import AVKit
import OSLog
import SwiftUI
import RealityKit
import RealityKitContent

struct InitialImmersiveView: View {
    let logger = Logger(subsystem: SUBSYSTEM, category: "InitialImmersiveView")
    @Environment(\.scenePhase) var scenePhase
    @Environment(AppModel.self) var appModel
    
    private let rootEntity = Entity()
    
    var body: some View {
        RealityView { content, attachments in
            logger.info("\(#function) \(#line) `content, attachments in`")
            updateScene(content: content, attachments: attachments)
            
        } update: { content, attachments in
            
            logger.info("\(#function) \(#line) `update: { content, attachments in`")
            updateScene(content: content, attachments: attachments)

        } placeholder: {
            
            let _ = logger.info("\(#function) \(#line) `placeholder`")
            ProgressView()
            
        } attachments: {
            
            let _ = logger.info("\(#function) \(#line) `attachments`")
            
            Attachment(id: "OpenSkysphereView") {
                Button {
                    appModel.showingScene = .threeSixtySkyShpere
                } label: {
                    Text("Open Skysphere")
                }
            }
        }
        .onChange(of: scenePhase, { oldValue, newValue in
            logger.info("\(#function) \(#line) `onChange(of: scenePhase` scenePhase oldValue \(String(describing: oldValue)) scenePhase newValue \(String(describing: newValue))")
            switch newValue {
            case .active:
                logger.info("\(#function) \(#line) scenePhase newValue \(String(describing: newValue))")
            case .background:
                logger.info("\(#function) \(#line) scenePhase newValue \(String(describing: newValue))")
                unloadScenes()
            case .inactive:
                logger.info("\(#function) \(#line) scenePhase newValue \(String(describing: newValue))")
            @unknown default:
                logger.warning("\(#function) \(#line) scenePhase newValue \(String(describing: newValue))")
            }
        })
    }
    
    func updateScene(content: RealityViewContent, attachments: RealityViewAttachments) {
        logger.info("\(#function) \(#line)")
        guard scenePhase == .active else {
            logger.info("\(#function) \(#line) escaping since app backgrounded")
            return
        }

        if rootEntity.children.isEmpty {
            Task{
                await loadScenes(content: content, attachments: attachments)
            }
        }
    }
    
    func loadScenes(content: RealityViewContent, attachments: RealityViewAttachments) async {
        logger.info("\(#function) \(#line)")
        
        guard let openSkysphereViewButton = attachments.entity(for: "OpenSkysphereView") else {
            logger.error("\(#function) \(#line) missing attachment")
            assertionFailure("missing attachment")
            return
        }
        openSkysphereViewButton.position = [0.0, 0.1, -2.5]
        openSkysphereViewButton.scale = scaleForAttachements
        rootEntity.addChild(openSkysphereViewButton)
        content.add(rootEntity)
    }
    
    func unloadScenes() {
        logger.info("\(#function) \(#line)")
        rootEntity.children.removeAll()
    }
}