import SceneKit
import UIKit

/// Renders the actual catalog model once per variant, shared by all project rows.
@MainActor
final class TankThumbnailRenderer {
    static let shared = TankThumbnailRenderer()
    private let cache = NSCache<NSString, UIImage>()

    func image(for definition: TankDefinition) -> UIImage? {
        let key = definition.modelPath as NSString
        if let image = cache.object(forKey: key) { return image }
        guard let url = Bundle.main.url(forResource: definition.modelResourceName,
                                        withExtension: definition.modelFileExtension),
              let source = try? SCNScene(url: url, options: [.convertToYUp: true]) else { return nil }

        let scene = SCNScene()
        let model = SCNNode()
        for child in source.rootNode.childNodes { model.addChildNode(child.clone()) }
        // Bundle scenes may carry studio lights; use one consistent thumbnail setup.
        model.enumerateChildNodes { node, _ in
            node.light = nil
            node.camera = nil
        }
        // Underground catalog models need an additional quarter-turn after Y-up conversion.
        if definition.placement == .belowGround {
            model.eulerAngles.x = -.pi / 2
        }
        let container = SCNNode()
        container.addChildNode(model)
        scene.rootNode.addChildNode(container)
        // Measure in the parent's coordinate system, including the corrected orientation.
        let bounds = container.boundingBox
        let center = SCNVector3((bounds.min.x + bounds.max.x) / 2,
                               (bounds.min.y + bounds.max.y) / 2,
                               (bounds.min.z + bounds.max.z) / 2)
        let extent = SCNVector3(bounds.max.x - bounds.min.x,
                               bounds.max.y - bounds.min.y,
                               bounds.max.z - bounds.min.z)
        let radius = max(sqrt(extent.x * extent.x + extent.y * extent.y + extent.z * extent.z) / 2, 0.01)
        let camera = SCNNode()
        camera.camera = SCNCamera()
        camera.camera?.usesOrthographicProjection = true
        camera.camera?.orthographicScale = Double(radius * 0.64)
        camera.camera?.zNear = Double(radius * 0.01)
        camera.camera?.zFar = Double(radius * 20)
        camera.position = SCNVector3(center.x + radius * 0.65,
                                    center.y + radius * 0.7, center.z + radius * 3)
        camera.look(at: center)
        scene.rootNode.addChildNode(camera)
        let ambient = SCNNode()
        ambient.light = SCNLight()
        ambient.light?.type = .ambient
        ambient.light?.intensity = 300
        scene.rootNode.addChildNode(ambient)
        let light = SCNNode()
        light.light = SCNLight()
        light.light?.type = .omni
        light.light?.intensity = 800
        light.position = SCNVector3(center.x - radius, center.y + radius * 3, center.z + radius * 2)
        scene.rootNode.addChildNode(light)

        let renderer = SCNRenderer(device: nil, options: nil)
        renderer.scene = scene
        renderer.pointOfView = camera
        let image = renderer.snapshot(atTime: 0, with: CGSize(width: 600, height: 360),
                                      antialiasingMode: .multisampling4X)
        cache.setObject(image, forKey: key)
        return image
    }
}