//

// GeometryCache.swift

// ShapeScript Lib

//

// Created by Nick Lockwood on 06/08/2021.

// Copyright © 2021 Nick Lockwood. All rights reserved.

//

import Euclid

#if canImport(LRUCache)

import LRUCache

#endif

public final class GeometryCache {

private let cache: LRUCache<Key, (mesh: Mesh, associatedData: [Material: Any])>

/// The number of entries currently stored in the cache

public var count: Int { cache.count }

/// Initialize the cache with a given storage limit

/// - Parameter memoryLimit: The maximum amount of data to cache (in bytes)

public init(memoryLimit: Int = 1_000_000_000) {

self.cache = LRUCache(totalCostLimit: memoryLimit)

}

}

extension GeometryCache {

struct Key: Hashable {

let type: GeometryType

let material: Material?

let smoothing: Angle?

let transform: Transform

let flipped: Bool

let children: [Key]

}

subscript(mesh geometry: Geometry) -> Mesh? {

get { cache.value(forKey: geometry.cacheKey)?.mesh }

set {

guard let newValue else {

cache.removeValue(forKey: geometry.cacheKey)

return

}

cache.setValue(

(newValue, [:]),

forKey: geometry.cacheKey,

cost: newValue.memoryUsage

)

}

}

subscript(associatedData geometry: Geometry) -> Any? {

get {

cache.value(forKey: geometry.cacheKey)?

.associatedData[geometry.material]

}

set {

if var value = cache.value(forKey: geometry.cacheKey) {

value.associatedData[geometry.material] = newValue

cache.setValue(value, forKey: geometry.cacheKey)

}

}

}

}

private extension Mesh {

var memoryUsage: Int {

let vertexSize = MemoryLayout<Vertex>.stride

let polygonSize = 512 // Estimated

return polygons.reduce(0) { count, polygon in

count + polygonSize + polygon.vertices.count * vertexSize

}

}

}