import Foundation
import UIKit
import Display
import ComponentFlow
import MultilineTextComponent
import TelegramPresentationData
import AppBundle
import TelegramCore
import AccountContext
import SwiftSignalKit
import MetalEngine
import CallScreen
import AvatarNode
import ContextUI

final class VideoChatParticipantThumbnailComponent: Component {
    let call: VideoChatCall
    let theme: PresentationTheme
    let participant: GroupCallParticipantsContext.Participant
    let isPresentation: Bool
    let isSelected: Bool
    let isSpeaking: Bool
    let displayVideo: Bool
    let interfaceOrientation: UIInterfaceOrientation
    let action: (() -> Void)?
    let contextAction: ((EnginePeer, ContextExtractedContentContainingView, ContextGesture) -> Void)?
    
    init(
        call: VideoChatCall,
        theme: PresentationTheme,
        participant: GroupCallParticipantsContext.Participant,
        isPresentation: Bool,
        isSelected: Bool,
        isSpeaking: Bool,
        displayVideo: Bool,
        interfaceOrientation: UIInterfaceOrientation,
        action: (() -> Void)?,
        contextAction: ((EnginePeer, ContextExtractedContentContainingView, ContextGesture) -> Void)?
    ) {
        self.call = call
        self.theme = theme
        self.participant = participant
        self.isPresentation = isPresentation
        self.isSelected = isSelected
        self.isSpeaking = isSpeaking
        self.displayVideo = displayVideo
        self.interfaceOrientation = interfaceOrientation
        self.action = action
        self.contextAction = contextAction
    }
    
    static func ==(lhs: VideoChatParticipantThumbnailComponent, rhs: VideoChatParticipantThumbnailComponent) -> Bool {
        if lhs.call != rhs.call {
            return false
        }
        if lhs.theme !== rhs.theme {
            return false
        }
        if lhs.participant != rhs.participant {
            return false
        }
        if lhs.isPresentation != rhs.isPresentation {
            return false
        }
        if lhs.isSelected != rhs.isSelected {
            return false
        }
        if lhs.isSpeaking != rhs.isSpeaking {
            return false
        }
        if lhs.displayVideo != rhs.displayVideo {
            return false
        }
        if lhs.interfaceOrientation != rhs.interfaceOrientation {
            return false
        }
        if (lhs.action == nil) != (rhs.action == nil) {
            return false
        }
        if (lhs.contextAction == nil) != (rhs.contextAction == nil) {
            return false
        }
        return true
    }
    
    private struct VideoSpec: Equatable {
        var resolution: CGSize
        var rotationAngle: Float
        var followsDeviceOrientation: Bool
        
        init(resolution: CGSize, rotationAngle: Float, followsDeviceOrientation: Bool) {
            self.resolution = resolution
            self.rotationAngle = rotationAngle
            self.followsDeviceOrientation = followsDeviceOrientation
        }
    }
    
    final class View: ContextControllerSourceView {
        private static let selectedBorderImage: UIImage? = {
            return generateStretchableFilledCircleImage(diameter: 20.0, color: nil, strokeColor: UIColor.white, strokeWidth: 2.0)?.withRenderingMode(.alwaysTemplate)
        }()
        
        private var component: VideoChatParticipantThumbnailComponent?
        private weak var componentState: EmptyComponentState?
        private var isUpdating: Bool = false
        
        private let extractedContainerView: ContextExtractedContentContainingView
        
        private let backgroundLayer: SimpleLayer
        
        private var avatarNode: AvatarNode?
        private let title = ComponentView<Empty>()
        private let muteStatus = ComponentView<Empty>()
        
        private var selectedBorderView: UIImageView?
        
        private var videoSource: AdaptedCallVideoSource?
        private var videoDisposable: Disposable?
        private var videoBackgroundLayer: SimpleLayer?
        private var videoLayer: PrivateCallVideoLayer?
        private var videoSpec: VideoSpec?
        
        override init(frame: CGRect) {
            self.extractedContainerView = ContextExtractedContentContainingView()
            
            self.backgroundLayer = SimpleLayer()
            self.backgroundLayer.backgroundColor = UIColor(rgb: 0x1C1C1E).cgColor
            
            super.init(frame: frame)
            
            self.addSubview(self.extractedContainerView)
            self.targetViewForActivationProgress = self.extractedContainerView.contentView
            
            self.extractedContainerView.contentView.layer.addSublayer(self.backgroundLayer)
            
            self.extractedContainerView.contentView.clipsToBounds = true
            self.extractedContainerView.contentView.layer.cornerRadius = 10.0
            
            self.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(self.tapGesture(_:))))
            
            self.activated = { [weak self] gesture, _ in
                guard let self, let component = self.component else {
                    gesture.cancel()
                    return
                }
                if let participantPeer = component.participant.peer {
                    component.contextAction?(participantPeer, self.extractedContainerView, gesture)
                }
            }
        }
        
        required init?(coder: NSCoder) {
            fatalError("init(coder:) has not been implemented")
        }
        
        deinit {
            self.videoDisposable?.dispose()
        }
        
        @objc private func tapGesture(_ recognizer: UITapGestureRecognizer) {
            if case .ended = recognizer.state {
                guard let component = self.component, let action = component.action else {
                    return
                }
                action()
            }
        }
        
        func update(component: VideoChatParticipantThumbnailComponent, availableSize: CGSize, state: EmptyComponentState, environment: Environment<Empty>, transition: ComponentTransition) -> CGSize {
            self.isUpdating = true
            defer {
                self.isUpdating = false
            }
            
            let previousComponent = self.component
            
            let wasSpeaking = previousComponent?.isSpeaking ?? false
            let speakingAlphaTransition: ComponentTransition
            if transition.animation.isImmediate {
                speakingAlphaTransition = .immediate
            } else {
                if let previousComponent, previousComponent.isSelected == component.isSelected {
                    if !wasSpeaking {
                        speakingAlphaTransition = .easeInOut(duration: 0.1)
                    } else {
                        speakingAlphaTransition = .easeInOut(duration: 0.25)
                    }
                } else {
                    speakingAlphaTransition = .immediate
                }
            }
            
            self.component = component
            self.componentState = state
            
            transition.setFrame(layer: self.backgroundLayer, frame: CGRect(origin: CGPoint(), size: availableSize))
            
            transition.setPosition(view: self.extractedContainerView, position: CGRect(origin: CGPoint(), size: availableSize).center)
            transition.setBounds(view: self.extractedContainerView, bounds: CGRect(origin: CGPoint(), size: availableSize))
            transition.setPosition(view: self.extractedContainerView.contentView, position: CGRect(origin: CGPoint(), size: availableSize).center)
            transition.setBounds(view: self.extractedContainerView.contentView, bounds: CGRect(origin: CGPoint(), size: availableSize))
            self.extractedContainerView.contentRect = CGRect(origin: CGPoint(), size: availableSize)
            
            let avatarNode: AvatarNode
            if let current = self.avatarNode {
                avatarNode = current
            } else {
                avatarNode = AvatarNode(font: avatarPlaceholderFont(size: 17.0))
                avatarNode.isUserInteractionEnabled = false
                self.avatarNode = avatarNode
                self.extractedContainerView.contentView.addSubview(avatarNode.view)
            }
            
            let avatarSize = CGSize(width: 50.0, height: 50.0)
            let avatarFrame = CGRect(origin: CGPoint(x: floorToScreenPixels((availableSize.width - avatarSize.width) * 0.5), y: 7.0), size: avatarSize)
            transition.setFrame(view: avatarNode.view, frame: avatarFrame)
            avatarNode.updateSize(size: avatarSize)
            if component.participant.peer?.smallProfileImage != nil {
                avatarNode.setPeerV2(context: component.call.accountContext, theme: component.theme, peer: component.participant.peer, displayDimensions: avatarSize)
            } else {
                avatarNode.setPeer(context: component.call.accountContext, theme: component.theme, peer: component.participant.peer, displayDimensions: avatarSize)
            }
            
            let muteStatusSize = self.muteStatus.update(
                transition: transition,
                component: AnyComponent(VideoChatMuteIconComponent(
                    color: .white,
                    content: component.isPresentation ? .screenshare : .mute(isFilled: true, isMuted: component.participant.muteState != nil && !component.isSpeaking)
                )),
                environment: {},
                containerSize: CGSize(width: 36.0, height: 36.0)
            )
            let muteStatusFrame = CGRect(origin: CGPoint(x: availableSize.width + 5.0 - muteStatusSize.width, y: availableSize.height + 5.0 - muteStatusSize.height), size: muteStatusSize)
            if let muteStatusView = self.muteStatus.view as? VideoChatMuteIconComponent.View {
                if muteStatusView.superview == nil {
                    self.extractedContainerView.contentView.addSubview(muteStatusView)
                }
                transition.setPosition(view: muteStatusView, position: muteStatusFrame.center)
                transition.setBounds(view: muteStatusView, bounds: CGRect(origin: CGPoint(), size: muteStatusFrame.size))
                transition.setScale(view: muteStatusView, scale: 0.65)
            }
            
            let titleSize = self.title.update(
                transition: .immediate,
                component: AnyComponent(MultilineTextComponent(
                    text: .plain(NSAttributedString(string: component.participant.peer?.compactDisplayTitle ?? "User \(component.participant.id)", font: Font.semibold(13.0), textColor: .white))
                )),
                environment: {},
                containerSize: CGSize(width: availableSize.width - 6.0 * 2.0 - 12.0, height: 100.0)
            )
            let titleFrame = CGRect(origin: CGPoint(x: 6.0, y: availableSize.height - 6.0 - titleSize.height), size: titleSize)
            if let titleView = self.title.view {
                if titleView.superview == nil {
                    titleView.layer.anchorPoint = CGPoint()
                    titleView.isUserInteractionEnabled = false
                    self.extractedContainerView.contentView.addSubview(titleView)
                }
                transition.setPosition(view: titleView, position: titleFrame.origin)
                titleView.bounds = CGRect(origin: CGPoint(), size: titleFrame.size)
            }
            
            if component.displayVideo, let videoDescription = component.isPresentation ? component.participant.presentationDescription : component.participant.videoDescription {
                let videoBackgroundLayer: SimpleLayer
                if let current = self.videoBackgroundLayer {
                    videoBackgroundLayer = current
                } else {
                    videoBackgroundLayer = SimpleLayer()
                    videoBackgroundLayer.backgroundColor = UIColor(white: 0.1, alpha: 1.0).cgColor
                    self.videoBackgroundLayer = videoBackgroundLayer
                    self.extractedContainerView.contentView.layer.insertSublayer(videoBackgroundLayer, above: avatarNode.layer)
                    videoBackgroundLayer.isHidden = true
                }
                
                let videoLayer: PrivateCallVideoLayer
                if let current = self.videoLayer {
                    videoLayer = current
                } else {
                    videoLayer = PrivateCallVideoLayer(enableSharpening: false)
                    self.videoLayer = videoLayer
                    self.extractedContainerView.contentView.layer.insertSublayer(videoLayer.blurredLayer, above: videoBackgroundLayer)
                    self.extractedContainerView.contentView.layer.insertSublayer(videoLayer, above: videoLayer.blurredLayer)
                    
                    videoLayer.blurredLayer.opacity = 0.25
                    
                    if let input = component.call.video(endpointId: videoDescription.endpointId) {
                        let videoSource = AdaptedCallVideoSource(videoStreamSignal: input)
                        self.videoSource = videoSource
                        
                        self.videoDisposable?.dispose()
                        self.videoDisposable = videoSource.addOnUpdated { [weak self] in
                            guard let self, let videoSource = self.videoSource, let videoLayer = self.videoLayer else {
                                return
                            }
                            
                            let videoOutput = videoSource.currentOutput
                            videoLayer.video = videoOutput
                            
                            if let videoOutput {
                                let videoSpec = VideoSpec(resolution: videoOutput.resolution, rotationAngle: videoOutput.rotationAngle, followsDeviceOrientation: videoOutput.followsDeviceOrientation)
                                if self.videoSpec != videoSpec {
                                    self.videoSpec = videoSpec
                                    if !self.isUpdating {
                                        self.componentState?.updated(transition: .immediate, isLocal: true)
                                    }
                                }
                            } else {
                                if self.videoSpec != nil {
                                    self.videoSpec = nil
                                    if !self.isUpdating {
                                        self.componentState?.updated(transition: .immediate, isLocal: true)
                                    }
                                }
                            }
                        }
                    }
                }
                
                transition.setFrame(layer: videoBackgroundLayer, frame: CGRect(origin: CGPoint(), size: availableSize))
                
                if let videoSpec = self.videoSpec {
                    videoBackgroundLayer.isHidden = component.isSelected
                    videoLayer.blurredLayer.isHidden = component.isSelected
                    videoLayer.isHidden = component.isSelected
                    
                    let rotationAngle = resolveCallVideoRotationAngle(angle: videoSpec.rotationAngle, followsDeviceOrientation: videoSpec.followsDeviceOrientation, interfaceOrientation: component.interfaceOrientation)
                    
                    var rotatedResolution = videoSpec.resolution
                    var videoIsRotated = false
                    if abs(rotationAngle - Float.pi * 0.5) < .ulpOfOne || abs(rotationAngle - Float.pi * 3.0 / 2.0) < .ulpOfOne {
                        videoIsRotated = true
                    }
                    if videoIsRotated {
                        rotatedResolution = CGSize(width: rotatedResolution.height, height: rotatedResolution.width)
                    }
                    
                    let videoSize = rotatedResolution.aspectFilled(availableSize)
                    let videoFrame = CGRect(origin: CGPoint(x: floorToScreenPixels((availableSize.width - videoSize.width) * 0.5), y: floorToScreenPixels((availableSize.height - videoSize.height) * 0.5)), size: videoSize)
                    let blurredVideoSize = rotatedResolution.aspectFilled(availableSize)
                    let blurredVideoFrame = CGRect(origin: CGPoint(x: floorToScreenPixels((availableSize.width - blurredVideoSize.width) * 0.5), y: floorToScreenPixels((availableSize.height - blurredVideoSize.height) * 0.5)), size: blurredVideoSize)
                    
                    let videoResolution = rotatedResolution.aspectFitted(CGSize(width: availableSize.width * 3.0, height: availableSize.height * 3.0))
                    
                    var rotatedVideoResolution = videoResolution
                    var rotatedVideoFrame = videoFrame
                    var rotatedBlurredVideoFrame = blurredVideoFrame
                    var rotatedVideoBoundsSize = videoFrame.size
                    var rotatedBlurredVideoBoundsSize = blurredVideoFrame.size
                    
                    if videoIsRotated {
                        rotatedVideoBoundsSize = CGSize(width: rotatedVideoBoundsSize.height, height: rotatedVideoBoundsSize.width)
                        rotatedVideoFrame = rotatedVideoFrame.size.centered(around: rotatedVideoFrame.center)
                        
                        rotatedBlurredVideoBoundsSize = CGSize(width: rotatedBlurredVideoBoundsSize.height, height: rotatedBlurredVideoBoundsSize.width)
                        rotatedBlurredVideoFrame = rotatedBlurredVideoFrame.size.centered(around: rotatedBlurredVideoFrame.center)
                    }
                    
                    rotatedVideoResolution = rotatedVideoResolution.aspectFittedOrSmaller(CGSize(width: rotatedVideoFrame.width * UIScreenScale, height: rotatedVideoFrame.height * UIScreenScale))
                    
                    transition.setPosition(layer: videoLayer, position: rotatedVideoFrame.center)
                    transition.setBounds(layer: videoLayer, bounds: CGRect(origin: CGPoint(), size: rotatedVideoBoundsSize))
                    transition.setTransform(layer: videoLayer, transform: CATransform3DMakeRotation(CGFloat(rotationAngle), 0.0, 0.0, 1.0))
                    videoLayer.renderSpec = RenderLayerSpec(size: RenderSize(width: Int(rotatedVideoResolution.width), height: Int(rotatedVideoResolution.height)), edgeInset: 2)
                    
                    transition.setPosition(layer: videoLayer.blurredLayer, position: rotatedBlurredVideoFrame.center)
                    transition.setBounds(layer: videoLayer.blurredLayer, bounds: CGRect(origin: CGPoint(), size: rotatedBlurredVideoBoundsSize))
                    transition.setTransform(layer: videoLayer.blurredLayer, transform: CATransform3DMakeRotation(CGFloat(rotationAngle), 0.0, 0.0, 1.0))
                }
            } else {
                if let videoBackgroundLayer = self.videoBackgroundLayer {
                    self.videoBackgroundLayer = nil
                    videoBackgroundLayer.removeFromSuperlayer()
                }
                if let videoLayer = self.videoLayer {
                    self.videoLayer = nil
                    videoLayer.blurredLayer.removeFromSuperlayer()
                    videoLayer.removeFromSuperlayer()
                }
                self.videoDisposable?.dispose()
                self.videoDisposable = nil
                self.videoSource = nil
                self.videoSpec = nil
            }
            
            if component.isSelected || component.isSpeaking {
                let selectedBorderView: UIImageView
                if let current = self.selectedBorderView {
                    selectedBorderView = current
                    
                    speakingAlphaTransition.setTintColor(layer: selectedBorderView.layer, color: component.isSpeaking ? UIColor(rgb: 0x33C758) : component.theme.list.itemAccentColor)
                } else {
                    selectedBorderView = UIImageView()
                    self.selectedBorderView = selectedBorderView
                    selectedBorderView.alpha = 0.0
                    self.extractedContainerView.contentView.addSubview(selectedBorderView)
                    selectedBorderView.image = View.selectedBorderImage
                    
                    selectedBorderView.frame = CGRect(origin: CGPoint(), size: availableSize)
                    
                    speakingAlphaTransition.setAlpha(view: selectedBorderView, alpha: 1.0)
                    ComponentTransition.immediate.setTintColor(layer: selectedBorderView.layer, color: component.isSpeaking ? UIColor(rgb: 0x33C758) : component.theme.list.itemAccentColor)
                }
            } else if let selectedBorderView = self.selectedBorderView {
                if !speakingAlphaTransition.animation.isImmediate {
                    if selectedBorderView.alpha != 0.0 {
                        speakingAlphaTransition.setAlpha(view: selectedBorderView, alpha: 0.0, completion: { [weak self, weak selectedBorderView] completed in
                            guard let self, let component = self.component, let selectedBorderView, self.selectedBorderView === selectedBorderView, completed else {
                                return
                            }
                            if !component.isSelected && !component.isSpeaking {
                                selectedBorderView.removeFromSuperview()
                                self.selectedBorderView = nil
                            }
                        })
                    }
                } else {
                    self.selectedBorderView = nil
                    selectedBorderView.removeFromSuperview()
                }
            }
            
            if let selectedBorderView = self.selectedBorderView {
                transition.setFrame(view: selectedBorderView, frame: CGRect(origin: CGPoint(), size: availableSize))
            }
            
            return availableSize
        }
    }
    
    func makeView() -> View {
        return View(frame: CGRect())
    }
    
    func update(view: View, availableSize: CGSize, state: EmptyComponentState, environment: Environment<EnvironmentType>, transition: ComponentTransition) -> CGSize {
        return view.update(component: self, availableSize: availableSize, state: state, environment: environment, transition: transition)
    }
}

final class VideoChatExpandedParticipantThumbnailsComponent: Component {
    final class Participant: Equatable {
        struct Key: Hashable {
            var id: GroupCallParticipantsContext.Participant.Id
            var isPresentation: Bool

            init(id: GroupCallParticipantsContext.Participant.Id, isPresentation: Bool) {
                self.id = id
                self.isPresentation = isPresentation
            }
        }

        let participant: GroupCallParticipantsContext.Participant
        let isPresentation: Bool
        
        var key: Key {
            return Key(id: self.participant.id, isPresentation: self.isPresentation)
        }

        init(
            participant: GroupCallParticipantsContext.Participant,
            isPresentation: Bool
        ) {
            self.participant = participant
            self.isPresentation = isPresentation
        }

        static func ==(lhs: Participant, rhs: Participant) -> Bool {
            if lhs === rhs {
                return true
            }
            if lhs.participant != rhs.participant {
                return false
            }
            if lhs.isPresentation != rhs.isPresentation {
                return false
            }
            return true
        }
    }

    let call: VideoChatCall
    let theme: PresentationTheme
    let displayVideo: Bool
    let participants: [Participant]
    let selectedParticipant: Participant.Key?
    let speakingParticipants: Set<EnginePeer.Id>
    let interfaceOrientation: UIInterfaceOrientation
    let updateSelectedParticipant: (Participant.Key) -> Void
    let contextAction: ((EnginePeer, ContextExtractedContentContainingView, ContextGesture) -> Void)?

    init(
        call: VideoChatCall,
        theme: PresentationTheme,
        displayVideo: Bool,
        participants: [Participant],
        selectedParticipant: Participant.Key?,
        speakingParticipants: Set<EnginePeer.Id>,
        interfaceOrientation: UIInterfaceOrientation,
        updateSelectedParticipant: @escaping (Participant.Key) -> Void,
        contextAction: ((EnginePeer, ContextExtractedContentContainingView, ContextGesture) -> Void)?
    ) {
        self.call = call
        self.theme = theme
        self.displayVideo = displayVideo
        self.participants = participants
        self.selectedParticipant = selectedParticipant
        self.speakingParticipants = speakingParticipants
        self.interfaceOrientation = interfaceOrientation
        self.updateSelectedParticipant = updateSelectedParticipant
        self.contextAction = contextAction
    }

    static func ==(lhs: VideoChatExpandedParticipantThumbnailsComponent, rhs: VideoChatExpandedParticipantThumbnailsComponent) -> Bool {
        if lhs.call != rhs.call {
            return false
        }
        if lhs.theme !== rhs.theme {
            return false
        }
        if lhs.displayVideo != rhs.displayVideo {
            return false
        }
        if lhs.participants != rhs.participants {
            return false
        }
        if lhs.selectedParticipant != rhs.selectedParticipant {
            return false
        }
        if lhs.speakingParticipants != rhs.speakingParticipants {
            return false
        }
        if lhs.interfaceOrientation != rhs.interfaceOrientation {
            return false
        }
        if (lhs.contextAction == nil) != (rhs.contextAction == nil) {
            return false
        }
        return true
    }
    
    private final class ScrollView: UIScrollView {
        override func touchesShouldCancel(in view: UIView) -> Bool {
            return true
        }
    }
    
    private struct ItemLayout {
        let containerSize: CGSize
        let containerInsets: UIEdgeInsets
        let itemCount: Int
        let itemSize: CGSize
        let itemSpacing: CGFloat
        
        let contentSize: CGSize
        
        init(containerSize: CGSize, containerInsets: UIEdgeInsets, itemCount: Int) {
            self.containerSize = containerSize
            self.containerInsets = containerInsets
            self.itemCount = itemCount
            self.itemSize = CGSize(width: 84.0, height: 84.0)
            self.itemSpacing = 6.0
            
            let itemsWidth: CGFloat = CGFloat(itemCount) * self.itemSize.width + CGFloat(max(itemCount - 1, 0)) * self.itemSpacing
            self.contentSize = CGSize(width: self.containerInsets.left + self.containerInsets.right + itemsWidth, height: self.containerInsets.top + self.containerInsets.bottom + self.itemSize.height)
        }
        
        func frame(at index: Int) -> CGRect {
            let frame = CGRect(origin: CGPoint(x: self.containerInsets.left + CGFloat(index) * (self.itemSize.width + self.itemSpacing), y: self.containerInsets.top), size: self.itemSize)
            return frame
        }
        
        func visibleItemRange(for rect: CGRect) -> (minIndex: Int, maxIndex: Int) {
            if self.itemCount == 0 {
                return (0, -1)
            }
            let offsetRect = rect.offsetBy(dx: -self.containerInsets.left, dy: 0.0)
            var minVisibleRow = Int(floor((offsetRect.minX) / (self.itemSize.width + self.itemSpacing)))
            minVisibleRow = max(0, minVisibleRow)
            let maxVisibleRow = Int(ceil((offsetRect.maxX) / (self.itemSize.width + self.itemSpacing)))

            let minVisibleIndex = minVisibleRow
            let maxVisibleIndex = min(self.itemCount - 1, (maxVisibleRow + 1) - 1)

            return (minVisibleIndex, maxVisibleIndex)
        }
    }
    
    private final class VisibleItem {
        let view = ComponentView<Empty>()
        
        init() {
        }
    }

    final class View: UIView, UIScrollViewDelegate {
        private let scrollView: ScrollView
        
        private var component: VideoChatExpandedParticipantThumbnailsComponent?
        private var isUpdating: Bool = false
        
        private var ignoreScrolling: Bool = false
        
        private var itemLayout: ItemLayout?
        private var visibleItems: [Participant.Key: VisibleItem] = [:]
        
        override init(frame: CGRect) {
            self.scrollView = ScrollView()
            
            super.init(frame: frame)
            
            self.scrollView.delaysContentTouches = false
            self.scrollView.canCancelContentTouches = true
            self.scrollView.clipsToBounds = false
            self.scrollView.contentInsetAdjustmentBehavior = .never
            if #available(iOS 13.0, *) {
                self.scrollView.automaticallyAdjustsScrollIndicatorInsets = false
            }
            self.scrollView.showsVerticalScrollIndicator = false
            self.scrollView.showsHorizontalScrollIndicator = false
            self.scrollView.alwaysBounceHorizontal = false
            self.scrollView.alwaysBounceVertical = false
            self.scrollView.scrollsToTop = false
            self.scrollView.delegate = self
            self.scrollView.clipsToBounds = true
            
            self.addSubview(self.scrollView)
        }
        
        required init?(coder: NSCoder) {
            fatalError("init(coder:) has not been implemented")
        }
        
        func scrollViewDidScroll(_ scrollView: UIScrollView) {
            if !self.ignoreScrolling {
                self.updateScrolling(transition: .immediate)
            }
        }
        
        private func updateScrolling(transition: ComponentTransition) {
            guard let component = self.component, let itemLayout = self.itemLayout else {
                return
            }
            
            var validListItemIds: [Participant.Key] = []
            let visibleListItemRange = itemLayout.visibleItemRange(for: self.scrollView.bounds)
            if visibleListItemRange.maxIndex >= visibleListItemRange.minIndex {
                for i in visibleListItemRange.minIndex ... visibleListItemRange.maxIndex {
                    let participant = component.participants[i]
                    validListItemIds.append(participant.key)
                    
                    var itemTransition = transition
                    let itemView: VisibleItem
                    if let current = self.visibleItems[participant.key] {
                        itemView = current
                    } else {
                        itemTransition = itemTransition.withAnimation(.none)
                        itemView = VisibleItem()
                        self.visibleItems[participant.key] = itemView
                    }
                    
                    let itemFrame = itemLayout.frame(at: i)
                    
                    let participantKey = participant.key
                    
                    var isSpeaking = false
                    if let participantPeer = participant.participant.peer {
                        isSpeaking = component.speakingParticipants.contains(participantPeer.id)
                    }
                    
                    let _ = itemView.view.update(
                        transition: itemTransition,
                        component: AnyComponent(VideoChatParticipantThumbnailComponent(
                            call: component.call,
                            theme: component.theme,
                            participant: participant.participant,
                            isPresentation: participant.isPresentation,
                            isSelected: component.selectedParticipant == participant.key,
                            isSpeaking: isSpeaking,
                            displayVideo: component.displayVideo,
                            interfaceOrientation: component.interfaceOrientation,
                            action: { [weak self] in
                                guard let self, let component = self.component else {
                                    return
                                }
                                component.updateSelectedParticipant(participantKey)
                            },
                            contextAction: component.contextAction
                        )),
                        environment: {},
                        containerSize: itemFrame.size
                    )
                    if let itemComponentView = itemView.view.view {
                        if itemComponentView.superview == nil {
                            itemComponentView.clipsToBounds = true
                            
                            self.scrollView.addSubview(itemComponentView)
                            
                            if !transition.animation.isImmediate {
                                itemComponentView.layer.animateAlpha(from: 0.0, to: 1.0, duration: 0.15)
                                transition.animateScale(view: itemComponentView, from: 0.001, to: 1.0)
                            }
                        }
                        transition.setFrame(view: itemComponentView, frame: itemFrame)
                    }
                }
            }
            
            var removedListItemIds: [Participant.Key] = []
            for (itemId, itemView) in self.visibleItems {
                if !validListItemIds.contains(itemId) {
                    removedListItemIds.append(itemId)
                    
                    if let itemComponentView = itemView.view.view {
                        if !transition.animation.isImmediate {
                            transition.setScale(view: itemComponentView, scale: 0.001)
                            itemComponentView.layer.animateAlpha(from: 1.0, to: 0.0, duration: 0.2, removeOnCompletion: false, completion: { [weak itemComponentView] _ in
                                itemComponentView?.removeFromSuperview()
                            })
                        } else {
                            itemComponentView.removeFromSuperview()
                        }
                    }
                }
            }
            for itemId in removedListItemIds {
                self.visibleItems.removeValue(forKey: itemId)
            }
        }
        
        func update(component: VideoChatExpandedParticipantThumbnailsComponent, availableSize: CGSize, state: EmptyComponentState, environment: Environment<Empty>, transition: ComponentTransition) -> CGSize {
            self.isUpdating = true
            defer {
                self.isUpdating = false
            }
            
            self.component = component
            
            let itemLayout = ItemLayout(
                containerSize: availableSize,
                containerInsets: UIEdgeInsets(top: 10.0, left: 10.0, bottom: 10.0, right: 10.0),
                itemCount: component.participants.count
            )
            self.itemLayout = itemLayout
            
            let size = CGSize(width: availableSize.width, height: itemLayout.contentSize.height)
            
            self.ignoreScrolling = true
            if self.scrollView.bounds.size != size {
                transition.setFrame(view: self.scrollView, frame: CGRect(origin: CGPoint(x: 0.0, y: 0.0), size: size))
            }
            let contentSize = CGSize(width: itemLayout.contentSize.width, height: size.height)
            if self.scrollView.contentSize != contentSize {
                self.scrollView.contentSize = contentSize
            }
            self.ignoreScrolling = false
            
            self.updateScrolling(transition: transition)
            
            return size
        }
    }

    func makeView() -> View {
        return View()
    }

    func update(view: View, availableSize: CGSize, state: EmptyComponentState, environment: Environment<EnvironmentType>, transition: ComponentTransition) -> CGSize {
        return view.update(component: self, availableSize: availableSize, state: state, environment: environment, transition: transition)
    }
}