// ViewportView.swift
// A single viewport pane — MTKView wrapper with gesture handling.

import SwiftUI
import MetalKit

// MARK: - Single Viewport Pane

struct ViewportPane: View {
    let renderer: ViewportRenderer
    let label: String

    var body: some View {
        GeometryReader { geo in
            ZStack(alignment: .topLeading) {
                MetalViewRepresentable(
                    renderer: renderer,
                    size: geo.size
                )
                .ignoresSafeArea()
                .gesture(orbitGesture)
                .gesture(zoomGesture)
                .onTapGesture(count: 2) {
                    renderer.camera.reset()
                }

                // Viewport label
                Text(label)
                    .font(.caption2.weight(.medium))
                    .foregroundStyle(.white.opacity(0.5))
                    .padding(.horizontal, 8)
                    .padding(.vertical, 4)
                    .background(.black.opacity(0.3), in: RoundedRectangle(cornerRadius: 4))
                    .padding(8)
            }
        }
    }

    private var orbitGesture: some Gesture {
        DragGesture(minimumDistance: 1)
            .onChanged { value in
                renderer.camera.orbit(
                    deltaX: Float(value.translation.width) * 0.15,
                    deltaY: Float(value.translation.height) * 0.15
                )
            }
    }

    private var zoomGesture: some Gesture {
        MagnifyGesture()
            .onChanged { value in
                renderer.camera.zoom(scale: Float(value.magnification))
            }
    }
}

// MARK: - UIViewRepresentable

struct MetalViewRepresentable: UIViewRepresentable {
    let renderer: ViewportRenderer
    let size: CGSize

    func makeCoordinator() -> ViewportCoordinator {
        ViewportCoordinator(renderer: renderer)
    }

    func makeUIView(context: Context) -> MTKView {
        guard let device = renderer.device ?? MTLCreateSystemDefaultDevice() else {
            fatalError("Metal is not supported on this device.")
        }

        let mtkView = MTKView(frame: .zero, device: device)
        mtkView.delegate = context.coordinator
        mtkView.colorPixelFormat = .bgra8Unorm_srgb
        mtkView.depthStencilPixelFormat = .depth32Float
        mtkView.clearColor = MTLClearColor(red: 0.224, green: 0.224, blue: 0.224, alpha: 1.0)
        mtkView.preferredFramesPerSecond = 120
        mtkView.enableSetNeedsDisplay = false
        mtkView.isPaused = false
        mtkView.framebufferOnly = false
        mtkView.isMultipleTouchEnabled = true

        return mtkView
    }

    func updateUIView(_ mtkView: MTKView, context: Context) {
        let scale = mtkView.contentScaleFactor
        mtkView.drawableSize = CGSize(
            width: size.width * scale,
            height: size.height * scale
        )
    }
}

// MARK: - Coordinator

final class ViewportCoordinator: NSObject, MTKViewDelegate {
    let renderer: ViewportRenderer

    init(renderer: ViewportRenderer) {
        self.renderer = renderer
    }

    func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {
        renderer.viewportSize = SIMD2<Float>(Float(size.width), Float(size.height))
    }

    func draw(in view: MTKView) {
        guard let drawable = view.currentDrawable,
              let descriptor = view.currentRenderPassDescriptor
        else { return }
        renderer.draw(drawable: drawable, passDescriptor: descriptor)
    }
}