import ARKit
import CoreLocation
import CoreMotion
import SceneKit
import SwiftUI

// MARK: - ARSunOverlayView

struct ARSunOverlayView: UIViewRepresentable {
    @Binding var sunNodesReady: Bool
    let vm: SunseekerViewModel

    func makeCoordinator() -> Coordinator {
        Coordinator(sunNodesReady: $sunNodesReady, vm: vm)
    }

    func makeUIView(context: Context) -> ARSCNView {
        let view = ARSCNView(frame: .zero)
        view.delegate = context.coordinator
        view.scene = SCNScene()
        view.automaticallyUpdatesLighting = true

        let config = ARWorldTrackingConfiguration()
        config.worldAlignment = .gravityAndHeading  // north = -Z axis
        view.session.run(config)

        context.coordinator.attach(to: view)
        return view
    }

    func updateUIView(_ uiView: ARSCNView, context: Context) {}

    static func dismantleUIView(_ uiView: ARSCNView, coordinator: Coordinator) {
        uiView.session.pause()
        coordinator.stop()
    }

    // MARK: - Coordinator

    final class Coordinator: NSObject, ARSCNViewDelegate, CLLocationManagerDelegate {

        private weak var sceneView: ARSCNView?
        private let vm: SunseekerViewModel
        @Binding private var sunNodesReady: Bool

        // Scene node containers (replaced on each rebuild)
        private var arcRootNode      = SCNNode()
        private var currentSunNode   = SCNNode()
        private var isSceneBuilt     = false

        // Fallback timer for CoreMotion-only mode
        private var fallbackTimer: Timer?
        private var limitedTrackingStart: Date?

        init(sunNodesReady: Binding<Bool>, vm: SunseekerViewModel) {
            _sunNodesReady = sunNodesReady
            self.vm = vm
        }

        func attach(to sceneView: ARSCNView) {
            self.sceneView = sceneView
            sceneView.scene.rootNode.addChildNode(arcRootNode)
            sceneView.scene.rootNode.addChildNode(currentSunNode)
        }

        func stop() {
            vm.stop()
            fallbackTimer?.invalidate()
        }

        // MARK: - ARSCNViewDelegate — per-frame update

        func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
            guard vm.isReady else { return }

            // Build arc once
            if !isSceneBuilt {
                DispatchQueue.main.async { self.buildScene() }
            }

            // Update current sun orb every frame
            if let cur = vm.currentPosition {
                let pos = vm.worldPosition(for: cur, radius: 1.8)
                currentSunNode.position = pos
            }
        }

        func session(_ session: ARSession, cameraDidChangeTrackingState camera: ARCamera) {
            switch camera.trackingState {
            case .limited(let reason):
                print("[Sunseeker] Tracking limited: \(reason)")
                if limitedTrackingStart == nil {
                    limitedTrackingStart = Date()
                    // After 5s of limited tracking, switch to CoreMotion attitude fallback
                    fallbackTimer = Timer.scheduledTimer(withTimeInterval: 5, repeats: false) { [weak self] _ in
                        self?.activateCoreMotionFallback()
                    }
                }
            case .normal:
                limitedTrackingStart = nil
                fallbackTimer?.invalidate()
                fallbackTimer = nil
            case .notAvailable:
                break
            @unknown default:
                break
            }
        }

        // MARK: - Scene Building

        private func buildScene() {
            guard sceneView != nil else { return }

            // Remove old nodes
            arcRootNode.childNodes.forEach { $0.removeFromParentNode() }
            currentSunNode.childNodes.forEach { $0.removeFromParentNode() }

            let arc = vm.arc
            let radius: Float = 1.8
            var positions: [SCNVector3] = []

            // Hourly marker spheres + time labels
            for (date, pos) in arc {
                guard pos.elevation > -5 else { continue }
                let worldPos = vm.worldPosition(for: pos, radius: radius)
                positions.append(worldPos)

                let sphere = SCNSphere(radius: 0.018)
                sphere.firstMaterial?.diffuse.contents = UIColor.systemYellow.withAlphaComponent(0.85)
                sphere.firstMaterial?.lightingModel = .constant
                let markerNode = SCNNode(geometry: sphere)
                markerNode.position = worldPos
                arcRootNode.addChildNode(markerNode)

                // Time label (only on even hours to avoid clutter)
                let calendar = Calendar.current
                let hour = calendar.component(.hour, from: date)
                if hour % 2 == 0 {
                    let labelNode = makeTextNode(text: hourLabel(from: date), color: .white, fontSize: 0.04)
                    labelNode.position = SCNVector3(worldPos.x, worldPos.y + 0.06, worldPos.z)
                    arcRootNode.addChildNode(labelNode)
                }
            }

            // Continuous arc line
            if positions.count >= 2 {
                let lineNode = makeLineNode(through: positions, color: UIColor.systemYellow.withAlphaComponent(0.55))
                arcRootNode.addChildNode(lineNode)
            }

            // Sunrise marker
            if let riseDate = vm.riseSet.rise {
                let risePos = SunMath.calculateSunPosition(date: riseDate, coordinate: vm.coordinate!)
                let wPos = vm.worldPosition(for: risePos, radius: radius)
                arcRootNode.addChildNode(makeSpecialMarker(at: wPos, color: .systemOrange, label: "Sunrise \(hourLabel(from: riseDate))"))
            }

            // Sunset marker
            if let setDate = vm.riseSet.set {
                let setPos = SunMath.calculateSunPosition(date: setDate, coordinate: vm.coordinate!)
                let wPos = vm.worldPosition(for: setPos, radius: radius)
                arcRootNode.addChildNode(makeSpecialMarker(at: wPos, color: .systemRed, label: "Sunset \(hourLabel(from: setDate))"))
            }

            // Current sun orb (large, animated glow)
            if let cur = vm.currentPosition {
                let orb = SCNSphere(radius: 0.055)
                orb.firstMaterial?.diffuse.contents   = UIColor.systemOrange
                orb.firstMaterial?.emission.contents  = UIColor.systemYellow
                orb.firstMaterial?.lightingModel      = .constant
                let orbNode = SCNNode(geometry: orb)
                orbNode.position = vm.worldPosition(for: cur, radius: radius)

                // Pulse animation
                let pulse = CABasicAnimation(keyPath: "scale")
                pulse.fromValue  = SCNVector3(1, 1, 1)
                pulse.toValue    = SCNVector3(1.3, 1.3, 1.3)
                pulse.duration   = 1.2
                pulse.autoreverses = true
                pulse.repeatCount  = .infinity
                orbNode.addAnimation(pulse, forKey: "pulse")

                let label = makeTextNode(text: "Now", color: .systemYellow, fontSize: 0.05)
                label.position = SCNVector3(0, 0.09, 0)
                orbNode.addChildNode(label)
                currentSunNode.addChildNode(orbNode)
            }

            isSceneBuilt = true
            sunNodesReady = true
        }

        // MARK: - Node Factories

        private func makeSpecialMarker(at pos: SCNVector3, color: UIColor, label: String) -> SCNNode {
            let root   = SCNNode()
            let sphere = SCNSphere(radius: 0.035)
            sphere.firstMaterial?.diffuse.contents  = color
            sphere.firstMaterial?.emission.contents = color.withAlphaComponent(0.5)
            sphere.firstMaterial?.lightingModel     = .constant
            let markerNode = SCNNode(geometry: sphere)
            markerNode.position = pos
            root.addChildNode(markerNode)

            let labelNode = makeTextNode(text: label, color: .white, fontSize: 0.04)
            labelNode.position = SCNVector3(pos.x, pos.y + 0.07, pos.z)
            root.addChildNode(labelNode)
            return root
        }

        /// Creates a billboard SCNText node that always faces the camera.
        private func makeTextNode(text: String, color: UIColor, fontSize: CGFloat) -> SCNNode {
            let scnText = SCNText(string: text, extrusionDepth: 0)
            scnText.font = UIFont.systemFont(ofSize: fontSize * 100, weight: .medium)
            scnText.firstMaterial?.diffuse.contents = color
            scnText.firstMaterial?.lightingModel    = .constant
            scnText.isWrapped = false

            let textNode = SCNNode(geometry: scnText)
            textNode.scale = SCNVector3(fontSize / 100, fontSize / 100, fontSize / 100)
            // Billboard constraint — always face camera
            let constraint = SCNBillboardConstraint()
            constraint.freeAxes = .Y
            textNode.constraints = [constraint]
            // Centre text
            let (min, max) = textNode.boundingBox
            textNode.pivot = SCNMatrix4MakeTranslation((max.x - min.x) / 2, 0, 0)
            return textNode
        }

        /// Builds a line strip SCNNode connecting all positions.
        private func makeLineNode(through positions: [SCNVector3], color: UIColor) -> SCNNode {
            guard positions.count >= 2 else { return SCNNode() }

            let vertices: [SCNVector3] = positions
            var indices: [Int32] = []
            for i in 0..<(vertices.count - 1) {
                indices.append(Int32(i))
                indices.append(Int32(i + 1))
            }

            let vertexSource = SCNGeometrySource(vertices: vertices)
            let element = SCNGeometryElement(
                indices: indices,
                primitiveType: .line
            )
            let geometry = SCNGeometry(sources: [vertexSource], elements: [element])
            geometry.firstMaterial?.diffuse.contents = color
            geometry.firstMaterial?.lightingModel    = .constant
            return SCNNode(geometry: geometry)
        }

        private func hourLabel(from date: Date) -> String {
            let fmt = DateFormatter()
            fmt.dateFormat = "ha"
            fmt.amSymbol   = "am"
            fmt.pmSymbol   = "pm"
            return fmt.string(from: date)
        }

        // MARK: - CoreMotion Fallback

        private func activateCoreMotionFallback() {
            // In fallback mode we rely on CMMotionManager attitude (already running in SunseekerViewModel)
            // and just keep the scene nodes updated via the 1s tick in the VM.
            print("[Sunseeker] Switched to CoreMotion fallback — ARKit tracking unavailable.")
        }
    }
}

// MARK: - Degree helpers

private extension Double {
    var radians: Double { self * .pi / 180.0 }
}