// MetalContext.swift
// Shared Metal state across the entire app.
// Creates and configures renderers for each viewport pane.

import Metal
import Observation

@Observable
final class MetalContext {
    let device: MTLDevice
    let library: MTLLibrary
    let sceneGraph: SceneGraph

    // Up to 4 renderers (for quad split)
    let renderers: [ViewportRenderer]

    // Layout state
    var viewportLayout: ViewportLayout = .single

    init() {
        guard let device = MTLCreateSystemDefaultDevice() else {
            fatalError("Metal is not supported on this device.")
        }
        guard let library = device.makeDefaultLibrary() else {
            fatalError("Failed to create Metal library.")
        }

        self.device = device
        self.library = library
        self.sceneGraph = SceneGraph.defaultScene(device: device)

        // Create 4 renderers with preset cameras
        let presets: [(CameraPreset, String)] = [
            (.perspective, "Perspective"),
            (.top, "Top"),
            (.front, "Front"),
            (.right, "Right"),
        ]

        var rends: [ViewportRenderer] = []
        for (preset, _) in presets {
            let cam = OrbitalCamera()
            preset.configure(cam)
            let renderer = ViewportRenderer(camera: cam)
            renderer.configure(device: device, library: library)
            renderer.sceneGraph = sceneGraph
            rends.append(renderer)
        }
        self.renderers = rends
    }

    // MARK: - Add primitives

    func addPrimitive(_ type: PrimitiveType) {
        let data: PrimitiveMeshData
        let name: String

        switch type {
        case .cube:
            data = PrimitiveGenerator.cube()
            name = uniqueName("Cube")
        case .plane:
            data = PrimitiveGenerator.plane()
            name = uniqueName("Plane")
        case .uvSphere:
            data = PrimitiveGenerator.uvSphere()
            name = uniqueName("Sphere")
        case .icosphere:
            data = PrimitiveGenerator.icosphere()
            name = uniqueName("Icosphere")
        case .cylinder:
            data = PrimitiveGenerator.cylinder()
            name = uniqueName("Cylinder")
        case .cone:
            data = PrimitiveGenerator.cone()
            name = uniqueName("Cone")
        case .torus:
            data = PrimitiveGenerator.torus()
            name = uniqueName("Torus")
        }

        let obj = SceneObject(name: name, type: .mesh)
        obj.meshHandle = MeshUploader.upload(
            vertices: data.vertices,
            wireVertices: data.wireVertices,
            faceCount: data.faceCount,
            edgeCount: data.edgeCount,
            label: name,
            device: device
        )
        obj.boundingBoxMin = data.boundingBoxMin
        obj.boundingBoxMax = data.boundingBoxMax

        // Place at cursor (origin for now) with slight offset to avoid overlap
        let existingCount = sceneGraph.allObjects.filter { $0.type == .mesh }.count
        obj.transform.position = SIMD3<Float>(Float(existingCount) * 3.0, 0, 0)

        sceneGraph.select(nil)
        sceneGraph.addObject(obj)
        sceneGraph.select(obj)
    }

    func deleteSelected() {
        guard let selected = sceneGraph.selectedObject else { return }
        sceneGraph.removeObject(selected)
    }

    private func uniqueName(_ base: String) -> String {
        let existing = sceneGraph.allObjects.map { $0.name }
        if !existing.contains(base) { return base }
        var i = 1
        while existing.contains("\(base).\(String(format: "%03d", i))") {
            i += 1
        }
        return "\(base).\(String(format: "%03d", i))"
    }
}

// MARK: - Primitive types

enum PrimitiveType: String, CaseIterable, Identifiable {
    case cube      = "Cube"
    case plane     = "Plane"
    case uvSphere  = "UV Sphere"
    case icosphere = "Icosphere"
    case cylinder  = "Cylinder"
    case cone      = "Cone"
    case torus     = "Torus"

    var id: String { rawValue }

    var icon: String {
        switch self {
        case .cube:      "cube"
        case .plane:     "square"
        case .uvSphere:  "globe"
        case .icosphere: "circle"
        case .cylinder:  "cylinder"
        case .cone:      "triangle"
        case .torus:     "circle.circle"
        }
    }
}