/// AssetLoader - Asset management and loading system
/// NO PLATFORM-SPECIFIC IMPORTS ALLOWED IN THIS MODULE
/// Handles loading of 3D models, textures, animations, and audio files

import Foundation

// MARK: - Asset Types

/// Asset loading result
public enum AssetResult<T> {
    case success(T)
    case failure(AssetError)
}

/// Asset loading errors
public enum AssetError: Error, LocalizedError {
    case fileNotFound(String)
    case invalidFormat(String)
    case corruptedData(String)
    case unsupportedVersion(String)
    case outOfMemory
    
    public var errorDescription: String? {
        switch self {
        case .fileNotFound(let path):
            return "Asset file not found: \(path)"
        case .invalidFormat(let format):
            return "Invalid asset format: \(format)"
        case .corruptedData(let reason):
            return "Corrupted asset data: \(reason)"
        case .unsupportedVersion(let version):
            return "Unsupported asset version: \(version)"
        case .outOfMemory:
            return "Out of memory while loading asset"
        }
    }
}

/// Asset handle for reference counting and management
public struct AssetHandle<T>: Hashable, Sendable where T: Hashable {
    public let id: UUID
    public let path: String
    
    public init(id: UUID = UUID(), path: String) {
        self.id = id
        self.path = path
    }
    
    public func hash(into hasher: inout Hasher) {
        hasher.combine(id)
    }
}

// MARK: - Mesh Data

/// Mesh data structure (vertex and index buffers)
public struct MeshData: Sendable, Hashable {
    public var name: String
    public var vertices: [MeshVertex]
    public var indices: [UInt32]
    public var bounds: BoundingBox
    
    public init(name: String, vertices: [MeshVertex], indices: [UInt32], bounds: BoundingBox) {
        self.name = name
        self.vertices = vertices
        self.indices = indices
        self.bounds = bounds
    }
    
    public func hash(into hasher: inout Hasher) {
        hasher.combine(name)
    }
}

/// Vertex structure for mesh data
public struct MeshVertex: Sendable, Hashable {
    public var position: SIMD3<Float>
    public var normal: SIMD3<Float>
    public var uv: SIMD2<Float>
    public var tangent: SIMD3<Float>
    public var boneIndices: SIMD4<UInt8> // For skeletal animation
    public var boneWeights: SIMD4<Float> // For skeletal animation
    
    public init(position: SIMD3<Float>, normal: SIMD3<Float>, uv: SIMD2<Float>,
                tangent: SIMD3<Float> = .zero, boneIndices: SIMD4<UInt8> = .zero,
                boneWeights: SIMD4<Float> = .zero) {
        self.position = position
        self.normal = normal
        self.uv = uv
        self.tangent = tangent
        self.boneIndices = boneIndices
        self.boneWeights = boneWeights
    }
}

/// Bounding box for culling
public struct BoundingBox: Sendable, Hashable {
    public var min: SIMD3<Float>
    public var max: SIMD3<Float>
    
    public init(min: SIMD3<Float>, max: SIMD3<Float>) {
        self.min = min
        self.max = max
    }
}

// MARK: - Texture Data

/// Texture data structure
public struct TextureData: Sendable, Hashable {
    public var name: String
    public var width: Int
    public var height: Int
    public var format: TextureFormat
    public var data: Data
    public var mipLevels: Int
    
    public init(name: String, width: Int, height: Int, format: TextureFormat, data: Data, mipLevels: Int = 1) {
        self.name = name
        self.width = width
        self.height = height
        self.format = format
        self.data = data
        self.mipLevels = mipLevels
    }
    
    public func hash(into hasher: inout Hasher) {
        hasher.combine(name)
    }
}

/// Texture format
public enum TextureFormat: Sendable, Hashable {
    case rgba8
    case rgba16f
    case rgba32f
    case dxt1
    case dxt5
    case bc7
}

// MARK: - Animation Data

/// Skeletal animation data
public struct AnimationData: Sendable, Hashable {
    public var name: String
    public var duration: Float
    public var ticksPerSecond: Float
    public var channels: [AnimationChannel]
    
    public init(name: String, duration: Float, ticksPerSecond: Float, channels: [AnimationChannel]) {
        self.name = name
        self.duration = duration
        self.ticksPerSecond = ticksPerSecond
        self.channels = channels
    }
    
    public func hash(into hasher: inout Hasher) {
        hasher.combine(name)
    }
}

/// Animation channel (per-bone)
public struct AnimationChannel: Sendable, Hashable {
    public var boneName: String
    public var positionKeys: [KeyFrame<SIMD3<Float>>]
    public var rotationKeys: [KeyFrame<SIMD4<Float>>]
    public var scaleKeys: [KeyFrame<SIMD3<Float>>]
    
    public init(boneName: String, positionKeys: [KeyFrame<SIMD3<Float>>],
                rotationKeys: [KeyFrame<SIMD4<Float>>], scaleKeys: [KeyFrame<SIMD3<Float>>]) {
        self.boneName = boneName
        self.positionKeys = positionKeys
        self.rotationKeys = rotationKeys
        self.scaleKeys = scaleKeys
    }
}

/// Animation keyframe
public struct KeyFrame<T: Sendable & Hashable>: Sendable, Hashable {
    public var time: Float
    public var value: T
    
    public init(time: Float, value: T) {
        self.time = time
        self.value = value
    }
}

// MARK: - Skeleton Data

/// Skeletal hierarchy for character animation
public struct SkeletonData: Sendable, Hashable {
    public var bones: [Bone]
    public var rootBoneIndex: Int
    
    public init(bones: [Bone], rootBoneIndex: Int = 0) {
        self.bones = bones
        self.rootBoneIndex = rootBoneIndex
    }
}

/// Individual bone in skeleton
public struct Bone: Sendable, Hashable {
    public var name: String
    public var parentIndex: Int?
    public var offsetMatrix: float4x4
    
    public init(name: String, parentIndex: Int?, offsetMatrix: float4x4) {
        self.name = name
        self.parentIndex = parentIndex
        self.offsetMatrix = offsetMatrix
    }
}

// MARK: - Asset Manager

/// Main asset management system
public actor AssetManager {
    
    private var meshCache: [String: MeshData] = [:]
    private var textureCache: [String: TextureData] = [:]
    private var animationCache: [String: AnimationData] = [:]
    private var skeletonCache: [String: SkeletonData] = [:]
    
    private var loadedAssets: Set<String> = []
    
    public init() {}
    
    // MARK: - Lifecycle
    
    public func initialize() {
        print("    ✓ Asset manager initialized")
    }
    
    public func shutdown() {
        meshCache.removeAll()
        textureCache.removeAll()
        animationCache.removeAll()
        skeletonCache.removeAll()
        loadedAssets.removeAll()
        
        print("    ✓ Asset manager shutdown (cleared caches)")
    }
    
    // MARK: - Mesh Loading
    
    /// Load a 3D mesh from file
    public func loadMesh(path: String) async -> AssetResult<MeshData> {
        // Check cache first
        if let cached = meshCache[path] {
            return .success(cached)
        }
        
        // Load from disk
        guard let data = try? Data(contentsOf: URL(fileURLWithPath: path)) else {
            return .failure(.fileNotFound(path))
        }
        
        // Parse mesh format (OBJ, FBX, GLTF, etc.)
        guard let mesh = parseMeshData(data: data, path: path) else {
            return .failure(.invalidFormat(path))
        }
        
        // Cache and return
        meshCache[path] = mesh
        loadedAssets.insert(path)
        
        return .success(mesh)
    }
    
    private func parseMeshData(data: Data, path: String) -> MeshData? {
        // Simplified placeholder - would parse actual formats
        // For sports games: support FBX (player models), GLTF (stadiums), custom formats
        
        // Create a simple test mesh (placeholder)
        return createTestMesh(name: path)
    }
    
    private func createTestMesh(name: String) -> MeshData {
        // Create a simple cube for testing
        let vertices: [MeshVertex] = [
            MeshVertex(position: SIMD3<Float>(-1, -1, -1), normal: SIMD3<Float>(0, 0, -1), uv: SIMD2<Float>(0, 0)),
            MeshVertex(position: SIMD3<Float>(1, -1, -1), normal: SIMD3<Float>(0, 0, -1), uv: SIMD2<Float>(1, 0)),
            MeshVertex(position: SIMD3<Float>(1, 1, -1), normal: SIMD3<Float>(0, 0, -1), uv: SIMD2<Float>(1, 1)),
            MeshVertex(position: SIMD3<Float>(-1, 1, -1), normal: SIMD3<Float>(0, 0, -1), uv: SIMD2<Float>(0, 1)),
        ]
        
        let indices: [UInt32] = [0, 1, 2, 0, 2, 3]
        
        let bounds = BoundingBox(
            min: SIMD3<Float>(-1, -1, -1),
            max: SIMD3<Float>(1, 1, 1)
        )
        
        return MeshData(name: name, vertices: vertices, indices: indices, bounds: bounds)
    }
    
    // MARK: - Texture Loading
    
    /// Load a texture from file
    public func loadTexture(path: String) async -> AssetResult<TextureData> {
        // Check cache first
        if let cached = textureCache[path] {
            return .success(cached)
        }
        
        // Load from disk
        guard let data = try? Data(contentsOf: URL(fileURLWithPath: path)) else {
            return .failure(.fileNotFound(path))
        }
        
        // Parse texture format (PNG, JPG, DDS, KTX, etc.)
        guard let texture = parseTextureData(data: data, path: path) else {
            return .failure(.invalidFormat(path))
        }
        
        // Cache and return
        textureCache[path] = texture
        loadedAssets.insert(path)
        
        return .success(texture)
    }
    
    private func parseTextureData(data: Data, path: String) -> TextureData? {
        // Simplified placeholder - would use image decoding libraries
        // For sports games: support DDS (compressed), PNG, JPG, HDR textures
        
        // Create a simple test texture
        return createTestTexture(name: path)
    }
    
    private func createTestTexture(name: String) -> TextureData {
        // Create a 2x2 test texture (white)
        let width = 2
        let height = 2
        var data = Data(count: width * height * 4)
        for i in 0..<(width * height * 4) {
            data[i] = 255
        }
        
        return TextureData(name: name, width: width, height: height, format: .rgba8, data: data)
    }
    
    // MARK: - Animation Loading
    
    /// Load skeletal animation from file
    public func loadAnimation(path: String) async -> AssetResult<AnimationData> {
        // Check cache first
        if let cached = animationCache[path] {
            return .success(cached)
        }
        
        // Load from disk
        guard let data = try? Data(contentsOf: URL(fileURLWithPath: path)) else {
            return .failure(.fileNotFound(path))
        }
        
        // Parse animation format
        guard let animation = parseAnimationData(data: data, path: path) else {
            return .failure(.invalidFormat(path))
        }
        
        // Cache and return
        animationCache[path] = animation
        loadedAssets.insert(path)
        
        return .success(animation)
    }
    
    private func parseAnimationData(data: Data, path: String) -> AnimationData? {
        // Simplified placeholder - would parse FBX/GLTF animations
        // For sports games: running, shooting, passing, tackling animations
        return createTestAnimation(name: path)
    }
    
    private func createTestAnimation(name: String) -> AnimationData {
        // Create a simple test animation
        let channel = AnimationChannel(
            boneName: "Root",
            positionKeys: [
                KeyFrame(time: 0.0, value: SIMD3<Float>(0, 0, 0)),
                KeyFrame(time: 1.0, value: SIMD3<Float>(1, 0, 0))
            ],
            rotationKeys: [
                KeyFrame(time: 0.0, value: SIMD4<Float>(0, 0, 0, 1)),
                KeyFrame(time: 1.0, value: SIMD4<Float>(0, 0, 0, 1))
            ],
            scaleKeys: [
                KeyFrame(time: 0.0, value: SIMD3<Float>(1, 1, 1)),
                KeyFrame(time: 1.0, value: SIMD3<Float>(1, 1, 1))
            ]
        )
        
        return AnimationData(name: name, duration: 1.0, ticksPerSecond: 30.0, channels: [channel])
    }
    
    // MARK: - Skeleton Loading
    
    /// Load skeletal hierarchy from file
    public func loadSkeleton(path: String) async -> AssetResult<SkeletonData> {
        // Check cache first
        if let cached = skeletonCache[path] {
            return .success(cached)
        }
        
        // Load from disk
        guard let data = try? Data(contentsOf: URL(fileURLWithPath: path)) else {
            return .failure(.fileNotFound(path))
        }
        
        // Parse skeleton format
        guard let skeleton = parseSkeletonData(data: data, path: path) else {
            return .failure(.invalidFormat(path))
        }
        
        // Cache and return
        skeletonCache[path] = skeleton
        loadedAssets.insert(path)
        
        return .success(skeleton)
    }
    
    private func parseSkeletonData(data: Data, path: String) -> SkeletonData? {
        // Simplified placeholder
        return createTestSkeleton()
    }
    
    private func createTestSkeleton() -> SkeletonData {
        let rootBone = Bone(name: "Root", parentIndex: nil, offsetMatrix: matrix_identity_float4x4)
        return SkeletonData(bones: [rootBone], rootBoneIndex: 0)
    }
    
    // MARK: - Cache Management
    
    public func unloadAsset(path: String) {
        meshCache.removeValue(forKey: path)
        textureCache.removeValue(forKey: path)
        animationCache.removeValue(forKey: path)
        skeletonCache.removeValue(forKey: path)
        loadedAssets.remove(path)
    }
    
    public func clearCache() {
        meshCache.removeAll()
        textureCache.removeAll()
        animationCache.removeAll()
        skeletonCache.removeAll()
        loadedAssets.removeAll()
    }
    
    public func getCacheSize() -> (meshes: Int, textures: Int, animations: Int, skeletons: Int) {
        return (meshCache.count, textureCache.count, animationCache.count, skeletonCache.count)
    }
}

// MARK: - Matrix Helper

extension float4x4 {
    static var identity: float4x4 {
        return matrix_identity_float4x4
    }
}