView.beginUpdates()

            self.tableView.setEditing(false, animated: true)

            self.tableView.endUpdates()

        }

    }

    func createReplyAction() ->  UIAlertAction {

        return UIAlertAction(title: "Reply", style: .default) { (action) in

            self.performSegue(withIdentifier: .segueReply, sender: self)

        }

    }

    func createReplyAllAction() ->  UIAlertAction {

        return UIAlertAction(title: "Reply All", style: .default) { (action) in

            self.performSegue(withIdentifier: .segueReplyAll, sender: self)

        }

    }

    func createForwardAction() -> UIAlertAction {

        return UIAlertAction(title: "Forward", style: .default) { (action) in

            self.performSegue(withIdentifier: .segueForward, sender: self)

        }

    }

}

// MARK: - TableViewCell Actions

extension EmailListViewController {

    private func createRowAction(image: UIImage?,

                                 action: @escaping (UITableViewRowAction, IndexPath) -> Void

        ) -> UITableViewRowAction {

        let rowAction = UITableViewRowAction(style: .normal, title: nil, handler: action)

        if let theImage = image {

            let iconColor = UIColor(patternImage: theImage)

            rowAction.backgroundColor = iconColor

        }

        return rowAction

    }

    func flagAction(forCellAt indexPath: IndexPath) {

        guard let row = model?.row(for: indexPath) else {

            Log.shared.errorAndCrash(component: #function, errorString: "No data for indexPath!")

            return

        }

        if row.isFlagged {

            model?.unsetFlagged(forIndexPath: indexPath)

        } else {

            model?.setFlagged(forIndexPath: indexPath)

        }

        tableView.beginUpdates()

        tableView.setEditing(false, animated: true)

        tableView.reloadRows(at: [indexPath], with: .none)

        tableView.endUpdates()

    }

    func deleteAction(forCellAt indexPath: IndexPath) {

        model?.delete(forIndexPath: indexPath) // mark for deletion/trash

    }

    func moreAction(forCellAt indexPath: IndexPath) {

        self.showMoreActionSheet(forRowAt: indexPath)

    }

}

// MARK: - SegueHandlerType

extension EmailListViewController: SegueHandlerType {

    enum SegueIdentifier: String {

        case segueAddNewAccount

        case segueShowEmail

        case segueCompose

        case segueReply

        case segueReplyAll

        case segueForward

        case segueFilter

        case segueFolderViews

        case noSegue

    }

    private func setup(composeViewController vc: ComposeTableViewController,

                       composeMode: ComposeTableViewController.ComposeMode = .normal,

                       originalMessage: Message? = nil) {

        vc.appConfig = appConfig

        vc.composeMode = composeMode

        vc.originalMessage = originalMessage

        vc.origin = folderToShow?.account.user

    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        switch segueIdentifier(for: segue) {

        case .segueReply:

            guard let nav = segue.destination as? UINavigationController,

                let destination = nav.topViewController as? ComposeTableViewController,

                let indexPath = lastSelectedIndexPath,

                let message = model?.message(representedByRowAt: indexPath) else {

                    Log.shared.errorAndCrash(component: #function, errorString: "Segue issue")

                    return

            }

            setup(composeViewController: destination, composeMode: .replyFrom,

                  originalMessage: message)

        case .segueReplyAll:

            guard let nav = segue.destination as? UINavigationController,

                let destination = nav.topViewController as? ComposeTableViewController,

                let indexPath = lastSelectedIndexPath,

                let message = model?.message(representedByRowAt: indexPath) else {

                    Log.shared.errorAndCrash(component: #function, errorString: "Segue issue")

                    return

            }

            setup(composeViewController: destination, composeMode: .replyAll,

                  originalMessage: message)

        case .segueShowEmail:

            guard let vc = segue.destination as? EmailViewController,

                let indexPath = lastSelectedIndexPath,

                let message = model?.message(representedByRowAt: indexPath) else {

                    Log.shared.errorAndCrash(component: #function, errorString: "Segue issue")

                    return

            }

            vc.appConfig = appConfig

            vc.message = message

            vc.folderShow = folderToShow

            vc.messageId = indexPath.row //that looks wrong

        case .segueForward:

            guard let nav = segue.destination as? UINavigationController,

                let destination = nav.topViewController as? ComposeTableViewController,

                let indexPath = lastSelectedIndexPath,

                let message = model?.message(representedByRowAt: indexPath) else {

                    Log.shared.errorAndCrash(component: #function, errorString: "Segue issue")

                    return

            }

            setup(composeViewController: destination, composeMode: .forward,

                  originalMessage: message)

        case .segueFilter:

            guard let destiny = segue.destination as? FilterTableViewController  else {

                Log.shared.errorAndCrash(component: #function, errorString: "Segue issue")

                return

            }

            destiny.appConfig = appConfig

            destiny.filterDelegate = model

            destiny.inFolder = false

            destiny.filterEnabled = folderToShow?.filter

            destiny.hidesBottomBarWhenPushed = true

        case .segueAddNewAccount:

            guard let vc = segue.destination as? LoginTableViewController  else {

                Log.shared.errorAndCrash(component: #function, errorString: "Segue issue")

                return

            }

            vc.appConfig = appConfig

            vc.hidesBottomBarWhenPushed = true

            break

        case .segueFolderViews:

            guard let vC = segue.destination as? FolderTableViewController  else {

                Log.shared.errorAndCrash(component: #function, errorString: "Segue issue")

                return

            }

            vC.appConfig = appConfig

            vC.hidesBottomBarWhenPushed = true

            break

        case .segueCompose:

            guard let nav = segue.destination as? UINavigationController,

                let destination = nav.rootViewController as? ComposeTableViewController else {

                    Log.shared.errorAndCrash(component: #function, errorString: "Segue issue")

                    return

            }

            setup(composeViewController: destination)

        default:

            Log.shared.errorAndCrash(component: #function, errorString: "Unhandled segue")

            break

        }

    }

    @IBAction func segueUnwindAccountAdded(segue: UIStoryboardSegue) {

        // nothing to do.

    }

}

//enums to simplify configurations

enum ActionDescriptor {

    case read, more, flag, trash

    func title(forDisplayMode displayMode: ButtonDisplayMode) -> String? {

        guard displayMode != .imageOnly else { return nil }

        switch self {

        case .read: return NSLocalizedString("Read", comment: "read button")

        case .more: return NSLocalizedString("More", comment: "more button")

        case .flag: return NSLocalizedString("Flag", comment: "read button")

        case .trash: return NSLocalizedString("Trash", comment: "Trash button")

        }

    }

    func image(forStyle style: ButtonStyle, displayMode: ButtonDisplayMode) -> UIImage? {

        guard displayMode != .titleOnly else { return nil }

        let name: String

        switch self {

        case .read: name = "read"

        case .more: name = "more"

        case .flag: name = "flag"

        case .trash: name = "trash"

        }

        return UIImage(named: "swipe-" + name)

    }

    var color: UIColor {

        switch self {

        case .read: return #colorLiteral(red: 0.2980392157, green: 0.8509803922, blue: 0.3921568627, alpha: 1)

        case .more: return #colorLiteral(red: 0.7803494334, green: 0.7761332393, blue: 0.7967314124, alpha: 1)

        case .flag: return #colorLiteral(red: 1, green: 0.5803921569, blue: 0, alpha: 1)

        case .trash: return #colorLiteral(red: 1, green: 0.2352941176, blue: 0.1882352941, alpha: 1)

        }

    }

}

enum ButtonDisplayMode {

    case titleAndImage, titleOnly, imageOnly

}

enum ButtonStyle {

    case backgroundColor, circular

}