import ARKit

guard ARWorldTrackingConfiguration.isSupported else {
    showUnsupportedDeviceMessage()
    return
}

import SwiftUI
import RealityKit

struct ARExperienceView: View {
    var body: some View {
        RealityView { content in
            // content is RealityViewCameraContent on iOS
            let sphere = ModelEntity(
                mesh: .generateSphere(radius: 0.05),
                materials: [SimpleMaterial(
                    color: .blue,
                    isMetallic: true
                )]
            )
            sphere.position = [0, 0, -0.5]  // 50cm in front of camera
            content.add(sphere)
        }
    }
}

struct PlacementView: View {
    @State private var modelColor: UIColor = .red

    var body: some View {
        RealityView { content in
            let box = ModelEntity(
                mesh: .generateBox(size: 0.1),
                materials: [SimpleMaterial(
                    color: .red,
                    isMetallic: false
                )]
            )
            box.name = "colorBox"
            box.position = [0, 0, -0.5]
            content.add(box)
        } update: { content in
            if let box = content.entities.first(
                where: { $0.name == "colorBox" }
            ) as? ModelEntity {
                box.model?.materials = [SimpleMaterial(
                    color: modelColor,
                    isMetallic: false
                )]
            }
        }

        Button("Change Color") {
            modelColor = modelColor == .red ? .green : .red
        }
    }
}

RealityView { content in
    if let robot = try? await ModelEntity(named: "robot") {
        robot.position = [0, -0.2, -0.8]
        robot.scale = [0.01, 0.01, 0.01]
        content.add(robot)
    }
}

// Box
let box = ModelEntity(
    mesh: .generateBox(size: [0.1, 0.2, 0.1], cornerRadius: 0.005),
    materials: [SimpleMaterial(color: .gray, isMetallic: true)]
)

// Sphere
let sphere = ModelEntity(
    mesh: .generateSphere(radius: 0.05),
    materials: [SimpleMaterial(color: .blue, roughness: 0.2, isMetallic: true)]
)

// Plane
let plane = ModelEntity(
    mesh: .generatePlane(width: 0.3, depth: 0.3),
    materials: [SimpleMaterial(color: .green, isMetallic: false)]
)

let box = ModelEntity(
    mesh: .generateBox(size: 0.1),
    materials: [SimpleMaterial(color: .red, isMetallic: false)]
)

// Make it respond to physics
box.components.set(PhysicsBodyComponent(
    massProperties: .default,
    material: .default,
    mode: .dynamic
))

// Add collision shape for interaction
box.components.set(CollisionComponent(
    shapes: [.generateBox(size: [0.1, 0.1, 0.1])]
))

// Enable input targeting for gestures
box.components.set(InputTargetComponent())

RealityView { content in
    // Anchor to a horizontal surface
    let floorAnchor = AnchorEntity(.plane(
        .horizontal,
        classification: .floor,
        minimumBounds: [0.2, 0.2]
    ))

    let model = ModelEntity(
        mesh: .generateBox(size: 0.1),
        materials: [SimpleMaterial(color: .orange, isMetallic: false)]
    )
    floorAnchor.addChild(model)
    content.add(floorAnchor)
}

struct DraggableARView: View {
    var body: some View {
        RealityView { content in
            let box = ModelEntity(
                mesh: .generateBox(size: 0.1),
                materials: [SimpleMaterial(color: .blue, isMetallic: true)]
            )
            box.position = [0, 0, -0.5]
            box.components.set(CollisionComponent(
                shapes: [.generateBox(size: [0.1, 0.1, 0.1])]
            ))
            box.components.set(InputTargetComponent())
            box.name = "draggable"
            content.add(box)
        }
        .gesture(
            DragGesture()
                .targetedToAnyEntity()
                .onChanged { value in
                    let entity = value.entity
                    guard let parent = entity.parent else { return }
                    entity.position = value.convert(
                        value.location3D,
                        from: .local,
                        to: parent
                    )
                }
        )
    }
}

.gesture(
    SpatialTapGesture()
        .targetedToAnyEntity()
        .onEnded { value in
            let tappedEntity = value.entity
            highlightEntity(tappedEntity)
        }
)

RealityView { content in
    let entity = ModelEntity(
        mesh: .generateSphere(radius: 0.05),
        materials: [SimpleMaterial(color: .yellow, isMetallic: false)]
    )
    entity.position = [0, 0, -0.5]
    content.add(entity)

    _ = content.subscribe(to: SceneEvents.Update.self) { event in
        let time = Float(event.deltaTime)
        entity.position.y += sin(Float(Date().timeIntervalSince1970)) * time * 0.1
    }
}

// WRONG -- no device check
struct MyARView: View {
    var body: some View {
        RealityView { content in
            // Fails silently on unsupported devices
        }
    }
}

// CORRECT -- check support and show fallback
struct MyARView: View {
    var body: some View {
        if ARWorldTrackingConfiguration.isSupported {
            RealityView { content in
                // AR content
            }
        } else {
            ContentUnavailableView(
                "AR Not Supported",
                systemImage: "arkit",
                description: Text("This device does not support AR.")
            )
        }
    }
}

// WRONG -- synchronous load blocks the main thread
RealityView { content in
    let model = try! Entity.load(named: "large-scene")
    content.add(model)
}

// CORRECT -- async load
RealityView { content in
    if let model = try? await ModelEntity(named: "large-scene") {
        content.add(model)
    }
}

// WRONG -- entity ignores gestures
let box = ModelEntity(mesh: .generateBox(size: 0.1))
content.add(box)

// CORRECT -- add collision and input components
let box = ModelEntity(
    mesh: .generateBox(size: 0.1),
    materials: [SimpleMaterial(color: .red, isMetallic: false)]
)
box.components.set(CollisionComponent(
    shapes: [.generateBox(size: [0.1, 0.1, 0.1])]
))
box.components.set(InputTargetComponent())
content.add(box)

// WRONG -- duplicates entities on every state change
RealityView { content in
    // empty
} update: { content in
    let sphere = ModelEntity(mesh: .generateSphere(radius: 0.05))
    content.add(sphere)  // Added again on every update
}

// CORRECT -- create in make, modify in update
RealityView { content in
    let sphere = ModelEntity(mesh: .generateSphere(radius: 0.05))
    sphere.name = "mySphere"
    content.add(sphere)
} update: { content in
    if let sphere = content.entities.first(
        where: { $0.name == "mySphere" }
    ) as? ModelEntity {
        // Modify existing entity
        sphere.position.y = newYPosition
    }
}

// WRONG -- no permission handling
RealityView { content in
    // Black screen if camera denied
}

// CORRECT -- check and request permission
struct ARContainerView: View {
    @State private var cameraAuthorized = false

    var body: some View {
        Group {
            if cameraAuthorized {
                RealityView { content in
                    // AR content
                }
            } else {
                ContentUnavailableView(
                    "Camera Access Required",
                    systemImage: "camera.fill",
                    description: Text("Enable camera in Settings to use AR.")
                )
            }
        }
        .task {
            let status = AVCaptureDevice.authorizationStatus(for: .video)
            if status == .authorized {
                cameraAuthorized = true
            } else if status == .notDetermined {
                cameraAuthorized = await AVCaptureDevice
                    .requestAccess(for: .video)
            }
        }
    }
}