iOS/Sources/App/Frontend/WebView/WebViewController+EmptyState.swift

import Shared
import UIKit

// MARK: - Empty State

extension WebViewController {
    func setupEmptyState() {
        let emptyState = WebViewEmptyStateWrapperView(server: server) { [weak self] in
            self?.hideEmptyState()
            self?.refresh()
        } settingsAction: { [weak self] in
            self?.showSettingsViewController()
        } dismissAction: { [weak self] in
            self?.hideEmptyState()
        }

        view.addSubview(emptyState)

        emptyState.translatesAutoresizingMaskIntoConstraints = false

        NSLayoutConstraint.activate([
            emptyState.leftAnchor.constraint(equalTo: view.leftAnchor),
            emptyState.rightAnchor.constraint(equalTo: view.rightAnchor),
            emptyState.topAnchor.constraint(equalTo: view.topAnchor),
            emptyState.bottomAnchor.constraint(equalTo: view.bottomAnchor),
        ])

        emptyState.alpha = 0
        emptyStateView = emptyState
    }

    func showEmptyState() {
        UIView.animate(withDuration: emptyStateTransitionDuration, delay: 0, options: .curveEaseInOut, animations: {
            self.emptyStateView?.alpha = 1
        }, completion: nil)
    }

    @objc func hideEmptyState() {
        UIView.animate(withDuration: emptyStateTransitionDuration, delay: 0, options: .curveEaseInOut, animations: {
            self.emptyStateView?.alpha = 0
        }, completion: nil)
    }

    // To avoid keeping the empty state on screen when user is disconnected in background
    // due to inactivity, we reset the empty state timer
    @objc func resetEmptyStateTimerWithLatestConnectedState() {
        let state: FrontEndConnectionState = isConnected ? .connected : .disconnected
        updateFrontendConnectionState(state: state.rawValue)
    }

    func emptyStateObservations() {
        // Hide empty state when enter background
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(hideEmptyState),
            name: UIApplication.didEnterBackgroundNotification,
            object: nil
        )

        // Show empty state again if after entering foreground it is not connected
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(resetEmptyStateTimerWithLatestConnectedState),
            name: UIApplication.willEnterForegroundNotification,
            object: nil
        )
    }

    func removeEmptyStateObservations() {
        NotificationCenter.default.removeObserver(self, name: UIApplication.didEnterBackgroundNotification, object: nil)
        NotificationCenter.default.removeObserver(
            self,
            name: UIApplication.willEnterForegroundNotification,
            object: nil
        )
    }
}