// Copyright © 2022 Rangeproof Pty Ltd. All rights reserved.

import UIKit
import Combine
import UniformTypeIdentifiers
import GRDB
import DifferenceKit
import SessionUIKit
import SignalUtilitiesKit
import SessionMessagingKit
import SessionSnodeKit
import SessionUtilitiesKit

final class ThreadPickerVC: UIViewController, UITableViewDataSource, UITableViewDelegate, AttachmentApprovalViewControllerDelegate, ThemedNavigation {
    private let viewModel: ThreadPickerViewModel
    private var dataChangeObservable: DatabaseCancellable? {
        didSet { oldValue?.cancel() }   // Cancel the old observable if there was one
    }
    private var hasLoadedInitialData: Bool = false
    public var navigationBackground: ThemeValue? { .backgroundPrimary }
    
    var shareNavController: ShareNavController?
    
    // MARK: - Intialization
    
    init(using dependencies: Dependencies) {
        viewModel = ThreadPickerViewModel(using: dependencies)
        
        super.init(nibName: nil, bundle: nil)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    deinit {
        NotificationCenter.default.removeObserver(self)
    }
    
    // MARK: - UI
    
    private lazy var titleLabel: UILabel = {
        let titleLabel: UILabel = UILabel()
        titleLabel.font = .boldSystemFont(ofSize: Values.veryLargeFontSize)
        titleLabel.text = "shareToSession"
            .put(key: "app_name", value: Constants.app_name)
            .localized()
        titleLabel.themeTextColor = .textPrimary
        
        return titleLabel
    }()
    
    private lazy var databaseErrorLabel: UILabel = {
        let result: UILabel = UILabel()
        result.font = .systemFont(ofSize: Values.mediumFontSize)
        result.text = "shareExtensionDatabaseError".localized()
        result.textAlignment = .center
        result.themeTextColor = .textPrimary
        result.numberOfLines = 0
        result.isHidden = true
        
        return result
    }()
    
    private lazy var noAccountErrorLabel: UILabel = {
        let result: UILabel = UILabel()
        result.font = .systemFont(ofSize: Values.mediumFontSize)
        result.text = "shareExtensionNoAccountError"
            .put(key: "app_name", value: Constants.app_name)
            .localized()
        result.textAlignment = .center
        result.themeTextColor = .textPrimary
        result.numberOfLines = 0
        result.isHidden = true
        
        return result
    }()

    private lazy var tableView: UITableView = {
        let tableView: UITableView = UITableView()
        tableView.themeBackgroundColor = .backgroundPrimary
        tableView.separatorStyle = .none
        tableView.register(view: SimplifiedConversationCell.self)
        tableView.showsVerticalScrollIndicator = false
        tableView.dataSource = self
        tableView.delegate = self
        
        return tableView
    }()
    
    // MARK: - Lifecycle
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        navigationItem.titleView = titleLabel
        ThemeManager.applyNavigationStylingIfNeeded(to: self)
        
        view.themeBackgroundColor = .backgroundPrimary
        view.addSubview(tableView)
        view.addSubview(databaseErrorLabel)
        view.addSubview(noAccountErrorLabel)
        
        setupLayout()
        
        // Notifications
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(applicationDidBecomeActive(_:)),
            name: UIApplication.didBecomeActiveNotification,
            object: nil
        )
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(applicationDidResignActive(_:)),
            name: UIApplication.didEnterBackgroundNotification, object: nil
        )
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        startObservingChanges()
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        
        stopObservingChanges()
        
        // When the thread picker disappears it means the user has left the screen (this will be called
        // whether the user has sent the message or cancelled sending)
        viewModel.dependencies.mutate(cache: .libSessionNetwork) { $0.suspendNetworkAccess() }
        viewModel.dependencies[singleton: .storage].suspendDatabaseAccess()
        Log.flush()
    }
    
    @objc func applicationDidBecomeActive(_ notification: Notification) {
        /// Need to dispatch to the next run loop to prevent a possible crash caused by the database resuming mid-query
        DispatchQueue.main.async { [weak self] in
            self?.startObservingChanges()
        }
    }
    
    @objc func applicationDidResignActive(_ notification: Notification) {
        stopObservingChanges()
    }
    
    // MARK: Layout
    
    private func setupLayout() {
        tableView.pin(to: view)
        
        databaseErrorLabel.pin(.top, to: .top, of: view, withInset: Values.massiveSpacing)
        databaseErrorLabel.pin(.leading, to: .leading, of: view, withInset: Values.veryLargeSpacing)
        databaseErrorLabel.pin(.trailing, to: .trailing, of: view, withInset: -Values.veryLargeSpacing)
        
        noAccountErrorLabel.pin(.top, to: .top, of: view, withInset: Values.massiveSpacing)
        noAccountErrorLabel.pin(.leading, to: .leading, of: view, withInset: Values.veryLargeSpacing)
        noAccountErrorLabel.pin(.trailing, to: .trailing, of: view, withInset: -Values.veryLargeSpacing)
    }
    
    // MARK: - Updating
    
    private func startObservingChanges() {
        guard dataChangeObservable == nil else { return }
        
        noAccountErrorLabel.isHidden = viewModel.dependencies[singleton: .storage, key: .isReadyForAppExtensions]
        tableView.isHidden = !viewModel.dependencies[singleton: .storage, key: .isReadyForAppExtensions]
        
        guard viewModel.dependencies[singleton: .storage, key: .isReadyForAppExtensions] else { return }
        
        // Start observing for data changes
        dataChangeObservable = self.viewModel.dependencies[singleton: .storage].start(
            viewModel.observableViewData,
            onError:  { [weak self, dependencies = self.viewModel.dependencies] _ in
                self?.databaseErrorLabel.isHidden = dependencies[singleton: .storage].isValid
            },
            onChange: { [weak self] viewData in
                // The defaul scheduler emits changes on the main thread
                self?.handleUpdates(viewData)
            }
        )
    }
    
    private func stopObservingChanges() {
        dataChangeObservable = nil
    }
    
    private func handleUpdates(_ updatedViewData: [SessionThreadViewModel]) {
        // Ensure the first load runs without animations (if we don't do this the cells will animate
        // in from a frame of CGRect.zero)
        guard hasLoadedInitialData else {
            hasLoadedInitialData = true
            UIView.performWithoutAnimation { handleUpdates(updatedViewData) }
            return
        }
        
        // Reload the table content (animate changes after the first load)
        tableView.reload(
            using: StagedChangeset(source: viewModel.viewData, target: updatedViewData),
            with: .automatic,
            interrupt: { $0.changeCount > 100 }    // Prevent too many changes from causing performance issues
        ) { [weak self] updatedData in
            self?.viewModel.updateData(updatedData)
        }
    }
    
    // MARK: - UITableViewDataSource
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return self.viewModel.viewData.count
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell: SimplifiedConversationCell = tableView.dequeue(type: SimplifiedConversationCell.self, for: indexPath)
        cell.update(with: self.viewModel.viewData[indexPath.row], using: viewModel.dependencies)
        
        return cell
    }
    
    // MARK: - Interaction
    
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.deselectRow(at: indexPath, animated: true)
        
        ShareNavController.attachmentPrepPublisher?
            .subscribe(on: DispatchQueue.global(qos: .userInitiated))
            .receive(on: DispatchQueue.main)
            .sinkUntilComplete(
                receiveValue: { [weak self, dependencies = self.viewModel.dependencies] attachments in
                    guard
                        let strongSelf = self,
                        let approvalVC: UINavigationController = AttachmentApprovalViewController.wrappedInNavController(
                            threadId: strongSelf.viewModel.viewData[indexPath.row].threadId,
                            threadVariant: strongSelf.viewModel.viewData[indexPath.row].threadVariant,
                            attachments: attachments,
                            approvalDelegate: strongSelf,
                            using: dependencies
                        )
                    else { return }
                    
                    self?.navigationController?.present(approvalVC, animated: true, completion: nil)
                }
            )
    }
    
    func attachmentApproval(
        _ attachmentApproval: AttachmentApprovalViewController,
        didApproveAttachments attachments: [SignalAttachment],
        forThreadId threadId: String,
        threadVariant: SessionThread.Variant,
        messageText: String?
    ) {
        // Sharing a URL or plain text will populate the 'messageText' field so in those
        // cases we should ignore the attachments
        let isSharingUrl: Bool = (attachments.count == 1 && attachments[0].isUrl)
        let isSharingText: Bool = (attachments.count == 1 && attachments[0].isText)
        let finalAttachments: [SignalAttachment] = (isSharingUrl || isSharingText ? [] : attachments)
        let body: String? = (
            isSharingUrl && (messageText?.isEmpty == true || attachments[0].linkPreviewDraft == nil) ?
            (
                (messageText?.isEmpty == true || (attachments[0].text() == messageText) ?
                    attachments[0].text() :
                    "\(attachments[0].text() ?? "")\n\n\(messageText ?? "")" // stringlint:ignore
                )
            ) :
            messageText
        )
        let userSessionId: SessionId = viewModel.dependencies[cache: .general].sessionId
        let swarmPublicKey: String = {
            switch threadVariant {
                case .contact, .legacyGroup, .group: return threadId
                case .community: return userSessionId.hexString
            }
        }()
        
        shareNavController?.dismiss(animated: true, completion: nil)
        
        ModalActivityIndicatorViewController.present(fromViewController: shareNavController!, canCancel: false, message: "sending".localized()) { [dependencies = viewModel.dependencies] activityIndicator in
            dependencies[singleton: .storage].resumeDatabaseAccess()
            dependencies.mutate(cache: .libSessionNetwork) { $0.resumeNetworkAccess() }
            
            /// When we prepare the message we set the timestamp to be the `dependencies[cache: .snodeAPI].currentOffsetTimestampMs()`
            /// but won't actually have a value because the share extension won't have talked to a service node yet which can cause
            /// issues with Disappearing Messages, as a result we need to explicitly `getNetworkTime` in order to ensure it's accurate
            /// before we create the interaction
            dependencies[singleton: .network]
                .getSwarm(for: swarmPublicKey)
                .tryFlatMapWithRandomSnode(using: dependencies) { snode in
                    try SnodeAPI
                        .preparedGetNetworkTime(from: snode, using: dependencies)
                        .send(using: dependencies)
                }
                .subscribe(on: DispatchQueue.global(qos: .userInitiated))
                .flatMapStorageWritePublisher(using: dependencies) { db, _ -> (Interaction, [Network.PreparedRequest<String>]) in
                    guard let thread: SessionThread = try SessionThread.fetchOne(db, id: threadId) else {
                        throw MessageSenderError.noThread
                    }
                    
                    // Update the thread to be visible (if it isn't already)
                    if !thread.shouldBeVisible || thread.pinnedPriority == LibSession.hiddenPriority {
                        _ = try SessionThread
                            .filter(id: threadId)
                            .updateAllAndConfig(
                                db,
                                SessionThread.Columns.shouldBeVisible.set(to: true),
                                SessionThread.Columns.pinnedPriority.set(to: LibSession.visiblePriority),
                                SessionThread.Columns.isDraft.set(to: false),
                                using: dependencies
                            )
                    }
                    
                    // Create the interaction
                    let sentTimestampMs: Int64 = dependencies[cache: .snodeAPI].currentOffsetTimestampMs()
                    let destinationDisappearingMessagesConfiguration: DisappearingMessagesConfiguration? = try? DisappearingMessagesConfiguration
                        .filter(id: threadId)
                        .filter(DisappearingMessagesConfiguration.Columns.isEnabled == true)
                        .fetchOne(db)
                    let interaction: Interaction = try Interaction(
                        threadId: threadId,
                        threadVariant: threadVariant,
                        authorId: userSessionId.hexString,
                        variant: .standardOutgoing,
                        body: body,
                        timestampMs: sentTimestampMs,
                        hasMention: Interaction.isUserMentioned(db, threadId: threadId, body: body, using: dependencies),
                        expiresInSeconds: destinationDisappearingMessagesConfiguration?.expiresInSeconds(),
                        expiresStartedAtMs: destinationDisappearingMessagesConfiguration?.initialExpiresStartedAtMs(
                            sentTimestampMs: Double(sentTimestampMs)
                        ),
                        linkPreviewUrl: (isSharingUrl ? attachments.first?.linkPreviewDraft?.urlString : nil),
                        using: dependencies
                    ).inserted(db)
                    
                    guard let interactionId: Int64 = interaction.id else {
                        throw StorageError.failedToSave
                    }
                    
                    // If the user is sharing a Url, there is a LinkPreview and it doesn't match an existing
                    // one then add it now
                    if
                        isSharingUrl,
                        let linkPreviewDraft: LinkPreviewDraft = attachments.first?.linkPreviewDraft,
                        (try? interaction.linkPreview.isEmpty(db)) == true
                    {
                        try LinkPreview(
                            url: linkPreviewDraft.urlString,
                            title: linkPreviewDraft.title,
                            attachmentId: LinkPreview
                                .generateAttachmentIfPossible(
                                    imageData: linkPreviewDraft.jpegImageData,
                                    type: .jpeg,
                                    using: dependencies
                                )?
                                .inserted(db)
                                .id,
                            using: dependencies
                        ).insert(db)
                    }
                    
                    // Process any attachments
                    try Attachment.process(
                        db,
                        attachments: Attachment.prepare(attachments: finalAttachments, using: dependencies),
                        for: interactionId
                    )
                    
                    // Using the same logic as the `MessageSendJob` retrieve 
                    let attachmentState: MessageSendJob.AttachmentState = try MessageSendJob
                        .fetchAttachmentState(db, interactionId: interactionId)
                    let preparedUploads: [Network.PreparedRequest<String>] = try Attachment
                        .filter(ids: attachmentState.allAttachmentIds)
                        .fetchAll(db)
                        .map { attachment in
                            try attachment.preparedUpload(
                                db,
                                threadId: threadId,
                                logCategory: nil,
                                using: dependencies
                            )
                        }
                    
                    return (interaction, preparedUploads)
                }
                .flatMap { (interaction: Interaction, preparedUploads: [Network.PreparedRequest<String>]) -> AnyPublisher<(interaction: Interaction, fileIds: [String]), Error> in
                    guard !preparedUploads.isEmpty else {
                        return Just((interaction, []))
                            .setFailureType(to: Error.self)
                            .eraseToAnyPublisher()
                    }
                        
                    return Publishers
                        .MergeMany(preparedUploads.map { $0.send(using: dependencies) })
                        .collect()
                        .map { results in (interaction, results.map { _, id in id }) }
                        .eraseToAnyPublisher()
                }
                .flatMapStorageWritePublisher(using: dependencies) { db, info -> Network.PreparedRequest<Void> in
                    // Prepare the message send data
                    guard
                        let threadVariant: SessionThread.Variant = try SessionThread
                            .filter(id: info.interaction.threadId)
                            .select(.variant)
                            .asRequest(of: SessionThread.Variant.self)
                            .fetchOne(db)
                    else { throw MessageSenderError.noThread }
                    
                    return try MessageSender
                        .preparedSend(
                            db,
                            interaction: info.interaction,
                            fileIds: info.fileIds,
                            threadId: threadId,
                            threadVariant: threadVariant,
                            using: dependencies
                        )
                }
                .flatMap { $0.send(using: dependencies) }
                .receive(on: DispatchQueue.main)
                .sinkUntilComplete(
                    receiveCompletion: { [weak self] result in
                        dependencies.mutate(cache: .libSessionNetwork) { $0.suspendNetworkAccess() }
                        dependencies[singleton: .storage].suspendDatabaseAccess()
                        Log.flush()
                        activityIndicator.dismiss { }
                        
                        switch result {
                            case .finished: self?.shareNavController?.shareViewWasCompleted()
                            case .failure(let error): self?.shareNavController?.shareViewFailed(error: error)
                        }
                    }
                )
        }
    }

    func attachmentApprovalDidCancel(_ attachmentApproval: AttachmentApprovalViewController) {
        dismiss(animated: true, completion: nil)
    }

    func attachmentApproval(_ attachmentApproval: AttachmentApprovalViewController, didChangeMessageText newMessageText: String?) {
    }
    
    func attachmentApproval(_ attachmentApproval: AttachmentApprovalViewController, didRemoveAttachment attachment: SignalAttachment) {
    }
    
    func attachmentApprovalDidTapAddMore(_ attachmentApproval: AttachmentApprovalViewController) {
    }
}